David J. Eicher writes:

Decades of astrophysical research beginning in the late 19th century established the universe as we see it, culminating with the Big Bang theory. We now know the universe is about 13.8 billion years old and at least 150 billion trillion miles across. But in recent years, astronomers have begun to address a staggering possibility — the universe we can observe, and in which we live, may be one of many that makes up the cosmos.

The suggestive evidence for this comes from several directions, from the idea of cosmic inflation, from string ttheory and the existence of the famous cosmological constant. Some of the notions that come out of these lines of evidence are pretty counterintuitive. Yet that doesn’t worry astronomers. “I fully expect the true nature of reality to be weird and counterintuitive,” says cosmologist Max Tegmark of the Massachusetts Institute of Technology, “which is why I believe these crazy things.”

The idea of multiple universes, or multiverses, poses the notion of the universe existing like a giant sponge. Each bubble is a distinct universe, like ours, but others could exist separated by giant voids.

What’s the evidence for all this? First, measurements of distant supernovae suggest the expansion of the cosmos is accelerating. Second, more and more evidence supports the inflationary scenario of the early history of the universe. Third, ideas about inflation suggest many Big Bangs may have occurred. Fourth, recent notions about string theory suggest universes of very different types may have formed. Altogether, these notions suggest it was possible, if not probable, that multiple universes of different types formed in the past, and they coexist with the familiar cosmos we can see. [Continue reading…]