Dark Matter

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Girl-With-A-Math-Fetish
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Dark Matter

Postby Girl-With-A-Math-Fetish » Thu Jul 17, 2014 5:43 am UTC

I'm not sure if this theory already exists. I'm sure it does, but it was something that came into mind a while back and it's been bugging me since.

Dark matter might just be regular matter trapped in another directional dimension. Perhaps, when the Big Bang came about, things were so energetic that several small black holes swallowed most of the matter (or that we are the product of such an action) and is storing it in another dimension. It would explain where all the mass in a black hole goes, too. Gradually, after the universe cooled and the black holes had time to evaporate, the matter was trapped in another dimension. It is conjectured that gravity is so weak because it spreads its entire force field across all dimensions, such that if a fourth dimension were to exist, it would tug in that direction, too. This "extra" matter cannot be seen because it isn't physically in our dimension, but can interact with the light and matter within ours because of the way gravity behaves. It would give galaxies the extra mass they need to behave the way they do, and other properties dark matter seems to have.

Is this a feasible theory? Why or why not? If so, how would one go about testing this theory? Could one perhaps, create a simulation of which there is a fourth dimension the particle system can be sucked into and interact with the normal matter gravitationally?

I probably said something really stupid somewhere, so forgive me if I did.
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Re: Dark Matter

Postby drachefly » Thu Jul 17, 2014 2:10 pm UTC

It's a little tricky to reconcile with the Bullet nebula evidence. There, the dark matter passed through itself readily, while visible matter did not. But I can see two solutions:

If our plane (locally) holds the plurality of the matter and there are lots and lots of hyperplanes the dark matter is split among, that would work.

Or if the two galaxies each had single-hyperplane dark partners that were also in different hyperplanes from each other. That would require a mechanism for producing such a separation.

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Re: Dark Matter

Postby Tub » Fri Jul 18, 2014 12:25 am UTC

That sounds a bit like bad sci-fi stories. "It's there, but you cannot see it, because it is in another dimension!" ;)

Here's a few of the problems I can see:

First of all, as drachefly mentioned, our observations have given us a pretty good understanding of the way dark matter interacts. If it was just regular matter, somehow removed from us, it would still electromagnetically react with itself - and dark matter just doesn't do that.
So you would not only have to somehow remove it from our visible universe, you'd also have to somehow remove it from itself, and that's more difficult than just slapping on another dimension.


Second, there's no evidence that would support a way to "convert" matter into dark matter. All evidence points to ~84% dark matter, both in the early universe and today. If dark matter was created by black holes, we'd expect the ratio to start low and rise over time.
Looking at the CMBR, we know the early universe was very uniform - it couldn't have contained many black holes, if any. But the CMBR also tells us that dark matter already existed back then - by the time the variations in the CMBR were formed, the ratio was already at 84% dark matter, and the dark matter was (almost) uniformly distributed.
There's no way a few small black holes would have been able to suck up 84% of the mass of the universe, transport it into another dimension, evaporate within at most a few thousand years and disperse the generated dark matter uniformly. There's no reason why such a grand process should have suddenly stopped, either.


Third, how would that extra dimension look?

We have three space dimensions. As far as we know, they're absolutely identical. If your extra dimension is indeed spacelike, we could look right through it; any matter inside wouldn't be "dark".
It could also be a second timelike dimension. There are several reasons why that would be bad for our health. And it wouldn't have the required properties either.
So you need a new kind of dimension with new, unique properties. Let's just say that integrating something like that into existing theories would be a challenge.



Girl-With-A-Math-Fetish wrote:It would explain where all the mass in a black hole goes, too.

Why would it go anywhere? It's right there, in the black hole. We know it's in there, because we can measure its gravity.

Outside of sci-fi, black holes aren't magical creatures. They're just very dense objects. There is no wormhole travel, they don't magically connect to alternate universes and they wouldn't just eject stuff into a fourth dimension.


Is the theory feasible? Unlikely. You'd need to properly define the nature of the new dimension, including the mechanism for moving matter into the new dimension. Then you'd need to integrate it into existing theories (relativity should suffice for now) and compare it to existing observations. If they check out, you can go find some testable properties of the new theory, then go and test it.

Personally, I'd rather grab occam's razor. "A different kind of matter" seems weird, but it's still the simpler option.


