Is this true?
http://www.theory.caltech.edu/people/patricia/exp3a.html [Broken] explains that gravitational waves need at least three dimensions (two dimensions to oscillate in, and one to travel in), so in a universe with two spatial dimensions there could be no so gravitational waves, which means that "curvature in 2+1 spacetime dimensions can only exist locally in regions where matter is present. I.e that means that for the example of a single point mass, the spacetime everywhere around the mass will be flat according to the Einstein equations." So, this backs up the statement on the page you linked to that "At least for FEWER than 4 dimensions on the large scale, that is 1 dimension of time, and 2 dimensions of space, it can be shown from general relativity that in such 'universes' the force of gravity does not exist in a vacuum. It cannot extend outside a body and cause other bodies to feel its effects."
As for the statement that more than three dimensions would also make life almost impossible because planets could no longer have stable orbits, this is confirmed by something written by Stephen Hawking on http://www.hawking.org.uk/text/physics/quantum.html [Broken]:
So....it is improbable for life to arise in 4D+ universes...wow, that sucks majorly
In Greg Egan's "Diaspora" he describes in detail a 5 dimensional Star with a “rotational pole” described as a single 2-sphere on the star's 4-dimensional hypersurface that stays fixed in space as the star rotates. in the book very complex life evolved in this polar region: http://gregegan.customer.netspace.net.au/DIASPORA/17/17.html
very speculative [it IS scifi after all- even if well thought-out and reasonable] and quite fascinating!
I still dont see why it is impossible, wouldnt a 5D universe have different laws than a 3D universe does? why do we apply our laws to their laws?
In a 5D (4D + time) universe Newtonian gravity would be proportional to
r-3 not r-2 and gravitational orbits would be unstable, they would decay. Therefore no galaxy, no star, no planets and no life!
They are assuming a universe with the same basic laws but just a different number of spatial dimensions. So yes, if you come up with totally different laws you might be able to imagine a 5D universe where life is possible.
If the 5th dimension is assumed compacted, this problem goes away.
Somehow, I feel a strong inclination to bet that life occassionally arises in 4D anyway.
"So yes, if you come up with totally different laws you might be able to imagine a 5D universe where life is possible."
Yes I am assuming that the laws would either be tweaked or completely different in a 5D universe
And maybe a 5D's universe life isnt the same as our life a 3D/4D life...I know it sounds stupid but what if it isnt something we can even begin to fathom...like some weird non-organic life
That assumes higher order dimensional universes exist. It they do, so be it. Do they have observational consequences in this universe? I seriously doubt that. Let's try to reign in our observations to this universe.
Well...yeah, were assuming, we have no way of testing them or testing the theory that states them...I am just fascinated by other dimensional universes
Chronos did you get my last PM?
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