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jdmack
2007-Feb-15, 01:17 PM
The say that a little learning is a dangerous thing, so the premises of my question may be incorrect. But I'll give this my best shot.

If I understand things correctly, the presence of matter curves or warps three dimensional space. Am I correct in assuming that when this happens, space is curving into a fourth physical dimension?

Let me assume for the moment that the answer to that question is "yes." If dark matter is some sort of matter than can only be detected by its gravitational effect on things, is it possible that dark matter is simply four-dimensional matter?

I hope this question doesn't come across as woo-woo. I've always been fascinated by Carl Sagan's bit about Flatland in "Cosmos" and wondered what we might experience if there was a physical fourth dimension.

J. D.

Kwalish Kid
2007-Feb-15, 02:23 PM
The say that a little learning is a dangerous thing, so the premises of my question may be incorrect. But I'll give this my best shot.

If I understand things correctly, the presence of matter curves or warps three dimensional space. Am I correct in assuming that when this happens, space is curving into a fourth physical dimension?
No. The change is in the geometry of 3D space some changes also occur in the 4D relationship of 3D space and time.

Let me assume for the moment that the answer to that question is "yes." If dark matter is some sort of matter than can only be detected by its gravitational effect on things, is it possible that dark matter is simply four-dimensional matter?
If there are four dimensions, then that suggests that all matter is four dimensional, we just don't see the other dimension for some reason.

There are suggestions from string theory that extradimensions are related to so-called dark energy. (That is, the theory says that there is no dark energy, it is just that the extra dimensions leech away the attractive force of gravity over long distances.) There is a Scientific American article about this theory out there (from at least two years ago).

satori
2007-Feb-15, 10:23 PM
is it possible that dark matter is simply four-dimensional matter?
matter is, the cosmologists want to have this stuff inside our universe
barionic matter had to much heat and preassure left from the BB to form compact structures early in the universe
to get the observed patterns of radiating barionic matter, they need a stuff that interacts only (mainly) gravitationaly
such a kind of matter can form a background matrix of gravitating lumps, which act as facilitators for barionic stuff to gather and coalese
cosmologists are very happy with their computer models, when say make use of such a kind of matter
furthermore is it "seen" indirectly in many different branches of astronomy
it seems everybody is happy with this stuff and they are in no need of exotic ideas about extra dimensions " thank you very much"...
dark energy is a different animal alltogether, nobody realy likes that...
here the doors are wide open for new strange ideas... but of course one has to first understand the problem in the first place, before one can hope to solve it...
cosmologists ( GR-people) heave learnt to instinctively reject the notion of an "outer" bedding space for our universe, they seem to have no need for it and shy away from arbitrary concepts

triclon
2007-Feb-16, 02:22 AM
The 4th dimension you speak of is actually "Time." Yes warped space also means warped time (this is all part of the theory of realitivity which says that space and time are combined into a 4 dimensional thing called "spacetime.") Gravity is actually the warping of space, so dark matter would also warp time (since time and space are both part of spacetime) but this effect is no different then how visible matter creates gravity so we're still back to square one.

RussT
2007-Feb-16, 02:36 AM
Since Non-Baryonic Dark Matter is completely collisionless with itself or ANY form of baryonic matter, and it goes right through all baryonic Matter, the real question is how do you get it to alter it's inertial straight line path at all???

Kwalish Kid
2007-Feb-16, 05:05 AM
Since Non-Baryonic Dark Matter is completely collisionless with itself or ANY form of baryonic matter, and it goes right through all baryonic Matter, the real question is how do you get it to alter it's inertial straight line path at all???
Non-baryonic matter does interact through collisions. Just not through electromagnetism. They can have mass, even if they don't have a charge, and they can interact, potentially, through the strong and week nuclear forces.

Most collisions that we think about are not really collisions, but the interaction of the electomagnetic fields of the objects that we see. It is exceedingly rare to find that two particles that don't interact through EM (and aren't already in a nucleus together) would hit each other.