Ever since I read about the possibility of multiverses, I have been intrigued. Since then, I had imagined that the multiverses would exist because of the possibility that there are really 11 dimensions in the universe, but this article [via Jack] presents a different possibility: there are multiverses out there all within our given 3- or 4-dimensional universe but we don't see them because they are so far away their light could not have gotten to us yet.
Our definition of "the universe" has been changing since the invention of the first telescope when we peered out into the cosmos and learned that the Earth is not the totality of existence.
But the universe is a lot bigger than what we could ever see with a telescope.... Our universe is just the spherical amount of light that has had time to reach us. If we wait another billion years for more light to reach us, our definition of the universe would change... [emphasis added].
Someone standing on a planet trillions of lightyears away would have a completely different picture of "the universe" based on how much light has reached their planet.
By definition there's no way to get to these other bubble universes because we'd have to travel faster than the speed of light. [emphasis in the original].
What a neat perspective!