The Aether by Skinners' School

Cover art by Mitansh C.

Contents About The Magazine

Latest Discoveries

Fermi Paradox

Invar: A magnet that won't behave

Measurements in Space

Dark Matter

Interstellar Travel

Q&A with Dr Christopher Berry

How does GPS Work

Terraforming Mars

Katherine Johnson

Ingenuity

Book Recommendations

The Aether Quiz

Citations

About the Magazine Welcome to the second issue of The Aether, Skinner s' School's science magazine. Written and designed by the Sixth Form science prefects - as well as staff and guest writers - this magazine aims to help inform you about some of the most interesting, relevant and cutting edge topics in modern science over a range of scienti c and mathematical disciplines.

This time we delve into the unknown abyss, far out of our reach (for now)…

Space! This is a special issue focusing on Space, from the Fermi paradox and Dark Matter to Interstellar Travel.

Meet the Editors MC - Hello Readers! My name is Mitansh, and I am a Biology and Chemistry writer. For this issue I will be exploring how the distances to, and masses of planets are calculated and the effects that travelling in space may have on the human body. MB - Hi! My name is Matthew, and I am a maths and physics writer. In this issue, I will be talking about how basic geometry makes G P S wo r k , a n d o n e o f t h e ge n i u s mathematicians of NASA in the space race, Katherine Johnson. ZG - Greetings! I am Zavié, and in this issue, I will be showing how and why Dark Matter does matter. I will also focus on the Breakthrough Starshot Project and the possibility of Anti-Matter/Matter drives for space travel, and hope that you will nd the interview with Dr Berry as inspiring as I did. May you all live long and prosper.

BW - Hey, I'm Ben and I will be taking you on a journey exploring the presence (or seeming lack thereof) of Alien Life! HT - Hi, I'm Henry a Chemistry and Physics writer. In this issue, I will be taking you through Terraforming Mars. Guest Writers AB - Arthur Branch is an upper sixth student at the Skinners' School who has an interest in sports and a fascination in space exploration and has kindly written an article on the recent Ingenuity helicopter Dr. Andrew Bebb - Dr. Bebb is the head of physics at the Skinners' School who has overlooked the production of the magazine and written an article for this issue on Invar, a rather peculiar magnet and the subject of his PhD

Particle Physics

July 29th 2021

First Ever Double Open Charm Tetraquark discovered at LHCb

A tetraquark is a particle composed of two quarks and two antiquarks. The particle, which was found by researchers at the Large Hadron Collider, is designated as Tcc+ and is comprised of two charm quarks, an antiup quark, and an anti-down quark. When a particle contains a charm quark but no charm antiquark, it is considered to have open charm; thus, this tetraquark has double open charmness, the rst ever experimentally veri ed to have such a property. Furthermore, that the mass of the charm quark is signi cantly greater than up or down quarks (with the charm a second-generation quark and the up and down rst generation) means that the Tcc+ is also the rst tetraquark to have two heavy quarks and two light antiquarks. The Tcc+ is also the longest lived tetraquark discovered so far. Z.G.

Biology:

12 August 2021

New Marmoset Species

Biology:

4 November 2021

Molnupiravir

The MHRA (Medicines and Healthcare products Regulatory Agency) has approved the anti-viral medicine Lagevrio (Molnupiravir) developed by Ridgeback Biotherapeutics and Merck Sharp & Dohme (MSD). [1] The drug, to be taken orally, is a major step towards treating the virus who may be at risk due to an underlying health condition to reduce deaths. It is aimed at people with mild to moderate COVID-19 and at least one risk factor of developing a severe illness, i.e. diabetes (mellitus), heart disease or obesity. [1] The drug works by interfering with the virus’ replication in the body. [1] If the virus can’t multiply then the levels of the virus in the body remain low and the white blood cells (leukocytes) can ght the existing viruses in the body ensuring that the disease doesn’t progress further. According to the MHRA the medicine had been rigorously tested for its ‘safety, quality and e ectiveness’ and UK is the rst country to approve the medicine. M.C.

Space: 25th December 2021 Launch of the James Webb Space Telescope After 25 years in production, the JWST is expected to revolutionise our understanding of the universe. After launch, it will take fty major deployment events, including of the sunshield and the largest space mirror ever constructed, before it is ready to y out to its orbit at about 1 million miles from the earth around the second Lagrangian Point. Named after the second director of NASA, and costing $10 billion, the greater resolution and range should mean that having successfully launched on Christmas day 2021, the perfect Christmas gift of the JWST will herald a new era of astronomical discovery. Z.G.

Illustration of the James Webb Space Telescope on a transparent background by NASA. This image is in the Public Domain. Source: In citations

The Fermi Paradox Ben Wilson

When we sit under the stars at night and look up into the vast sky (or perhaps sit down and enjoy the latest episode of Rick and Morty or Dr Who) many of us ask ourselves the question: are there aliens out there in the stars, and will we ever meet them? So let’s give it some thought.

A Sense of Scale Our universe is immense. Just our observable universe (the portion we can see limited by the speed of light which is shrinking all the time) is greater than 90,000,000,000 light years in diameter, and is home to at least one-hundredbillion galaxies, with each individual Galaxy being estimated to contain between 100,000,000,000 1,000,000,000,000 stars. This, in a more visual form, roughly translates to 10,000 stars for every grain of sand on Earth in our observable universe. However, this number isn’t particularly useful answer our question. Even if there are Aliens in far off galaxies in the universe, it’s highly unlikely we’ll be able to detect them, this is due to the expansion and scale of the universe; even if we were to develop incredibly fast space travel, it would take billions of years to reach them, travelling through the emptiest areas in the universe, making resupplying your spaceship and anyone unlucky enough to be on board nigh-on impossible. So let’s focus on our home galaxy: the Milky Way.

Image Credit: Courtesy of Wikimedia Commons. 'Milky way', Pablo Carlos Budassi, Source in citations

Our home galaxy, a member of the Local Group and thought to have formed 14 billion years ago, is home to 400 billion stars, and 20 billion Sun-like stars. Of these only around a fth have an Earth like planet in their hospitable zone (the area around a star suitable to supporting life).The distance this zone is from the centre is dependent on the size and type of star and is often known as the ‘Goldilocks Zone’ (not too hot, not too cold, some would say just right). This is the area around a star in which water can remain a liquid, currently thought to be a requirement for the development of life as its involved in almost all biological processes. If only 0.1% of these select planets developed intelligent life, there would be over 1,000,000 planets with life in our galaxy alone. But this isn’t all there is to consider.

A visual guide to Goldilocks Zone, with Kepler-22b as an example of a potentially life enabling planet. Image Credit: NASA/Ames/JPL Source available in citations

Our Galaxy is old- very old. The Milky Way galaxy was formed approximately 13 billion years ago, but was-at the start-exceptionally volatile, and hence the rst habitable planets weren’t formed for another one or two billion years (or 11 billion years ago from today). Our own planet, Earth, is only 4.5 billion years old, so our planet is relatively young on the grand scale of habitable planets in our galaxy; the result of this is that life on other planets can be hypothesised to have had signi cantly longer to develop to, and past our stage in technological advancement. One method of measuring the technological advancement of an intelligent species uses the energy which that civilisation has control over to assess their development and scale. Proposed by a Russian astrophysicist named Nikolai Kardashev in 1964, it is ttingly known as the Kardeshev scale.

The Kardeshev Scale

Hence the paradox: an unimaginably large eld for seeds to sprout from, yet an empty stretch of land as far as the eye can see. Why?

The Kardshev Scale measures development in distinct stages:

For us to be able to evaluate this line of argument properly, it’s important that we are able to quantify what we’re evaluating(i.e. how much life should we be able to detect, and if it existed would it be comparable to us in its development?): this is where the Drake Equation comes in.

A Type I Civilisation controls all of the energy of its own planet (we’re currently at 0.73, and should reach type one within a few hundred years); A Type II Civilisation would be capable of harnessing all of the energy of its own star, ideas such as the Dyson Sphere explore this concept, although it still remains largely in the world of science ction; A Type III Civilisation has domain over its entire galaxy and its resources — a civilisation this advanced could seem near god-like to us, in a similar way our technology may have seemed to an early human.

The colonisation of an entire Galaxy may feel like an enormous challenge, but in all of this it’s important to remember just how long other forms of life may have had to do it. If we could develop spaceships which could sustain a population for at least 1000 years, we could colonise the entire Milky Way in only 2,000,000 years, a timescale dwarfed by the billions of years in which lifesustaining planets have existed in our galaxy. So if there have been millions, if not billions, of chances for life to develop, and many of them have had considerably longer to develop than we have… where is everyone?

THE FERMI PARADOX This discrepancy between our expectation and what we actually perceive as we scour the cosmos for a trace of life is known as the Fermi Paradox and is named after Enricho Fermi. The Paradox can be summarised as follows:

Life is Uncommon However, the scale of the universe is so extreme, that despite this rarity, life should be both plentiful in our galaxy and at a level which is detectable by us as a civilisation. No alien life is has ever been perceived by us, no messages, no signs of life

And thus nally, why haven’t we detected any life? Is it there out there at all?

THE DRAKE EQUATION Proposed by Frank Drake (Drake 1961), this is a method to mathematically estimate our paradox, and takes into account 7 key factors to determine the number of civilisations we should be able to detect in our home galaxy:

• How often life-enabling stars are formed • The fraction of those with planets orbiting them • The fraction of those planets held in orbit within • • • •

the ‘goldilocks zone’ The fraction of these on which life develops The fraction of that life which evolves into an intelligent civilisation The fraction of those civilizations which develop a technology detectable through space (apologies for the excess of ‘fraction’s) And nally the length of time such civilisations have been producing signs detectable to humanity

Using this equation, we can now estimate the amount of detectable alien civilisations within our galaxy, so what’s the conclusion? This is where it gets tricky, while me may know fairly precisely the values for some of these factors (such as Star Formation) others are highly debated. The most debated of all is the formation of life, and how universal this process of dead matter forming selfreplicating patterns is within our universe. Some believe it occurs everywhere where the conditions are right- others that it’s incredibly rare. These barriers for the development of life and our eventual alien civilisation are known as Great Filters, and show us potential solutions to The Fermi Paradox.

N = R* fp ne fl fi ft L where R* is the rate of star formation in the Galaxy, fp is the fraction of stars with planetary systems, ne is the average number of planets around each star, fl is the fraction of planets where life developed, fi the fraction of planets where intelligent life developed, and ft is the fraction of planets with technological civilizations

Great Filters: Ahead

Let’s consider the rst scenario, the lter is behind us. In this scenario one of the steps we as a species have taken must be almost impossible to pass; so which is it? Is it the formation of the rst cells? The integration of the primitive mitochondria into a host cell to increase energy production (these cells make up every animal cell on the planet)? Is it the formation of multi cellular organisms or perhaps something more evolutionary in nature? After all big brains are a massive investment in terms of energy evolutionarily, and despite them it took hundreds of thousands of years for us to go from rocks and sticks to space travel. Perhaps intelligence doesn’t tend to pay off past a certain threshold, and we are an evolutionary anomaly.

The next scenario is less comforting; the Great Filter may be ahead of us. What this would mean is that life has developed to our point in the past, perhaps billions of times- but has always failed to either sustain itself for a large period of time or has been unable to develop any further into a Type II or III civilisation. This is deeply unsettling. In order for this event to be a Great Barrier, it would have to be incredibly devastating; even if humanity were to experience an event which set us back thousands of years, we would eventually recover and resume our progress towards becoming an advanced civilisation. That would merely be a roadblock on our journey, not a barrier.

In this scenario we are incredibly rare, and may be the rst living things to be truly conscious of the grand universe we’ve been born into, a whole universe just waiting for us to arrive. Life on other planets could be limited to simpler, non societal, organisms, purely single celled organisms or perhaps be completely barren of life altogether. While possibly less exciting and a tad disappointing, colonisation and exploration of the galaxy could be freer and less guarded if this were the case; out of whole universe of potential intelligent life, we are the rst.

So whatever this barrier is, it must be something which cannot be recovered from or moved past, and something so common, that nearly every developing Alien society encounters and is either stopped or eliminated by it. Perhaps a new technology which is far more dangerous than perceived, maybe a runaway chain reaction in the climate of the planet which makes it inhospitable to life, perhaps AI getting out of control. The options here are varied and plentiful, but if a barrier lies ahead on our road, we need to tread carefully. Some have suggested that advanced civilisations may be monitoring the development of life in their galaxy, and neutralising it before it can become a threat. Whatever form this barrier takes, our odds of survival would be dire. As a result of this, nding evidence of life on other planets may be less exciting and encouraging than you might expect. The more common life, and especially life like us, is in the universe, the higher the odds that the lter lies ahead of us on our road to a Type III Civilisation - and the more real the threat of impending doom becomes for us as a species. Our best hope for a bright future for humanity is that the vast universe is as it perplexing appears- empty and dead. Millions of homes to ll with people and life.

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Great Filters: Behind

Invar: A Magnet That Won’t Behave (...and 126 years later we still do not know why...) Dr. Bebb At Skinners’, we start learning about magnets and electromagnetism in year 8. Beginning with north and south poles, iron lings and eld lines, then on to coils of current-carrying wire with soft iron cores picking up paper clips. At GCSE we use these ideas to explain motors, generators and the transformers that are so vital for the National Grid. We delve even deeper into the weird world of magnetism in A Level Physics, but even that is just skimming the surface.

about detecting x-ray radiation in the hospital to study magnetic materials which seemed to break the rules of physics. In scienti c research, you rarely work alone. I was lucky enough to have joined a research team with Dr Jon Duffy and Dr Jon Taylor; both experts on magnetism and materials. It was the millennium, and I was starting to get my head around the theories of magnetism when a scienti c paper was published which got everyone talking. Its author claimed to have nally solved a puzzle which had frustrated physicists for over a hundred years.

Invar, Guillaume and Srajer

Magnetism is a tricky phenomenon to understand well. What we think of as a simple but spooky push or pull when we bring two bar magnets together can actually be broken down into many different, interrelated bits of physics, with exotic names like ferromagnetism and Pauli spin paramagnetism. There exists a wonderful interview with the Nobel laureate Richard Feynman, in which he explains why explaining magnetism is so dif cult to do well (link at the end of this article). As of 2022, we have several excellent theories which can predict the properties of a wide range of magnetic phenomena, from hard disk drives to particle accelerators. These theories work incredibly well for most magnetic systems, but not all. There are plenty of unsolved mysteries in magnetism.

