Dark matter and the fabric of space time,

  • #1

Main Question or Discussion Point

{Moderator's note: Moved to Cosmology forum.]

Dark matter and the fabric of space time,

Can someone with a real knowledge base of physics and the current accepted theories, please explain why the fabric of space is not the candidate for the elusive dark matter?
Having read extensively about dark matter, Einsteins theory on Spacetime, the increasing speed of expansion of the universe, and the creation of space after the big bang, the only issue that is difficult to explain in relation to this hypothesis is the issue of galaxies moving apart at increasing speeds. A possible explanation however could be that the fabric of spacetime may be thinner / weaker/ less dense at the outer regions and is expanding more rapidly as it creates its own space and thereby is pulling everything with it. If you think of a gas cloud expanding in a large box, it gradually gets less dense the bigger it gets and one can visualise the speed of expansion at the outer edges increasing as the resistance and pressure decreases.Could this be happening at the edge of our universe?
It is not clear why the fabric of space is not being considered as the catalyst that would solve all the gravitational issues of the universe instead of dreaming up some strange concept that seems to mirror Einsteins infamous Cosmological Constant.
Of course, if spacetime was accepted as the answer, then the search would be on to discover what actually is spacetime and the challenge here might be far greater than trying to find Neutrinos passing through underground detectors trying to prove some nonsensical abstract theory quaintly coined Dark Matter.
I suppose it all hinges on where the money is.
 
Last edited by a moderator:

Answers and Replies

  • #2
PeterDonis
Mentor
Insights Author
2019 Award
30,169
9,334
Can someone with a real knowledge base of physics and the current accepted theories, please explain why the fabric of space is not the candidate for the elusive dark matter?
First, you appear to be confusing dark matter with dark energy. See below for more on that.

Second, "the fabric of space" is not really a meaningful term (nor is "fabric of spacetime", which you use later on in your post, and which at least recognizes that it should be spacetime, not space). That kind of terminology does appear in pop science sources, but it's not actual valid science.

the only issue that is difficult to explain in relation to this hypothesis is the issue of galaxies moving apart at increasing speeds
And the name for whatever it is that is causing this is dark energy, not dark matter. "Dark matter" is the name for whatever it is that is causing galaxy rotation curves to be different from what we would expect them to be based on the matter we can see.

A possible explanation however could be that the fabric of spacetime may be thinner / weaker/ less dense at the outer regions and is expanding more rapidly as it creates its own space and thereby is pulling everything with it.
No, this is not a "possible explanation" because it doesn't even mean anything. There is no property of spacetime that corresponds to being "thinner/weaker/less dense" in some places as compared to others.

Instead of speculating (and you should read the PF rules on personal speculation), you would do better to take the time to learn what our best current model actually says, and why it includes dark energy and dark matter. A good recent cosmology textbook, such as Liddle's, will cover all of that.

It is not clear why the fabric of space is not being considered as the catalyst that would solve all the gravitational issues of the universe instead of dreaming up some strange concept that seems to mirror Einsteins infamous Cosmological Constant.
Dark energy doesn't just "mirror" the cosmological constant, it is the cosmological constant--at least, that's the simplest hypothesis, which is the one our best current model adopts since we have no evidence for it being more complicated than that. It is not some "strange concept" that physicists dreamed up; it pops straight out of the simplest way of deriving the Einstein Field Equation.

Furthermore, the cosmological constant can be thought of as an intrinsic property of spacetime, so it plays the same role as you are envisioning for "the fabric of space". It just plays it in a way that means something given what we know about spacetime.

I suppose it all hinges on where the money is.
This is just silly. Our best current model of cosmology is driven by the need to account for all of the data we have.
 
  • #3
PeterDonis
Mentor
Insights Author
2019 Award
30,169
9,334
Since the OP question is based on personal speculation, this thread is closed.
 

Related Threads on Dark matter and the fabric of space time,

Replies
2
Views
851
  • Last Post
Replies
17
Views
5K
  • Last Post
Replies
2
Views
692
Replies
22
Views
3K
Replies
8
Views
6K
  • Last Post
2
Replies
30
Views
3K
Replies
18
Views
1K
  • Last Post
Replies
9
Views
2K
Replies
4
Views
633
  • Last Post
Replies
3
Views
2K
Top