S U BATOMIC PHYS ICS
Components of matter
The stuff of the Universe is all made from fields – the basic ingredients of the Universe – and their particles. All particles are ripples in fields and have energy. Matter can refer to atoms, the basic building blocks of what we percieve as the material Universe around us – fire, mountains, eyelashes, rockpools, salt – and indeed the components out of which atoms are made, including electrons and the protons and neutrons that make up the atom’s nucleus. Or it can refer to what are called the elementary matter particles of nature: electrons, muons, taus, the three types of neutrinos, the six types of quarks — all of the types of particles which are not the force-carrier particles: the photon, gluons, the W and Z particles ... and, potentially, the graviton (!).
The density of the Universe is made up of both energy and matter. Contrary to a popular belief following on from the most famous equation in modern physics, E=mc2, energy and matter are not interchangeable expressions of the same thing.
Hadrons (made of quarks) Matter is an ambiguous term and it can be used to describe several different kinds of ‘stuff’. Energy is never stuff, but it’s something that all stuff has. Particles can have two types of energy: mass-energy – this is the E= mc2 type of energy, which does not depend on whether and how a particle moves; and motion-energy – energy that is zero if a particle is stationary and becomes larger as a particle moves faster.
Baryons (3 quarks) Exotic 38 observed 36 predicted
Neutrons
Protons
This means that a cube of average space nearly 16,000 kilometres across would contain the equivalent of a grain of sand.
Average density of the Universe The European Space Agency’s Planck space observatory has ascertained that the density of the Universe is equal to critical density, with a 0.5% margin of error (see green curve below).
Mesons (2 quarks)
Atomic matter
27 observed 5 predicted
STUFF
The actual density of atomic matter: equivalent to roughly 1 proton per 4 cubic metres
Atoms
Leptons Where is all the missing energy and matter? Over 95% of the Universe is undetectable ...
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Electrons
Molecules
Energy/mass density of Universe: equivalent to 5.9 protons per cubic metre
Muon
A grain of sand could contain around 1,000,000,000,000,000,000,000 protons and neutrons (assuming an average of 20 hadrons per atom in silcon dioxide ... sand).
Relative size of the Universe
Tau
EXOTIC PARTICLES Top Quark Most massive elementary particle, equivalent to 184 protons (the same as a tungsten atom), but very short-lived at 5 x 10 –25 seconds. Produced only in very high-energy collisions in a particle accelerator or cosmic ray collisions in the upper atmosphere.
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Density is important! The yellow curve represents a closed, high density Universe which expands for several billion years, then ultimately turns around and collapses under its own weight. The green curve represents a flat, critical density Universe in which the expansion rate continually slows down. The blue curve shows an open, low density Universe whose expansion is also slowing down, but not as much as the previous two because the pull of gravity is not as strong. The red curve shows a Universe in which there is a large fraction of dark energy – a combination of pressure and energy density – which is causing the expansion of the Universe to speed up. There is growing evidence that our Universe is following the red curve.
Neutrinos
Beta-endorphin – natural opioid neurotransmitter peptide that acts like morphine.
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Higgs Boson A product of the quantum excitation of the Higgs Field. A predicted part of the Standard Model, the Higgs Field exists throughout spacetime and lends mass to fundamental particles. Huge energies are required to produce it: it has a mass of over 130 protons.
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Tau A short-lived lepton particle (2.9 x 10 –13 seconds), it is negatively charged. It is almost 3,500 times more massive than an electron
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Now
10 Billions of years
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Life