That’s me (Dr Bebb) with Dr Duffy and Dr Taylor, relaxing at the end of a month-long experiment

In 1999 I had just left my job as an NHS Medical Physicist to start a three-year PhD at the University of Warwick. I was going to use what I had learned

Invar is bizarre. Most materials expand when heated and contract when they are cooled. Not Invar. Invar is a very speci c alloy of Iron and Nickel, or Iron and Platinum, and over a wide range of temperatures these alloys exhibit zero thermal expansion, meaning that they do not expand or contract when the temperature is changed. In 1895 Swiss physicist Charles Guillaume discovered Invar’s strange properties and he was awarded the Nobel Prize for Physics in 1920 for this work. Invar has countless industrial, medical, and military applications. A material that does not change its dimensions when heated up is less likely to warp or fail, and will remain precise under a range of conditions. In the middle of the last century, you would have to wait for a TV set to warm up after switching it on before you would see any picture; that was until they starting making the components out of Invar. Scientists knew that Invar’s odd behaviour probably had something to do with magnetism, as both types of Invar were magnetic and there is a known phenomenon called ‘magnetostriction’. This is where a sudden change in magnetic properties of a material, at a certain temperature, can cause the material to shrink. The thinking was that in Invar this magnetic shrinking was perfectly offset by the thermal expansion, so that the material seemed to not expand as it was heated. The only problem was this: there did not seem to be any measurable change in the magnetism at the temperatures where Invar does not expand. In 1999 George Srajer, a physicist from the Argonne National Laboratory in Illinois, USA, published a

Magnetism arises from charged particles such as electrons moving in a loop. To make an electromagnet, you send a current (moving electrons) in a coil of wire (a loop). On an atomic scale, magnetism arises from the electrons making tiny loops of current as they orbit the nucleus. In most materials these little atomic magnets do not line up in the same direction and so the resulting magnetic eld is zero. Only in some metals, such as Iron, Nickel and Cobalt, do these tiny atomic magnets all align to produce a permanent magnetic eld we can measure. However, there is a second kind of loop that the electrons make. Just like the Earth loops around the Sun in its orbit (a year) but also spins on its axis (a day), the electrons spin on their axis as they orbit the nucleus. This means that there are two separate components (magnetic moments) to these tiny atomic magnets: the orbital and the spin.

effect would be zero. You could have a change in magnetostriction without any sudden change in the overall magnetism. Problem solved. Most scienti c techniques used to measure magnetism cannot separate out the contributions from the spin and orbital motion, but there was one method called Magnetic Compton Scattering (MCS) that could. MCS only measures the spin part of the magnetism, so would be able to tell if that component changes with temperature. Srajer and his team used this technique and published their results in the Journal of Physics: Condensed Matter; a respected peer-reviewed publication. Their data showed a clear change in the spin part of the magnetism, just as predicted, which if con rmed would explain the Invar effect. As the temperature of the Invar increased, the magnetism shifted between the spin and orbital components, leading to a magnetostriction which perfectly counterbalanced the thermal expansion. There was talk in the community of a “trip to Stockholm”.

The results of Srajer’s experiment, which appeared to show a difference in the spin part of the magnetism for Invar at different temperatures, exactly as had been hypothesised. Reproduced from: Magne c Atoms exhibit permanent magnetism (a magnetic moment) due to the loops electrons (charged particles) make as they orbit the nucleus, and spin on their axis. Diagram reproduced in part from Itou et al. 2013. Applied Physics Letters 102 082403, published online 27 February 2013.

Srajer’s hypothesis was that the magnetism in Invar comes in part from the spin of the electrons and in part from their orbital motion, but that the magnetostriction effect resulted only from the spin. If any change to the spin part of the magnetism was exactly balanced by an opposite change to the orbital part, then the overall change to the magnetic

Compton sca ering studies of the Invar alloy Fe3Pt, G Srajer et al., J. Phys.: Condensed Ma er 11 1289 (1999).

Synchrotron Light and Magnetic Compton Scattering One of the reasons my research team at Warwick was so excited by Srajer’s work is that MCS was exactly the kind of experiment we specialised in doing. MCS requires a highly focused beam of high energy x-rays which are then scattered off the electrons in a sample of material and measured carefully. If you did this twice, once with the material

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paper which seemed to solve this century old problem. Physicists throughout the world working in the eld were extremely excited, as the last time someone made a discovery related to Invar, they had won a Nobel Prize.

To obtain the high-energy x-rays we needed, you need a special facility called a synchrotron. These are particle accelerators in which electrons move at nearly the speed of light. They are housed in huge, windowless, donut-shaped buildings which can take about half an hour to walk around inside. Some scientists cycle or rollerblade as its quicker. As the electrons speed around the circuit, they emit laserlike beams of x-rays. Experiment hutches, called beamlines, are built around the loop to utilise these x-rays. Each beamline is a lead-lined bunker to protect the users against the ionising radiation. To be inside the hutch when the x-ray beam is on would be fatal. When our team read the Srajer paper, we urgently applied for synchrotron time at two of the world leading facilities; the ESRF in Grenoble, France, and Spring-8 in Japan. Time on these machines is in extremely high demand, and we needed months of time to get the data needed to either con rm or disprove Srajer’s work. Luckily, our proposals were accepted and we were off to Japan and France.

Magnetic Compton Scattering (MCS): when the scattered x-ray light from the sample is measured, the difference between the signal with an applied eld up and applied eld down is only sensitive to the spin part of the electron’s magnetic moment.

Dr Taylor takes a shift running the experiment at Spring-8, Japan, while in the background Dr Bebb (then Mr Bebb) analyses the data...

The European Synchrotron Radiation Facility is a huge electron accelerator. As the electrons move around the track at nearly the speed of light, they emit high energy x-rays at a tangent to the circle. Experiments are built around these rays in what are called ‘experiment beamlines’. Courtesy of ESRF Public Facts and Figures/Press Kit Last Accessed 27/01/22. Source

in a large magnetic eld with north pole up, and then again with the north pole down, then the difference in the measurements came from the spin part of the electron's magnetism only. This is extremely dif cult to do because the difference between the up- and down signals is a few parts in a million, so extremely long and careful measurements needed to be made, often taking months of round the clock work.

A pure sample of Invar, carefully mounted and painstakingly aligned, ready for the month-long

The European Synchrotron Radia on Facility, Grenoble, France. A par cle accelerator which produces high-energy, focused x-rays to inves gate ma er. The experimental hall and storage ring building of the ESRF. (Courtesy: P.Ginter/ ESRF). Source

dark. Your watch said 9 o’clock, but it was 9pm and not 9am as your brain was telling you. We were particularly surprised that our team had been awarded so much precious beam time at the synchrotron in Japan. We quickly gured out why when we got to Japan. At that time of year, in the region where Spring-8 was situated, it was the (very) rainy season (and crawling bug season) and so all the local scientists sensibly had gone on vacation. We had to watch out for venomous spiders and giant centipedes as we worked. The sinister glowing eyes of racoon-dogs followed us from the synchrotron to our accommodation at night, and we had to check for (and remove) dozens of tiny frogs which had a habit of hiding away in our experiment. After many weeks of working in this strange scienti c limbo, jet lagged and in a very foreign country, we nally had collected all the data we needed.

Plagues of frogs, giant Dobson ies and racoondogs. There was a reason we were given so much synchrotron beam time in Japan!

Working at a synchrotron is a surreal experience. The walls are oddly curved. Late at night, the sounds of the accelerator, the high voltages and cooling systems, is extremely eerie. These are sometimes remarkably busy places, bustling with scientists and engineers, but often you do not see other human for hours. We needed to collect data 24 hours a day, for several weeks at a time, and the experiment had to be constantly staffed. So, we worked in shifts. When you were not setting up the experiment, or monitoring that was running correctly, you were analysing the data as it emerged bit-by-bit. There were no windows, so sometimes you would step outside for some air and be shocked that it was

Disproof: Or How Science Should Work We had been able to do a better experiment than Srajer. By measuring over a much longer time the uncertainty in our data was signi cantly lower. It was

that is exactly how science is supposed to work. A hypothesis is an idea to be tested by careful experiment and observation, and only if that hypothesis passes rigorous testing, by multiple other scientists, does it warrant elevation to a theory or a law. Science is humanity’s current best guess about how the universe works. What separates science from many other elds of human thought is that, in some ways, it wants to be proven wrong. When a hypothesis is disproved, it simply challenges scientists to produce an even better set of models to explain the world about us. One small part of our data. By measuring the Invar material for a longer period than Srajer, and by carefully aligning the crystal sample each me, we were able to get be er data: and with the be er data the apparent di erence in the spin magne sm had vanished.

It has been 126 years since Guillaume discovered Invar’s weird properties and, even today, we still cannot explain it. Perhaps there’s another Nobel Prize in store for the person who can. Perhaps that person could be you.

much less ‘noisy’. When everything had been checked and double checked, the difference in the spin-part of the magnetism that Srajer had reported for different temperatures was simply not there in our data. We published our experiment in the peer reviewed journal Physical Review B. We had been able to show that Srajer’s hypothesis was wrong. The Invar effect could not be explained by magnetostriction; the magnetism shifting from spin to orbital components as the temperature changed.

That’s me (and Dr Blanch from TWGGS) on the day we graduated and became doctors. The oppy Oxford Caps were worth the years of hard work, I think.

Charles Guillaume was awarded the 1920 Nobel Prize for Physics for his discovery of Invar Courtesy of Wikipedia Commons, this image is in the public domain. Source available in cita ons

The Invar experiment was just one of the experiments that was published in a peer-review journal as part of my PhD, and in 2004 I was awarded my doctorate based on this work. I know George Srajer was not thrilled with our ndings, but

Mitansh Choksi

Inspired by the recent Perseverance Rover this article focuses on astronomy and how we can calculate the masses of celestial bodies and distances between planets and galaxies. Many of you must have come across facts such the distance between the Earth and the Sun or how long would it take to travel to the nearest star system. However, how many of you have wondered "How do scientists calculate the distance between the Sun and the Earth?" or "How can we calculate the mass of planets?". The answer is de nitely not using a large set of scales.

Mass of the Earth Now that we know the radius of the earth we can calculate it's mass. Newton's Universal Law of Gravitation states that every particle attracts another particle with a force along a line. The force is directly proportional to the product of the masses and inversely proportional to the square of the distances between them. We can use the equation from Newton's Universal Law of Gravitation:

F =G

Radius of the Earth Since we inhabit the Earth, I thought it would be interesting to start here. Our journey begins at calculating the radius of the earth as this is the rst step to calculating other masses as you will later nd out. In 200 B.C.E. the Greek mathematician, Eratosthenes calculated the distance between Syene (present day Aswan) and Alexandria to be equivalent to 5000 stadia. If we take the 1 stadium to be equal to approximately 0.157 km then the distance Eratosthenes calculated was approximately 785 km. On the summer solstice, when the sun was directly above Syene he calculated that on the same day in Alexandria the angle of the sun's rays from the vertical is 7.2o (this was before the Greeks had accepted the unit of degrees, Eratosthenes had 1 actually said it was of a circle). Now he could 50 calculate the circumference of the earth by the 7.2 785 = calculating: where C = the 360 C circumference. Using C = 39250 km. He was then able to calculate the radius of the earth, we can use the equation Cir c u m f er en ce = 2π r to get the radius equal to approximately 6,246 km which is astoundingly similar to the modern day radius of earth 6,371 km.

M1M2 d2

Where F = Gravitational force between two objects, G = gravitational constant, M1 = Mass of object 1(kg), M2 = is the mass of object 2 (kg) and d = the distance (m) between two object's centres of gravity. When we apply this in context we can set M1 to be the mass of an object on earth, even a person and M2 to be the mass of the earth. The distance is the distance between the centres of gravity of the two objects which is the distance between the centre of the earth and the person, which is the radius of the earth (we can use the modern day value here which is 6,371 km) and F is the gravitational force between two the two objects we must calculate the force using Newton's second law which states that F = m a, where m= mass and a= acceleration. G= 6.67 x 10-11 which was discovered by Henry Cavendish in 1798. Let's try and calculate the mass of the earth using the formula: 1) Given that F = m a , we can substitute m a into the equation to get: m a

M1M2 d2

2) The acceleration on earth as you know is approximately 9.81 ms-2. We then begin to rearrange the formula. Note that the mass is the mass in 'ma' is the mass of the person or object on earth as it the object that accelerates towards the earth, this we can label it M1. 3) M1a × d 2 = G × M1M2. As many of you must spot here that M1 must cancel out when we divide it:

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Measurements in Space

G × M1M2 Therefore we are left M1 with: a × d 2 = G × M2 a × d2 =

5) Now we simply divide the gravitational constant on both sides to get:

a × d2 = M2 G

6) Now when we substitute the correct values in, using standard units, so distance is (6371000 metres), the acceleration is 9.81 ms-2 and the gravitational constant is 6.67 x 10-11, we will get the mass of the earth, which is approximately 5.97 X 1024 kg.

The Earth-Sun Distance The Earth to Sun distance is known as a Astronomical Unit (A.U.) and can be calculated in many different ways. Astronomers throughout history have been measuring trying to measure distances to planets and the sun for a very long time. In 1619, Johannes Kepler published his third law which is that 'The planetary orbital period squared it proportional to it it's semi major axis cubed' (the semi-major axis is half the distance of the diameter of an ellipse). When we look at it mathematically it may appear more simple: P 2 ∝ a 3 . Here P is the planetary orbital period and a is the distance in terms of Astronomical Unit. The formula is also equal, thus P 2 = a 3. Using the formula we can work out the ratios of the distances of planets in the solar system from the sun relative to the earth to sun distance. For example, Mars' orbital period is 1.88 years, which means it takes Mars 1.88 years to travel around the 3

sun once. If we rearrange the formula to P 2 = a. If we substitute the value of 1.88 in for P, a equals 1.52 AU. Which means for Mars to orbit the sun in 1.88 years it must be 1.52 AU from the sun. Likewise we can calculate the distances for all the other planets in the solar system. However the question remains 'How far is one AU?'.

In 1672, Giovanni Cassini worked out the distance to Mars using what is known as the parallax method. Before we develop into how Cassini worked out the distance, let's understand what the parallax method is. Take your nger or thumb, or any nearby object and put it in front of your eyes. If you shut one eye you will notice that the nger (or any other object) in front of your eye appears to have moved relative to all other objects behind the nger. If you repeat this

with the other eye then you will see that the nger shifts again. This is because your eyes are slightly far apart and viewing the nger from two different points. If you work out the angle that your nger shifts by and know the distance between you eyes you can work out the distance from your eyes to your nger using simple geometry. In 1672, Cassini sent an astronomer, Jean Richer, to the French Guiana to measure the angle to Mars. While Richer was measuring the angle in Guiana, Cassini was measuring the angle from Paris. If you are wondering why Cassini sent Richer so far away, then try the experiment with the nger again. You will notice that the further the nger is to you, bigger the shift. Which means a greater chance of error, to reduce this, the distance between the two points from where the angle is being observed is increased. When Richer returned, Cassini was able to work out the parallax angle and the distance to Mars using trigonometry.

dm =

x ta n θ

x Distance to Mars (dm)

Earth

Mars

Then using Kepler's equations he could work out the distance to the Sun. In the modern day technology allows us to calculate this value more accurately using radar. However, we use parallax to calculate distances to planets and stars much farther away then Mars.

