A Universe Full of Stars – One Universe or Many?

multiverse

Visiting Kielder

The astronomical observatory in Kielder has been on my list of places to visit ever since I moved to the UK and it only took me three and a half years to go there. The observatory is located in Northumberland, England, one of the darkest places in the UK, and it recently celebrated its 10th year. The primary function of this facility is outreach via public events. From Aurora nights to talks on Space and the Universe we live in, there are over 40 events per month you can attend. If you are lucky and the Cloud Gods are not in a mood, you will even be able to look at stars and galaxies through the telescopes at the observatory. Unfortunately, on the night I visited the observatory the cloud cover in that area prevented us from observing the night sky. Typical! However, the team there made up for it. They were funny, knowledgeable and engaging and I really enjoyed their talks on Space and Cosmology.

Kielder Obsevatory
The Kielder Observatory, Source: kielderobservatory.org

The final talk was given by a cosmologist and I have to say, I really loved his presentation. He talked about our Universe, the distance between the stars and the fact that we live in a Universe that is rapidly expanding. This made me think about The Multiverse Theory – is it metaphysics, is it a philosophy or just a belief? Is there a way of testing it?

Some scientists believe that there are universes that exist parallel to each other, that each of those parallel worlds has a copy of you reading this very post right now or doing something completely different with your life. Other theories suggest that those universes have completely different fundamental laws of physics.

We currently don’t have any proof that we live in one of many universes, but some of our theories and observations suggest exactly that and this is why a growing number of scientists believe in the Multiverse. In particular, Dark Energy and the Inflation Theory lead to the belief that our Universe might be one of many.

Dark Energy 

Edwin Hubble
Edwin Hubble

While working on explaining how gravity works, two of the greatest minds in physics – Newton and Einstein thought they were presented with a paradox. They both concluded that if gravity is always attractive and every object in the Universe attracts every other object, the Universe should have collapsed on itself as result of the gravitational pull between galaxies. However, that clearly wasn’t the case and in 1929, Edwin Hubble solved that problem and made one of the greatest discoveries in physics – our Universe has been expanding from the moment of its creation and it’s in a constant state of change. As every discovery in science, this too, led to many other questions and in particular – what is causing the inflation and overcoming the gravitational pull of the 100 billion galaxies in our Universe? Drumroll please, the answer is dark energy.

Dark Energy is a repulsive force or anti-gravity, that pushes stars and galaxies away from each other. It appears this energy is strong enough to push the entire universe away, to overcome the gravitational pull of galaxies, and yet we don’t know what it is. However, physicists have been able to measure the amount of dark energy because of the way it affects the expansion of the Universe. Even though, they don’t agree on what dark energy is, one thing is for certain and that is if the amount of dark energy was different life as we know it may not exist at all. We live in a universe that has the exact amount of dark energy we need for life to emerge. If there was more dark energy, space would expand too quickly, which will prevent the creation of stars and galaxies. On the other hand, if there was less repulsive energy, the universe would collapse on itself because of the gravitational pull of the many different objects.

Why is the amount of energy just right to allow for the formation of stars and galaxies? Are we just that lucky? This is where the Multiverse Theory comes into play. The fact that we find ourselves in a Universe with the exact amount of dark energy to support life suggests that there are a number of universes that have different amounts of dark energy, and we simply find ourselves in our universe because is one of the many possibilities. Here is where most scientists would like to disregard this idea, but they can’t put forward any other explanation for the amount of dark energy we can observe.

Another question that arises from Hubble’s discovery is – what is the Universe expanding into? It is believed that there are three possible types of an expanding universe and they are called flat, open and closed universes. May I just point out that I am really concerned that scientists have decided to call one of the possibilities Flat Universe because of all the Flat Earthers out there. To all of you lost souls who believe that we live on a flat Earth, please don’t read into this.  But back to the topic at hand. If we were living in a flat universe, it would expand forever, but it is believed the expansion rate will slow down to zero after an infinite amount of time. If the universe were open, it would expand forever and if were closed it would eventually collapse on itself, leading to another big bang. Which Universe do we live in?

Inflation Theory

In a nutshell, the Inflation Theory proposes a period of extremely fast expansion after the Big Bang. It was proposed in 1981 and it was first developed by Alan Guth in 1979. The Universe is still expanding but at a lower rate and it appears to be the same in every direction (isotropic). This and the fact that the cosmic microwave background radiation is distributed equally leads us to believe that the Universe is flat. Yes, we may live in a Flat Universe.

Scientists suggest that after the Big Bang some areas grew faster than others, creating bubbles of space-time that might have developed into separate universes, with their own laws of physics.  But what if the Universe is expanding eternally? This will inevitably lead to the creation of so-called bubble universes, whose properties differ from universe to universe, covering all physical possibilities.

I would like to end the post with a quote from Alan Guth, theoretical physicist and cosmologist:

“It’s hard to build models of inflation that don’t lead to a multiverse. It’s not impossible, so I think there’s still certainly research that needs to be done. But most models of inflation do lead to a multiverse, and evidence for inflation will be pushing us in the direction of taking the idea of a multiverse seriously.”

Do you believe in the Multiverse? Do you think there is a parallel universe, where there is another one of you? Do you believe we live in a world with an endless number of universes, where Big Bangs happen all the time, everywhere? How far can you stretch your imagination?

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