The idea of multiple universes has received significant traction within the market place of ideas in the last few years. Unfortunately, the multiverse hypothesis is outside the bounds of empirical observation, thus making it un-falsifiable. Due to this, many scientists have dismissed the multiverse hypothesis as nothing other than mathematical speculation. Despite these limitations, in recent news, scientists have discovered a specific pattern of gravitational waves predicted by the theory of inflation imprinted into the cosmic microwave background radiation. It is surprisingly difficult to created models of inflation that do not involve multiple universes. In light of these findings, the evidence that gives credence to inflation also gives weight to the multiverse hypothesis.
So what is the theory of inflation? When physicists trace the history of the universe back to the first few hundred thousand years, they encountered a metaphysical barrier that not scientific theory could suffice. Approximately 380,000 years after the big bang, the universe was cool enough to emit light. This light was fossilized in the form of cosmic microwave background radiation, allowing scientists to directly observe the universe as it was 380, 000 years old. Prior to this time, the universe was an inferno too hot to emit light. Although physicists had theories that explained how the universe ticked during this time, they had no way to empirically confirm many of these theories.
The theory that takes physicists to the earliest time in the universe’s history is the theory of inflation. The theory of inflation (perhaps a better term is hypothesis) states that the universe exponentially inflated like a balloon a fraction of a fraction of a second after the big bang. Gravity was switched on backwards, acting as a repulsive force that increased with distance. In less than a billionth of a second, the universe went from the size of an atom to the size of a grapefruit. In fact, according to inflation, the vacuum of space expanded quicker than light speed. Although objects within the vacuum cannot travel faster than light speed, the vacuum—to be terse—can do whatever the hell it wants. For reasons that aren’t entirely understood, this exponential expansion was short-lived.
Scientists fell in love with the theory of inflation because it explained the locked uniformity of the cosmic microwave background radiation. The matter in the universe is conglomerated into galaxies randomly sprinkled throughout the cosmos. This being the case, one would expect that the temperature of the universe would vary by location in the same why that an island varies in temperature by its geographical placement in the sea. Yet the heat emitted by the universe is surprisingly uniform. In particular, the heat on one side of the universe has not had enough time to mix with the heat on the other side of the universe.
The theory of inflation explains this locked uniformity. When the universe was packed into a size no larger than the period at the end of this sentence, the heat within the cosmos was uniform. The universe then exponentially inflated, sending the same amount of heat in every direction. Scientists had no way to test this hypothesis until recently. In particular, the theory of inflation predicts a specific pattern of gravitational ways that should be imprinted into the cosmic microwave background radiation. In recent news, scientists found that the gravitational waves predicted by inflation are imprinted into the cosmic microwave radiation, thus giving credence to the theory.
A consequence of the theory of inflation is that the universe occupies a very small pocket in a much larger mega universe. In fact, the theory of inflation predicts that our universe is infinite and gave rise to many other universe. When the universe inflated faster than the speed of light, the expansion ripped the vacuum of spacetime into separate pieces, or multiple universes. The constants that the laws of physics take in these dis-attached universes could vary considerably. Thus, the recent findings that give credence to the theory of inflation also give weight to the multiverse hypothesis.
Many people have dismissed the idea of string theory, multiple universes and inflation on the grounds that these ideas are not testable. However, such pessimism is unwarranted. The ability to peer outside the Milky Way to the other side of the universe was a pipe dream for anyone before the 20th century, and the theory of inflation was nothing other than mathematical conjecture until recent evidence suggested otherwise. With these insights, scientists are beginning to paint a picture of the universe further than the eye can see.
By Nathan Cranford