The distance to other stars Now that we know the distance to the sun we can calculate the distance to other stars using the sun as a reference point and some more trigonometry. The more astute of you will see that we are back at the parallax method. When you view a distant star, you will see it at certain point in the sky. If the star is viewed again some months later, the star will have appeared to have shifted slightly, this is known as the parallax e ect, here the star hasn't moved but the earth has moved in its orbit.

Mass of Stars

Image Credit: Courtesy of Wikimedia Commons. 'Stellar parallax parallel lines from observation base to distant background' by PdeQuant. Creative Commons Attribution- Share Alike 4.0 International. Source available in citations.

Looking at the diagram, we can see that as the e a r t h m o v e s t h ro u g h i t s o r b i t w e g e t a measurement of 2 AU across the base of the triangle. This distance is needed as we are using trigonometry. Of course we can no longer use astronomical units as the distances are so great and the further away we get, the shift in parallax angle is smaller and smaller. This means we must adjust our units and equations slightly. We brie y touched on the subject that if the distance to the object far away was increased the relative shift we see decreases, which is why Richer was in the French Guiana. If we were to use normal degrees to calculate the angle then there would be a considerable margin of error in our calculations. Thus, we have split one degree even further. In a circle we have 360 degrees. If we divided 1 degree by 60, we would get an even smaller angle and we name this arcminutes. However, even this is not suitable to measure accurately, so we divide one arcminute by 60 again to get one arcsecond. Which means we have divided our circle into 1,296,000 arcseconds. Now to the AU. Astronomical units are quite useful however they're still quite small to measure the distance to the nearest star. So we ask ourselves 'What is the distance at which the parallax angle is 1 arcsecond?'. The answer is one parsec (parallax second). Of course this is respect to 1 AU, so one parsec is equivalent to 206, 265 AU. With our distance and units appropriate for the calculation, we can look at the calculation. The 1 parallax formula is D = . Where D equals the p distance in parsecs, and p is the parallax angle in arcseconds. It's not quite easy to measure arcseconds precisely with your average telescope from Earth. If we were to do that we wouldn't be able to measure very far. To combat this, we have sent up a satellite in space Gaia, which measures the parallax angles to a few ten millionths of an arcsecond. Astronomers can then use this to calculate the distances to stars and planets in our galaxy.

This is slightly complicated relative to everything we've done so far so please bear with me a little longer. Calculating the masses of single distant stars is rather di cult. However, we can calculate the masses of stars in a binary system. A binary system is where two stars are caught in each other's gravity and revolve around each other. Once again this is not so straight forward as there are two types of binary systems. Visual binary systems can be viewed through a telescope. Spectroscopic Binary Systems can't be viewed through a telescope, they usually just appear as one star however when we produce spectra we can see that they are two stars. In the Doppler-e ect objects moving towards us tend to shift towards the blue end of the visible light spectrum and objects moving away from us move toward the red end of the spectrum (redshift). In the spectra produced for binary systems, the star that is relatively moving towards us is shifts to the blue end and the star that is moving away shifts to the red end of the spectrum. Therefore, looking at light over time tells us that there are indeed two stars.

An Artist's impression of the binary star system GG Tauri-A Image Credit: ESO/L. Calçada. Courtesy of Eso. Creative Commons Attribution 4.0 International Licence. Source available in Citations.

Here, we will use Kepler's Third Law again however, this time it's in a slightly di erent form. Isaac Newton re ned Kepler's third law to accommodate masses of stars in a binary system.

P 2 = (M1 + M2)a 3 Here, P is the orbital period of the stars relative to us, a is the distance in-between the stars in the binary system and (M1 + M2) is the total mass of the stars in the binary system. You must realise by now that to use the equation we need two things, the orbital period of the stars and the distances between them. To obtain the data, astronomers produce radial velocity curves. This may sound complicated (and it

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is slightly) however the concept is not too di cult. In a radial velocity curve, the velocity of a star from the Doppler shift is plotted against the time. From it we can calculate how long a star takes to complete an orbit and how fast it completes the orbit. From this we can calculate the circumference of the orbit. Once we have circumference it's a bit of easy maths to calculate the radius and voilà, you have the distance in-between the stars (the 'a' value). We can rearrange the equation to make the masses the subject by dividing a3 on both sides to get:

P2 = (M1 + M2) a3 We now substitute the values for orbital period and distance in-between stars to get the total mass of the stars. By now you must be wondering 'What about all those stars not in binary systems?'. The answer is actually straightforward. Once we have enough data on the masses of other stars and the luminosity of stars - Luminosity refers to the brightness of star in respect to the brightness of the Sun. For stars we use the unit LSun which means if a star has luminosity 10 LSun it is 10 times brighter than the Sun. - we see that there is a relationship. This is known as the mass-luminosity relationship.

along what is known as the Main Sequence. The Main Sequence is fundamentally a part of a star's life cycle. A star spends most of it's time in the Main Sequence. Main Sequence stars fuse hydrogen into helium in the core, once the hydrogen runs out the star exits the main sequence. Smaller stars than the Sun become white dwarfs, fusion is no longer carried in their cores, however they still radiate some heat, and eventually these white dwarfs transit into black dwarfs. Black dwarfs are still hypothetical, the universe is not yet old enough for the rst white dwarfs to become black dwarfs. Stars with a similar size to the Sun are slightly di erent, the outer layers of the star collapsing inwards, this increases temperature until the star starts fusing helium into heavier elements such as carbon. This fusion gives energy for the star to swell into a red giant. Red giants are cooler than the Main Sequence stars, they too fade into white dwarfs. Stars much bigger than the Sun fuse much heavier elements as iron in their cores and explode in super novae (fundamentally a massive reworks display in space), ejecting the contents of the star into surrounding space, which can leave behind a neutron star. If the Star is big enough then it can it can collapse into a black hole. The stars along the Main Sequence are arranged by mass in respect to the Sun. Brighter and hotter stars appear towards the top and colder and dimmer stars appear towards the bottom. If we determine the luminosity and temperature of a star and it happens to fall along the Main Sequence then we can known it's mass.

A graph showing Mass-luminosity relation Image Credit: Courtesy of Wikimedia Commons. 'Isochrone ZAMS Z2pct' by RJHall. This image is in the Public Domain. Source available in citations.

With the graph we can determine the mass of a distant star based on it's luminosity.

Hertzsprung-Russell Diagram The Hertzsprung-Russell Diagram also allows us to calculate the mass of stars. The diagram shows Luminosity against temperature of the star. If we plot all the stars we have observed they appear

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Image Credit: Courtesy of Wikimedia Commons. 'HRDiagram' by Richard Powell. Creative Commons Attribution-Share Alike 2.5 Generic. Source available in Citations.

Dark Matter Zavié Goutorbe Dark Matter remains one of the great mysteries of science. Though much evidence supports its existence, and while the currently accepted model of the universe, or Lambda-CDM (short for Lambda Cold Dark Matter), is reliant on its existence, precisely what dark matter is, or even whether it exists, remains unknown. First used to mean any observable body in the universe that was dark by Henri Poincaré in response to work by Lord Kelvin, who after studying the Milky Way had stated that “many of our stars, perhaps a great majority of them, may be dark bodies”, dark matter took on its modern meaning of the observable missing mass of an astronomical object in 1933 when Fritz Zwicky published a seminal paper. Zwicky had scrutinised the Coma Cluster, and estimated that the motion of the cluster suggested that it had a mass 400 times what could be seen. Though Zwicky’s calculations were not exactly correct, his premise (that missing mass that was as yet unaccounted for existed) was; that said, despite being a genius astronomer, Zwicky was an abrasive man whose ideas were not taken seriously, and so it took until Vera Rubin’s pioneering work on galaxies and galaxy clusters for dark matter to be properly acknowledged.

Origins

making up over 80% of the matter in the universe, Dark Matter accounts for approximately 27% of the Mass-Energy in the universe as opposed to the 68% comprised by Dark Energy. It is also believed that dark matter slows down the expansion of the universe acting as an attractive force. Conversely, Dark Energy behaves as a repulsive force, and causes the acceleration and expansion of the universe. Combined, Dark Energy, as represented by the Cosmological Constant (Lambda or Λ), and Dark Matter form the currently accepted model of the universe, the Λ-CDM. Di erent types of dark matter have been hypothesised, which rely on the speed at which the body is spinning. The type of dark matter depends upon the velocity at which it is moving. Cold Dark Matter, which has a low velocity (or free-streaming rate) is the one which ts the Λ-CDM (or LambdaCold Dark Matter) model. Other forms are Warm and Hot Dark Matter, the latter of which is said to be neutrinos due to their rapid motion, which move at faster rates than Cold Dark Matter. Fuzzy Dark Matter is a further recent proposal to account for the de ciencies of Cold Dark Matter, but the exceptionally light particulate nature of this suggestion is what signi cantly reduces the credibility that can be attributed to it.

Dark matter is believed to exist based on a series of observations, including of galaxy clusters, the Bullet cluster, the CMBR (Cosmic Microwave Background Radiation) and gravitational lensing. The motion of galaxies in clusters is dependent on the mass of the system, which can be deduced to search for dark matter; more mass means a higher velocity. With the Bullet cluster, a particular cluster where two galaxies have collided, the apparent centre of mass is not at the baryonic centre of mass, and can be explained by Dark Matter. Additionally, temperature uctuations in the CMBR can only be accounted for with Dark Matter. The same conclusion with respect to the existence of dark matter can also be applied to Gravitational lensing, when light is bent around a mass.

Evidence

It may also be worth noting distinctions between Dark Matter and Dark Energy before we explore Dark Matter any further. Dark Matter was rst predicted in the 1930s, whereas Dark Energy was rst proposed in the 1990s. Supposedly, in addition to

Λ-CDM

Image of the Bullet Cluster Image Credit: Wikimedia Commons; Pablo Carlo Budassi. Source in Citations

INVESTIGATION OF THE SUSPECTS

Experiments to detect dark matter usually involve large-scale, underground setups - but not always, as we shall see. What dark matter is remains unknown- here are some options as to what this Fantastic Beast is, and how researchers might nd it.

WIMPs (Weakly Interacting Massive Particles)

WIMPs are predicted by a host of theories, perhaps most notably Supersymmetry, which itself has not been experimentally veri ed. As a result, detection of WIMPs could vindicate the work of an entire generation of physicists and eld of physics (String Theorists and String Theory), as well as solving dark matter. WIMPs are supposedly between one and one thousand times the mass of protons or 10 GeV to 10TeV, and they interact via the Weak Nuclear Force and Gravity. WIMPs have received the most attention from scientists, and consequently more experiments have been geared towards detecting WIMPs which include:

XENON1T Experiment

- Dark Bosons - GIMPs (Gravitationally interacting massive particles) - Sub GeV Dark Matter - Sterile Neutrinos

IceCube Neutrino Observatory Location: Amundsen-Scott South Pole Station, Antarctica Modus Operandi: Yes, I know it says Neutrino detector. But that’s precisely what this site does: detect neutrinos. But as a result of one type of WIMP that would interact with a fermion, a neutrino would be produced, which can be detected as a pulse of light by any one of 5160 optical detectors at the station. Detections: Results of analysis from 2011-18 to be released soon.

DEAP-3600 Location: SNOLAB, Sudbury, Canada Modus Operandi: Signifying Dark Matter Experiment Using Pulse-shape discrimination, DEAP is spherically shaped, with a two-inchthick acrylic vessel containing 3.6 tons of liquid argon, ultra-cooled to -180 degrees Celcius. Detection: Pulses detected due to the scattering of the dark matter particle from the argon will be detected, the same method as with XENON1T, but using a di erent noble gas.

Location: National Gran Sasso Laboratories, Gran Sasso Mountains, Italy Modus Operandi: If a WIMP passes through the detection equipment, a 3.2 ton tank of supercooled liquid xenon, it will strike a xenon atom, which should recoil, producing streams of electrons and photons, which can be detected as light. Detections: May ultimately have disproven WIMPs entirely, in favour of either axions (hot dark matter axions instead of cold dark matter) or dark bosons. An excess of electrons detected means that it cannot have been WIMPs that were interacting in the tank.

DEAP-3600 Experiment Set-UPImage Credit:

Image Credit: Mark Ward, Creative Commons Attribution-Share Alike 3.0 Unported license., Source in Citations

Other Open Cases :

Upcoming Experiments with WIMPs LUX-Zeplin

Fermilab is also heavily involved in the hunt for dark matter, notably organising PICO, also based at SNOLAB, which detects recoiling nuclei with bubble chambers; the Darkside experiment, also at Gran Sasso; and the Cryogenic Dark Matter search experiment in Minesotta.

Location: Sanford Undergound Research Facility, Lead, South Dakota, USA Modus Operandi: E ectively the same as XENON1T method, but with a seven-ton tank. Multiple detectors using liquid xenon will use state of the art detectors to nd S1 and S2 signals, the S1 from collisions with xenon nuclei to release photons, and the S2 as secondary scintillation signals of electrons that are separated from their atom as dark matter particle passes following the interaction with the initial nucleus from the S1 signal. Detectors: Functional from 2020-25.

HAYSTAC

Other proposals include the DARWIN experiment, which will be a next generation detector of Brobdingnagian size, lled with 50 tons of liquid xenon- you may wish to consider that the annual production of xenon worldwide is 70 tons. DARWIN’s scale should be su cient to enable the search for WIMPs down to the neutrino oor, where dark matter interactions with xenon would be drowned out by neutrinos, despite their notable weak-interaction.

Location: Yale University, USA Modus Operandi: Quantum squeezing, where electromagnetic pulses, in this case microwave, are used to reduce the quantum uctuations and thus the uncertainty in the detections of potential axions, is the genius behind the work at the HAYSTAC. D e t e c t i o n s : F i r s t s e t o f re s u l t s i n 2 0 1 7 demonstrated a re nement of the technique; now pushing on to detect axions. Thus far, no axions have been detected between certain rest energy upper and lower bounds.

WIMPs may also be detected through their gravitational e ects on visible matter; one experiment which aims to exploit such aspects is at the National Institute of Standards and Technology (NIST). One billion millimetre-sized pendulums could nd the mass of the dark matter particle when passing through the set-up, inducing correlated disturbances in the swings of the pendulums, and would be e ective if the mass is at least one billion billion (1x10^18) times that of a proton, or half a grain of salt.

AXIONS

Predicted by Roberto Peccei and Helen Quinn in 1977, the axion would resolve a violation of Quantum Chromodynamics (the strong C-P problem) and has no charge.

BASE (Baryon Antibaryon Symmetry Experiment)

Location: CERN, Switzerland Modus Operandi: Highly sensitive detectors are able to analyse characteristics of single-trapped antiprotons which are contained in a cryogenic or supercooled Penning trap, and other particles, which may be axion-like, that are trapped in their stead. The antiprotons are supplied by CERN’s Antiproton Decelerator, to which the small-scale experiment is connected. Although not purposebuilt for Axion detection, BASE shows promising signs. Detections: Research suggests axions at a certain range in the traps should turn into detectable photons; a limit on the mass range has already been set.

