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from the Now-you-see-it-now-you-don't-because-it's-dark? dept.
A galaxy has been found containing no dark matter, but that proves dark matter is real?
A distant galaxy that appears completely devoid of dark matter has baffled astronomers and deepened the mystery of the universe's most elusive substance.
[...] In the Milky Way there is about 30 times more dark matter than normal matter. The latest observations focused on an ultra-diffuse galaxy – ghostly galaxies that are large but have hardly any stars – called NGC 1052-DF2.
The team tracked the motions of 10 bright star clusters and found that they were travelling way below the velocities expected. "They basically look like they're standing still," said van Dokkum.
The velocities gave an upper estimate for the galactic mass of 400 times lower than expected. "If there is any dark matter at all, it's very little," van Dokkum explained. "The stars in the galaxy can account for all of the mass, and there doesn't seem to be any room for dark matter."
Paradoxically, the authors said the discovery of a galaxy without dark matter counts as evidence that it probably does exist. A competing explanation for the fast-orbiting stars is that the way gravity drops off with distance has been misunderstood – but if this were the case, all galaxies should follow the same pattern.
https://www.theguardian.com/science/2018/mar/28/galaxy-without-any-dark-matter-baffles-astronomers. The findings are published in the journal Nature.
(Score: 3, Interesting) by HiThere on Saturday March 31 2018, @05:08PM
The problem here is "What do you mean 'matter'?". All we know is that *something* is acting on gravity the way matter would. That's something that we usually attribute to matter, but we don't see it, so we're calling it dark matter until we detect something. Or come up with a better explanatory theory.
The thing is, just because is has a name doesn't say much about it. I could take a bagel and name it "hopscotch", but that wouldn't make it jump. All that we really "know" is a perturbation in gravity.
Even that's overstating the case, but here we're starting to get closer to psychology than physics. Just accept that actual knowledge is impossible, and the best we can do is make estimates worth acting on. Normal English usage doesn't map well onto either physics or psychology, but the words we use shape the thoughts we communicate. Within your own mind you've got lots of things that modify the words you use, attached images, feelings, perhaps even sub-text dialogs. Those get stripped off when you talk to someone else. So the Whorfian Hypothesis is true for spoken, and even more written, thoughts, even though the strong form isn't true for personal thought.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.