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Dave Ortz
2006-Jul-15, 10:20 PM
I just finished reading "Parallel Worlds" by Michio Kaku and I was wondering if the dark matter around galaxies could be from the infinities of parallel worlds just beyond our "real" world and galaxy?

It seems to me this form of dark matter could gravitationally influence our "real" world and manifest itself as dark matter.

Ken G
2006-Jul-15, 11:37 PM
Welcome to the forum. I think the point here is, in physics we need to have very specific rules about how things work, for the concepts to be of any use. We could speculate on parallel worlds and what they might do, but how are you going to constrain their action on our universe? You need a very specific theory or it's useless. By contrast, we already do have a specific theory about how cold dark matter would operate, and using that specific theory we get very nice agreement with the behavior we see. We still have to speculate on the existence of something we cannot otherwise observe (at present), but it follows well defined rules. Also, there is the potential to someday observe and discover just what dark matter is. So in summary, the dark matter idea has two key advantages:
1) it obeys laws of physics we already have in place for the visible matter, and interacts with visible matter according to normal gravity
2) there is the potential for actually observing it in other ways and checking our expectations.
So the question to ask yourself is, how does the concept of "parallel universes" compare in regard to these two principles? When a specific theory is put forth that can accomplish these two things, that is the time to take the idea seriously, but not before. On the other hand, every great idea must have started at some point as just some kind of idle speculation, so there's no harm in wondering!