Today we’re talking Multiverse! The theory that there are multiple universes has been around for some time.
For as long as there has been a universe, space has been expanding, and it continues to expand. As far as we know, our universe is a single expanding blob of spacetime speckled with trillions of galaxies.
This said, our universe is big, but also finite – or it could be infinitely big!
Both these theories are possibilities, however, if the universe is infinite, there are only so many ways that matter can arrange itself within it. Eventually, the matter must arrange itself in similar ways. If that sounds confusing, think of the universe like a deck of cards; If you shuffle that deck, there's just so many orderings that can happen. If you shuffle that deck enough times, the orders will have to repeat. Similarly, with an infinite universe and only a finite number of complexions of matter, its arrangement must repeat.
That said, if a multiverse does exist, there would also be infinite versions of you. Alternative versions of you might be doing the same thing you’re doing right now, but probably have vastly different career and life choices.
Around 13.7 billion years ago, everything we know of was an infinitesimal singularity. Then, according to the Big Bang theory, it burst into action, inflating faster than the speed of light in all directions, for a tiny fraction of a second. As the inflation slowed, a flood of matter and radiation appeared, creating the classic Big Bang fireball. It began to form atoms, molecules, stars and galaxies that populate the vastness of space that surrounds us.
The mysterious process of inflation and the Big Bang have convinced some researchers that multiple universes are possible, or even very likely. According to theoretical physicist Alexander Vilenkin, inflation didn't end everywhere at the same time. While it ended for everything that we can detect from Earth 13.8 billion years ago, cosmic inflation continues in other places. This is called the theory of eternal inflation.
Recent discoveries in physics and astronomy point to the idea that our universe may be one of many universes populating a grander multiverse. The key to proving these theories lies in string theory, which attempts to reconcile a mathematical conflict between quantum mechanics and the theory of relativity. From a physics point of view, parallel universes are one of those theories that are very difficult to test, yet, we have made great steps to understanding it, especially if we compare it to when the idea of multiverse began, back in 1926.
What is beyond the edge of the observable space around us? No one knows for sure, and until we do, the thought that our universe extends infinitely is for sure an interesting one.