Dark matter as matter in parallel universes

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Discussion Overview

The discussion revolves around the hypothesis that dark matter could be explained as matter from parallel universes interacting gravitationally with our own universe. Participants explore the implications of this idea, including how gravity might behave across dimensions and the potential effects on the formation of galaxies and life.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant proposes that if gravity is not confined to three spatial dimensions, matter from parallel universes could exert gravitational influence on our universe, acting like dark matter.
  • Another participant challenges this idea, stating that dark matter does not interact well with itself, which would imply that it cannot simply be normal matter from a parallel universe.
  • There is a discussion about the properties of dark matter, including its inability to lose energy and fall into gravitational wells like normal matter does.
  • Participants mention the Bullet Cluster observation, where dark matter from colliding galaxies passes through each other, supporting the idea that dark matter interacts primarily through gravity.
  • Questions are raised about the nature of dark matter interactions, with some suggesting that gravity is the main force at play, possibly with limited short-range interactions.

Areas of Agreement / Disagreement

Participants express differing views on the nature of dark matter and its interactions. While some find the idea of dark matter as matter from parallel universes intriguing, others argue against it based on the known properties of dark matter. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Participants note that the hypothesis relies on assumptions about the nature of gravity and the behavior of matter across dimensions, which are not universally accepted. The discussion also highlights the complexity of dark matter interactions, which are not fully understood.

  • #91


Misericorde said:
Uh huh, yet they predict and let us develop technology for all that it lacks the elegance you seem to want.
LQC also makes predictions (and could have done so before if it hadn't been prematurely abandoned). Eg, it predicts that neither WIMPS nor MACHOS, etc will be found, and that dark energy will ultimately go to zero (when there is nothing more to feed on in the parent universe), although the time-scale for this is unclear.
It is not that I "want elegance", it's just that I see inelegance elsewhere in physics, in which it is caused by external effects. Eg, if you didn't know that the Earth was slowly rotating, you would just have to accept that Newton's law of motion, F=ma, was a mess, needing to have some strange extra terms (the Coriolis force, etc) to make it correct.
As foir technology, comparing any theories should produce that, it's nothing to do with which is better.
 
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  • #92


DavidMcC said:
LQC also makes predictions (and could have done so before if it hadn't been prematurely abandoned). Eg, it predicts that neither WIMPS nor MACHOS, etc will be found, and that dark energy will ultimately go to zero (when there is nothing more to feed on in the parent universe), although the time-scale for this is unclear.
Er, what? Where does it make these predictions? And if so, how the hell does it explain our observations of dark matter?
 
  • #93


Chalnoth said:
Er, what? Where does it make these predictions? And if so, how the hell does it explain our observations of dark matter?

Ditto.
 
  • #94


The parallel universe part of your idea doesn't seem to hold water. If gravity was acting in more than 3 dimensions, then it would spread out faster than it currently does (1/r^2). I think this has been well measured and precluded.

On the other hand, I've seen some papers in the ArXive (xxx.lanl.gov) that indication that idea of self-interacting dark matter has some merit.

There is also a non-mainstream theory (developed by serious physicists, not fringe guys, but still not generally accepted) called "mirror matter" that proposes that there are two mutually invisible types of matter living in the same space. I don't know if I follow the argument that well, but it has to do with having two types of matter that violate CP conservation in opposite ways.

Other than the "mirror matter" development, I haven't seen much in the way of a theory of what that self interacting dark matter might be. One paper proposed an analogy to electrodynamics within dark matter, but they didn't go so far as to propose a different type of equivalent matter that was somehow different.

Perhaps these researchers are being deliberately cautious until they come across a good enough theory to hang their collective hats on.
 

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