Can we find other universes?
The multiverse hypothesis suggests that our Universe could be just one of any number of other universes.
There are many competing interpretations about how and where these other universes might exist. One well known sci-fi idea is that throwing a die will spawn six universes, each differing only in which side of the die lands facing up.
Until now there has been little experimental evidence to prove or disprove any of the theories. If other universes do exist, they could be so far away that their light may never reach us. They could exist in another reality which we cannot detect, or any number of other possibilities.
How can we test for something we cannot observe?
Researchers at the Perimeter Institute for Theoretical Physics have been looking for the fingerprints left behind in the cosmic microwave background radiation (CMB).
The young universe was filled with an opaque, dense, fog-like plasma. About 389 thousand years after the big bang, the Universe had cooled enough that atoms could finally form. This allowed light to travel freely through space and the Universe became transparent. This light is known as the CMB radiation and has been travelling ever since, growing fainter as the Universe has continued to expand.
The team created computer simulations of collisions between our Universe and other universes, and how it would affect the CMB. These simulations showed that there would likely be a circular “bruise” left in the background radiation if such a collision had occurred.
Unfortunately they have not been able to find any evidence for a collision in maps of the CMB radiation from our sky.
This doesn’t disprove the idea that other universes are nearby. It does make it less likely though.
While the team wasn’t the first to think of the collision idea, they were the first to think of a way to test for the presence of other universes. It’s an important first step.
The hunt continues.
Ilc 9yr moll4096” by NASA / WMAP Science Team – http://map.gsfc.nasa.gov/media/121238/ilc_9yr_moll4096.png. Licensed under Public domain via Wikimedia Commons.