• Question: do you beleive in dark matter?

    Asked by chrisvw to Adam, Catherine, Karen, Leila, Nazim on 10 Mar 2012.
    • Photo: Karen Masters

      Karen Masters answered on 10 Mar 2012:

      There’s definitely something in galaxies and clusters of galaxies which has gravity but we can’t otherwise see. I’ve seen that data and done that maths for myself.

      I also find the arguments about nucleosynthesis quite convincing – turns out the details of how much of the different elements were formed just after the Big Bang depend on the amount of normal matter in the Universe. And the data tells us that that amount is much less than what we know is there from its gravity – so there is some matter out there which has gravity and which isn’t normal matter (like atoms etc).

      That’s all dark matter is – a name for our ignorance about what explains the difference between the matter we detect by gravity, and the matter we can see.

    • Photo: Adam Stevens

      Adam Stevens answered on 10 Mar 2012:

      I agree with Karen – dark matter is a bad name, because it just means that there’s stuff that we don’t understand and can’t see properly. You could say it was a metaphor for the gaps in our scientific knowledge, but saying that wouldn’t make you any friends at party.

    • Photo: Nazim Bharmal

      Nazim Bharmal answered on 10 Mar 2012:

      As a scientist, we are taught to look at the evidence for something (like how far away a star really is, or is climate change caused by humans) and then we say how probable it is: some things are really likely like climate change.

      Dark matter is something for which we have lots of good evidence, so yes, I do believe in it. But the more interesting question is: what is dark matter? And why is there so much of it? And a really interesting question is: why is there any normal matter, the atoms that make up us and the stars and galaxies that we can see with our eyes? That is a real puzzle scientist are also trying to solve.

    • Photo: Leila Battison

      Leila Battison answered on 10 Mar 2012:

      Like the others, I believe in dark matter as a *something* that can explain why galaxies work the way they do, and all the information we have collected from the instruments observing the universe.

      I think ‘believe’ is the wrong word really, because it implies a faith in that particular conclusion. Scientists don’t generally ‘believe’ in theories, they either accept the evidence that supports them, or they think the evidence that doesn’t support them is more important, and so reject that as a theory (ideally coming up with a better one in its place). The idea of dark matter is, at the moment, the best theory that fits with the evidence, even if it’s not a very complete theory!

      Some scientists are trying to work out what dark matter is and how it works by running complicated computer models for the formation of galaxies from clouds of gas in space. Doing this, they can work out exactly the properties of this mysterious substance, and try to work out a way of working out what it is.

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