Oh btw, you might like this video I stumbled upon when googling references for my post. Not very informative without context, but it has a fractal-like beauty:
https://www.youtube.com/watch?v=UXK_EWwKDJ4

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Re: Dark Matter

Postby Girl-With-A-Math-Fetish » Fri Jul 18, 2014 4:10 am UTC

Hehe they used that animation in the recent HTUW and Through the Wormhole episodes. I personally follow the fractal universe theories, and so much of this universe is fractal in nature... but that's for another discussion. And hmm... far as saying for certain that we only have three spatial dimensions, I'm still skeptical about that. But I guess dark matter wouldn't be in a fourth spatial dimension. Also, I was also suggesting that we would be the "dark matter" to what we see as the dark matter. The universe would have been much denser then, allowing for more matter to be sucked in. That's where my reasoning came from, hehe. I thought it was still speculated where the stuff eaten up by a black hole went.
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Re: Dark Matter

Postby PM 2Ring » Sat Jul 19, 2014 1:03 pm UTC

Girl-With-A-Math-Fetish wrote:[...] I personally follow the fractal universe theories, and so much of this universe is fractal in nature... but that's for another discussion.

Do you mean Fractal cosmology, or Fecund universes, or possibly both? :)
But yes, those topics do deserve their own thread(s).

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Re: Dark Matter

Postby doogly » Sat Jul 19, 2014 4:42 pm UTC

It be neat if there were some parity between us and the dark matter, but its behavior in halos and clusters makes that very unlikely. Although by mass there's much more of it, it doesn't interact electromagnetically at all and likely has only very weak, if any, interaction with itself. So it can't form structure, whether here or in some 'hidden' dimension.

Regarding extra dimensions, you can put very tiny compactified ones in your theory, but if you want them to be macroscopic you have a lot of explaining to do for the 1/r^2 decay of gravity.
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Re: Dark Matter

Postby Girl-With-A-Math-Fetish » Sun Jul 20, 2014 6:58 am UTC

PM 2Ring wrote:
Girl-With-A-Math-Fetish wrote:[...] I personally follow the fractal universe theories, and so much of this universe is fractal in nature... but that's for another discussion.

Do you mean Fractal cosmology, or Fecund universes, or possibly both? :)
But yes, those topics do deserve their own thread(s).


I follow the theory that states the universe is fractal in nature. There has to be some underlying mathematical reason behind why everything appears to follow a Cantor Tree or Lichtenberg figure pattern. It's probably linked in some way to the Golden ratio. :P
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Re: Dark Matter

Postby Copper Bezel » Sun Jul 20, 2014 8:19 am UTC

Girl-With-A-Math-Fetish wrote:But I guess dark matter wouldn't be displaced in a fourth spatial dimension.

I don't know physics, but this is a logic / semantics thing: "in another dimension" really is a science fiction concept and misuse of the term, and a "dimension" is an axis, whether spatial or otherwise. If there's an extra spatial dimension with special properties and matter can displace itself there, we're actually all still in four-dimensional space at all times, and we simply only perceive the matter that shares our slice of the fourth dimension; displaced matter is moved along the fourth dimension, not into it.
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Re: Dark Matter

Postby Girl-With-A-Math-Fetish » Sun Jul 20, 2014 11:15 am UTC

Copper Bezel wrote:
Girl-With-A-Math-Fetish wrote:But I guess dark matter wouldn't be displaced in a fourth spatial dimension.

I don't know physics, but this is a logic / semantics thing: "in another dimension" really is a science fiction concept and misuse of the term, and a "dimension" is an axis, whether spatial or otherwise. If there's an extra spatial dimension with special properties and matter can displace itself there, we're actually all still in four-dimensional space at all times, and we simply only perceive the matter that shares our slice of the fourth dimension; displaced matter is moved along the fourth dimension, not into it.


I was referring to it's actual terminology. Some people regard "time" as a dimensional axis, so that's why I was clarifying it.
Well think of a Flatlander. The Flatlander lives in two-space, but that two-space is actually in three-space. Unless something from the three-space were to pass through their plane of existence, they wouldn't notice the object save for its gravitational interaction. However, the fact that dark matter has no electromagnetic interaction does make this theory far weaker.
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Re: Dark Matter

Postby Copper Bezel » Sun Jul 20, 2014 7:50 pm UTC

I'm sorry, I think maybe I was unclear, and I think you're responding to a different idea than the one I was emphasizing. I think I understand the concept: we'd exist in a three-space slice of a four-space universe, yes, and four-dimensional objects could intersect with our slice and seem to appear from nowhere in three dimensions and so on. But all I mean was that matter wouldn't go "into" or "out of" the fourth dimension, it would move along it, which is why I inserted "displaced" there. It's always existing in all four dimensions, as are all the familiar three-dimensional objects that make up our universe and are trapped against moving along that last spatial dimension.

