For nearly 100 years, physicists have been trying to reconcile the physics of the smallest building blocks of the universequantum physics) with the physics of the galactically large Einstein’s Theory of General Relativity). But they kept running into one requirement that was hard to swallow: their theories only worked if we live in a multiverse—if our universe is one of many.

For example, Erwin Schrödinger’s equation explaining the collapse of a quantum wave requires a multiverse. And String Theory, which postulates that the universe is made of infinitesimally small vibrating strings of energy, also must include a multiverse. Trouble is, no one can prove the multiverse exists, much less what it’s like, or whether we can interact with it. Still, the math looks promising.

That begs the question: if there are other universes, can we ever visit them?

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