Dark Matter Exists | Cosmic Variance


There’s a superb post up on the Cosmic Variance blog about the paper released today that details new observations which conclusively prove the existence of Dark Matter. (Dark Matter is material that doesn’t emit or absorb electro-magnetic radiation so we can’t “see” it, but which does create gravitational fields which we can detect…

“Dark matter, by hypothesis, doesn’t interact directly with ordinary matter, so we can imagine moving the ordinary stuff while leaving the dark stuff behind. If we then check back and determine where the gravity is, it should be pointing either at the left-behind dark matter (if there is such a thing) or still at the ordinary matter (if not).

Happily, the universe has done exactly this for us. In the Bullet Cluster, more formally known as 1E 0657-56, we actually find two clusters of galaxies that have (relatively) recently passed right through each other. It turns out that the large majority (about 90%) of ordinary matter in a cluster is not in the galaxies themselves, but in hot X-ray emitting intergalactic gas. As the two clusters passed through each other, the hot gas in each smacked into the gas in the other, while the individual galaxies and the dark matter (presumed to be collisionless) passed right through. […] As hinted at in last week’s NASA media advisory, astrophysicists led by Doug Clowe (Arizona) and Maxim Markevitch (CfA) have now compared images of the gas obtained by the Chandra X-ray telescope to ‘maps’ of the gravitational field deduced from weak lensing observations. […] And the answer is: there’s definitely dark matter there!”

The authors of the blog are reputable professional astrophysicists and cosmologists. This article is the best general treatment of the news that I’ve seen posted online. (This is what blogging ought to be!)

The upshot is that we have proof that we have until now only known of the tiniest part of the material that makes up our Universe. There’s much more out there. We now know it’s out there. We have no idea what it is. Cool huh?

Read the rest here: Dark Matter Exists | Cosmic Variance

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  1. John Woolfolk Cruse says

    I know that this is a very silly question, but is dark matter a 21st century equivalent of the luminous Ether?

  2. It’s not a silly question at all. Lots of people, myself included, wondered the same thing. But assuming this result described in the article verifies, we don’t have to wonder any more.
    Unlike the luminous Ether, we have apparently directly detected dark matter. So we’re going to have re-do our models to make sure that they now include its existence.
    It’s not too big a deal in cosmology because cosmological models have been including the existence of dark matter for a very long time (since it was first detected in the anomalies of galactic rotation curves). There are still lots of questions to answer – whether we must include hot or cold versions of dark matter, whether there is still some role that a modified version of gravity (if it exists) will play, and just what or where the “dark energy” is coming from…

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