But yeah, displaced matter doesn't seem to be a very good analogue for dark matter. I get that. I was just talking about the concept in the abstract and how it would be described and things.

On which note - doogly, I took your post to mean that if gravity can propagate across all four spatial dimensional axes and all are "open," then it should diminish with r cubed instead of r squared. But could this extra-special spatial dimension be one of those compactified, closed ones you referred to, and still be "enough space" to shove a particle sideways into, so that it's off our slice of the four-space, even if pushing it further would loop it back around? Do any of those words make sense in that order?
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Re: Dark Matter

Postby doogly » Sun Jul 20, 2014 7:54 pm UTC

If the question is "Can we make this coherent and consistent enough to just be regular wrong," then I'm going with "Maybe?" You'd need some weird force pinning all the dark matter there.

It would be like, "Let's model this situation with introducing a new way for things to move (spacial axis) but also introduce forces so that nothing actually undergoes motion along this."
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Re: Dark Matter

Postby Copper Bezel » Sun Jul 20, 2014 8:14 pm UTC

Yeah, that's what I was picturing. Thanks for translating my not-even-wrong into regular-wrong. = )
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Re: Dark Matter

Postby Tub » Sun Jul 20, 2014 8:54 pm UTC

Girl-With-A-Math-Fetish wrote:And hmm... far as saying for certain that we only have three spatial dimensions, I'm still skeptical about that.

Well, three that matter in large-scale interactions, and dark matter has only been observed in large-scale. The other hypothetical rolled-up dimensions don't really matter here.

Girl-With-A-Math-Fetish wrote:Some people regard "time" as a dimensional axis, so that's why I was clarifying it.

If by "some people" you mean "any physicist who knows his formulas", then yes.

Girl-With-A-Math-Fetish wrote:Well think of a Flatlander. The Flatlander lives in two-space, but that two-space is actually in three-space. Unless something from the three-space were to pass through their plane of existence, they wouldn't notice the object save for its gravitational interaction.

In the flatland universe, the third dimension is very special, because otherwise the whole premise wouldn't work.

If all three flatland dimensions were equal, flatlanders wouldn't be different than a piece of paper in our universe. It can turn and move in all three dimensions, it can receive photons from objects outside their slice etc. Flatland really isn't how one should imagine us being in a fourth dimension.

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Re: Dark Matter

Postby doogly » Sun Jul 20, 2014 9:26 pm UTC

It's great for thinking about social justice though!
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Re: Dark Matter

Postby drachefly » Mon Jul 21, 2014 9:54 pm UTC

The force that keeps the hyperplanes from moving in that fourth dimension? Isn't it obvious? We're pinned in the nodes or antinodes of the standing wave of dark energy, which is, ah, somehow coherent over cosmic length-scales.

Yeah, that's it.

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Re: Dark Matter

Postby doogly » Mon Jul 21, 2014 10:29 pm UTC

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Re: Dark Matter

Postby andyisagod » Tue Jul 22, 2014 6:58 am UTC

doogly wrote:If the question is "Can we make this coherent and consistent enough to just be regular wrong," then I'm going with "Maybe?" You'd need some weird force pinning all the dark matter there.

It would be like, "Let's model this situation with introducing a new way for things to move (spacial axis) but also introduce forces so that nothing actually undergoes motion along this."


Oh sure when someone on the internet wants to localise the standard model on a brane it's crazy when Arkani-Hamed does it he gets over 1000 citations.

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Re: Dark Matter

Postby p1t1o » Tue Jul 22, 2014 3:11 pm UTC

Tub wrote:
Girl-With-A-Math-Fetish wrote:Some people regard "time" as a dimensional axis, so that's why I was clarifying it.

If by "some people" you mean "any physicist who knows his formulas", then yes.


Time is a dimensional quantity, yes - but I was under the impression that it is only analogous to a spacial dimension and not an actual dimension like the three we know and love?

For example, a cube of diamond travels sedately along the time-axis at 1s/s just like we do. But it also has a fixed length - it has no fixed length in the "time" direction, it just "moves" "along" "it".

