The Big Ideas in Science Simply Explained sampler

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THE BIG IDEAS IN SCIENCE SI MP LY E XPL A INED

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N ET U C IEEENT CSE O RP OTSW

08 TUNE UP YOUR BRAIN

Memory, problem-solving, brain-training

HT EWTAEOLEPTTHS

26 DIET TRENDS

The science of fasting and microbiome tests

32 COMBATING PTSD

Deleting memories to beat the condition

38 BREAKING GENETIC LAWS

Changing gene drives to eradicate disease

40 MDMA FOR PSYCHOTHERAPY

How ecstacy could help treat alcoholism

ATNOCPI ETNWT ELEI TF SE

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48 THE WALK OF PREHISTORIC LIFE

Robots reveal how ancient creatures moved

54 BUILDING A NEANDERTHAL BRAIN Bringing our ancient cousins to life

PTHWTY EOS EP I CT SS

62 BEFORE THE BIG BANG

What really happened 13.8 billion years ago

68 THE PROBLEM WITH GRAVITY

A new theory to rewrite the laws of physics

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62 98

74 HOW TO TIME TRAVEL

From wormholes to cosmic strings

82 THE REAL SCHRÖDINGER'S CAT

New research to prove the feline could exist

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90 THE END OF MOORE'S LAW

The new tech to replace silicon chips

94 DEEP LEARNING

The next big steps in artificial intelligence

98 INTERVIEW: JIM AL-KHALILI

On why we can trust artificial intelligence

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6. DECISION-MAKING So-called free will and the emotionally fraught business of choice

Every decision we make is arrived at through hugely complex neurological processing.

Although it feels as though you have a choice, the action that you ‘decide’ to take is entirely dictated by automatic neural activity. Brain imaging studies show that a person’s action can be predicted by their brain activity up to 10 seconds before they themselves become aware they are going to act.

This has huge implications for our concept of free will, which scientists and philosophers are still grappling with today.

Multiple neuroscientific studies show that even those important decisions that feel worked out are just as automatic as knee-jerk reactions (although more complex). The sense of volition seems to be a clever illusion perpetrated by our brains, and the illusion is useful because it gives us a sense of responsibility – and causes us to moderate our behaviour accordingly.

Decision-making starts with the amygdala: a set of two almond-shaped nuclei buried deep within the brain, which generate emotion. The amygdala registers the information streaming in through our senses and responds to it in a split second, sending signals throughout the brain. These produce an urge to run, fight, freeze or grab, according to how the amygdala values various stimuli.

Before we act on the amygdala’s signals, however, the information is usually processed by more sophisticated brain areas, including some that produce conscious thoughts and emotions. Areas concerned with recognition

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work out what’s going on, t hose concerned wit h memory compare it with previous experiences, and those concerned with reasoning, judging and planning get to work on constructing various action plans.

The best plan – if we are lucky – is then selected and executed. If any of this process goes wrong, we are likely to dither, or do something silly.

The various stages of decision-making are marked by different types of brain activity.

Fast (gamma) waves, with frequencies of 25 to 100 Hz, produce a keen awareness of the multiple factors that need to be considered to arrive at a decision. If you are trying to choose a sandwich, for instance, gamma waves generated in various cells within the brain’s ‘taste’ area compare the taste of ham, hummus, wholemeal, and so on. Although it may seem useful to be aware of the full range of choices, too much information makes decision-making more difficult, so irrelevant factors get dismissed quickly and unconsciously. So, for example, at the sandwich counter, the cheese and tomato option might trigger only the tiniest flurry of neuronal excitement.

After this surge of activity marking the comparison stage, the brain switches to slowwave activity (12 to 30 Hz). This extinguishes most of the gamma activity, leaving just a single ‘hotspot’ of gamma waves which marks

NEUROSCIENCE

TUNE UP YOUR DECISION-MAKING ■ Make a list of your bad decisions and look for links. Were they all compromises, for example, or made hastily? When you identify a link, analyse the mental strategy that you used, and try deliberately using the opposite strategy for a while. If the problem seems to be haste, for example, delay the decision, and be ready to acknowledge any vaguer, subtler factors that come to mind.

