The Level I multiverse theory involves the idea that if the size of the universe approaches infinity, portions of will be repeated, over and over again. Therefore, there can be an infinite number of Earths populated with copies of you. However, there can still be differences between these worlds because there are an infinite number of possible histories for these worlds. For instance, in one of these worlds, World War II never happened, and in another you decided to wear a blue shirt today instead of a green one.
The Level II multiverse theory involves the idea that our universe is a single bubble in a sea of other universal bubbles known as the multiverse. It is a bit like bubble wrap, in which each individual bubble is its own universe. The bubble universe is founded upon the notion that different parts of the multiverse are expanding and inflating at different rates and times. Thus, when one part of the multiverse ceases to inflate, a pocket, or bubble universe, is formed. In the multiverse, the bubble universes can overlap with one another. Though we cannot pass into a neighboring universe, these universes can interact with one another, whether it be through gravitational or wave-like interactions as some electromagnetic waves may be able to pass into other dimensions. Finally, the physical laws that govern each bubble in the multiverse could be vastly different. For example, perhaps in one of these universes the speed of light is slower because of the bubble’s different laws of physics.
In the Level III multiverse theory, every decision we make creates an alternate universe. Thus, things that we attribute to random chance are actually not random at all. For example, every time we roll a die, we know that there is a one out of six chance that we will observe a four. However, in this multiverse theory, we will observe every alternative option, so while we thought we randomly rolled a four, in actuality, we split the universe into six parallel universes, each observing a different number. As a result, all outcomes are achieved, just in different, parallel universes. Every decision we make splits the universe into another parallel universe. So if we choose to turn left one day instead of right, the universe splits and there is now an alternate universe where you turned right instead. This also works for larger decisions in life. For instance, you are given three job offers: one, two, and three. In one universe, you choose one, and you meet your future soul mate, and you two eventually die as a happy old couple. In another universe, you choose job two, where you are highly stressed all the time, and eventually die prematurely of a heart-attack. Finally, in another universe you pick job three where you get divorced seventeen times and never experience true happiness. In essence, every decision we make affects the universe and ultimately could change the outcomes of our lives.
So maybe you are unique. In this world, universal pocket, or parallel universe, at least, you are unique. While the multiverse theories may be intriguing, there is no definite way to test any of them. So perhaps they will forever stay untested theories, and you will forever stay unique.
Sources:
http://blogs.law.harvard.edu/abinazir/2011/06/15/what-are-chances-you-would-be-born/
http://www.space.com/18811-multiple-universes-5-theories.html
https://www.quantamagazine.org/20141110-multiverse-collisions-may-dot-the-sky/
http://www.astronomy.pomona.edu/Projects/moderncosmo/Sean's%20mutliverse.html
- Andrew Afable