Gran Sasso Ntional Park, location of the XENON-1T experiment. Image Credit: Wikimedia Commons. Davy Landman. Source in Citations

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Alternatives

The lack of any detection of WIMPs thus far has opened the door to other possibilities. Dark Bosons should be able to explain the extent of electron recoil in the Xenon1T experiment. Additionally, dark bosons should be bound together by gravity to form Boson stars. The interactions of such celestial bodies may be detectable by gravitational wave detectors. Feebly interacting, and lighter than any other candidate, the prediction that Dark Bosons are detectable in King Plots, or would a ect the linear relationship between the energy levels of isotopes, seems to have been backed up by recent studies.

than cold. In 2018, it was suggested that e orts to nd them should be abandoned altogether, and recent results to nd them came back empty handed.

Primordial Black Holes could constitute dark

matter to some extent by way of their gravitational attraction.

Even if dark matter does t the cosmological simulations and models, what dark matter is remains in the dark. There are various candidates hypothesised by various theories, with various experiments being run to try and con rm these potential solutions to varying degrees of success. It’s a bit like a scaled-up game of Cluedo. There are many dark matter candidates, which are mostly massive particles; many experiments are on the go GIMPs (Gravitationally interacting massive to try and whittle the eld down to the answer. One particles): Gravitational eld singularities which only thing is for sure: MACHOs, or Massive Compact interact gravitationally, GIMPs could explain why Halo Objects, were discredited, as they cannot other e orts have failed to detect dark matter. account for all the missing mass. On the other hand, WIMPs (Weakly Interacting Massive Particles) and Axions are considered to be the most Sub GeV Dark Matter : The SENSEI promising candidates. Sub-GeV Dark Matter, Sterile experiment at Fermilab was the rst to search for Neutrinos and Dark Bosons are further alternatives. dark matter through electron recoil, and placed Lastly, Primordial Black Holes, which formed very bounds of 500keV and 4MeV as the minimum and early in the universe, are believed to compose some percentage that is not the entirety of dark matter. maximum rest energies of a dark matter candidate, Not all physicists are convinced, though, that Dark which is one million times lighter than a proton. Matter is the solution, with some resorting to modifying Sterile g r a v i t y. T h e most famous Neutrinos: of these Separate from M o d i e d the three G r a v i t y theories is generations of MoND, or neutrinos M o d i e d which are a N e w t o n i an part of the D y n a m i c s. Lepton class in While Modi ed the Standard G r a v i t y Model, sterile theories are neutrinos are able to explain hard to detect c e r t a i n observations because they that Dark do not interact Matter cannot, with matter as the reverse is 2021 Dark Matter Map. I mage Credit: Wikimedia Commons Author: Dark Energy Survey. they move also true. Source in Citations through space. An experiment at the Lawrence Livermore National Laboratory in the US and the Colorado School of Mines aims to detect sterile neutrinos as a product of the decay of Beryllium-7 into Lithium-7 through the measurement of the recoil energy of the latter. That said, while Sterile Neutrinos o er a possible solution to the problem of matter-antimatter asymmetry (that there is more matter than antimatter in the universe) in addition to answering “what is dark matter?”, they are candidates primarily for warm dark matter rather

E ectively, t h e f u t u re announces a lot of experimental work to be done in continuing to map and search for Dark Matter, and even theoretical work to be done if none of the candidates that I have outlined actually turn out to be correct. Dark matter research is still one of the most open areas of research, and much knowledge of it remains elusive.

Conclusion

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DARK BOSONS

Interstellar Travel Introduction

Antimatter/Matter

For the main article in our space special we will be traversing into how we can explore the vast expanses of space. Travelling to other galaxies, solar systems and alien planets is an exiting notion with opportunities of discovering new phenomena and the possibilities of discovering new life forms whether or not they may be sentient. However that’s an entirely di erent article. We are here to discuss how we can travel into deep space. It isn’t as easy as travelling to the Moon or Mars (to be honest even that is quite di cult and very expensive), in fact it is a lot harder, partly because of the vast distances we have to travel and the time it can take to travel there. We must also combat the problem of keeping astronauts healthy after spending so long exposed to radiation in space and zero gravity.

How it works: The Dirac equation, which won English physicist Paul Dirac the Nobel Prize in 1933, demonstrates the existence of antimatter in addition to matter. Matter particles have the same mass as their corresponding antiparticles, but di erent properties such as charge. When matter and antimatter come into contact, they annihilate, with the total mass of the particles converted into energy as gamma ray photons. If a controlled annihilation of su cient magnitude could occur, then it would be easily su cient to provide su cient energy to propel a craft. Advantages: 100% E cient, all the mass of the fuel would be converted into energy. Only ten milligrams of antimatter would su ce to travel to Mars; that said, this would cost around $250 million. Although the gamma ray photons produced could cause

This is an artist's rendition of an antimatter propulsion system. Matter - antimatter annihilation o ers the highest possible physical energy density of any known reaction substance. Courtesy of Wikimedia Commons. By NASA/MSFC. This image is in the Public Domain Source in

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Citations

harmful e ects to the crew and mechanisms, using positrons (a.k.a. anti-electrons) reacting with electrons instead of protons and antiprotons, makes gamma rays 400 times less energetic, and so less ionising. Always planning for the worst, the NASA Institute for Advanced Concepts (NIAC), which is working on the rst manned mission to Mars, has been exploring Anti-Matter/Matter drives, since should a mishap occur, the damage would be contained to a small reference area, perhaps one kilometre in radius; the same cannot be said for a hypothetical disaster with a nuclear ssion reactor. Equally, Anti-Matter/Matter fuel would drive the vessel forward at a heady speed; current planned crewed missions to Mars, such as the Mars Reference Mission, which is to be chemically, solar and nuclear- powered, should take 180 days; by contrast, that could be shortened to 45 days if AntiMatter/Matter technology were used. Some experts even think that Anti-Matter/Matter technology could enable crafts to voyage at 10% or even 40% of the speed of light. Disadvantages: The two photons are emitted in opposite directions to conserve momentum, so to enable thrust, the photon must be re ected by some sort of mirror, which could be di cult to conceive. Additionally, while the reaction is perfectly e cient, the causation of the reaction requires high energies to drive the particle and antiparticle into contact, so the net e ciency is not as great. The question of storage is also problematic; the matter and antimatter must be sealed magnetically to avoid coming into contact in an uncontrolled situation, so even containing the fuel consumes energy as the magnetic eld must be induced by a current, which must be provided from another source. Synthesising the required antimatter at a purpose-built facility and then transporting the contents to the launch site may also prove tricky. Then there is also the question of actually producing the antimatter; this is notoriously di cult, with entire particle accelerators necessary to produce only atoms of antimatter. Until the Fermilab production was closed in 2011, the facility had generated only a nanogram per year. Verdict: This may actually be more feasible than the current consensus would have it, with six research teams at the ‘Antimatter Factory’ at CERN dedicated to the task of studying Antimatter. It is worth investigating in, but should not be seen as a viable solution or salvation, certainly not in the short-term. But maybe by the 23rd century, this approach will be as commonplace as the voyages of the U.S.S. Enterprise in Star Trek would leave us to believe. 5/10

Breakthrough Starshot How it works: This is the approach of the Breakthrough Starshot Project, founded in 2016 by Stephen Hawking and billionaire Yuri Milner, and chaired by Harvard astronomer Avi Loeb. A part of the Breakthrough Initiatives, Starshot will research and develop crafts capable of travelling at 20% of the speed of light to visit Alpha Centauri, the nearest star system to ours, within the next generation. With an investment of $100 million, a journey that would take 100,000 years with current technology is hoped to be reduced to 22 years thanks to this endeavour. Launched from a mothership in earth orbit, 1000 probes with a mass of no more than a few grams would be propelled by the energy generated by a gigantic laser array. The laser array, engineered and constructed, would generate coherent beams which converge in the sky and send the probes on their way. The probes would be solar sails, capable of capturing the energy of the laser beams (or rather re ecting the light of the laser so that the momentum of the light is transferred to the sail), and accelerating away towards their target destination. Advantages: The backing and investment is present, the scientists are present, and the technology of the individual elds will continue to improve. Though the extent of the laser array may be somewhat concerning, there is reason to be optimistic. The laser would have to pulse a beam 100 gigawatts in power for several minutes each launch over a signi cant distance, form the ground to space; already, the most powerful laser in the world in Japan has been able to function at two petawatts, though only for one picosecond. But progress is on the cards. There is also a precedent, with the solar probe IKAROS, though massive at 2.2 kilograms, having been launched successfully by the Japanese Aerospace Exploration Agency to Venus. Disadvantages: The laser array would have to be gargantuan, covering an area on the ground about 250 acres or one square kilometre in size. The margins for error to direct the probe with the laser are small, and the timescale, to have arrived at Alpha Centauri by 2060, is potentially deceptively short. Should the enterprise be considered a failure if it does not meet its goals? And what if it does? Does it matter that the craft sent will not be crewed? It is clearly the intent of those involved to send a probe, not humans, to another solar system. Scaling up for a human to be transported if so wished would be even more complex. More importantly, how would the electronics of the probe fare over such a distance? With the probe having to have a minuscule mass for a sail of a fourmetre span, there may not be enough room for the

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thrusters, cameras, power supplies and communications equipment, though the advances on materials science, particularly in the area of graphene, could render these fears obsolete. Verdict: It remains to be seen whether the rate of development will be su cient to meet the established though somewhat exible deadlines, and how all the aspects will coalesce into a single project, especially if those who originated the project are not in place to see it through to the end. Nonetheless, in 2017, Breakthrough Starshot researchers conducted their rst tests with probes in low earth orbit, and then in 2019 another was able to take 4000 or so pictures of the earth from a height of 30,500m above the surface. And there is a genuine vision in place to attain interstellar travel. Matthew McConnaughey’s Cooper could soon be a real-life hero, rather than just a character in a movie. 8/10

Alcubierre Warp Drive The main issue with most conventional means of space travel is how very slow they are. Just a short hop to our nearest solar neighbour, Alpha Centauri, will take decades even at a signi cant fraction of the speed of light. If we ever want to travel far out across our universe, we need to overcome the universal speed limit. Theoretically, it's not that hard for me to get to Alpha Centauri in less than the 4.4 years you would expect, simply due to time dilation at high speeds, which can be easily calculated from special relativity. I hop into a spaceship moving at 95% the speed of light, I go there and back and it only takes me 2.7 years from my perspective. This can be made arbitrarily short by simple moving faster. But for an observer back on earth, nearly 9 years would pass. This is not great if you want to create a multisolar system civilisation. So we need some way to get to our destination that takes only a short time for both those travelling and those eagerly awaiting their return. Enter the concept of the Alcubierre metric.

the very beginning of the universe. Two points (we will call them ‘observers’) that started right next to each other will begin to separate. Despite the fact they started still relative to each other, they will move apart due to the expansion of space-time. It is even possible for these observers to separate at speeds faster than light. Neither is travelling faster than light, yet still, they separate at these enormous speeds. The idea that Alcubierre had in his 1994 paper was to try and use these ideas to move a spacecraft through the universe at faster than light speed, without the craft itself travelling faster than light (locally). If you could create an expansion of spacetime behind the ship that moves an object away from earth, and a contraction of spacetime in front of the ship that pulls the craft towards another star, then the craft can travel faster than light relative to an observer outside there ‘bubble’ of spacetime, yet still obey the laws of physics as they are travelling slower than light through their local patch of spacetime. Advantages: It can reach a destination that is lightyears away in a very short time. Disadvantages: You may be (quite reasonably) wondering quite how feasible this idea of expanding and contracting spacetime at will is. This is extremely maths heavy, with the eld equations and lots of abstract maths entering the picture. Check out Alcubierre’s paper if you want to see the full explanation. However, even though the maths checks out as possible, the energy requirements would be huge, well beyond the mass-energy of the observable universe. Solutions to this problem use properties of hypothetical exotic matter such as forms with negative mass, but these have no practical evidence and little theoretical evidence. Another issue is even if you could get it working, it would be almost unusable as the pilot would not be able to communicate with the extremities of the bubble, so would not be able to shut it down and stop. This would mean that to stop, it would have to be acted upon by some machine at the destination, so humanity would have to get to the destination conventionally before the drive can even be used. This means it can’t be used for exploration, so humanity will always be limited as to its reach. Verdict: Although the drive would be immeasurable more useful than conventional means of space travel, it also has far more problems, not only how to get it working, but whether it is even possible, and the dangers it would pose to the destination and inhabitants. In reality, if this is even possible, a civilisation that could create this may not even deem it worth the extraordinary e ort and energy required. 3/10

Effects of Space on the Human Body How it works: This concept rests on the ideas presented by general relativity to do with the shape of space-time. To visualise this, let's think back to

Creating a sustainable and e cient way of traveling in space is in itself di cult as you may have already

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Space is full of radiation, from Solar Energetic particles to Galactic Cosmic Rays. The atmosphere on Earth protects us from dangerous radiation however, in space there is no atmosphere to protect us. Solar energetic particles (SEPs) can be dangerous missions beyond the earth's atmosphere as they can easily pass the skin and damage the DNA in our cells which can give rise to cancers or in severe cases 'acute radiation sickness' [4] . You may perhaps be thinking that it's a simple matter of protecting ourselves from SEPs by staying inside our spaceship when there is an in ux of SEPs. Which is appropriate, however SEPs are not the only type of radiation we need to be worried about. Galactic Cosmic rays are a type of ionising radiation they're essentially nuclei of atoms travelling at almost the speed of light [4]. Once again, they mostly pass through the body, since atoms are mostly empty space, though this time the radiation has a lot more energy and spacecrafts can't protect against it so, if the radiation hits human cells it can damage the DNA and cause mutations [2]. In our solar system we are relatively protected from cosmic rays as the radiation is de ected from the Sun's magnetic eld. The Sun has a its own solar cycle which takes approximately 11 years to complete. During solar minimum in the cycle the Sun's magnetic eld is weaker when compared to solar maximum where it is relatively strong and largely protects the solar system from cosmic rays [4]. If we wanted to make a voyage to the Moon for a

prolonged time or a longer trip to Mars we would choose to travel close to the solar maximum which means that we would mostly have to worry about SEPs. But what about if we want to travel into outer space to di erent solar systems (when technology has su ciently advanced to make these trips feasible and economically viable)? Currently there is no de nitive method and research is still being carried to to look for solutions to keep humans safe from dangerous radiation in outer space. Another problem is lack of gravity. Microgravity or a complete lack of gravity is a problem as humans have evolved and adapted to live with the gravity on Earth. [5] The cardiovascular system works to pump blood around the body very quickly and stop it pooling in the legs. This can become a problem in prolonged ights as the cardiovascular system has to deal with an increased pressure in the upper body which can lead to problems with vision. According to NASA, spending each month in space leads to approximately 1.0%-1.5% loss in mineral density. [1] Over a longer time period it can increase the risk of fractures. A secondary e ect is a higher risk of kidney stones because of more minerals in the urine. A lack of gravity also causes loss of muscle mass.[5] This is particularly concerning as a lower muscle mass will result in loss of strength. To counteract these e ects astronauts have to exercise while in space to keep their muscles exercised and keep their bones strong. Without this when astronauts return from space to earth, or any planet with gravity, the astronauts will be weaker and may their muscles may not be able to support them. Before we embark or interstellar travel we need to do a lot more research on the e ects of space travel on the body and more importantly own we can reduce the negative e ects. This is an ongoing eld of research with new ndings emerging from time to time.

