There can be no parallel universe

It doesn't matter what is more understandable. If we are talking about a astonomical theory, than astronomical terms and words need to be used. As such, there are two different ideas of what the "universe" is. By basic english definition, it is everything. All mater, all energy, all spacetime, everything. According to science and for all practical purposes, it is the result of the big bang. The universe is about 93 billion lightyears in diameter. This presents a potential logical fallacy, as we do not know if there is more outside the arms of our universe. It is entirely possible that at a distance of 300 billion light years, an entirely different big bang has it's own universe. This obviously shows that the basic english definition and the science definition are not nessicarily talking about the same thing (since that other big bang would be considered part of our single universe by the english definition). Of course, since this is a debate about science, the science definitions should be what we are using in our arguments. My opponent argues that we will never see these other universes. Unless my opponent knows the future, this is merely speculation. For countless centuries we thought that we would never be able to fly. We thought that we'd never be able to reach the stars, or the moon, or any other place. This, of course, is not to say that we will get there or that we won't. But only that one cannot say we will never get there. And even if we never get there, that doesn't prove that they don't exist. I can say, fairly surely, that we'll never get to the core of Mercury (probably out of not wanting to), but that doesn't mean it doesn't exist. As such, there are actually several multi-verse theories, all deriving from different physical theories. The two that I particular enjoy following are the many worlds (which is the belief that everytime a choice is made, the universe splits into two, where one side the choice is made, and the other, it is not). This is derived from quantum mechanics and a denial that the wavefunction can collapse. A common example of wavefunction collapse is observing the spin of a proton. It is theorized that the proton has both a positive spin and a negative spin (both wavefunctions), until it is observed, in which case, one wave fuction collapses and so we observe only one spin. If we look at it later again, we may see the same spin, or a different spin. What MWI theorizes is that rather than the wavefunction being destoried, it merely exists elsewhere (an alternative usiverse where we would see the spin as the opposite as in this universe). The other common multi-verse theory is based off of M-theory, which is derived from string theory. This is not a theory of divergent universes from wave functions, like MWI. But that there is more than our current universe, and it goes into theorize what existed before the big bang, and what caused it. Namely the collision of p-branes creates a d-brane (a universe) on the surface of the p-branes (which exist in 11+ dimenstions, not just the 4 we experience). This leads to the obvious potential that our d-brane unverise is not unique and that there could be countless more, just like our solar system and our galaxy are not unique. Between these two theories (and the many more lesser known) and our current, limited understanding of physics, astronomy, and cosmology, it is entirely pausable that there may be more than just our universe.