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Asked by rowellhayes to Ben, Clare, Ezzy, Mario, Sam on 15 Mar 2012. This question was also asked by westmorepenney.
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Clare Burrage answered on 14 Mar 2012:
All of the particles and atoms that we know of, and all of the stars and planets and dust that we can see only make up 4% of our universe!
The rest is made up of two things that we call dark matter and dark energy. We really don’t know very much about what these substances are, but without them we can’t explain why our universe is behaving in the way it is. We call them both ‘dark’ because they don’t emit light, and so we can’t see them with our telescopes.
Dark matter lives inside galaxies, and we need it to explain how fast the stars in the galaxy are rotating around the center (they are going a lot faster than we think they should – especially at the edges of the galaxy!). Dark matter makes up 22% of our universe.
Dark energy is everywhere in our universe, and we need it to explain why the expansion of the universe is speeding up. Dark energy makes up 74% of our universe.
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Elizabeth Pearson answered on 15 Mar 2012:
There’s matter, stuff, which makes up around 4%.
Then you have dark matter, about 22%. We know about that because we don’t see enough to keep galaxies together.
Finally there’s dark energy to make up the rest. For some reason the expansion of the universe is speeding up when we always thought it should be slowing down. To explain this people suggested dark energy.
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Mario Campanelli answered on 15 Mar 2012:
protons, nucleons and electrons, as well as photons (light), and electron neutrinos constitute the vast majority of the observed universe, since the average temperature of the universe is -270C, and only the lighters particles of each kind can survive
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