Imagine leaving Earth in a rocket. Leaving the solar system. Leaving the universe. It would be impossible to leave our universe behind as you would have to go faster than the speed of light, but work with me here.
You are cruising through the void for millions of years, only to find another universe with another solar system, another Earth, and another galaxy inside it.
The multiverse might be a prediction of the physical theories that define the beginning of the universe. Or it might not. New research shows it's difficult to say.
What is multiverse theory?
A large old universe.
When our universe was less than a trillionth of a trillionth of a second old, it went crazy. The universe got really, really big in the fraction of a second it took.
How big? It's hard to say, because this concept is very hypothetical, but "way bigger than you might think" should suffice. Inflation models call for a universe that is at least 1052 times bigger than the observable volume of the universe. The observable patch is already 90 billion light-years across, so it's nearly incomprehensible that the true extent of our universe is so large.
The universe expanded after the Big bang. The science photo library is owned by Mark garLICK.
Inflation can solve a lot of problems in the standard Big Bang model, like the fact that the universe is vastly different from each other. Inflation ripped them apart, but according to inflation theory, those regions were once quite cozier and got to know each other well.
It may not be done because of inflation. It may never be done. This idea describes how the universe at the grandest scales may always be inflating, with only tiny pockets pinching off to become normal patches like our own. The islands would be separated by a gulf of nothingness, with the islands flying away from each other faster than light.
The island universes would never meet and could never talk to each other. It would be hard to find evidence of their existence.
To inflate or not.
Without direct evidence, could we make an educated guess as to whether the multiverse is likely or not? How could we figure out if we were just one bubble in a giant bathtub filled with foam expanding faster than light?
The first step is to measure inflation. There is evidence that inflation happened in the early universe, but the jury is still out on that. If inflation had occurred, you'd see that the fluctuations in the microwave background have a pattern that matches what happened when the universe was 380,000 years old. There is no other theory that matches that pattern of light.
That's good. "inflation" isn't a single theory. It's a class of theories. Different models assume different causes and effects of the event. It's too early to tell which of the theories are correct, as all of them are based on hypothetical models of the early universe.
Physicists think that eternal inflation is a consequence of models of inflation. If inflation is correct, then eternal inflation is also likely correct, and the multiverse might be real.
The multiverse is judged.
The existence of the multiverse is a big deal. There is an infinite number of pocket universes if eternal inflation is correct. Each one could potentially support its own laws of physics. If the number of ways to arrange matter and energy is finite, then an infinite multiverse demands repeated copies of the same physical situation, even if any particular combination of physical configurations is incredibly rare.
That means there's a copy of you at some distance away. Another copy past that. And another. And another. You're doing the same thing.
A team of physicists claims in a recent paper that eternal inflation is a common feature of most, if not all, inflation models and that the multiverse is likely if that is the case. They put a large number of inflation models through a grinder, varying the types of models and the model parameters, counting which ones were a one-and-done affair and which ones led to eternal inflation and a multiverse.
It's complicated.
They found that eternal inflation wasn't as common as they thought. Their explanation for why they thought eternal inflation was generic was that they only studied a limited set of models. They found that many viable inflation models didn't lead to an inflating scenario.
It's difficult to get a handle on measuring the commonality of eternal inflation since we don't have a good grasp of inflation models and how they work. It's not possible to answer the question of genericness with a single answer because there's so much we don't know about inflation.
Is there another person out there who is reading the same article? It's difficult to say.
Live Science published the original article.
