Need help with a question about alternate universes! "Universe X"? "Reality X"?

Question

I've been doing some research on String Theory and the 11 (or 10!) dimensions of reality. I seem to remember my 8th grade teacher talking about this a bit, specifically about alternate realities or universes and I remember her talking about "something X" It was like "Universe X" or "Reality X" or something to that effect but I can't remember it exactly. She described it as a (or many?) parallel universe(s?) to ours but with one minor change. Like a universe where your life was exactly the same except for the fact that you wore a green sweater on November 21, 1998 instead of a blue one, or a universe where you chose to go to a different college, or whatever. Does this ring a bell with anyone?

I'm pretty sure it was "----- X"

HELP! :)

Answer 1

There are at least two different ways one can come to the same hypotheses.  First is the quantum mechanical picture. Interacting systems (particles, fields, etc) have their states described by probability density functions which means that if an onteraction has many outcomes, each outcome is present.  One outcome is selected when the interaction is observed (measured) by an outside observer - the others are not realized.  The famous Schrodinger's Cat problem is one example of this indeterminancy - the life of a cat hangs on whether a radioactive substance decays (a quantum event).  But the cat is in a box and you can't tell if it is dead or alive until you open the box.  By the rules of quantum mechanics, the cat is both dead and alive until you make the observation by opening the box.  Many folks have opined that these unused states all get realized in different universes - thus each event branhces into a different universe.  And since you cna't realize two (or more) mutally exclusive outcomes to an event in one universe, all teh other universe have to be unobservable to each other.

The second multiverse hypotheses comes out of string theory but it its not a philosophical as the quantum version.  String theory (It is really more of a working hypothese rather than a sceintific theory) needs the multiverse explanation to cover its embarrassment of riches.  String theory predicts something like 10^500 possible universes without providing any guidance to picking out he one we exist in.  Ouch! So positing that all the universes are realized, and unobservable to each other is one way to avoid having to deal with this overwhelming number of possibilities.  It still begs the quesiton of how do you find our universe out of all these possibillities.

Answer 2

this is muultiverse sure you shuld know it.

according to this hypothesis whenever there is a choice the universe splits into as many numbers as the choices are. these  universes are completley isolated from each other . it wasnt a much popular idea though . this is awikipedia link http://en.wikipedia.org/wiki/Multiverse