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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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Where was dark energy debunked?
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If you consider a simulation 'debunking'. Given that it was only posited to exist due to mathematical calculations, that's good enough for me.
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I'm not an expert, but I can't help thinking that dark matter and dark energy are the equivalent of aether from when we did not understand electromagnetism, and the current state of our knowledge (relativity, quantum mechanics, etc) is just an intermediate step in the full understanding, and future physicists will laugh at us for this dark matter thing.
I'll mansplain it 4u: The intergalactic void is not at 0K temp. So, there's some energy there. Since it's so vast, there's pretty much energy. Now and then, this energy is quantized into a photon buzzing off in some direction. These photons sometimes disappears into the void again, or goes on and will eventually push on a galaxy. This stream of EM radiation is anti-gravity (also called dark enery). What we usually call gravity is the abscence of this radiation, its shadow. The pictures they have produced shows this shadow between galaxies. Such shadows is also what keeps the moon in orbit around the earth and the Earth in orbit around the sun. The need for dark matter comes from the fact that this field (anti-gravity) is weaker inside the galaxy where we are and can measure it. It's much stronger at the outskirts of the galaxy where it hits at full force. Comprende? :)
There has never been what I would consider "evidence" of dark matter, just evidence of a lack of understanding of matter, gravity, or space.
Of course you don't mention what it would take for you to consider evidence, your mind is clearly already made up from putting 'evidence' in scare quotes. But in any case - go ahead and explain the bullet cluster then. I expect your take on things will be fascinating, it might even clear all this up for us.
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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?
Given the vast distances involved, this is more like plus-que-parfait.
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Personally I think that the galaxy rotation problem, and consequently the bullet cluster problem, is a relativistic effect and no dark matter exists.
I.e. the existing visible matter warps space in such a way that it increases the rotation speed of the galaxy.
Any mass in space warps the space around it. It is proven again and again, with gravitational waves being the latest proof.
So a very simple explanation is gravity from the mass of the galaxy warps space in such a way that mass around it seems sped up.
Dark matter does not exist, Dark matter is just the name of a theory that scientists have come up with to describe some anomalous gravity data they got when they looked at how the universe was put together mainly how galaxies interact with each other.
As they could see something is interacting with the galaxies yet they could not directly detect what is causing the interaction they called it dark and as the general consensus is that in order for this amount of interaction it has to come from somewhere and the only stuff in the universe that we currently know can interact with gravity on this scale is matter the theory is that some kind of undetectable matter exists so they called it dark matter but the theory does allow for other kinds of causes of the interaction. Its an ongoing evolving theory like all theories.
Talking about dark matter like it is actual stuff is the same when people talk about anonymous like its an actual group instead of a descriptor or talking about the public when it could mean anyone.
The theory and picture is till cool though.
DE and DM are observations.
No, they aren't. They're unsupported ideas about how to explain certain observations. And as soon as they make testable predictions which turn out to actually be the case, they can be science.
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In the Einstein universe, are they (matter & energy) not simply different states of the same thing?
Yes if one isn't being super pedantic. Your "states" analogy is reasonable. To say matter and energy are the same thing isn't exactly accurate but it's good enough for all but the most picky of purposes. But applying that relationship to so called dark matter and dark energy is a little bit fraught because we don't actually know what dark matter and dark energy are. As a result you are understandably conflating some things.
The terms "dark matter" and "dark energy" are sort of placeholder terms to explain some phenomena that we don't entirely understand yet and they are more marketing terms than precise terms of art. We don't actually know for certain that what we call "dark matter" is actually matter or that "dark energy" is actually energy. We just have some observations we haven't been able to adequately explain so we needed some short hand terms to explain what we are seeing in terms of the models we have. One of three things is happening. Either we are seeing something new, we are making measurement errors, or our models are wrong. Possibly some combination of all three.
Dark matter arises out of the fact that we see some observations that don't make sense based on the amount of baryonic ("normal") matter we can quantify. Our models of how gravity works tell us that for our observations to match our models there must be a lot more matter than we can see presuming our models are correct. So called dark energy arises out of our observations and measurements of the rate of expansion of the universe but it's even less well understood than dark matter.
