Is our Universe just one of many in an infinite, ever-expanding multiverse? What exactly is
the multiverse? Is it just a speculation of us humans or could it be that our universe
is a part of a multiverse? In this article we will discuss these questions. We have used
the theory of multiple universes in cosmology, physics, philosophy, astronomy, religion,
science fiction, comic books and fantasy. But we will look at the scientific aspect
of it. We will only focus on the evidences and facts and observations made by astronomers
and then draw a conclusion on the topic. The three dimensional world which we witness
in our daily lives may just be an illusion where there is no distinction between past,
present and future. But how is it possible? How can we be so wrong about something so
familiar? These questions bother almost all astronomers and physicist. It’s a groundbreaking
possibility that opens up a whole different world for us. We will discuss an important
Question. What if alternative Universes are being formed all the time? The Big Bang might
not be a unique event. We might live In a duplicate parallel reality among the many
other parallel realities. Somewhere there’s a duplicate of you, me and everyone else.
Are we in a Universe or a Multiverse? Uniqueness is an idea so usual that no one
questions it. A recent picture of the cosmos is coming to light, where nothing is unique.
This recent picture challenges the notion of Uniqueness, in which duplicates of things
are unavoidable. There might be duplicates, not only of objects but of me, you and everyone
else. And if it’s right, where are they? Why haven’t we seen them? There was a time
when the word Universe meant everything that existed, the notion of more than one universe
seemed impossible. But if we go beyond our Milky Way and even beyond the distant galaxies
and beyond the end of the observable Universe, we might find that our Universe is not alone.
There might be other Universes, in-fact, there might be new universes being born all the
time might have stars and even a planet that looks familiar. We may be live in an expanding
sea of Multiverse! Some of these might not have the basic requirements for the formation
of matter. Others might have planets, stars and Galaxies that look familiar to us but
with a slight difference. And if there are many other Universes out there, some might
be even identical to ours except for the slightest Details. For Example, in any other parallel
reality, it might be possible I am the Prime Minister of India. And if the multiverse exists,
we will have to encounter a lot of possibilities that might exist. There could be other places
where duplicates of me would exist and would think, act and speak in the same way as I
do, but with some slight differences. Is it science, is it religion, is it Philosophy?
As a Physicist we should not and we don’t ask these questions. We follow the logic,
and the logic leads there. There was a time when people thought Earth was at the centre
of the Cosmos and everything else that exists revolved around us. Then scientists like Galileo
and Copernicus showed us it’s the sun that’s at the centre of our solar system. And our
solar system is just a little neighbourhood in our Gigantic Galaxy. And our galaxy, it’s
among the billions of galaxies that make up our universe. These ideas sounded shocking
and outrageous when they were first suggested, but now we don’t even think to question
these ideas. The idea of different alternate universes or the multiverse might be the same.
It just requires a radical change in our perspective of the cosmos.
So let’s talk about where did the idea of Multiverse came from? What are the evidences of its existence?
Well, a lot of astonishing discoveries and theories have suggested we may be a part of
the multiverse. The very first among them is the Big Bang, the theory of the origin
of our universe. According to this theory, our Universe began 13.8 billion years ago
in a very hot and dense, violent explosion of a very tiny primordial nugget. Over millions
and millions of years the universe cooled down and it lead to the formation of Stars,
galaxies and planets. The universe is still expanding because of that explosion. But there’s
one major piece of this theory that’s missing. The Big Bang tells nothing about what caused
the explosion, throwing everything outwards. What caused the BANG? So, what furled the
violent explosion? What force could set everything moving outwards?
In 1979, a young physicist Alan Guth laid the foundation of the idea of the multiverse.
He and his mate Henry tie wanted to know how the particles might have been formed during
the early universe. Alan discovered something exceptional about their equation, about how
new particles were formed in the early universe. In the math of his equations he found out
the evidence that in the harsh environment of the early Universe the Gravity can be repulsive!
And act in reverse. This repulsive gravity would drive apart everything around it and
repel it, causing a massive expansion. This force was so powerful that it could take a
molecule and blow it up-to the size of a Galaxy in less than a billionth of a billionth of
a blink of the eye. This spectacular realisation gave birth to the theory of Inflation. This
powerful Gravity caused the Bang in the Big Bang. This repulsive gravity caused the Universe
to expand outwards. Two Russian physicist Andrei Linde and Alex Vilenkin found out that
the Equations of Inflation had an appalling secret, our Universe may not be alone! Alex
Vilenkin had attended one of Alan Guth’s talk on inflation. He was so fascinated about
the idea that he slept on it for months. He thought, “what exactly happens at when the
Inflation ends?” The more he wondered about inflation, the more he wondered about what
would make it stop? He then realised after months that the end of Inflation doesn’t
happen everywhere at once and if it doesn’t happen everywhere at once, there might be
a place where it might be still happening. In this theory, the Big Bang was not a Unique
event, there were many Big Bangs that happened before ours and many more might occur after
that. New big bangs always occur and an alternative Universe is always being formed yielding an
eternally expanding Universe. They incited the idea that inflation is a never ending
phenomenon. We know this idea as the eternal inflation. Vilenki explained the idea to others, but
the problem was that his ideas could not be observed. Because not only the universes were
expanding but also the space between them and nothing would reach us. And other scientists
would lose faith in listening to his theory when they were told by him we cannot observe
it. Eventually, with no sound evidence to support his theory, he lost hope and shut
down his work on the idea. On the other hand, his friend Andrei stuck to the idea and it
would take Vilenki 10 years when he would return to his idea because of the unexpected
support it gained from observations and studies, later.
The theory of Multiverse gained unexpected unanticipated from the two areas of science.
