This is big news, no doubt, but it seems like they're being a bit careless with headlines like "NASA Finds Direct Proof of Dark Matter."
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"Little is known about it; all that the numerous searches for dark matter particles have done is rule out various hypotheses, but there have never been any 'positive' results," said Markevitch.
This remains true. The direct detection of a particle of dark matter will certainly qualify as "direct proof of dark matter." This particular discovery, while extremely significant, is better described by the sentence toward the end of the second article:
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For the first time in history, astronomers caught dark matter at work.
A lot of people are saying this is proof of dark matter (and by that I'm assuming they mean some new kind of nonbaronic matter, as is usually meant) but I'm not so sure this line is true:
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Despite considerable evidence for dark matter, some scientists have proposed alternative theories for gravity where it is stronger on intergalactic scales than predicted by Newton and Einstein, removing the need for dark matter. However, such theories cannot explain the observed effects of this collision.
Even if it turns out that current modified gravity models can't account for this that doesn't necessarily mean no such model can
ever deal with this. I'll admit those ideas will start to look pretty unappealing (and a lot of people already found them unappealing as it is) if they have to keep on jumping through hoops and piling on complexities to keep working but I'm just not convinced at this point that this proves they can't work.
This is just another piece in the puzzle--a big one--not the final one by a long shot.