I'm certainly not expressing myself well, tl;dr - I was under the impression that it is useful to regard time as a dimension but it is not the same as length/breadth/width/n-other physical dimensions.

How wrong am I?

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Re: Dark Matter

Postby doogly » Tue Jul 22, 2014 3:29 pm UTC

It's a dimension, but it is time-like rather than space-like. It's certainly not "the same."
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Re: Dark Matter

Postby p1t1o » Wed Jul 23, 2014 8:05 am UTC

"time-like" & "space-like" - yes, those are the words I should have used!

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Re: Dark Matter

Postby Copper Bezel » Wed Jul 23, 2014 4:41 pm UTC

But the time-like and a space-like dimension can be interchanged in extreme conditions, and one way of describing c is as a sort of unit conversion between them, right? (I mean, I can't come close to putting this in proper terms, but in SR and GR, the timelike dimension has a lot in common with a spatial one, right?)
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Re: Dark Matter

Postby Frenetic Pony » Wed Jul 23, 2014 10:35 pm UTC

doogly wrote:It's a dimension, but it is time-like rather than space-like. It's certainly not "the same."


Rather, it is treated as a "timelike dimension" currently, though generally regarded as more open for reinterpretation than other aspects of physics. As in, there are more people interested in new interpretations of time, and more papers on reinterpretations of time, and large books that might be titled "And what exactly is the deal with time anyway?" than there are reinterpretations of our 3 spacelike dimensions.

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Re: Dark Matter

Postby gladiolas » Thu Aug 14, 2014 2:37 am UTC

Has this been suggested before?
Maybe there are many different forms of dark matter and dark energy. As an analogy, it would be a little like scientists 200 years ago referring to transuranic elements as "dark matter", and X-rays as "dark energy". Maybe there's a whole 'nother bunch of periodic tables and planets and life forms...

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Re: Dark Matter

Postby Tub » Thu Aug 14, 2014 9:08 am UTC

Certainly. Dark matter is just a catch-all term for some unknown matter that adds mass to the universe, but doesn't interact electromagnetically. The search for its nature includes the possibility of multiple sources.

For example, neutrinos fit the definition of dark matter, and were a good candidate for a while. By now we know that they have mass and are part of the answer to the dark matter problem, but we also know that they cannot be all of the dark matter out there. They're not heavy enough to account for all the hidden mass we measure, and they're too fast to fit the observations.

Whether the remaining dark matter is one particle, two particles or a thousand is difficult to say, since we cannot measure them individually. I'm not aware of any observations that would require different particles with different properties, but that doesn't mean there's only one.


Though don't get your hopes up about periodic tables and planets: Dark matter doesn't interact electromagnetically or strongly; only gravitationally and (maybe) weakly. Thus, it cannot form small scale structure: neither elements (nuclei are bound with the strong force; electrons are bound to nuclei electromagnetically), nor molecules (electromagnetic force), nor planets (which form due to collisions of smaller-sized objects, so electromagnetic force again. Dark matter can pass right through itself).

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Re: Dark Matter

Postby eSOANEM » Thu Aug 14, 2014 2:53 pm UTC

Neutrinos wouldn't form the galactic dark matter halos we see. If Neutrinos are involved, they are far from the majority of the missing mass.
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Re: Dark Matter

Postby krogoth » Fri Aug 15, 2014 3:02 pm UTC

I keep seeing only 3 dimensions, length time and mass. Direction of length I'm not sure about but these settle so much easier with me. even if that isn't an answer.
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Re: Dark Matter

Postby doogly » Fri Aug 15, 2014 3:17 pm UTC

This makes no sense, and even less sense in the context of this thread.
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Re: Dark Matter

Postby lgw » Sat Aug 16, 2014 12:45 am UTC

I've been amusing myself with the idea that there are 10 or 20 kinds of dark matter, each fundamentally different in some way. For example, matter with analogs to the proton and electron, but bound so tightly that at present energy levels, or even at the energy levels present when the universe was 100 kY old, they don't happen to encounter photons with energy levels high enough to nudge an electron up to the next permitted energy level; or perhaps an entirely parallel EM-like force and charge-carriers that don't work "properly" due to some wonky fine structure constant.

There are, after all, many "tunable constants" in out universe that just happen to be tuned finely to values such that life-as-we-know-it could arise. That would all seem less unlikely if there were in fact several kinds of matter, and all the others were "poorly tuned", such that they can't even form structures, and so are just dead weight.
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