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Dark Matter (mander.xyz)

submitted 1 month ago by fossilesque@mander.xyz to c/science_memes@mander.xyz

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[-] Johanno@feddit.org 18 points 1 month ago

The thing is a bit more complex.

We have a theory of the big bang,which could not be disproven yet.

This theory would expect that our current universe would slow down in expansion.

However our observations show that expansion is accelerating.

Introduce dark energy. It is supposed the mystical force which expands the universe.

(not sure if I get the following right) This force acts on every atom. But it is weak on its own, even the weak gravitational force is stronger. However over great distance the force is bigger than the gravitation.

Then there is dark mater. Our visible universe was made into a simulation where they use all the physics we know of to simulate the currently visible situation. However the simulation did not behave like what we see. It only works when they added a lot of matter. But matter that you can't see? "dark matter"

Then they formed new theories that both dark matter and energy needed to exist or our universe wouldn't look like it looks today.

Now I am no scientists but it is possible that we are completely wrong here.

[-] rbesfe@lemmy.ca 19 points 1 month ago* (last edited 1 month ago)

Dark matter isn't based on simulations, it's entirely observational.

We observe here that matter generates a gravitational force proportional to the amount of matter present, and we know that to an extreme degree of precision, but when we look at big things like galaxies the force required to shape and move them in the ways we observe would require more matter than we observe within them.

[-] sonori@beehaw.org 7 points 1 month ago

To expand on this, we also have mapped it out and know that the amount of dark matter varies wildly between galaxies, with some having basically none while others have far more dark matter than observable matter in them. There’s also a lot of stuff with the early universe that only works if you have something with gravity that doesn’t otherwise interact significantly with matter.

As Angela Collier puts it, dark matter is not a theory, it is a set of observations.

[-] meanmon13@lemmy.zip 14 points 1 month ago* (last edited 1 month ago)

I'm pretty sure that dark matter/energy is just this generation's aether.

[-] ShaunaTheDead@fedia.io 20 points 1 month ago

"dark" in scientific terms just means unexplained. We're very, very, very, and I cannot stress this enough... VERY sure that dark matter and dark energy exist, but they will remain "dark" until we discover what they are/what's causing the effects that we see. Aether was just unfounded non-sense that was based on practically nothing.

[-] mindbleach@sh.itjust.works 8 points 1 month ago

Aethyr was a reasonable insistence that light can't be half as fucky as we now know it is.

[-] ShaunaTheDead@fedia.io 3 points 1 month ago

Light is pretty fucky. Like taking the shortest route to it's target through TIME! What the fuck light?!

[-] mindbleach@sh.itjust.works 1 points 1 month ago

Not necessarily forward, maybe.

[-] Tlaloc_Temporal@lemmy.ca 2 points 1 month ago

I'll agree on Dark Matter, things like the Bullet Cluster need something more than modifyed gravity, but I'm not so sure about Dark Energy. As far as I know, Dark Energy is the difference in the energy we measure in space and the energy necessary to fuel the acceleration of expansion. This whole idea could change radically with a new understanding of space or the nature of the universe.

Dark Matter is a relatively known unknown; we know there must be some thing here, and are nearly certain it's more than just a force. Dark Energy is an unknown unknown; something doesn't match up, but we don't know what.

[-] ShaunaTheDead@fedia.io 2 points 1 month ago

I saw a paper on here recently that basically said they've explained dark energy through what they called "cosmological coupling" of black holes. Basically, black holes absorb space over time, and since space has a base level of energy and energy is kind of a form of mass then the black holes are gaining mass over time and so they are less massive in the past than they are today. I don't 100% understand why that explains dark energy, but it is a very new paper and as far as I know hasn't been peer reviewed yet, so who knows!

Here's the paper: https://www.ifa.hawaii.edu/2023/02/first-observational-evidence-linking-black-holes-to-dark-energy/

[-] Tlaloc_Temporal@lemmy.ca 1 points 1 month ago* (last edited 1 month ago)

Interesting. I've heard about cosmological coupling before, I wonder if PBS Spacetime or Dr. Becky have mentioned this theory yet.

Showing that BH energy density stays constant, like the proposed cosmological constant, is quite interesting, but I also don't understand the leap to how that drives expansion. If vacuum energy was everywhere, I can see how that would push things apart and push harder as space grew, but if vacuum energy exists in BHs I can't make the connection to a repulsive force. Perhaps this is a event horizon resonance mode or something? Where event horizons exists for everything, and they're size and relativistic motion press upon the universe? I don't know.

Wikipedia seems to have this paper's theory listed already (here), though reception seems mixed.

EDIT: Yes, I knew I'd heard of this before. Both PBS Spacetime and Dr. Becky have fairly technical videos on this. Dr. Becky in particular does a great analysis of the paper, as the growth of supermassive BHs is her specialty.

Also, both the proposed Dark Energy and these cosmologically coupled BHs end up exibiting negative pressure in their energy. This is how more energy = more expansion. Exactly how that happens is a complicated relativistic relationship, but it's not unique to this paper.

[-] ShaunaTheDead@fedia.io 1 points 1 month ago

Yeah I figured it maybe also had something to do with the distribution of matter throughout the universe. We assumed when we made predictions of the distant past that the supermassive black holes at the center of galaxies were the same mass as they are today, but if they were less massive then it might help explain why black holes didn't gather as much material into it's orbit as we would have thought.

I think you're right though that it has more to do with the negative pressure that space and the black holes seem to exert although I must admit I don't really understand what that means or how you would get a negative pressure from a black hole or from space.

[-] pigup@lemmy.world 7 points 1 month ago* (last edited 1 month ago)

Ummm... Only thing we're sure of is that those gravitational effects exist. Dark matter and dark energy are theorized to explain the real gravitational effects that we don't understand. We don't "know of their existence," there are other theories to explain the gravitational effects.

[-] kraftpudding@lemmy.world 5 points 1 month ago* (last edited 1 month ago)

They refuse

Miss me with that light shit

[-] wonderfulvoltaire@lemmy.world 2 points 1 month ago

Basically the force

[-] HawlSera@lemm.ee 1 points 1 month ago

At this point there's more evidence for psychic powers than Dark Matter, that is not praise for Parapsychology but rather condemnation of "Bro, it's real! Source: Trust me!" being Dark Matter's only evidence.