To the left is a map of the Milky Way Galaxy (our own galaxy), just to give you a perspective of the scale of the universe. It shows approximately 50 000 light years of the universe in which there are 200 billion stars!

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Image Credit: The Universe within 50000 Light Years, The Milky Way Galaxy by Richard Powell. Creative Commons Attribution-Share Alike 2.5 Generic. Source available in Citations.

read, albeit there are many suitable candidates. We will now focus on the e ects of space on the human body, because what is the point of creating a vessel to help us explore the stars if it cannot sustain human life. You may have heard of the International Space Station (ISS) which 'orbits 240 miles above earth' [1], astronauts typically don't spend longer than 6 months on the ISS. This is because of the dangers posed to the human body.

Q&A with Dr Christopher Berry Gravitational-wave astronomer CIERA Board of Visitors Research Professor at the Center for Interdisciplinary Exploration & Research in Astrophysics at Northwestern University Lecturer with the Institute for Gravitational Research, School of Physics & Astronomy at the University of Glasgow Exclusive Interview conducted by Zavié Goutorbe

Diagram of a LIGO detector. Image Credit: Wikimedia Commons. B.P. Abbott et al. Source in Citations

I didn’t really have a plan; I just went in a direction and saw what would happen. I went to study Natural Sciences specialising in Physics as an undergrad, which I enjoyed. It went well, I loved learning about how everything worked. I thought it would be nice to continue and do a PhD. In deciding what area to do the PhD in, I didn’t have a particular area in mind, so in the end I decided to go into astrophysics, because it brings together so many di erent pieces of physics (to study stars, you would need to understand gravity, celestial mechanics and orbits, atomic physics, nuclear physics, particle physics to understand neutrino uxes, etc.). I could put o a little bit longer which area I wanted to focus on. I applied for various PhDs in astronomy, and got an o er from the Institute of Astronomy in Cambridge. They’re particularly unusual in that you don’t have to pick your research area before starting. They encourage you to go and explore a little bit once you start. I think it is an excellent idea to try things out before committing. I knew I wanted to do something theoretical, rather than observational at the time, so I spoke to a few di erent people about projects going on, and that’s when I really learnt about gravitational waves. I’ve just kept going that way ever since. Following my curiosity and liking to know many di erent things is how I have ended up where I am. I have been lucky. Having recently won an IUPAP Young Scientist Prize, do you think that the contributions of scientists to society are suf ciently recognised?

I think scientists are very important to modern society and we can contribute a lot to making the world a better place. I think there’s a lot of prestige that comes with being a scientist. Although some people talk about the fact that experts aren’t given enough credit, scientists are still one of the most trusted professions. I think we su er a bit as people are often put o by science: they nd it di cult, which is very understandable, or it isn’t explained why what they are learning is useful. I would like to inspire people more, and enable them to understand that just because you nd something di cult when starting o , it doesn’t mean that you will always nd it di cult if you keep practising. You will get better!

There are some bene ts to prizes, it is nice to receive recognition, but a danger with prizes is often that they are often awarded to only one person, or a small group of people, when modern science is really very collaborative. It’s not really one person driving the breakthroughs, so it would be fairer to recognise the collaborative nature of science. Scienti c discovery is a team e ort. I believe that you have contributed to 146 publications of research. How do you decide which sort of new project you wish to look into further?

This varies a lot. For some projects, it is obvious what must be done, but not necessarily what you will nd. For example, when we collect new gravitational-wave data, we know that we want to analyse it and publish the results, but we don’t know what we will nd. We have been lucky to nd many exciting gravitational-wave sources. When you see the new data, you can get ideas like “I wonder if this is the case?”, “can we test this idea?”. Sometimes it can be that you want to prove yourself wrong. Sometimes it can be that you want to see if it possible to answer a question regardless of what the answer will be. Those projects are inspired by seeing the data, there’s not necessarily a plan in place before that. However, it is often good to have an idea of the really big questions you want to answer too. Not the type of questions you can answer by writing one paper and analysing a bit of the data, but the really big questions, “how do black holes form?” for example. That’s a really long-term goal. Knowing where you want to end up, you can start to chart out the smaller steps you need to get there. Then one paper is just a small piece in heading towards answering that big question. The LIGO/Virgo has very much been one such long-term project. How successful has the LIGO/Virgo endeavour been, and what does the future hold for the collaboration?

In my opinion, although I am somewhat biased, LIGO/Virgo (and I’m sure KAGRA will be), have been incredibly successful! They have founded a new eld of astronomy, gravitational-wave astronomy. It’s been many decades in the making, many thousands of people working to bring this into reality. It has been a huge investment by the science funding councils, and I think that has all paid o . We achieved our

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Did you have any particular inspirations, and what was your main interest as a student?

primary goal of making the direct rst observation of gravitational waves. We’ve opened up this new eld, and it has been more successful than I was anticipating. B e f o re w e h a d o u r g r a v i t a t i o n a l w a v e observations, we didn’t know that binary black holes (two black hole orbiting each other) existed. There were predictions that said they should, but others which were more pessimistic, and didn’t predict there would be any merging binary black holes. Our rst detection showed conclusively that there were merging binary black holes, and showed that in fact these were quite common! Then, on top of that, we have the observation of our rst binary neutron star, GW170817, which was remarkable. This was not only a gravitational-wave source, but was also observed across the entire electromagnetic spectrum. Now we’ve got this huge wealth of astronomical data, which was only possible thanks to the gravitational-wave detections. This is only the beginning. Gravitational-wave o b s e r v a t i o n s w i l l re v o l u t i o n i s e h o w w e understand black holes and neutron stars, and perhaps even sources we’ve not imagined yet. Which theory predicts gravitational waves, and are they detected purely by chance? And are they able to not be susceptible to noise, interference or glitches?

Gravitational waves are a prediction of special relativity, the theory which says that nothing can travel faster than the speed of light. This means that if you have a mass and you move it around,

the information that this is moving can’t travel instantaneously, so there needs to be a change in the gravitational eld that travels outwards, and that is some form of gravitational wave. Einstein realised this with special relativity, but didn’t know how to put gravity into the theory, and that’s what laid the groundwork for general relativity, the theory for gravity, which provides the exact prediction for what gravitational waves look like. So far everything has stood up to the predictions of general relativity. Gravitational waves are little stretches and squeezes of spacetime and the gravitational wave detector (like LIGO), has two arms with mirrors at the ends. We bounce lasers up and down, and you basically time how long it takes to go up and down. If a gravitational wave passes, you get the stretching and squeezing of spacetime. The mirrors are carefully suspended so they can move freely, so you get a slight time di erence in the time for light to move up one arm than the other. That’s how you measure a gravitational wave. Gravitational waves don’t interact strongly with matter, which is why they are so hard to detect. However, it does mean that you don’t need to worry about missing a signal because you are not looking in the right place. Gravitational waves will travel through the Earth happily. Our detectors can nd signals coming from pretty much any direction. They are not like telescopes that you need to point.

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LIGO Livingston Image Credit: Caltech/MIT/LIGO Laboratory, Public Domain, Source in Citations

We [Students] are often taught that repeatability and reproducibility are crucial for ensuring the validity of tests. How does this affect gravitational wave observations which can only be detected once but at multiple detectors?

First, we can never see the same signal twice, but we can see similar signals, so if you detect gravitational waves from something once, you’d expect to be able to do it again. We don’t have reproducibility of the same signal, but we can reproduce by looking for similar signals. In terms of being con dent in our results, the fact that we have multiple detectors is very important. We have the two LIGO detectors, which have a similar design, so you might not think that they are completely independent, but then Virgo and KAGRA have di erent designs. It’s the same basic principle, but the implementation is di erent. The fact that we have these gives us extra certainty. With the detectors being so far apart, they shouldn’t be a ected by the same sources of noise, so if they see the same signal, we know that we have detected a gravitational wave. In terms of what is taught at school for reproducibility, that reproducibility is very important, you want to make sure that other people can get the same results doing similar things, this is very important. However, we can’t control the Universe, we can’t make binary black holes merge to see what happens, we can only observe and see what the Universe gives us. Astronomy is like ecology, you can’t necessarily control what animals do in the wild, you just need to go out and observe them. Not all science is about experiments done in the lab where there are a series of steps that should give the same result. Would you say that that makes observational sciences more exciting because you don’t necessarily know what you’re going to get?

I wouldn’t be so bold. There’s a lot of excitement in the laboratory-based experiments as well because there’s the satisfaction of designing an experiment, and it going exactly as behaved. Also, a lot of serendipitous discoveries are made in this lab-based environment. You want something to happen but then something else does! I think all varieties of science are good in their own ways. One of the most fun things is when

you are making a new type of discovery, regardless of how that happens. You mentioned binary black hole mergers. Aside from that rst discovery, and that beautiful bloop which must have been incredible to have been a part of, GW190521, the most massive thus far discovered, was much talked of, and was a topic on which you published many papers- what are the repercussions and consequences?

GW190521 is one of the most interesting gravitational-wave signals that we have observed. It is unusual in that its source is more massive than anything seen before; nothing completely di erent, but it is the one at the top. The masses are signi cant for a couple of reasons: the rst is the mass of the nal black hole (when you have two black holes which come together and merge, they form a bigger black hole), and this black hole is over 100 solar masses (over 100 times the mass of our Sun). This is notable because that ts in a category we call intermediate-mass black holes. These have long been elusive. We knew of stellar-mass black holes (up to 100 solar masses), and supermassive black holes (over 10,000 solar masses), but not if there was anything in the middle. My hope is that we will nd more of them so that we can gure out if there is one continuous population, or if there is a gap in the middle which shows that supermassive black holes de nitely form a di erent way. There have also been neutrons stars in a class between standard neutron stars and black holes which have been detected. Could you comment on this?

For our rst observation of binary neutron stars (two neutron stars), GW170817, the masses of the stars that we saw there matched exactly the masses found from radio observation of pulsars. So that made a consistent picture. Then came a detection in our third observing run, GW190814, that was particularly interesting because the secondary (lighter) object in this binary has a mass about 2.6 solar masses. It’s in a range above where you might expect neutron stars to still exist, but at some point, neutron stars become so massive that they collapse down to a black hole. We are not entirely certain where that happens, because we don’t exactly know what neutron stars are made from, how this material behaves. There is no way we can replicate this material in the lab, it’s so extreme. But 2.6 solar

masses is enough such that it could be a black hole. It’s probably a black hole, but we can’t be certain… We’re starting to ll in the population of what the family of neutron stars and black holes looks, but we’ll need quite a few more detections to be sure about the details. At the opposite end of the scales, do you think that supermassive black holes will ever be detected using the LIGO/Virgo setup?

We know a few things about supermassive black holes, we know that every galaxy seems to have one. We know the masses of the black holes are correlated with the mass of the surrounding stars around them. But we don’t know how they form. Observing them with gravitational waves could teach us a lot. The gravitational-wave frequency is set by the orbital frequency, and this depends upon the mass of the binary. The bigger the system, the longer the orbital period, and the lower the frequency of the gravitational waves. For the supermassive black holes, you need to be down in millihertz or even lower. We can’t do that on the ground, because there’s too much noise from ground vibration. Earthquakes and ocean waves and all the rest, it’s too much. So, we need a space-based detector. There’s currently an ESA led mission, with NASA as a partner, called LISA (Laser Interferometer Space Antenna) currently due for launch 2034. This will be perfect for observing supermassive black holes. LISA is actually what I did my PhD on. There’s still enough time before it launches for you to get your PhD and become a gravitational-wave astronomer too! The LIGO/Virgo collaboration has enabled plot the exact locations of original events, are you able to perform a mapping of the Universe, or retrace to the Big Bang?

This is actually a current area of research. One thing that people have talked about is that if you map out the locations of sources, you can trace out the structure of the Universe. However, with our current detectors, we can only see so far, so we can’t really see how the Universe has evolved. There are plans for more sensitive detectors (3rd generation gravitational-wave detectors). With these, we’d be able to see stellar-mass black holes much further away: potentially all the stellar-mass black hole mergers ever! Using

these, you would be able to map out how the Universe’s structure formed. This can only take you as far back as there were black holes though, so it can’t necessarily tell you about the very start of the Universe. There are potentially other gravitational-wave signals that could come from earlier in the Universe, perhaps the rst fraction of a second. However, we don’t know if these exist yet. They are one of the things we are still searching for. Another map which was recently published was of dark matter content in a portion of the Universe. It supposedly challenges the predictions of Einstein’s theory of General Relativity. What effect might this have on gravitational wave astronomy and its discoveries?

Dark matter is the name we give to missing mass. We look at objects, there are many examples now of this in astronomy, and we can work out what their properties should be, how much mass should be there. We then work out how much mass there is based on what we see and take that away, and often there’s some missing mass. So, we ascribe this to being dark matter. People have suggested that maybe a lot of darkmatter is primordial black holes. These are not black holes formed from collapsing stars, but from dense parts of the very early Universe. From our observations, it looks as though primordial black holes can’t make up all of dark matter, although that depends on the masses of primordial black holes formed. At least some of the dark matter could potentially be black holes, but what we normally expect is that it’s some new type of particle which doesn’t interact with light, that we’ve not discovered yet. Maybe it’s something that our particle accelerators could produce, and that would be a big discovery… For gravitational waves we could maybe look for certain dark matter candidates in a couple of ways. One is you can look for gravitational waves produced by particular interactions of these dark matter particles with black holes. If you have a rotating black hole of the right mass, you can get certain types of dark matter, setting up a coherent pattern of motion, which can emit sort of a hum of gravitational waves, a continuous gravitational-wave signal. We can look for those gravitational-wave signals, and if we nd it, it would be evidence for this type of particle, and if we don’t, it would rule out that particle having a

certain mass range. We can also look for particles interacting with our detectors, so not look for gravitational waves, but look for them interacting with our detectors in a particular way. And we can put constraints on their existence based on that. These are things that people in the LIGO/ Virgo Collaboration are currently working on this. Another hypothesis people have put forward is that maybe there isn’t any dark matter. Maybe there’s some modi cation to our theory of gravity, which can explain things, and a whole host of other theories which have been put forward to do this. Unfortunately, as far as I’m aware, no theory explains all the observations. However, we still do check that the gravitational waves we observe are consistent with general relativity. So far it has passed every test. How exactly do the software screening and data analysis techniques work?

