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Asked by olives to Karen, Adam, Catherine, Leila, Nazim on 16 Mar 2012. This question was also asked by balletshoes1998.
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Karen Masters answered on 15 Mar 2012:
In some sense yes. We use dead stars – which explode in a particular kind of supernove which has a predictable brightness to estimate distances and then track how the universe has been expanding.
We can only learn about what we can see (or discover by it’s effect on things we see). And mostly what we can see is stars….
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Leila Battison answered on 16 Mar 2012:
Partly yes, but the universe in general holds lots of clues about its history. When we look at galaxies we can see they are moving away from us in all directions which must mean the universe is expanding.
If we look into the furthest reaches of space, we can see the cosmic microwave backgroud, which is a little bit of energy left over from the big bang.
Most of the stars we see are younger than the universe, so they can only tell a part of the story.
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Adam Stevens answered on 16 Mar 2012:
They’re the main things we have to look at past our solar system, so we have to work out ways we can get information about the history of the universe from them. There’s also things like gas clouds or solar nebulae, but often it’s the stars that are the most interesting.
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Nazim Bharmal answered on 20 Mar 2012:
Yes, in principle, partly by what the stars are made of and partly by how far away they are and how they are moving.
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