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Asked by fabrywakley to Ben, Clare, Ezzy, Mario, Sam on 11 Mar 2012.
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Mario Campanelli answered on 9 Mar 2012:
do you mean dark matter? well, we do not know…
the reason we think it is there is that we see that the orbital velocities of galaxies are not compatible with what we see, namely that their mass is all concentrated in the center, but with a much more spread-out distribution. Dark matter could be due to unknown astrophysical objects, or new kind of heavy particles; in that case, yes we could see them in our detectors
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Clare Burrage answered on 11 Mar 2012:
I’m not sure what you mean by dark dust. Maybe you mean dark matter, but if you don’t please ask again.
When we look at other galaxies in our universe we can see them rotating, but the stars at the edges of the galaxies are travelling much faster than we think they should be, based on our theories of physics and all the matter (stars and gas) that we can see in the galaxy. To explain what we see we need either a new theory of gravity or to add some new matter that we can’t see into the galaxy. Most scientist now prefer the second option, we add some new matter into the galaxy and this is what we call dark matter. But we don’t know very much about what it is, other than that we can’t see it.
There are experiments trying to detect dark matter. They look for collisions between dark matter and ordinary particles, which would happen very rarely. We can’t see the dark matter, but we can see its effects on the particles it knocks into. These experiments are buried deep underground where things are very quiet and so the experiment can be very sensitive.
I think, though, that until we know more about what dark matter is we won’t be able to try to trap it in our labs. -
Elizabeth Pearson answered on 11 Mar 2012:
I look at cosmic dust in the universe. It’s not dark matter, which I think is what you mean, but it’s still interesting.
If you just look with optical telescopes dust just gets in the way and blocks out all the light from stars behind it. The only way we can see it is from the dust clouds heat, which we haven’t been able to do because the atmosphere soaks up a lot of infra-red radiation. Now we have a giant, very fancy thermal camera in space called Herschel and we can look at the dust and we can see much further into the universe (and back in time) than we could before.
We do have a good idea what cosmic dust is. People try to study it in the lab, but it’s a bit tricky. In space it’s in a perfect vacuum, free floating with no gravity. This is quite hard to replicate, but they do try. Mostly it’s grains of silicon, oxygen and carbon based grains up to 0.1 mm, all the bits of fluff left over after a supernova that have clumped together. Very different to the kind you sweep under the sofa!
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