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Asaf Pe'er

Physics for all



Are there parallel universes?

Maybe.
The point is the following: we can make various observations and study various properties of the universe we live in. For example, among the properties we can measure are the expansion rate of the universe, its average density, temperature, chemical composition, etc. While we can measure some of its properties, we do not know WHY our universe has these particular properties and not others. For example, there is no convincing explanation to the question of why the universe we live in is not 3 times denser than what it really is. In order to resolve this issue, it had been hypothesized by several notable physicists (such as Stephen Hawking and others) that in addition to our universe there may exist other universes. These additional universes may exist in such distant places that cannot be observed, or in different dimensions. The physical properties of these additional universes may be different than those of our observable universe. If this is indeed the case, then really there is nothing special about our own universe.
Of course, the problem with this hypothesis is that we have no way of knowing if any such alternative universe external to ours truly exist, neither we can measure its properties. As such, many scientists argue that the idea of parallel universes is outside the realm of physics (or science), since physics deals only with things that can be measured.
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