Alternate dimensions have been proven to exist, but there are many theories to explain how they are created. The prevailing theory is that whenever you make a choice (such as flipping a coin), your universe splits into 2 dimensions, one where you got heads, the other where you got tails. Another theory is that if you or any person in any reality believes it exists, it does. Another theory, perhaps the most favorable, is that is you want it to exist, it does. Sadly, none of the theories presented match all the evidence, and there is no perfect explanation. See also: Other dimensional beings.