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■ Brainstorm before a decision, then sleep on it before acting. Like creative thought, good decision-making benefits from unconscious incubation, in which the brain drifts around, rummaging through memories that might be useful. Sleep is an extreme case of incubation, and your dreams may throw up important clues that make your decision clearer upon waking.

the chosen option.

Although there is no ‘you’ outside your brain to direct what it’s doing, you can help it to make good decisions by placing yourself in a situation which is likely to make the process run more smoothly. Doing something that is physically or mentally stimulating before making a decision will help your brain produce the initial gamma waves that generate awareness of the competing options. Getting over-excited, on the other hand, will prevent the switch to the slow brainwaves, making it much harder to single out a choice. Subjecting yourself to high emotion may also warm up the connecting pathways from the amygdala to the action areas of your brain, causing panicky or impulsive behaviour.

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■ Mentally step back from the situation and ask yourself what others might do. This will force your brain to look at the situation from a new perspective, which may reveal factors you had not previously taken into account.

■ Write down your favoured option, then highlight the emotional words.

If you delete the highlighted words, is the decision still looking good? If not, these words are your real reasons for the decision.

‘Attractive’ or ‘exciting’ may be valid factors in deciding on a date, but not so good if you’re choosing an accountant.

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WHAT SCIENCE HAS TO SAY ABOUT... INTERMITTENT FASTING, PERSONALISED NUTRITION & MICROBIOME PROFILING

DIET TRENDS

HEALTH

INTERMITTENT FASTING Is the 5:2 diet any better than cutting your calorie intake over the longterm? And are there any risks? words by H AY L E Y B E N N E T T

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ff the back of some best-selling diet books, fasting is more popular than it’s ever been. All you have to do is keep your calories down for a couple of days each week, eat what you like the rest of the time and you’ll still lose weight.

That’s the gist of the 5:2 diet anyway. But with popularity comes scrutiny, and scientists are now trying to work out whether there is any benefit to fasting diets that you can’t get from a normal calorie restriction diet – in other words, just eating less all the time.

Krista Varady, who is based at the University of Illinois in Chicago, has been researching intermittent fasting as an alternative to everyday calorie restriction. “People quit those diets after about a month or two as they just get sick of the daily deprivation,” she says. “With alternate-day fasting, or 5:2, you basically get a break from dieting every other day, or five days a week.”

Some of Varady’s early studies were carried out on mice. But the way she sees it, there’s only so much you can learn from animals with “perfect adherence”; if you put a mouse on a diet, there’s really not much the mouse can do about it. People, however, are another matter.

“It doesn’t matter if the diets produce all these amazing results if people can’t actually stick to them,” says Varady.

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A USER’S GUIDE TO

TIME TRAVEL Einstein’s General Theory of Relativity has raised another issue, which has given numerous scientists sleepless nights because it makes one thing pretty much unavoidable: time machines... words by M A R C U S C H OW N illustrations by M E R I J N H O S

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PHYSICS

...It comes down to the fact that, in Einstein’s theory, time is not absolute,

Watch a clip from How to Build a Time Machine bbc.in/2TYdbGI

ticked off by a universal clock with which everyone agrees, but instead is relative. “I can’t talk to you in terms of time – your time and my time are different,” wrote the English novelist Graham Greene.

According to Einstein, the rate at which time flows for someone depends on how fast they’re moving relative to you and the strength of the gravity they’re experiencing. If you can find a way to jump from a region where time flows at one rate to a region where it flows at a slower rate, you can go back in time – you’ll have made a time machine.