We have two main ways for searching for signals from binaries. One is to say we know what these signals should look like, we can calculate these using our theory of gravity, using numerical simulations or careful calculations, so we can get a bunch of templates and match these to the data. This is called matched ltering. You have your data, you look through it for templates, you see where the templates overlap… You build up lots of statistics based on how often you’d expect a match if there was no signal, and then you compare your candidates to that distribution to say if they’re a signi cant detection or not. The second way doesn’t assume a particular signal, but it does assume that you should have the same signal in multiple detectors. It looks for coherence between the data in multiple detections, and tries to reconstruct what the signal looks like, and ags interesting things based on that. What is a day in the life like for a research professor?

The job is very varied, with no particular standard day, however the day often will involve lots of emails, lots of meetings, lots of reading and writing, which individually doesn’t sound exciting, but when you add it all up, it can be a lot of fun.

have a di erent path. What works for one person is not necessarily going to work for someone else. You should always need to consider what is the right thing for you to do, and what is the right thing for you to do at this time. The right thing to do at one point is not necessarily the right thing to do at a later point. For example, the gravitational-wave astronomy community has changed quite a bit over the last few years where we’ve gone from quite small from before the detections to much bigger now. I think it’s useful to think about where you want to be and the ways that can help you get there, but be willing to consider alternatives and new things. If you’re interested in going into a career in science, I think it’s important to try and build the skills which are really valuable there. Starting o at school level, it’s working on your mathematics, that opens up a lot of doors, and going forwards, undergraduate maybe going on to think about a PhD, is working on your coding, your computer programming, that’s very, very useful. Investigate what you nd interesting, allow yourself to be curious, and see where that takes you.

NASA illustration of LISA. Image Credit: WIkimedia Commons. Author is NASA. Source in Citations This interview was held on the 3rd July 2021. We would like to thank Dr. Berry for taking the time to answer our questions

What advice would you give to an aspiring astronomer or scientist in general?

I think that it’s very important to remember that everyone is di erent, and everyone’s going to

Matthew Bentham

Since humans rst needed to travel, there have been methods used to help navigate. In prehistoric times, this could be done using landmarks, like large mountains or rivers. Improvements where made with astronomy, as the stars could be used by the ancients to determine direction. Map-making allowed for far m o re p re c i s e n a v i g a t i o n , e s p e c i a l l y a s trigonometry was developed. Yet it wasn’t until the 1990s that techniques were developed that would tell you exactly where you were, regardless of the continent you were on. This was the creation of GPS, the global positioning system.

NAVSTAR global positioning system is an ingenious idea, managed by the US air force, that allows accurate time and location data to any applicable device across the planet, as well as all of the information gathered from monitoring this, such as speed an direction. But how does it actually work? To understand the extensive mathematical operations used to obtain location data, a simpli cation is rst required. Instead of imagining a complex three-dimensional globe, imagine you are stood in a very large eld. We can assign a cartesian coordinate system to the eld (an x-y plane), giving you a two-digit coordinate. If you want to obtain your location, and have a few friends who can shout very loudly, then all you need is some simple geometry. Friend A will shout very loudly their position, perhaps (600, 300), and the time, 7 seconds past midday. You check your watch. It reads 9 seconds past midday. Assuming you calibrated your two watches before starting the experiment, this tells you something very important. The signal has taken 2 seconds to travel from Friend A to you. Using speed=distance/time, and given

the speed of sound is 330 m/s, you can calculate that this means you are 660m away from Friend A. If you plot all of the points that are exactly 660m from the point (600, 300), then you get a circle. You know that you are on that circle somewhere.

Another Friend may then shout out another location and time. Maybe, the signal took 1 second to travel, and they are at position (500, 700). Again, you can calculate that you are 330m away, from that location, and plotting all of the points that are 330m away from that location gives you another circle, containing a set of positions you could be. Alone, these two circles are fairly useless. However together, there are only two points you could possibly be, where the circles intersect each other. You could just guess which of these two locations you are in, perhaps one of them is preposterous as it is far away from where you know you roughly are, but if you want to be really sure, you could get another friend (maybe 3 is a bit ambitious for a mathematician), and they can also give a time and location. This narrows down the location to only one place. Now if we are to introduce back some of the initial complexity, we need to change a few parts of our model. Firstly, we are not using friends shouting in a eld, instead we use satellites orbiting the earth. They communicate using electromagnetic radiation, which travels at the speed of light. Finally, now we are back in 3D

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How Does a GPS Work?

space, the set of points a certain distance from a location is not a circle, so instead of drawing a circle around the transmitted position, we draw a sphere.

Each orbiting satellite is equipped with a very accurate atomic clock (most deviate by less than a second every 100 million years!), and a transmitter to transmit where it is and the time the signal was sent. A receiver on the ground then calculates the distance to each of those satellites, and draws spheres around their broadcasted location, at the point these spheres all intersect is the location of the receiver. With the extra dimension comes an added degree of freedom, so you need yet another satellite to really pin down the location. Theoretically, GPS can function ne without a forth satellite, as the point where the spheres all intersect with three gives two locations, one on the surface of earth, and one thousands of kilometres into space. Your probably on earth. You maybe wondering why there is any point in having the super accurate atomic clocks inside the satellites. If the signals travel at the speed of light, then being out by even 1 millisecond will mean that the distance could be wrong by 300km! The atomic clocks are calibrated so carefully that the error in modern GPS is only about 10m. In fact, the calibration is so accurate that it has to account for relativity (they are moving much quicker relative to us, which brings in special relativity, and the gravitational pull is less, which brings in general relativity. Both of these cause time dilation, which means the clock slowly becomes out of sync with earth!) But there is a problem, although the bulky satellites have room for an atomic clock, they are large and expensive, which makes it inconvenient for the

average person to carry around a receiver. But the times need to be synced if the microsecond di erences are to be spotted. This is where the fourth satellite comes in handy, as using some clever mathematics, you can compute a time to a similar degree of accuracy as the atomic clocks on the satellite by solving what is the equivalent of a simultaneous equation to make the fourth satellite’s sphere line up with the other three’s intersection.

So why do we use satellites? They are really expensive to get into space, and near impossible to repair if one fails. But the bene ts of satellites lie in their coverage. A satellite at an orbit radius of 20000km can see a considerable potion of the earths surface. The aim is for a receiver to be covered by as many satellites as possible so that the accuracy can be improved. By having the satellites in a high earth orbit, only 24 satellites need to be maintained to provide full global coverage. By comparison, if towers were to be used, thousands would be required, and the signals would be easily blocked by the landscape. GPS is hugely bene cial for modern society, from individual hiking trips to the careful manning of automated agriculture, it has played a large role in providing the next step in connectivity.

Terraforming Mars Henry Taylor Terraforming is the process of creating a habitable environment for human life on another planet. Some are hopeful of our prospects of being able to colonise another planet, however there are doubts over this possibility. And if it is possible, should we colonise another planet?

Is terraforming Mars possible? The atmosphere of Mars at the moment would not sustain human life. The atmosphere is too thin (about 100 times thinner than Earth’s atmosphere) and contains little oxygen, with the majority of the atmosphere composed mainly of carbon dioxide, nitrogen and argon. Liquid water cannot exist on Mars surface, most of all water exists as ice.

The hostile atmosphere poses threats to terraforming

Another challenge that faces those wanting to colonise Mars is the scarcity of food on the planet, there is no food naturally available on Mars and it is very di cult to create food from the raw materials on the planet. There is also very little protection from ultraviolet rays hitting the surface, which would cause ultraviolet levels to be too high for us to survive. In order to create an atmosphere suitable to human life, the atmospheric pressure would need to be increased. Presently the atmosphere is less than 1% of Earth’s atmosphere pressure. Gases would need to be released into the atmosphere to increase the pressure and temperatures at the surface. Some scientists believe this will thicken the atmosphere. There are some carbon dioxide sources on the planet, that can be utilized to

increase the amount of ‘greenhouse gases’ and therefore contribute to the warming of the planet. These sources include the polar ice caps, mineral deposits and dust particles in Martian soil. There are a number of proposed methods to unlocking the CO2 in the ice caps; spreading dust on the ice caps, therefore increasing the amount of solar radiation absorbed, or using explosives. However this would only result in a limited increase in atmospheric pressure, about an increase to 1.2% of Earth’s atmospheric pressure. Using the dust particles in the soil and mineral deposits can achieve a higher yield of carbon. The dust particles

Some question whether we will ever have the technology capable of completely terraforming Mars

would achieve an increase in pressure to around 4% of Earth’s atmosphere. The mineral deposits could achieve an increase in pressure of just less than 5% of Earth’s atmosphere. However there are major hurdles to using these as carbon sources, they would require extensive strip mining to fully maximise the release of CO2. For example, dust particles in the soil would require strip mining of the planet’s surface to a depth of around 100 yards. The most promising carbon source is the carbonbearing minerals deep in the planet. This could provide enough CO2. to reach the required pressure. But the extent of these deposits are unknown.

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What was the past atmosphere on Mars like?

Should we be pursuing efforts to terraform Mars?

Some argue that if we were able to create a hospitable atmosphere, it would slowly be lost to space and render the planet uninhabitable again.

Experts believe that Mars has the highest possibility of successful terraforming There is evidence that Mars had a thicker atmosphere compared to its atmosphere today, with the atmosphere allowing water to run on the surface. Studies suggest the existence of water on the surface of the planet, there is evidence of dry riverbeds and minerals that can only form in the presence of water on Mars. Several Mars rovers have also sited water-soaked rocks on the surface. There are many theories as to why the atmosphere changed so drastically over billions of years, to this now inhospitable atmosphere. One theory suggests that due to the lack of magnetic eld protection, the atmosphere was slowly stripped of lighter molecules by solar radiation. This caused the atmosphere to thin and the particles to escape to space.

Many argue that all this scienti c research and money being invested in these studies and explorations are a waste. They would argue that these resources would be better placed in tackling our current crises on Earth, such as the climate crisis. Instead of trying to make another planet habitable we should be preventing Earth from becoming uninhabitable, by reducing the worst impacts of climate change. Some would argue that humans will destroy Mars just like we have on Earth, and deplete the natural resources there. Then where would we go? They would argue that we cannot just run from our problems, but must try and x the current crises on Earth. However many would argue the opposite, that pursuits in this eld will lead to greater scienti c discoveries that in turn will bene t the planet. The future colonises on Mars will require a large amount o f re n e w a b l e , s u s t a i n a b l e p o w e r. S i m i l a r technologies could then be implemented on Earth, helping solve the climate crisis. E cient and reliable food sources will need to created for any future colonies on Mars, using limited resources. It is thought that many technology breakthroughs will occur due to further research and space explorations, which could greatly bene t Earth. For this reason many would justify the large costs as the technology can be used on Earth. Some would even argue that this is essential for the continued existence of the human race. With the rising threats of climate change, or the possibility of a nuclear war, or even the slim chance a meteorite hits Earth, an extinction event could occur. If we could set up a colony on another planet then humans would still be able to live on, and prevent the extinction of humanity.

Many question whether we will ever be able to live on Mars

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Katherine Johnson Matthew Bentham

The space race is arguably one of the most important scienti c achievements humanity has ever partaken in, which brought about numerous discoveries and advances in elds from material science to mathematics. It has a gargantuan e ort, with NASA employing over 400,000 people in the mid-1960s. The public face of NASA, its leadership and a s t ro n a u t s , w e re r i g h t f u l l y praised for there work, but out of sight the true driving force worked furiously without credit, and perhaps most critical of these were Katherine Johnson, who overcame numerous boundaries, both mathematical and societal, in her work to put humanity on the moon. Katherine Johnson was noticeably intelligent from an extremely young age. She raced far beyond her peers, joining High School at the age of 10 (4 years ahead of the standard), and collage at 15. It was here that she met the lecture William Clayton, the third AfricanAmerican with a PhD in mathematics, who mentored her, with the ambition that she would be able to pursue mathematics as a career. When she graduated (with the highest possible honours, of course) she became a teacher. She taught with a high dedication for her students, determined to prepare them for a world where they would have to face the prevalent racism of 1930’s America. Then, at the end of the 1930s, West Virginia made the decision to remove the segregation in their education system. They chose three students to take places in the best graduate schools in the state, and Katherine was one of them. She studied mathematics, before leaving the program to start a family with her husband James Goble. After a few years, Katherine spotted an opportunity in a position at the NACA (NASAs previous form). It was here that she worked as a “computer” (a person who computes the long and arduous mathematics needed in orbital

mechanics), and she impressed her supervisor, fellow West Vi rg i n i a n D o ro t h y Va u g h n , earning herself a permanent position. Yet again though, the segregation of people of colour, and the misogyny present in the s o c i e t y, f o r m e d b a r r i e r s , preventing her from progressing. Yet, this did not stop Katherine, and at every opportunity she showed her superiors exactly why she was such an invaluable asset, using her brilliant mathematical mind to solve the mathematics for the trajectory of the spacecraft, a notoriously hard eld, where even the tiniest errors can lead to disastrous consequences. Katherine had a hand in many of the major missions of this era, including the trajectory of the Mercury 7 mission, which made Alan Shepard the rst American in space. She also played a large part in the calculations for many of the Apollo missions, including 11. She also worked on the Space Shuttle missions, as well as numerous other missions, becoming known by her colleagues for her capabilities in a large variety of mathematical elds. After retiring from NASA in 1986, she worked h a rd t o e n c o u r a g e s t u d e n t s f ro m a l l backgrounds, particularly young girls and people of colour, to pursue carers in the sciences. She was an inspiration to a great many people, and it was wonderful that in recent years she has started to get some of the recognition that she deserves. In 2015, Barack Obama gave her the Presidential Medal of Honour. The year after, a non- ction work called ‘Hidden Figures’ was published, detailing her life, which was later turned into a lm of the same name that won dozens of awards. She died recently at the start of 2020, at the age of 101.

Arthur Branch

Written October 2021 monitoring the ight back in California at NASA’s Jet Propulsion Laboratory did not receive news of a successful ight until around three hours later. Telemetry had to be forwarded from Ingenuity to Perseverance and onto the Mars Reconnaissance Orbiter which then sent a signal to NASA’S Deep Space Network in Madrid con rming powered ight on another celestial body.

