B Does Dark Matter Have a Periodic Table?

[saddlestone-man]

TL;DR Summary

Is there any theory for the structure of Dark Matter?

Hello All

There is much discussion on the existence of Dark Matter.

Should we think of Dark Matter as having macro structure, ie comprising elementary particles, leading to atoms and a Dark Periodic Table?

best regards ... Stef

 

[weirdoguy]

Should we think of Dark Matter as having macro structure, ie comprising elementary particles, leading to atoms and a Dark Periodic Table?

No because dark matter does not interact electromagnetically (per definition) so it cannot form atom-like systems.

 

[saddlestone-man]

Hmmm ... OK. So Dark Matter can't form matter-like structure.

Since it associates itself with matter (eg galaxies) and always causes an attractive force, why can't it be considered as Dark Gravity? Gravity doesn't interact electromagnetically either.

If it walks like a duck, talks like a duck, then it probably is a duck.

best regards ... Stef

 

[weirdoguy]

Gravity doesn't interact electromagnetically either.

This sentence makes no sense, since gravity is a phenomenon, not a thing (like matter) that can interact. Unlesse what you had in mind is gravitons, but then I'm not sure it is true that they don't interact electromagnetically.

 

[phinds]

@saddlestone-man you really should read some basic physics instead of just throwing out random questions on the internet.

 

[saddlestone-man]

Depending on how deep you want to delve into gravity, it's either a force that exists between all objects, anywhere in the Universe, or a distortion of Space-Time that manifests itself as a force between all objects.

Why can't there be an 'enhanced', as yet unknown, form of Gravity that shows itself as an increased attraction between matter, and which we choose to call Dark Matter.

What makes this attraction more like matter than the effect of enhanced gravity? As well as holding the matter of say a galaxy together more tightly, it would also distort the space-time between the galaxy and the rest of the Universe, making the galaxy seem more massive.

 

[lomidrevo]

What makes this attraction more like matter than the effect of enhanced gravity?

The terms you are using are bit confusing, what do you mean by "enhanced gravity"?

Truth is that we don't know what exactly is dark matter. There are several hypothesis or alternative explanations, see here. Modified gravity is one of the possible classes of theories to explain rotation curves of galaxies. However, there are observations which doesn't seems to be likely explained by modified gravity, for example:

The observed CMB angular power spectrum provides powerful evidence in support of dark matter, as its precise structure is well fitted by the Lambda-CDM model,[62] but difficult to reproduce with any competing model such as modified Newtonian dynamics (MOND)

The Bullet Cluster, the result of a recent collision of two galaxy clusters, provides a challenge for modified gravity theories because its apparent center of mass is far displaced from the baryonic center of mass.[67] Standard dark matter models can easily explain this observation, but modified gravity has a much harder time,[68][69] especially since the observational evidence is model-independent.

Do you mean modified gravity by "enhanced gravity"?

 

[saddlestone-man]

Many thanks lomidrevo for that explanation. Yes I guess I meant modified gravity, without knowing the term.
There goes my Dark Gravity Nobel Prize for Physics!

@saddlestone-man you really should read some basic physics instead of just throwing out random questions on the internet. ... doesn't help my understanding of complex physics and generally indicates a defensive attitude in whoever posts such a comment.

 

[lomidrevo]

Yes I guess I meant modified gravity, without knowing the term.
There goes my Dark Gravity Nobel Prize for Physics!

Not so quick!
General relativity (our best theory of gravity) is enormously successful, passing all the tests with fantastical accuracy. Also the current cosmological model lambda-CDM is very successful to explain the observed data. CMD stands for Cold Dark Matter, with following hypothesized properties:

non-baryonic:
It consists of matter other than protons and neutrons (and electrons, by convention, although electrons are not baryons).

cold:
Its velocity is far less than the speed of light at the epoch of radiation-matter equality (thus neutrinos are excluded, being non-baryonic but not cold).

dissipationless:
It cannot cool by radiating photons.

collisionless:
The dark matter particles interact with each other and other particles only through gravity and possibly the weak force.

Dark matter is widely accepted because it is much better in describing the observational data than any modified gravity theory. So you would do better to bet on dark matter.

 

[PeroK]

There goes my Dark Gravity Nobel Prize for Physics!

Perhaps that was never on the cards!

 

[phinds]

... doesn't help my understanding of complex physics

and you really think that the way to understand complex physics is by asking questions on the internet? Good luck with that.

 

[PeterDonis]

Unlesse what you had in mind is gravitons, but then I'm not sure it is true that they don't interact electromagnetically.

Gravitons have zero charge, so they don't interact electromagnetically.

 

[PeterDonis]

The OP question was answered in the second post, and pretty much everything after that is speculation and off limits here at PF.

Thread closed.