The recognition that time is not what you think it is goes back to the Special Theory of Relativity that Einstein published in 1905, and it all hinges on the unique properties of the speed of light. Einstein realised that nothing can travel faster than light – it is the cosmic speed limit of our Universe. This makes light uncatchable by anything. He also discovered that intervals of space and time stretch like elastic as massive objects move through them. By a cosmic conspiracy this means that everything measures exactly the same speed for a light beam, no matter how fast that thing is travelling or in which direction.

To be a little more precise, moving clocks run slow.

So, if someone flies past you – and it has to be at a speed approaching 300,000 kilometres per second – then their clock will run slow compared to yours. If they could ever reach the speed of light – which is impossible for a material body, though possible for a massless entity such as a particle of light (a photon) – time would come to a complete standstill.

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TECHNOLOGY

CAN WE TRUST ARTIFICIAL INTELLIGENCE? Deep learning is used in everything from speech recognition software to the assessment of mortgage applications. The only trouble is, we don’t really know how it works…

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words by P E T E R B E N T L E Y

ILLUSTRATION: SAM FREEMAN

eep learning does it all: face recognition, language translation, game-playing. It’s an approach that has transformed the field of artificial intelligence (AI) and is the AI flavour of the decade.

But how does deep learning work? And can we trust it to work for safety critical applications such as self-driving cars?

We generally like computer algorithms to be as transparent as possible and this is not the case with deep learning.

In essence, deep learning is a clever rebranding of an earlier computer learning method called artificial neural networks (ANNs). Dating back to the beginning of computers, ANNs are programs that simulate networks of neurons like those in our brains.

They’re hugely simplified and don’t work in quite the same way that real neurons do, but nevertheless, they enable computers to learn (see ‘How a neural network works’, on page 96).

WE CANNOT SEE INSIDE THESE GIANT NEURAL NETWORKS AND THAT IS NOT A GOOD THING

HIDDEN DEPTHS Research on neural networks started in the 1950s and as the ideas were refined it soon became clear that neural networks were not as good as some other approaches in machine learning (the branch of AI dedicated to helping computers learn from data in order to make classifications and predictions). As a result,

research in the area began to wane by the early 1990s and learning methods that relied on clever statistics started to dominate.

This all changed about 20 years ago. British pioneer Geoff Hinton (University of Toronto and head of Google’s Brain Team Toronto) and Jürgen Schmidhuber (IDSIA Dalle Molle Institute for AI, Switzerland) introduced new, more efficient ways to train neural networks containing far more layers. Suddenly networks could have hundreds of ‘hidden’ layers – rows of neurons that sit between the input neurons, which are connected directly to sensors, and the output neurons, which provide the results. When combined with new ways of connecting the neurons to each other, the result was massively more powerful. The breakthrough coincided with the age of big data, cloud computing and fast processors. By 2006 it was possible to create gigantic ‘deep’ networks, train them with vast quantities of data and use huge numbers of fast computers all working in sync.

This ‘deep learning’ was the start of the newest revolution in AI. Although still based on a simplified model of how the brain functions, it relies on networks of thousands or millions of neurons simulated in software. Given enough data and enough computers to enable the networks to adapt and learn in response to the data, the result is like a little software brain.

If it’s been trained to recognise faces, then the little brain can be placed into a camera, so that when you take a photo it finds faces and ensures they are in focus. If it’s been trained 5

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THE BIG IDEAS IN SCIENCE S I M P LY E X P L A I N E D This BBC Science Focus Special Edition reveals the latest research in the fields of neuroscience, health, ancient life, physics and technology.

IN THIS ISSUE… What if the Big Bang wasn’t the beginning How gene drives could eradicate disease The truth about brain training games The robots revealing how ancient life walked The black hole that could prove Einstein wrong Why scientists are growing Neanderthal brains

PLUS – subscribers to BBC Science Focus Magazine receive FREE UK postage on this special edition

5 ways to time travel – from wormholes to cosmic strings

What science says about personalised nutrition, fasting and microbiome profiling

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