PDA

View Full Version : Could extremely large dimensions also be unobservable?

tommac
2011-Apr-01, 01:22 PM
Ive read about very small dimensions that are "rolled up" etc ... to the point that we couldnt detect them but would it also be possible to have super gigantic spacial dimensions that were so huge that we couldnt detect them either?

The thought here is that if they were on a scale that was so huge that any movement in that dimension would not be detectable so that x+n =~ x. and if we couldnt detect any movement within that dimension then could we detect that it was actually there?

WayneFrancis
2011-Apr-01, 02:13 PM
well our three spacial dimensions are like that now if you pick a small enough n.

Seriously, For all we know the X,Y & Z dimensions could be infinite in length....how much bigger do you want? In the spatial coordinates we have now is moving from X to X + .001m ≈ X? If the extent of our space is -∞ → +∞ we still see traveling 1m = 1m. If the universe is 1x1030m we would still see travelling 1m = 1m

The issue with rolled up small dimensions is that even if you travel 1m you don't really go anywhere...you've just gone a gazillion loops around that dimension and can never get further away from your starting point then 1/2 of the dimension length.

caveman1917
2011-Apr-01, 03:13 PM
Large dimensions can be unobservable depending on how you observe. If you are stuck to a 2d plane and can only observe in those 2 dimensions, it doesn't matter how big any 3rd dimension might be. If i understand things correctly, that's how string theory deals with extra large dimensions, all the particles (except the graviton) being 'stuck' to our 4d brane, hence the rest is unobservable even though they may be large.

EigenState
2011-Apr-01, 09:01 PM
Greetings,

The following page at the Perimeter Institute for Theoretical Physics might prove useful regarding the question initially posed: Superstring Theory (http://www.perimeterinstitute.ca/Outreach/What_We_Research/Superstring_Theory/). Approximately half way down the page there is a subsection entitled Where are the Extra Dimensions? which discusses the possibilities of both small and large extra dimensions.

Best regards,
EigenState

tommac
2011-Apr-04, 02:42 PM
Thanks! This is very useful information!

Greetings,

The following page at the Perimeter Institute for Theoretical Physics might prove useful regarding the question initially posed: Superstring Theory (http://www.perimeterinstitute.ca/Outreach/What_We_Research/Superstring_Theory/). Approximately half way down the page there is a subsection entitled Where are the Extra Dimensions? which discusses the possibilities of both small and large extra dimensions.

Best regards,
EigenState