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Scientists Capture First Image of Dark Matter Web (inhabitat.com)
Kristine Lofgren writes: Scientists have long suspected that the universe is woven together by a vast cosmic connector but, until now, they couldn't prove it. Now, for the first time ever, scientists have captured an image of a dark matter bridge, confirming the theory that galaxies are held together by a cosmic web. Using a technique called weak gravitational lensing, researchers were able to identify distortions of distant galaxies as they are influenced by a large, unseen mass -- in this case, a web of dark matter. In order to create a composite image that shows the dark matter web, scientists had to look at more than 23,000 galaxy pairs located 4.5 billion light-years away. "Results show the dark matter filament bridge is strongest between systems less than 40 million light years apart," reports Phys.Org. The findings have been published in the journal Monthly Notices of the Royal Astronomical Society.
From TFA, "...researchers were able to identify distortions of distant galaxies as they are influenced by a large, unseen mass, such as dark matter." That means that what they have are images that appear to imply the existence of Dark Matter, and are hard to explain any other way, not that the images actually show us Dark Matter. That doesn't mean that it doesn't demonstrate that Dark Matter exists, it's just that the images aren't as cut and dried as the article's headline implied. It also means that there's still wiggle room for those who are certain that it doesn't exist. Still, it's a great step in the right direction.
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Oh dear, you've been studying science from the Daily Mail again, haven't you? There is most certainly an anomaly. We can avoid giving it a name: maybe call it "You-Know-What", or "The Nameless Anomaly". Or we can give it a name, perhaps one that most closely matches the characteristics of the anomaly - it appears like it's some kind of matter we can't see: we could call it Invisible Matter That Isn't Lit Up, or "The Shitz" or something. Whether dark matter proves to be a misapplication of a theoretical model, or actually a new form of matter ... dark matter is what everyone calls it. It's dark, and it appears to behave most like matter. It's a good name.
Some people are insufficiently discerning that they think this means we actually know what it is. But really, we just have a set of properties of the anomaly. I'm sure that if you can bring anyhting to the fight, then you'll be welcome to do your own research, and if you can help fill the "lack of understanding" hole, then fine. But I suspect you're just posting here to have a go at people who are actually getting on with it - and that's quite a well-known phenomenon ("putting them down") commonly associated with weaknesses in the person doing it. I'm sure that doesn't apply to you, though?
I have a PhD in theoretical physics. Not in cosmology, but I have some contact with people who do work on it.
So, 2) is astronomically unlikely. The experimental evidence comes from multiple independent sources spanning decades. It consists of simple things such as measuring the rotational speed of galaxies and more sophisticated measurements such as anisotropies in the cosmic microwave background. If you are willing to doubt this kind of evidence you might as well doubt GR itself.
As for 3), everyone and his dog likes to propose modified theories of gravity that would do away with dark matter. The problem is that reconciling them with the mountain of evidence for dark matter is really tough. The most popular candidates, MOND and entropic gravity are far from being able to do it. Until they do, we're stuck with 1).
entropy happens