Courtesy NASA/JPL-Caltech. Perseverance's Navcam View of Ingenuity's First Flight. Source in citations

One hundred and seventeen years ago, the Wright brothers successfully made the rst ight on our planet. On 19 April 2021, NASA’s Ingenuity Mars helicopter completed the rst ever powered, controlled ight on another planet. After taking a trip under the belly of the Perseverance rover which landed on the surface of Mars on 18 February, Ingenuity was successfully deployed after several manoeuvres. (Figure 2) Tests also had to take place to verify that Ingenuity was go for ight. The unlocking of the rotor blades was signi cant and then followed a slow spin up test and then a faster one more closely replicating actual ight. Its rst ight lasted 39 seconds taking o vertically, hovering at 3m including one 90-degree turn, then descending until a safe return to the surface (now named Wright Brothers’ eld) marking a historic moment of space exploration. Engineers

Flying on Mars is a signi cant challenge not only because of how far away it is from our home planet. Atmospheric pressure on Mars is 0.6% that of the pressure at sea level on Earth and so it becomes very hard to generate enough lift. Its pair of coaxial, counter-rotating, 1.2m length carbon bre rotors are incredibly light and so is the rest of the vehicle. The weight and then the speed of the rotors (2500rpm) allows Ingenuity to lift o the surface of Mars. Essentially, the helicopter must generate just over 6.7N (Ingenuity’s weight) of lift. However, gravity on Mars is 38% that o Earth which means only 38% of lift is needed to lift-o on Mars compared

Courtesy NASA/JPL-Caltech. First Aerial Color Image of Mars. Source in citations

Courtesy NASA/JPL-Caltech. Ingenuity's Complete Deployment. Source in citations

to lifting o from Earth. Ingenuity’s rst ight was only a small taster of what was to become. Following this de ning moment on another world, many more ights reaching new heights were to come. As of September 15, Ingenuity has own a spectacular 13 times far surpassing modest expectations of 5 ights as part of the initial demonstrations phase. Following ight 1’s rise to 3m above the surface, Ingenuity has reached new highs in distance, altitude and duration. 3 days after the initial ight, the helicopter underwent its rst horizontal movements during ight as part of its second

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Ingenuity

Courtesy NASA/JPL-Caltech. Ingenuity Spots Perseverance From the Air. Source in citations

A ight has yet to have travelled further but with ight 12 ying for longer for around 170 seconds. The 10th ight of Ingenuity was a signi cant milestone and another impressive success as the helicopter remained healthy and ready for future ights. Flight 11 was another trip to a new air eld whilst ensuring a several colour images of the Martian surface were taken along the journey before ight 12 took to the skies above the “South Séítah’ region or otherwise known as ‘Air eld H’ ying 450m. The most recent ight of Ingenuity

travelled at a speed of 3.3 m/s whilst snapping pictures of South Séítah once more! NASA’s Ingenuity remains healthy and in good shape following ights 1 to 13. Ingenuity faces new challenges however as seasons at Jezero crater change. Due to the helicopter far surpassing expectations and it being in its sixth operational month, atmospheric density on Mars could reach as low as 0.012 kgm-1 which is just 1% of Earth’s density down from a previous 1.2%-1.5% which Ingenuity was designed to y within. This problem can be solved but only through spinning the rotors faster than ever done before. To ensure this is possible during future ights, the helicopter is set to undergo a highspeed spin test of the rotors without taking o at a speed of 2,800 rpm which is around a 10% increase than before. Its 14th ight will then consist of a rotor speed of 2700 rpm to test all systems out. If all is successful, it will give NASA the opportunity to conduct several future ights to scout destinations for Perseverance at lower atmospheric densities. The main risks of these upcoming ights will be aerodynamic issues and how Ingenuity’s structure and design will withhold the new demands.

Courtesy NASA/JPL-Caltech/MSSS. Perseverance's Sel e with Ingenuity. Source in citations

This rst 13 ights have the potential to be so important looking ahead to future exploration of our solar system and beyond as this technology demonstration could transform the way we explore celestial bodies nearby. Now powered ight has been proven on another planet, new and upcoming rotorcraft could be used to scout areas for future missions for astronauts and rovers or access places that would otherwise be tough to get to. In fact, NASA already plan to send another helicopter mission across the solar system: the Dragon y mission to Titan (one of Saturn’s moons) aiming to arrive mid 2030s.

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outing where it travelled a horizontal distance of 4m. Flight 3, taking place just six days after the rst ight during a tight initial 30-day window, was where Ingenuity made its rst ight of 100m whilst also ying for the rst time for over a minute. Whilst this occurred, teams managed to capture a spectacular image of the Perseverance rover from the aerial perspective of Ingenuity. Compared to an almost awless rst few ights, ight 4 was problematic as take-o was postponed from 29 April to 30 April due to Ingenuity’s failure to transition into ight mode. The fourth ight was ultimately a success however travelling a record 266m. Flight 5 had a new destination to what is known as ‘Air eld B’. All previous ights had taken place within Wright Brothers Field, but Ingenuity ew 129m to a new air eld as Ingenuity completed its hugely successful demonstrations phrase. On 22 May, Ingenuity’s most eventful ight yet occurred with an anomaly at around 50 seconds after take-o . After around 150m of ying, Ingenuity began to tilt violently due to an anomaly found in the images from the navigation camera onboard. It led to one lost image as well as other images being given inaccurate timestamps. However, Ingenuity was able to land safely and only 5m away from the planned landing position, demonstrating the helicopter’s capability even during unexpected events like these. Due to ight 6’s anomaly, the camera navigation system was not used on ight 7 and 8 to not have a repeat of ight 6’s chaos. The most exciting and adventurous ights were still to come with ight 9 travelling an astonishing 625m for nearly three minutes becoming the furthest and longest ight at the time.

The World According to Physics

Being Mortal

It is perhaps the best piece of popular science that I have read. In engaging fashion, Professor Al-Khalili explains the basics of physics while adding further insights. Approachable, comprehensible, quite simply superb; Al-Khalili certainly succeeds in illuminating both the truths of established as well as novel physics.

Being Mortal is a fantastic, thought provoking book which explores the life when we get old. It o ers a view into the mind of the elderly and the struggles they face from the onset of oldaged diseases to their experience of care homes.

Author: Prof Jim Al-Khalili Review: 4.7 stars (Amazon, 593 reviews)

Author: Atul Gawande Review: 4.7 stars (Amazon, 14081 reviews)

Foundations of Organic Chemistry

Chemical Bonding by Mark J. Winter serves as a fantastic introduction for the curious student into a more detailed model for how atoms bond to one another. It follows on from the basic ideas of atomic orbitals and expands this thinking to molecular orbital theory in compounds as well as discussing some of the problems with VSEPR theory. A very good read for anybody with a further interest in chemistry. Author: Mark J. Winter Review: 4.5 stars (Amazon, 37 reviews)

The New Turning Omnibus

The New Turing Omnibus presents 66 articles, each introducing new topics from both the theoretical and practical sides of computer science. Whether you want to back up and add to your gcse and a level knowledge, or you just want to nd out about new interesting areas of the subject, you will nd an article that fascinates you in this book, and maybe you'll even nd yourself recreating some of the code examples for yourself. Author: Alexander Dewdney Review: 4.3 stars (Amazon, 65 reviews)

Chaos

Chaos is a really beautiful book, delving deep into the heart of the controversial theories of irregularity, challenging your preconceptions in science. It is hugely relevant to multiple disciplines, drawing on physics, maths, biology and computer science, to show how unpredictable nature truly is.

Do you have any Science book recommendations that you would like to share? Email us at: skinners.sciencemag@gmail.com, and we may publish you reviews next issue!

Author: James Gleick Review: 4.6 stars (Amazon, 1270 reviews)

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Book Recommendations

KS3 1. Physics: What is the name of the closest star to our sun?

KS5 11. Chemistry: Ethanol (the alcohol in drinks) is comprised of which three atoms?

2. Biology: Who famously discovered penicillin by accident after their petri dish was contaminated?

12. Physics: What is the charge on an up quark?

3. Physics: In a string of lights, one bulb breaks, yet the rest stay lit. What type of circuit is this?

13. Physics: What is the name of the principle by which lift is generated by pressure differences around aerofoils?

4. Chemistry: Diamond, graphite and nanotubes are all allotropes (different forms of the same element) of which element?

14. Physics: What is the derived SI unit for radioactivity, named after the scientist, to rst discover radioactivity (Bonus point: Which two other scientists shared the Nobel prize with ?)

5. Physics: What is the largest satellite of earth?

KS4 6. Chemistry: Which separation process can be used to separate crude oil? 7. Chemistry: What indicator is pink in alkaline solutions, but colourless in acidic ones? (Bonus points if you can spell it. I still can’t.) 8. Biology: What are the ve kingdoms used to classify living organisms? 9. Biology: True or False: Cancer is a communicable disease. 10. Physics: Which part of the EM spectrum does a TV remote use to transfer information?

15. Biology: What part of the body is the thermoregulatory centre?

Advanced 16. Physics: True or False: Quantum entanglement has the ability to transfer useful information instantaneously. 17. Physics:What percentage of the universe’s mass is predicted to be made of dark matter? 18. Biology: Which protein is used in a genetic engineering technique developed by Nobel prize winner Jennifer Doudna? 19. Physics: Which famous Scot uni ed the eld of electromagnetism with a set of four differential equations? 20. Biology: Name the ve main shapes of bacteria.

Answers: 1) Proxima Centauri, 2) Alexander Fleming, 3) Parallel Circuit, 4) Carbon, 5) The Moon, 6) Fractional Distillation, 7)Phenolphthalein 8) Animals, Plants, Fungi, Prokaryotes, Protists, 9) True(There are some cancers which are communicable), 10) Infrared, 11) Carbon, Oxygen, Hydrogen, 12) +2/3, 13) Bernoilli's Principle, 14) Bequerelle (BM: Marie Curie and Piere Curie), 15)The Hypothalamus , 16) False, 17) 24%, 18) CRISPR-Cas9, 19) James Clerk Maxwell, 20) Rod (bacilli), Spiral (spirilla), Corkscrew (Spirochaetes), Spherical (Cocci), Comma (vibrios) fi

The Aether Quiz

Citations Disclaimer: The Aether Science Magazine is for general informational and educational purposes only and is not a substitute for professional advice. We do not guarantee or vouch for the credibility of the information in the magazine nor third party links provided by citations, our social media account and our website. The magazine, social media accounts and the website is not intend to hurt any persons’ or organisations’ sentiment, opinion or beliefs and do not re ect our own views unless otherwise clearly stated nor is it intended to cause damage or incur losses to any person or organisation. Any information that you decide to use from the magazine, social media accounts and the website will be solely at you own risk and the magazine does not claim liability for any kind of losses or damages to you, any persons or organisations. We do not guarantee or endorse the links to third party websites available through our citations page and nor are they monitored, any use of third party websites is solely at your risk and we are not liable for any kind of losses or damages caused to you, any persons or organisations.

Available at:https://www.nature.com/articles/s41598-021-93943-w [Accesed August 2021] Silva, D. (2021), Adult female Schneider's marmoset (Mico schneideri), Available at: https://commons.wikimedia.org/wiki/ File:Schneider%27s_marmoset_female_in_Parana%C3%ADta.ti [L:ast Accessed January 2022], This le is licensed under the Creative Commons Attribution 4.0 International license.

Cover Mittermeier F. (2017),. Milky Way Stars Night Available at: https:// pixabay.com/photos/milky-way-stars-night-sky-night-2695569/ [Last Accessed 14 January 2022] 1675236. (2016),. Space stars star wars darck black Available at:https:// pixabay.com/illustrations/space-stars-star-wars-darck-black-1164579/ [Last Accessed 18 January 2022] 95C. (2021),. Planet Rings Astronomy Red Alien Exoplanet Available at: https://pixabay.com/illustrations/planet-rings-astronomy-redalien-5938849/ [Last Accessed 18 January 2022] iludeo. (2018),. Planet Illustration Exoplanet Room Available at:https:// pixabay.com/illustrations/planet-illustration-exoplanet-room-3308432/ [Last Accessed 18 January 2022] ChadoNihi., (2014),. Exoplanet Planet Alien Gas Giant Exomoon Available at:https://pixabay.com/illustrations/exoplanet-planet-aliengas-giant-571900/ [Last Accessed 18 January 2022] ntnvnc. (2018),. Spacecraft Spaceship Technology Rocket Ufo Design Available at:https://pixabay.com/illustrations/spacecraft-spaceshiptechnology-3589965/ [Last Accessed 18 January 2022]

N. Prantzos(2020), A probabilistic analysis of the Fermi paradox in terms of the Drake formula: the role of the L factor, Available at: https:// arxiv.org/pdf/2003.04802.pdf

Latest Discoveries [1] MHRA, (2021),. First oral antiviral for COVID-19, Lagevrio (molnupiravir), approved by MHRA Available at: https://www.gov.uk/ government/news/ rst-oral-antiviral-for-covid-19-lagevrio-molnupiravirapproved-by-mhra [Last Accessed on 15 November 2021] jorono. (2018),. Medicine Treatment Pill Capsule Available at: https:// pixabay.com/photos/medicine-treatment-pill-capsule-3308108/ [Last Accessed on 16 November 2021] Ouellette, J. (2021) Physicists discover new kind of tetraquark—the longest-lived yet found, Available at: https://arstechnica.com/science/ 2021/08/physicists-discover-new-kind-of-tetraquark-the-longest-livedyet-found/ [Last accessed August 2021] CERN on Phys.org, (2021) New exotic matter particle, a tetraquark, discovered Availabel at: https://phys.org/news/2021-07-exotic-particletetraquark.html [Last Accessed August 2021] OpenStreetMap contributors (2014) Location map of en:Large Hadron Collider (way #310046324) and en:Super Proton Synchrotron, Available at: https://commons.wikimedia.org/wiki/ File:Location_Large_Hadron_Collider.PNG [Last Accessed January 2022] This le is licensed under the Creative Commons AttributionShare Alike 2.0 Generic license Costa-Araujo, R. et al. (2021) An integrative analysis uncovers a new, pseudo-cryptic species of Amazonian marmoset (Primates: Callitrichidae: Mico) from the arc of deforestation, Nature (Online)

Fermi Paradox Pablo Carlos Budassi, Milky way, Available at: https:// commons.wikimedia.org/wiki/File:Milky_way.png NASA/Ames/JPL-Caltech(2011), Voyager 1 Encounters Stagnation Region, Available at: https://www. ickr.com/photos/nasablueshift/ 6474236765 Anders Sandberg, Eric Drexler and Toby Ord(2018), Dissolving the Fermi Paradox, Available at: . https://arxiv.org/pdf/1806.02404.pdf S. Jay Olson(2018), Life-hostile conditions in the early universe can increase the present-day odds of observing extragalactic life, Available at: https://arxiv.org/pdf/1704.04125.pdf

Keith B. Wiley(2011), The Fermi Paradox, Self-Replicating Probes, and the Interstellar Transportation Bandwidth, Available here: https:// arxiv.org/pdf/1111.6131.pdf

