Question: Why Are There Multiple Universes?
I've heard that physicists believe there are multiple universes, but why? I get that it's possible they could exist, but since no one can see them, how can anyone know for sure? Do physicists have good reasons for thinking there may be multiple universes?
Answer: The idea of multiple universes is very popular, not only in physics but also in popular culture. It's been used in a wide number of science fiction shows, and scientists continue to invoke it frequently as part of explaining physics to popular audiences. This question actually breaks
Do Physicists Believe in Multiple Universes?
Many physicists do believe that there are multiple universes, in some form or another. However, it's not particularly clear to me that you could necessarily say this is a majority viewpoint. Most physicists really don't deal with this question at all and, because there's no direct evidence one way or another. Many seem to consider it a distraction which interferes with time that could be spent focusing on more important ideas in physics.
However, if you get most of your physics knowledge from television shows - such as PBS' NOVA, The History Channel's The Universe, or pretty much anything on The Science Channel - then you can be forgiven for thinking that this is something that physicists spend a lot of their time focusing on. It makes for great television, that's for sure, and it's fun to write articles on.
Still, the physicists who do believe in multiple universes do so because invoking the idea of multiple universes takes care of some problems in the realms of particle physics and cosmology.
What Is the Reason for Believing in Multiple Universes?
The argument in favor of multiple universes tends to go something like this:
First, there's a strong understanding in cosmology of something called the fine-tuning problem, which is basically the idea that as we understand the way our universe is constructed, the more precarious our existence in it is. As physicists have examined the way the universe has changed over time since the big bang, they have come to believe that the early conditions of the universe, had they just been a microscopic bit different, would have caused a universe that is inhospitable to life.
In fact, if a universe spontaneously came into existence, physicists would expect it to spontaneously collapse or possibly ...