this post was submitted on 14 Oct 2024
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This headline is pretty dumb. Dark matter is not a myth, it's clearly there in the data, so it exists for sure. Now the name might be completely wrong as it's neither dark and may not be matter, but it still exists. We should have just called it Pete or something, so the name wouldn't imply anything about it's properties. But the press always seem to think dark matter is something thought up to fix something, but that's not the case at all.
The numbers in the data don't match up and the difference is what's labeled as "Dark matter", simply putting another label on it or dismissing it doesn't fix the underlying data not matching up. And it isn't like a fault in the data, we've seen it in ALL the data, no matter what you look at or how you look at it, the signs of dark matter can be seen.
I don’t know, so just asking but you say dark matter is not a myth, but the paper’s author says,
(emphasis added) Is this one of those situations where you agree but it sounds like you don’t?
Well that's a perfectly valid question, thank you for asking. I think the key word here is "direct". He is totally right, there is no direct evidence of dark matter, regardless of what it exactly is. We have a bunch of observations that don't match up with our expectations and models. Where the difference could be explained by adding non EM interacting matter, it's categorized as being caused by dark matter.
Great examples for this are the rotation curves of galaxies and the Bullet cluster, but there are others. The interesting thing about the rotation curves is they are all different. Not only different from our expectations, but also different from each other. We can clearly see the rotations don't match up, but we can't see why this would be the case. Since they differ from each other, it seems like a physical thing which is different in each galaxy, rather the some fundamental systematic difference in reality from our models. With the Bullet cluster the same thing, looking at that thing it's clear something really weird is going on. It's hard to figure out what is happening, but it would be explained by some non EM interacting material, so it gets put down to dark matter.
But neither of these examples are direct observations of dark matter. Dark matter doesn't interact with em, but does seem to interact gravitationally. Since almost all of our observations of the universe are using EM radiation. Be it optical, ir, radio, xray etc. Since dark matter doesn't interact with EM seemingly in any way, we can't observe it. We can only model it based on things we can see.
So in that way the author is kinda reasoning in circles, there is no direct evidence because by definition we can't directly observe it. And I feel like inferring the existence of something based on other observations is perfectly valid. For example elements on the periodic table and the planet Neptune are well known examples (among many others) of something that fell out of models and were later confirmed. And since the observations don't match up, we know for sure there is something there regardless of what label gets put on it. It even might turn out there are several things combined that have the end result we see, although Occam's razor would have something to say about that.
There are several things we are trying to learn more about dark matter. For example giant gravitational wave detectors can help to figure some stuff out. But great progress is also made in WIMP detection systems. I feel both of these paths would qualify as "direct" detection, if any of these pan out.
Great answer, thanks!