Invar: A Magnet That Won’t Behave (...and 126 years later we still do not know why...) Richard Feynman explains why you cannot easily explain magnets in eight minutes [https://www.youtube.com/watch?v=MO0r930Sn_8, Accessed on 20/01/22] Invar and Elinvar, C É Guillame, Nobel Lecture (December 11, 1920) [https://www.nobelprize.org/uploads/2018/06/guillaume-lecture.pdf, accessed on 20/01/22] Spin and orbital magnetization loops obtained using magnetic Compton scattering, M Itou et al., Applied Physics Letters 102 082403, published online 27 February 2013. Magnetic Compton scattering studies of the Invar alloy Fe3Pt, G Srajer et al., J. Phys.: Condensed Matter 11 1289 (1999). The European Synchrotron Radiation Facility, Grenoble, France [https:// www.esrf.fr/] Spring-8 Synchrotron Radiation Facility, Japan [http:// www.spring8.or.jp/en/] Spin-polarized electron momentum density distributions in the Invar system Fe3Pt, J Taylor, J Du y, A Bebb, J McCarthy, M Lees, M Cooper, and D Timms, Physical Review B 65 22 (2002). Image Credits: ESRF Public Facts and Figures/Press Kit [https://www.esrf.fr/ UsersAndScience/Publications/Highlights/2008/facts- gures/beamlines accessed on 27/01/22] Credit: P.Ginter/ESRF [https://www.eiroforum.org/esr034/ accessed on 27/01/22] The experimental hall and storage ring building of the ESRF. Measurements in Space Beck, K. (2020),. How to make calculate Arcsec Available at: https:// sciencing.com/space-science-kits-that-are-out-of-thisworld-13763827.html [Last Accessed 2 May 2021]

chenspec, (2021,. Education Doodle Wallpaper Learning Pencil Math Available at:https://pixabay.com/illustrations/education-doodlewallpaper-learning-6005876/ [Last Accessed on 18 January 2022] Clark, L. (2000)., Background Parallax Available at: https:// www.astro.princeton.edu/~dns/teachersguide/ParBkgd.html [Last Accessed on 1 May 2021] Eso,. (2014),. Artist’s impression of the double-star system GG Tauri-A Available at: https://www.eso.org/public/images/eso1434a/ [Last Accessed 3 May 2021] Creative Commons Attribution 4.0 International. Hamdy, M. (2017),. Distance to the Sun Available at: https:// thegreatestsciencediscoveries.wordpress.com/2017/02/08/distance-tothe-sun/ [Last Accessed on 1 May 2021] Kornreich, D. (2015), How do you measure the mass of a star? (Beginner) Available at: http://curious.astro.cornell.edu/about-us/82the-universe/stars-and-star-clusters/measuring-the-stars/394-how-doyou-measure-the-mass-of-a-star-beginner [Last Accessed 3 May 2021] Lucas, J. (2018),. What is Parallax? Available at: https:// www.space.com/30417-parallax.html [Last Accessed 1 May 2021] Lumen Learning, OpenStax College. (n,d)., Newton’s Universal Law of Gravitation Available at: https://courses.lumenlearning.com/physics/ chapter/6-5-newtons-universal-law-of-gravitation/ [Last Accessed 24 April 2021] Creative Commons Attribution Non-Commercial Share Alike 2.0 Generic. Lumen Learning, OpenStax College. (n,d)., Distances to and Brightness of Stars Available at: https://courses.lumenlearning.com/towsonastronomy-2/chapter/the-brightness-of-stars/ [Last Accessed 3 May 2021] Creative Commons Attribution 4.0 International. Lumen Learning, OpenStax College. (n,d)., Measuring Stellar Masses Available at: https://courses.lumenlearning.com/astronomy/chapter/ measuring-stellar-masses/ [Last Accessed 3 May 2021] Creative Commons Attribution 4.0 International. Lumen Learning, OpenStax College. (n,d)., Laws of Planetary Motion Available at: https://courses.lumenlearning.com/astronomy/chapter/ the-laws-of-planetary-motion/ [Last Accessed 1 May 2021] Creative Commons Attribution 4.0 International. PdeQuant, (2020),. Stellar parallax parallel lines from observation base to distant background Available at: https://commons.m.wikimedia.org/ wiki/ File:Stellar_parallax_parallel_lines_from_observation_base_to_distant_b ackground.png [Last Accessed 2 May 2021] Creative Commons Attribution-Share Alike 4.0 International. Powell, R. (2007),. HRDiagram Available at: https:// commons.m.wikimedia.org/wiki/File:HRDiagram.png [Last Accessed 3 May 2021] Creative Commons Attribution-Share Alike 2.5 Generic Redd, N.T. (2018) Main Sequence Stars: De nition and Life Cycle Available at: https://www.space.com/22437-main-sequence-stars.html [Last Accessed 18 June 2021] Richmond, M. (2012)., Who measured the solar system -- and how? Available at: http://spi .rit.edu/richmond/asras/measure_ss/ measure_ss.html#summer [Last Accessed 24 April 2021] Creative Commons Attribution 4.0 International. RJHall, (2007),. Isochrone ZAMS Z2pct.png Available at: https:// commons.m.wikimedia.org/wiki/File:Isochrone_ZAMS_Z2pct.png [Last Accessed 3 May 2021] The image is in the public domain. Dark Matter Al-Khalili, J., (2020), The World According to Physics, Princeton University Press, pp.192-205 Stuart, C., (February 2021), A Universe Full of See Through Stars, BBC Science Focus, Vol 360, pp.71-77. Kleinert, H., (14 Aug 2016), The GIMP Nature of Dark Matter, Electronic Journal of Theoretical Physics, Vol. 36, pp.1-12. SENSEI collaboration (2018), arXiv:1804.00088 Urton, J. (2017) Dark matter is likely 'cold,' not 'fuzzy,' scientists report after new simulations, Available at: https://phys.org/news/2017-07-darkcold-fuzzy-scientists-simulations.html [Accessed June 2021] CERN (2021), BASE opens up new possibilities in the search for cold dark matter, Available at: https://phys.org/news/2021-01-basepossibilities-cold-dark.html [Accessed June 2021] Gibney, E. (2020), Launch All-Out Hunt for Dark Matter Candidate, Available at:https://www.scienti camerican.com/article/last-chance-forwimps-physicists-launch-all-out-hunt-for-dark-matter-candidate/ [Accessed August 2021]

Letzter, R., (2020), Physicists Announce Potential Dark Matter Breakthrough, Available at: https://www.scienti camerican.com/article/ physicists-announce-potential-dark-matter-breakthrough/ [Accessed August 2021) Garisto, D., Possibility of Dark Bosons Entices Physicists, Available at:https://www.scienti camerican.com/article/possibility-of-dark-bosonsentices-physicists/ [Accessed August 2021] NIST, (2020), Dark Matter: A Billion Tiny Pendulums Could Detect the Universe’s Missing Mass, Available at: https://scitechdaily.com/darkmatter-a-billion-tiny-pendulums-could-detect-the-universes-missingmass/ [Accessed June 2021] DEAP-3600, (last updated 2018), DEAP-3600 Detector, Available at: http://deap3600.ca/deap-3600-detector/, [Accessed June 2021] LUX-ZEPLIN(UK), (2017), How it Works; The LZ Experiment; The noble liquid xenon, Available at: http://lz.ac.uk/lz-experiment/how-it-works/, [Accessed August 2021] Bucklin, S.M., (2017), A history of dark matter, Available at:https:// arstechnica.com/science/2017/02/a-history-of-dark-matter/ [Accessed June 2021] Backes, K.M., Palken, D.A., Kenany, S.A. et al. A quantum enhanced search for dark matter axions. Nature 590, 238–242 (2021). https:// doi.org/10.1038/s41586-021-03226-7 IMAGES: Pablo Carlos Budassi, (2020), Bullet cluster, Available at: https://commons.wikimedia.org/wiki/File:Bullet_cluster.png, [Last Accessed November 2021], Creative Commons Attribution-Share Alike 4.0 International license. Mark Ward, (2014), The DEAP 3600 detector under construction, Available at: https://commons.wikimedia.org/wiki/File:DEAP3600.jpg,, [Last Accessed August 2021], This work is free and may be used by anyone for any purpose. Davy Landman, (2013), Parco nazionale del Gran Sasso Settembre 2013, Available at: https://commons.wikimedia.org/wiki/ File:Parco_nazionale_del_Gran_Sasso_Settembre_2013.jpg [Accessed November 2021], Creative Commons Attribution-Share Alike 2.0 Generic Dark Energy Survey, (2021), DESDMmap2021, Available at: https:// commons.wikimedia.org/wiki/File:DESDMmap2021.png, [Accessed December 2021] Interstellar Travel TheDigitalArtist, (2015),. Stars Nebula Universe Available at:https:// pixabay.com/illustrations/stars-nebula-universe-artistic-1014109/ [Last Accessed 18 January 2022] [1] NASA (2021), The Human Body in Space [online] Available at: https://www.nasa.gov/hrp/bodyinspace [Last Accessed 7 August 2021] [2] NASA (n.d.), CRaTER: How Cosmic Rays A ect Humans [online] Available at: https:// lunar.gsfc.nasa.gov/lessonkit/CRaTERHow%20Cosmic%20Rays%20A ect%20Humans.pdf [Last Accessed 7 August 2021] [3] NASA (2019), How NASA will Protect Astronauts From Space Radiation at the Moon [online] Available at: https://www.nasa.gov/ feature/goddard/2019/how-nasa-protects-astronauts-from-spaceradiation-at-moon-mars-solar-cosmic-rays [Last Accessed 7 September 2021] [4] NASA (n.d.), Space Faring The Radiation Challenge [online] Available at: https://www.nasa.gov/sites/default/ les/atoms/ les/ radiationchallenge.pdf [Last Accessed 7 September 2021] [5] SITN, Harvard. (2013), The human body in space: Distinguishing fact from ction [online] Available at: https://sitn.hms.harvard.edu/ ash/ 2013/space-human-body/ [Last Accessed 7 August] Parks,J., (2021) Breakthrough Starshot: A voyage to the stars within our lifetimes, Astronomy Mag (Online), Available at: https://astronomy.com/ magazine/news/2021/06/breakthrough-starshot-a-voyage-to-the-starswithin-our-lifetimes [Last Accessed August 2021] CERN (n.d.) Antimatter, (online) Available at: https://home.cern/science/ physics/antimatter [Accessed August 2021] iegel, E., (S2020), Could We Achieve Interstellar Travel Using Only Known Physics?, Forbes, Available at: https://www.forbes.com/sites/ startswithabang/2020/07/28/could-we-achieve-interstellar-travel-usingonly-known-physics/ [Accessed August 2021]

NASA, JPL-Caltech (2021), Perseverance's Navcam View of Ingenuity's First Flight Available at: https://www.jpl.nasa.gov/images/pia24586perseverances-navcam-view-of-ingenuitys- rst- ight [Last Accessed on 18 January 2022] NASA, JPL-Caltech (2021), Ingenuity's Complete Deployment Available at:https://www.jpl.nasa.gov/images/pia24548-ingenuitys-completedeployment [Last Accessed on 18 January 2022] NASA, JPL-Caltech, MSSS (2021), Perseverance's Sel e with Ingenuity Available at:https://www.jpl.nasa.gov/images/pia24542-perseverancessel e-with-ingenuity [Last Accessed on 18 January 2022] NASA, JPL-Caltech (2021), First Aerial Color Image of Mars Available at:https://www.jpl.nasa.gov/images/pia24593- rst-aerial-color-image-ofmars [Last Accessed on 18 January 2022] Katherine Johnson Katherine Johnson Biography NASA. Avaliable at:: https:// www.nasa.gov/content/katherine-johnson-biography Katherine Johnson, Britannica. Avaliable at: https://www.britannica.com/ biography/Katherine-Johnson-mathematician Katherine Coleman Goble Johnson, MacTutor. Avaliable at: Katherine Coleman Goble Johnson

How does GPS Work? Thanks to Desmos for generously granting permission to use their graphing software to illustrate this article. Flickr, User: Adlopa (2014) gps-orbit-map. Avaliable at: https:// www. ickr.com/photos/adlopa/13102723053/ GPS.gov(2021) What is GPS?. Avaliable at: https:// www.gps.woc.noaa.gov/systems/gps/ [Last Accessed: 04/09/2021]

Terraforming Mars NASA (2018) Mars terraforming not possible using modern day technology Available at: nasa.gov/press-release/goddard/2018/marsterraforming Terraforming Mars: Experts debate how, why and whether (2004) Available at: space.com/190-terraforming-mars-experts-debate.html Rethinking the Mars Terraforming debate (2018) Available at: thespacereview.com/article/3551/1 ChadoNihi., (2014),. Red Planet Moon Alien Arid Abiocoen Ancient Available at: https://pixabay.com/illustrations/red-planet-moon-alienarid-571902/ [Last Accessed] Ingenuity NASA Mars. (2021), Flying on Mars Is Getting Harder and Harder. Available at: https://mars.nasa.gov/technology/helicopter/status/334/ ying-on-mars-is-getting-harder-and-harder/ NASA Space ight (2021) Available at: https://www.nasaspace ight.com/ Space.com (2021), Available at: https://www.space.com/ NASA, JPL-Caltech (2021), Ingenuity Spots Perseverance From the Air Available at:https://www.jpl.nasa.gov/images/pia24625-ingenuity-spotsperseverance-from-the-air [Last Accessed on 18 January 2022]

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Howell, E. (2016), Breakthrough in Antimatter Physics Has Some Dreaming of Starships, Air Space Mag, Available at: https:// www.airspacemag.com/daily-planet/breakthrough-antimatter-physicshas-some-dreaming-starships-180961497/ [Accessed August 2021] Steigerwald, B., (2006), New and Improved Antimatter Spaceship for Mars Missions, Available at: https://www.nasa.gov/exploration/home/ antimatter_spaceship.html [Accessed August 2021] Alcubierre, M. (1994) ‘The warp drive: hyper-fast travel within general relativity’ (Accreditation for image and information) NASA/MSFC. (1999) File:Antimatter Rocket.jpg Available at: https:// commons.m.wikimedia.org/wiki/File:Antimatter_Rocket.jpg [Last Accessed on 28 January 2022] This image is in the public domain Powell, R. (2007),. The Universe within 50000 Light Years The Milky Way Galaxy Available at: http://www.atlasoftheuniverse.com/ galaxy.html [Last Accessed 29 January 2022] Creative Commons Attribution-Share Alike 2.5 Generic Dr Christopher Berry Interview Abbott, B.P. et al. (2016) Simpli ed diagram of an Advanced LIGO detector, Available at: https://commons.wikimedia.org/wiki/ File:Simpli ed_diagram_of_an_Advanced_LIGO_detector.png [Last Accessed November 2021] Creative Commons Attribution 3.0 Unported Caltech/MIT/LIGO Laboratory (2009), Aerial View Of LIGO Livingston, Available at: https://commons.wikimedia.org/wiki/ File:Aerial_View_Of_LIGO_Livingston_599x400.jpg, [Accessed August 2021] public domain in the United States NASA (2010) NASA illustration of LISA, Available at:https:// commons.wikimedia.org/wiki/File:LISA-waves.jpg [Accessed November 2021] public domain in the United States because it was solely created by NASA.