If you travel long enough in one direction, you can return to the starting point of our universe.
Astrophysicists tend to agree that the universe is expanding, which means that the journey will take longer as time continues to advance. But if the universe is expanding, where is it expanding? Our universe is just one of many "bubbles" popping out of its own Big Bang.
Fraser Kane of the popular news site Universe Today said our universe could be one of many in a larger "multiverse".
“One of the super interesting and certainly rewarding ideas is that our cosmos is really just one universe in an even bigger multiverse. Each universe is a kind of soap bubble embedded in the cosmic void of the multiverse, expanding after its own Big Bang,”he said.
It looks like a huge cosmic foam with various bubbles of universes emerging. The theory says that in each of these universes, the laws of physics are completely different. The physics of our universe is dictated by a range of different physical constraints, such as how strong gravity is or how strong an interatomic bond is. In each next universe, these numbers will be different, depending on how the bones are laid.
“Maybe in another universe, gravity is repulsive,” said Mr. Kane.
In the vast majority of these universes, life could not have formed. But if you roll the dice an infinite number of times, then in one of the universes all the necessary conditions for the formation of life would be found.
“Any life form capable of perceiving the universe must have originated in the universe that is capable of generating life,” he explained.
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This sounds far-fetched, but astronomers have their own ways of measuring the universe to test a theory. If bubble universes are stretched far enough, they will begin to interact with each other. Based on these observations, there is some evidence that our universe interacts with others. By peering into the cosmic microwave background radiation (CMBR) left over from the Big Bang, scientists have discovered temperature fluctuations or anisotropy.
As the universe expanded, regions of different density of matter also expanded. Most of the temperature differences can be explained by the current model of how the universe has evolved.
“But there is one area that challenges our theory. It’s strange that the researchers who discovered it jokingly called it “the axis of evil,” explains Mr. Kane.
There are many theories explaining the "axis of evil", and most of them are more reasonable and more probable than this theory. But the idea is that a region of our universe is crashing into another. This area is billions of light-years past, so any overlapping effects of the laws of physics will not affect us. We have to keep observing to try and understand what it really is.