It is one of the great questions of life: what is beyond our universe? Is there life outside of our universe? And are there perhaps several universes?
There are countless stars, planets, galaxies and clusters in our universe. It is very likely that several – perhaps countless – universes exist. These universes are part of a larger whole. Researchers call this the multiverse.
At the moment there are several theories. There are scientists who think that there is one infinitely large universe, of which we only see a part. The different universes share the same space. Another theory is that several universes float like bubbles in a vacuum.
One bubble in a sea full of bubbles
According to the multiverse hypothesis, it all started with a vacuum containing energy (also called vacuum energy). Bubbles arose in this vacuum, each of which also contained a vacuum, which also contained energy. That energy caused the bubbles to expand. It is likely that some of these expanding bubbles collided with each other, possibly creating more bubbles. Each bubble in this story is a universe. In this hypothesis our universe would therefore be just one bubble in a ‘sea’ full of bubbles.
Why does our universe contain little dark energy?
As you may know, our universe originated 13.7 billion years ago. Before the big bang, there was one point – a so-called singularity – with all the energy to build the universe. At some point, this singularity started to expand, and scientists call it the Big Bang. The driving force behind the expansion of the universe is dark energy: a mysterious vacuum energy that acts as a kind of anti-gravity. Dark energy must exist, otherwise it is impossible to explain why the universe is expanding faster and faster.
At the moment, our universe seems to contain less dark energy than theories predict. How is this possible? Researchers have an idea about that too. However, this is metaphysics, because it cannot be proved. Scientists suspect that after the Big Bang, several universes emerged, each with their own laws of nature. In that scenario, our universe is one of many universes and ‘coincidentally’ is equipped with a set of natural laws that make life possible. In other words: we are here because we can. At the same time, this means that around our universe there may be many unlivable universes with more dark energy.
A multiverse or a creator
Our universe – and therefore also us humans – turn out to be the result of a perfect, but vulnerable coincidence: something else would have had to happen or we would not have been there. And how do you explain that as a researcher? Scientists call this issue ‘fine-tuning for life’. At the moment there are really only two solutions in circulation. The first argues that the beautifully attuned universe is the work of a higher power whose purpose was to create life. The second explains the “perfect cosmos” by stating that there are multiple universes, each with their own laws of nature. In this scenario, the universe we live in is not tuned in to us, but we are here because we can.
Is there life outside the universe?
We don’t even know if life is possible on planets other than Earth – let alone intelligent life – but the chances are very high. For example, in the universe there are many trillions or even quadrillions of planets. It is statistically impossible that there is no life beyond Earth. According to scientists at the University of Nottingham there are currently at least 36 intelligent civilizations in our galaxy, but that too cannot be proven. If life is possible within our universe, then it is likely that there is also life outside the universe. Even in other universes with greater amounts of dark energy, life is possible. “If we increase the amount of dark energy hundreds of times, that doesn’t seem enough to create a dead universe,” said study researcher Pascal Ealhi.
Criticism of the Multiverse
Although the multiverse seems to solve several problems in physics, not all physicists are enthusiastic. “I don’t like it,” Daniel Baumann revealed earlier in conversation with Scientias.nl. And Klaas Landsman, professor of mathematical physics at Radboud University Nijmegen, is not very enthusiastic either. According to him, the multiverse solution is circular reasoning. Landsman wrote the book ‘In all improbability†
How far can we see at most?
The space photo of the week shows how far we can see at the moment. Above you see a representation of the cosmic microwave background radiation. After the Big Bang, the universe was very hot. Then the universe cooled down. The cosmic microwave background radiation is radiation from the residual heat. 380,000 years after the Big Bang, the universe became transparent and this radiation could move freely for the first time. Scientists believe that the cosmic microwave background radiation can be used to search for traces of earlier universes (i.e. universes that formed before our universe). In fact, thirty so-called Hawking points have already been found. Fascinating science!