
New Hubble data suggests an ingredient missing from current dark matter theories - dnetesn
https://phys.org/news/2020-09-hubble-ingredient-current-dark-theories.html
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cozzyd
Here's the arXiv preprint:
[https://arxiv.org/abs/2009.04471](https://arxiv.org/abs/2009.04471)

As I understand, they see a discrepancy between simulation and observation of
some lensing observables. Could be something wrong with the calculation of the
observables, something wrong with the implementation of the simulations, or
(the exciting bit) with the physics put into the simulations. As a complete
non-expert on lensing observables and cosmological simulations, I'd guess it's
one of the first two. As mentioned in the text, there are many other
discrepancies between observations and simulations that are still unresolved.
This adds to that list.

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noizejoy
I’m not sure I understand the difference between “additional ingredient” and
“a higher concentration of”

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T-A
Dark matter models predict how the stuff is supposed to be distributed.

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dogma1138
Not all, LCDM does or can at least predict distribution, primordial/micro
black holes, MACHO's CBM etc. don't but then most of them rely on the same
distribution as normal matter (because for the most part they are just that,
as anything that falls within the existing standard model is well normal
matter).

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OpticalWindows
Will the James Webb telescope help detail such phenomenon better than the
hubble?

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Already__Taken
If you can do it with infrared then yes is the JWT rule of thumb.

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andrewflnr
The current top-level comments are infuriating. You demand that scientists be
honest, then accuse them of all-out fraud when they admit they have questions,
secure in your ignorance of the things they actually have figured out and
tried to tell you over and over again. You are more concerned with feeling
smart and skeptical than actually learning. You are the reason we can't have
nice things.

~~~
exmadscientist
For some reason, dark matter brings out the crazies. It was true when I worked
in physics, and it's still true now.

People need to understand that physicists do NOT consider dark matter to be
settled, in any sense! The experiments are not done to polish up any theory...
they're done because all of the theories are awful, and guidance from
observations is _necessary_ for further progress.

I also still fully stand by my previous comment on this subject:
[https://news.ycombinator.com/item?id=23666620](https://news.ycombinator.com/item?id=23666620)

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andrewflnr
I suspect the fact that you can't observe dark matter directly, but physicists
all seem to promote it, enables a combination of (at least superficially)
reasonable empirical skepticism and conspiracy-minded contrarianism to work
together. You have to expend a little bit of actual effort to see through the
logic, and if you have any inclination to believe Big Physics is lying to you,
then it's easy to just not bother. People forget that the universe does not
owe us comprehensibility.

Contrary to your linked comment, to this non-physicist, nearly all physicists
in public seem to say that, while the details are unknown, dark matter is
pretty much definitely a thing. AFAICT they're not wrong about there being
multiple lines of evidence for it. But if you mean "no one worth listening to"
says even that much, then I don't know any physicists worth listening to.

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ashildr
> but physicists all seem to promote it

It does not seem like it to me (non physicist with some physicist friends from
other fields who try to dumb down stuff to me).

In my world (SE) it seems like a proprietary binary that must be included for
the rest of an open source product describing the observable universe to work
very well. Everyone seems to hate it, but nobody wrote something better, yet.
Every competing implementation fails to work in other areas that we already
are using in production, extensively.

And when some professional, who read and understood the source code, starts
talking about it, a lot of people voice stupid ideas that they would not have
if they passed some lectures on the subject.

Edit to add: I envy physicists a little - the best thing for “them” to happen
seems to be if something does _not_ work in a very peculiar way.

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andrewflnr
Ok, but do any of them take seriously the idea that it doesn't exist at all?
It was my impression that even theories that try to modify gravity in ways
that also explain stuff like the CMB spectrum sort of end up inventing dark
matter anyway (IIRC TeVeS was the big one like that).

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dylan604
I'm waiting for the missing ingredient to be STRIIIINGS!!! Dark matter is
carried on strings that pop in and out, but only when you observe them. As
soon as you stop observing, it pops back in to keep things in equilibrium.
Next theory?

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koheripbal
I have a pet theory that repulsive and attractive forces exist at infinity at
ever increasing scales.

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WealthVsSurvive
I think the physicists are touchy about our layman's thoughts on this, and
they are correct in that there is little to no evidence to support claims like
this. However, I too, look at incompleteness, entropy, things like prime
number distribution, and chaos, and I can't help but think: it (everything)
really does seem to be destroying things only to bring them back again in a
novel form.

It's intuitive, it's not suggested by evidence, it's based in imagination
rather than reason, but I imagine the universe as a matter / energy creation
machine in which the forces that tear everything apart seem to be generative.
I think perhaps over time we will observe a correlation between the entropic
forces at the edge of the universe and the gravitational forces of dark matter
in the center of galaxies. I think dark matter is dark because its light
hasn't reached us as its trapped by gravity, yet its gravity is there. It's
new matter, and we don't know how it got there. I think we'll find the bridge
by looking into quantum mechanics, and how particles behave in relation to one
another when they're in conditions similar to those described at the point of
heat death of the universe, everything broken down, even time. When that
happens, what's the difference between any one thing and another? I'm not
entirely convinced: "well, nothing at all" is the answer. Do we know nothing
at all is stable? The big bang seems to suggest that nothing at all is
extremely unstable.

I think the physicists are touchy because imagination has replaced reasoning
in key areas. Whereas you and I would probably love to be told exactly why we
might be wrong about our crackpot musings in a field we upfront claim to know
little about.

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nynx
Honestly, I'm a little tired of the whole dark matter thing. There's no
evidence for it, and physicists keep coming up with more and more complex
models to fit the data when they don't actually understand what's going on
there.

Why haven't MOND or other theories become more popular?

Edit: MOND isn't great either - it just has a parameter that they tune until
it matches the observation.

Edit 2: I am not a physicist, I am simply a concerned citizen.

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yongjik
Honestly I'm not sure why some people oppose "dark matter" so much. We know
there's something out of ordinary, it behaves like matter, and it doesn't
interact with light (hence "dark"). Given that, "dark matter" is as
inoffensive a name as possible. People are acting like we named it
"quasiflavored eleven-dimensional supersymmetry carriers."

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daxfohl
I think it's a natural reaction after Einstein. The whole physics world was
certain about this Aether thing, and it turned out to be wrong and much more
beautifully solved by plain geometry. "Dark matter", taken at surface level,
sounds like going down the exact same rabbit hole.

There's a fundamental difference though. With dark matter, the evidence of the
stuff is much more direct and precise. We can determine the shape and
concentration of it. Aether on the other hand was a hand-wavy metaphysical
concept from the beginning. There was never any experimental evidence that
aether was a real thing; it was just a concept invented to patch up the
inherent inconsistencies in electromagnetic theory near the speed of light.

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duutfhhh
Or spacetime is that aether. This is like some dusty books have been claiming
that there's an invisible fluid substance around us that supports life, then
when science discovers oxygen, it says "See? There is no invisible ether or
anything like that around us, only atoms."