One was the String theory, and the other was a breathtaking discovery made by scientists
observing universe on a larger scale. A discovery that’s baffling if there’s only one universe,
but if we are a part of a multiverse, it's suitable to think of it. It’s related to
the expansion rate of our universe. Let us take an example, let’s take a baseball.
When the ball is thrown upwards in the air after sometime its velocity becomes zero and
it comes back to earth because of the gravitational pull of the Earth. Astronomers knew that the
universe was expanding and thought it would slow down in the same way because of the gravitational
pull of the stars and galaxies. But when the observations were made by the Astronomers,
they found out that the universe is not slowing down. It's expanding at an increasing rate.
This new discovery baffled them. It's just like throwing the ball up in the air and instead
of slowing down and coming back to the earth it keeps speeding up and moving away from
us eventually in the space and away. If we observe something like this with the ball,
we would assume there’s an invisible force behind it. Astronomers called it Dark Energy,
discovered by mainly three scientists Adam Riess, Saul Perlmutter and Australian astronomer
Brian Schmidt who won Nobel prize in 2011 for their discovery. It is the most important
discovery in the history of science. Discovering the dark energy and that it's causing the
universe to expand at a faster rate was shocking, but there was something more baffling and
it was the strength of Dark energy. Scientists could not explain why such a particular amount
of dark energy exists in our universe. This mystery can be easily solved if we are a part
of a multiverse. The idea that space contains any energy is strange. But quantum mechanics
shows us that there’s a lot of activity at the microscopic level, and the math suggests
that the amount of energy generated is enormous. But when the astronomers measured the amount
of dark energy present in our universe, it was 0.138×10-120, which seems an infinitesimal
amount. This amount of dark energy is tiny but if the dark energy would have been slightly
stronger, it would rip apart all the matter and we wouldn’t exist. So Why is the amount
of dark energy so less and so perfect for our existence? It’s a mystery for us, but
with the theory of multiverse we have a solution. The amount of dark energy differs in every
universe. In some it might be so less that the matter would collapse in on itself and
hence nothing could exist. In some, dark energy is large that matter could never get a chance
to form and hence nothing would exist there. The amount of dark energy in our universe
happens to be the right amount for our existence and differs in every universe. But still there’s
a major piece of the puzzle missing. How we know that there’s enough diversification
within the multiverse so that every value for dark energy including the curious value
found in our universe, can be found somewhere? The answer comes from a newly born area of
physics THE STRING THEORY. We all know that inside atoms are present,
the electrons and the nucleus. Inside the nucleus are protons and inside these are smaller
particles called quarks that make them. Physicist realised that these subatomic particles called
quarks are also made of something smaller tiny vibrating loops of energy or STRINGS!
It’s called the string theory. String theory states that everything that exists is made
of these strings at the fundamental level. Just like a string of violin produces a different
kind of notes, depending on how they vibrate. Strings can also create different particles
based on how they vibrate. This theory paved the way for one master equation that underlies
all the fundamental laws of physics, one master equation. But for the string theory to work,
the maths of the theory required something opposes common sense, a property that opens
the door for multiverse. Extra Dimensions of space. We all are familiar with the three
dimension Length, breadth and height. The fourth one being time, but let’s leave it
aside for now. But the mathematics of string theory proposes more than that. Its mathematics
works only when strings vibrate, not only in these three dimensions but in many more
dimensions. So where are these extra dimensions of space and why aren’t they visible to
us? Let’s think of a wire and look at it from a distance, it looks like a line, one
dimensional. But what about an ant that’s on the wire, it would see an extra-dimension.
And if we could shrink down billions of times than those ants, we will find extra dimensions
curled up into loop everywhere in the space. The shape of those dimensions determine how
these strings will vibrate and these vibrations of space define different original properties
of particles. So basically, these shapes of extra dimensions determines the underlying
basic features of the universe. They are like the DNA of our universe and determine how
our universe would behave. The major difficulty was that when the string theorist tried to
find the shape of these dimensions, they had a bizarre result. In the beginning there were
5 contestant shapes but eventually more shapes started coming and there were millions of
millions of different possible shapes, each appearing equally valid as the other. The
discovery was shocking. There were millions of millions of string theories now! String
theorist felt destroyed. What good is the theory that has millions of millions of solutions,
finding anything is impossible in there? But some string theorist thought to look at the
problem differently, a way that would lead to multiverse. They thought this is great,
there’s no reason to be depressed. Enormous diversification of the contestant shapes says
string theory fits perfectly for cosmology and multiverse. Eventually, string theorists
became convinced that the multiple solutions of the string theory represents a real and
a different universe. Each solution represented a different possible universe. String theory
was describing a multiverse! A very distinct multiverse.
Now there were three ideas that were all indicating towards a single theory, a same conclusion,
a multiverse. These were the Eternal inflation which we discussed in the first part, dark
energy and the string theory. These theories together revived the idea that Vilenkin and
Linde worked on 10 years before and were supporting the idea of a multiverse. Different lines
of research were focusing on one idea and ‘The Theory of Multiverse’ seemed convincing.
All the various alternate universes out there have a different amount of dark energy naturally, and
the unique shapes of these extra dimensions. Today many debate the idea of the Multiverse.
We can only wonder how these universes might look. Some might differ vastly from ours,
having features we cannot even imagine and some might be very similar to us.
Scientists like Alan Guth, Alex Vilenkin, Brian Greene and others continue to find more
clues for the multiverse while many are against the idea. The debate will go on but in the
coming future, who knows we might be able to prove its existence even more perfectly.
Thanks for watching everyone! What did you think about multiverse ? Can you believe all
the fascinating stuff that goes on with this theory? Let me know in the comments below,
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