this post was submitted on 17 Mar 2024
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[–] [email protected] 77 points 11 months ago* (last edited 11 months ago) (11 children)

This model combines two ideasβ€”about how the forces of nature decrease over cosmic time and about light losing energy when it travels a long distance. It's been tested and has been shown to match up with several observations, such as about how galaxies are spread out and how light from the early universe has evolved.

These hypotheses never seem to stand up to rigorous analysis. Still, always welcome the discussion.

[–] [email protected] 24 points 11 months ago (9 children)

Absolutely. On the one hand, having ~26% of the known universe consisting of a substance that we cannot detect directly leaves a lot of questions open. On the other hand; dark matter is postulated because otherwise things like galaxy rotation curves don't match what we believe they should be from general relativity, and this theory doesn't seem to address that.

https://en.wikipedia.org/wiki/Bullet_Cluster#Significance_to_dark_matter

Also, light 'losing energy' would be a violation of the first law of thermodynamics, unless it loses it 'to' somewhere.

[–] bouh 1 points 11 months ago (1 children)

At some point we may have to review some theories though. The idea that light would lose energy over extra long distances at least makes sense unlike some kind of latter that we can't detect and we can't figure out why it would either still be there but not more than it is.

This is kind of how time was supposed to be absolute. Einstein never received a Nobel for the theory of relativity because of how suspicious it seemed at the time.

[–] SpacetimeMachine 5 points 11 months ago (1 children)

There being a substance that does not interact with light at all doesn't seem that far fetched to me. There is nothing in the laws of the universe that says "Humans must be able to detect everything that exists because otherwise it wouldn't make sense."

It feels entirely possible that we won't be able to detect dark matter through any conventional means that we currently have.

[–] bouh -2 points 11 months ago (1 children)

It's not about humans. It's about science. "there is dark matter that doesn't interact with matter" can as well be "there is magic, and I cannot be proven wrong".

[–] [email protected] 3 points 11 months ago (1 children)

Dark matter does interact with matter, though: it interacts gravitationally. It just does not interact in other ways (that we know of yet). All you would have to do to disprove the existence of dark matter is to show that some things interact with it gravitationally but others don't. However, this is not what we see; what we actually see is a whole bunch of separate things that all experience the effect of the existence of dark matter in the same way. It's effectiveness as an explanation in this regard is exactly what makes it so difficult to dethrone.

[–] bouh -2 points 11 months ago (1 children)

Dark matter is exactly like adding a constant to your equation so that it fits the numbers.

[–] [email protected] 3 points 11 months ago

If by "constant" you mean "3D distribution that explains not just one equation but lots of separate observations", then sure, it's just like that.

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