Being that mass and energy rarely appear separately, would not the presence of 'dark energy' strongly infer the existence of 'dark matter'?
Mass is not the same thing as matter. You can have matter without mass such as with a photon. Mass is a property in some forms of matter, all of which move slower than c (the speed of light).
Dark matter does not exist
Dark matter certainly might exist. Or it might be measurement error. Or it might be model flaws. We simply aren't sure at this point. No one can say with any certainty that dark matter does not exist because the data isn't conclusive either way. Yes "dark matter" is something of a placeholder marketing term but it describes what appears to be a very real phenomena. There is some reasonable evidence to suggest dark matter is a real thing but none of it is conclusive at present. We have considerable confidence in some of our measurements so we have good reason to believe that measurement error is the least likely of the three possibilities. I've never heard a slam dunk explanation as to why we should favor dark matter being real over model error but I trust the professional physicists to sort it out in due course.
Dark matter is just the name of a theory that scientists have come up with to describe some anomalous gravity data they got when they looked at how the universe was put together mainly how galaxies interact with each other.
And that theory posits that there may be some form of matter we currently cannot directly observe. We don't know if that is the actual explanation but it's a necessity under current models if we presume they are correct.
Why would future physicists laugh at us. Anyone with any understanding doesn't laugh at aether as it was a good, though wrong, explanation of the properties of light and seemed more believable then the idea of an absolute speed limit and light traveling at the same speed no matter your frame of reference, which really did sound like a fantasy.
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but i thought the movement of galaxies WAS the expansion of the universe.
The movement of the galaxies can help us measure and observe the expansion of the universe but isn't the expansion itself. To use a simpler example, imagine a galaxy is an ant and that ant is standing on the surface of a balloon. The ant can walk around the balloon which is equivalent to the galaxies moving through space. Now inflate the balloon. The ant is moved because space (the balloon surface in this example) became larger but it wasn't because the ant itself moved. What happened is space expanded and everything in space moves a bit further apart as a result. But those objects in space (ants) are still free to move through space so the expansion of space doesn't explain everything we see by itself.
What we see is the galaxies moving (mostly) away from each other through space AND we see space expanding because they are moving away from each other faster than can be explained by simple movement through space. Space can expand faster than the speed of light because c is only the speed limit for matter moving through space. Space itself can expand arbitrarily fast as far as we know.
Galaxy rotation curves aren't related to the Bullet Cluster evidence. The Bullet Cluster shows gravitational lensing occurring where there is a lack of visible normal matter. What happened was that the two clusters collided and the regular matter, which can experience electromagnetic forces, gets mostly stopped in the middle of the collision due to friction of interstellar gas and dust. The anomalous lensing is occurring much further out do to the fact that dark matter just keeps going straight through and past the collision since it doesn't feel friction.
There appears to be a whole anti-DM subculture.
I don't think there are "anti-DM" people here outside of maybe a few wingnuts. There are lots of pro-evidence people here, myself included. The problem with dark matter is that there are at least three possible explanations, none of which have been conclusively ruled out. 1) Dark matter is indeed some form of matter as yet not fully understood, 2) Our measurements are in error somehow, and 3) our models for forces (gravity) are incorrect somehow.
I have a minor in applied physics so I'm not entirely uninformed though I'm not an expert. But I have yet to hear a single professional physicist clearly explain why we should favor the existence of dark matter as a preferable explanation to error in measurements or modeling errors. They seem to be strongly favoring dark matter being a real thing but all our "evidence" for it is indirect. It's perfectly reasonable that it might be explained by a better model similar to how relativity supplanted Newtonian mechanics. Invoking some form of exotic matter is perfectly reasonable too but the problem is that we have precisely zero direct measurements of such a thing. Until we do it's an open question.
That was a solid argument about 15 years ago, and scientists were making it. Then we launched the WMAP satellite, and measured the CMBR in great detail. The early universe was show to contain cold dark matter in the same proportion needed to explain galactic rotation, to two significant digits. (Cosmology with significant digits! Welcome to the future.)
There were many theories. One successfully predicted the next major observation, the others didn't. That's how science picks a winner.
Dark matter is still dark though - there are a great many theories about what it actually is, and little evidence that would pick a winner from them.
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