yea i know i just want to understand what the theory is saying



I dont know what you mean by the extra dimensions are compacted. My main question was do we exist simultaneously in other universes (according to the theory)? and if we don't, how would it be possible to fold through the 6th dimension to a different 5 dimensional life if the wave function of that life had already collapsed

The only parallel I've heard to describe what it means for extra dimensions being compacted is this:

Say you take a straw (like the kind you'd find at McDonald's). You can describe any point on the straw's surface using two dimensions: distance from one of the sides (1) and rotational angle from one of the stripes (2). If the straw's radius were really, really small, then we wouldn't be able to measure a difference between a point at angle 0 degrees and angle 180 degrees (or any other angle measurement), so because of that, we could accurately describe any point on the straw's surface by using one dimension: distance from one of the sides. The "angle" dimension is too compact for us to observe it.

But since in String Theory the additional dimensions are not spatial dimensions, that "shrinking something down until a dimension disappears" description isn't really useful.

We can't physically fold anything in spacetime to arrive at a different spot in the 5th dimension since spacetime is limited to only the first 4 dimensions. It would probably take a butt-ton of energy to travel to a different spot in the 5th dimension, if it's even possible.

Compactified means compact in the mathematical sense, which means there are limited in some sense - for example, if you would imagine the universe was 2D on the surface of a 3 dim sphere, this would be 2 compact dimensions of the surface-world - I just see this is also more or less described in the post by bentherdonethat, but there are some errors, see below. The standard 3 spatial dimensions we can see are unlimited and not compact.



I don't really understand what your definition of 'other universes' is.
1) if you mean the multiverse interpretation of quantum mechanics, then the answer is that this can not be tested and is therefore not a scientific theory (I can go more into detail, if this is what you mean).
2) If you think that this is some universe hidden in the extra dimensions of string theory, then the answer is no, those are compact dimensions with scales of the order of the planck scale!


the additional dimensions in string theory are spatial dimensions, but they are compactified - so actually this description is quite good, it just doesn't help with imagining dimensions N>3

This post was edited by rolle on Sep 2 2011 03:17am

Maybe I was thinking of M Theory, then?

no: M theory is a supposed unification of the different string theories, and they all contain compactified spatial dimensions.
i can't think of any meaningful (physical) theory with non-spatial extra dimensions except this 10+2 dim (2 time dimensions) supersymmetric gauge theory, but it seems to be not 'real' (awkward gauge-fixing of unitarity, strange looking action, etc), and ofc you would need to rewrite your vocabulary (and physics) concerning chronology

rewthebrave for president.

Im sorry I meant to say living simultaneously in other dimensions* not universes. And the video says that you could theoretically fold through the 6th dimension to a different life in the 5th dimension; and to me that implies that they are saying we exist simultaneously throughout the 5th dimension, else how would you be able to fold to a different you in that dimension, like the video says

And no I'm not refering to the multiverse interpretation of quantum mechanics unless thats part of string theory

this is pretty reading material and it reminded me of something..

ill preface this by saying: for anyone who hasnt played around with hallucinogenics ill say its akin to dreaming, you may see and feel a lot of things that might feel significant at that very moment but quickly fade from memory and attention when you hallucinate something new. some things you see stay with you they feel extraordinary or significant, right?

so one of these memories I have is of seeing myself lazily lift my hand up and I sort of split infinitely (like if you've ever aimed a web cam at what its feeding the computer: some infinite window that you can bend) and i could see all these other splits of myself go on, doing the same thing I am: looking at my lifted hand. and uh I just thought it looked really cool.

so my question to you is, do you think our brain is powerful enough to contact ourselves existing in different dimensions or times? like its just a funny thought but what if for whatever reason many versions of myself (like we're talking 10th dimension category) all lazily lifted their hand and looked at it

p.s. dont get me wrong im past the point where I think hallucinations are mystical or real or anything like that - for me its just something fun to do and anything we see is just what our brain projects onto our active consciousness/imagination

pps id love to trip with one of these mathematicians theorists that work on this kind of stuff

ah, ok. just to be very clear, I will repeat myself: In the (almost inevitable) case that string theory is correct, we *just live* in a spatially multidimensional world, but this is not macroscopically spectacular since only 3 dimensions are infinite - I don't know what you/the video wants to imply with this formulation 'different life', but there surely is no hidden second (macroscopic) life different from your real life, that's just silly .
the part about 'unfolding the dimension' is pure nonsense, which has zero relevance/connection to science.


where is the connection to multidimensions? you just saw projections of yourself in ordinary 3D space - I think you have a fundamentally flawed conception of the notion of a dimension.
your memory can be probably easily explained using ordinary psychology, not physics maybe the effect of hallucinatory drugs on a subconscious which has been exposed to many science-fiction movies?

Its the video posted by rewthebrew. its starts talking about the 5th dimension around the ~4:40 mark. You only have to watch about 2 minutes of it or so to understand where my question comes from


Also, you just said its almost inevitable that string theory is correct, but earlier you said it was crack pot nonsense??