IS OUR UNIVERSE just one bubble of existence in an infinite multiverse? The latest survey of the cosmic microwave background (CMB, also known as the radiation afterglow of the Big Bang) by the European Space Agency’s (ESA’s) Planck space telescope seemed to support an idea called “cosmic inflation.” Cosmic inflation is a sort of “injection” of energy that caused the universe to expand exponentially just moments after the Big Bang, when it was still smaller than an atom. This rapid inflation is seen by many as being the only explanation for the apparent even spread of energy in the early universe (by inflating the teeny tiny universe before it got the chance to spread slowly and get all “lumpy”). But a potential consequence of cosmic inflation is that, while most of the universe slowed down, tiny pockets could have continued their exponential inflation—creating offshoot “bubble” universes.
The universes pop off once they are formed.
Each universe may have different rules and outcomes.
Another tantalizing hint of the existence of other universes can be found in Planck’s cosmic microwave background survey. There is a mysterious cold spot (pictured below, far right) that, some have suggested, could be the “imprint” left behind by another universe before it separated from our own. Although there is nothing in current cosmological theory that explicitly rules out the existence of other universes, there is no hard evidence supporting the idea, either. But it is fun to imagine that it might be possible. One of the most commonly asked questions of Big Bang theorists is “what came before the Big Bang?” The standard answer is that there was nothing at all. Normally, we are quite comfortable with the idea of “nothing.” We are conditioned by experience to think of nothing as being an absence of something within a given area, but if space itself was created in the Big Bang, there cannot be “nothing” because there is nowhere to put the “something” that does not exist. Asking what came before the Big Bang is equally meaningless because “time” was created along with space—you cannot have a “before” because time did not exist. For a species that experiences the world by interacting with time and space, that is a slightly uncomfortable, brainblending concept. Luckily (depending on your point of view) there are physicists who believe that, far from being the beginning of all things, the Big Bang was just the moment our universe burst from the womb of a parent universe—just one offspring of a much larger multiverse. The idea that our universe is just one of countless others might seem (at best) incredible and (at worst) delusional, but remember this: We once thought our planet was unique, then we thought our solar system was unique, and, after that, we thought our galaxy was unique—is it such a stretch to imagine that our universe is not unique, as we like to believe? One of the problems with our universe being “the” universe is that it seems a little too perfect. It is a universe where the laws of physics are perfectly tuned for the creation of stars, galaxies, planets, and life—if just one aspect of those laws were different, then the universe as we know it would not exist. It is the same problem we once had with our planet. Looked at in isolation, Earth seems to have been perfectly “designed” for the creation of life— just the right distance from just the right sort of star with just the right atmosphere and just the right sort of magnetic field (and so on). Of course, we now know that there are countless other planets out there where conditions are not perfect and where life does not exist. We were just the winners in the planetary lottery. The multiverse would solve the problem of our “perfect” universe in the same way. Just as Earth won the planetary lottery, our universe won the cosmological lottery. It seems “perfect” because the conditions within it allowed us to evolve and marvel at its perfection. But there are countless other universes where conditions were not just right. You can compare it to a game of cards. If you were allowed to pull just one card from the deck, the chances of pulling out the card you were looking for is quite small, but if you were allowed to go through the whole deck, your card’s discovery becomes inevitable. The same applies to the multiverse: With infinite permutations of the laws of physics available, it is inevitable that one would be perfect for life. In many ways, a multiverse is a more comfortable concept to come to grips with than a perfect universe born from the void. Of course, eventually you have to ask where the first of these ancestor universes came from, and you are right back where you started!
When scientists analyzed the Planck CMB data, they noticed that a region of sky near the constellation Eridanus was colder than the surrounding region. This “cold spot” is a highly peculiar anomaly that might be an imprint mark left behind by another universe.
Another theory is that our universe was born within a black hole and that black holes within our cosmos are creating universes of their own.
1-Black hole
This is a black hole. She is quite happy munching her way through all the light and matter that strays too close to her irresistible gravitational pull. At her heart is a tiny ball of concentrated matter called a singularity, which gets increasingly compact as it gains mass, until it reaches near-infinite density.
2-Singularity bounces back
At this point, the standard theory suggests that space and time become so heavily distorted at the singularity that time stops. But one theory says that the singularity “bounces back” and punches a hole in spacetime (the fabric of the universe).
3-Big Bang
Here, the singularity begins to expand—creating a “Big Bang” from which a new universe is born, where the laws of physics might be slightly different from those of its parent universe.
4-Time stops in singularity
Back in the parent universe, just as time starts in the new universe, time stops at the singularity. Eventually, the original black hole collapses—severing the umbilical cord to the offspring universe.
5-Multiverse
There might be an infinite chain of universes, but only a few in which the laws of physics are conducive to life.
A singularity is created when the core of an extremely massive dead star collapses under its own weight.
M-theory (an offshoot of string theory) suggests that our three dimensional universe exists on a membrane that can be compared to a slice of bread. On that slice are all the stars and galaxies of our universe, but parallel to that are thousands of other universe slices—arranged in a sort of huge cosmic loaf—that butt up against our own but that we cannot detect. It is thought that this might account for the apparent weakness of gravity (compared to the other fundamental forces), which might be spread out through the whole cosmic loaf—with each slice only experiencing a fraction of the total gravitational force.
