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I know you explicitly asked for non-string theory answers, but I have to give one anyway -- sorry! There's an argument in string theory called the brandenberge
by pontus 5y ago
I know you explicitly asked for non-string theory answers, but I have to give one anyway -- sorry!
There's an argument in string theory called the brandenberger-vafa mechanism that I think is pretty clever:
Imagine that a bunch of particles and antiparticles travel along in one dimension. Because they can't spread out, they'll eventually collide and annihilate. However in 2d that's not the case: they're more likely to just miss each other all the time.
If you increase the dimension of the "particles" to strings, you can make a similar argument. In 2 (compactified) dimensions, strings will find each other but not in three.
Then if you start with some compactified space of 10d with a bunch of strings wrapped around various 2d subspaces, they will naturally constrain that space so that it can't expand. However, as strings move around randomly they'll tend to collide and unravel, allowing various 2d subspaces to cease being constrained and therefore expand.
If you analyze this carefully you can show that in fact three of the spatial dimensions will tend to expand while the six remaining ones will remain compactified.
- posterboy 5y ago> Imagine that a bunch of particles and antiparticles travel along in one dimension. Haha, thank you, hahaha, but no, thank you very much. > If you analyze this carefully you can show that in fact three of the spatial dimensions will tend to expand while the six remaining ones will remain compactified. While 1 is the domain of time, I pressume. Actually though, the universe is flat spread out, as is the surface of the earth, so the vertical axis, ie. gravity, also needs explained for the human experience to make sense. There are these types of questions like why is my right arm the left arm in the mirror but the head stays up? I forgot the canonical answer but it's evidently the case that the brain automatically creates a recibrocal to the mirror image which denies the fact that the "left" arm is still on your right side.
- messe 5y ago> I forgot the canonical answer but it's evidently the case that the brain automatically creates a recibrocal to the mirror image which denies the fact that the "left" arm is still on your right side. Generally the argument goes as follows: the mirror doesn't invert left and right. The image of your right arm is still on the right hand side of the image, just like your head remains at the top of the image. Instead it just inverts front and back.