Parallel Universes and Multiverses: Theory or Reality?

A few days ago there was quite a stir in the social media, NASA scientists have discovered a parallel universe! Such a sudden information made quite a stir among the science lovers. But after several days, it was known that nothing was actually found. That is, at the end of the day, this mysterious chapter of physics is still undiscovered by scientists. What does this parallel universe or multiverse actually mean? Are these just theories, or do they actually exist? Let's try to understand some incomprehensible theory of physics about parallel universe or multiverse. 

First of all, do not know what parallel universe or multiverse is called in common language! According to the theory of physics, in this vast universe of ours there are some parallel universes like ours, where time flows opposite to ours. That is, somewhere in the universe there is exactly such a universe, where maybe there is a Milky Way galaxy like ours, there are various nebulae. There is also a blue planet in the middle of the solar system called Earth, on which someone who probably looks like you is studying the theory of parallel universes with infinite interest. That is, somewhere in the universe there are some similar parallel universes, which are not aware of each other's existence. This is commonly called parallel universe.

parallel universe; image source: edtimes.com 

The reasons behind the emergence of this incredible theory are also quite surprising. Not one, but several theories of physics collectively point to the existence of parallel universes. Today we will try to know about the possibility of parallel universe through some different theories.

The possibility of time travel 

Although future travel or time travel is theoretically possible, scientists have faced several questions in the past regarding the possibility of time travel, one of which is the 'Grandfather Paradox'. Suppose a man travels back in time and kills his childhood grandfather. But if one can really do this, then his grandfather is not supposed to reach adulthood, not to marry, not to give birth to children after marriage, not even to have grandchildren. So, if someone went back in time and killed his grandfather, where did the killer himself come from? 

One possible answer to this question is a parallel universe. According to scientists, if someone wants to travel back in time, after entering a wormhole, he will enter another universe that looks similar, even if he kills someone like his grandfather while there, it won't have much effect. Because the killer never existed in the parallel universe that entered through the wormhole! Moreover, since time always moves forward, never backward, going into the past means entering a universe where time flows in reverse. And this scientific possibility is possible in a universe where time flows in reverse. This is basically how the possibility of parallel universes came to the fore when looking for answers to time travel complications.

Time travel through wormholes; image source: livescience.com

Schrodinger's cat theory
Perhaps the best explanation of parallel universes is found in quantum physics. Since quantum physics is a rather obscure mathematical probability-dependent field, we will discuss a very small example for ease of understanding. This theory is also known as the zombie-cat theory. 

 According to quantum physics, electrons can spin clockwise and anti-clockwise at the same time. That is, starting from a marble, a cricket ball, a football, even planets and stars follow a certain direction while rotating, but usually electrons do not. It can spin in both directions at the same time. 

 Now imagine, a rotating electron is kept in a closed room. The electron spin detector is attached to a device at the end of which is attached a hammer, in front of which is placed a glass test tube filled with a poisonous gas. If the electron spins clockwise, the detector will detect it and a hammer blow will break the test tube, releasing toxic gas and killing the cat. If the electron rotates anti-clockwise, no signal will reach the detector, so the hammer will not move, the test tube will remain intact, and the cat will survive. Now, exactly what happens in this case?

The answer is both simple and confusing. If the electron is moving clockwise, that means there is a dead cat in the room. If it is the other way around, i.e. the electron moves anti-clockwise, then there is a live cat in the room. But since we said the electron is spinning in both directions at the same time, theoretically there is now a cat in the room that is alive and dead at the same time! That is, according to the test results, there is a cat in that room, which is neither alive nor dead! Because of such possibilities it is called Zombie-Cat! 

 This strange law of quantum physics makes it mathematically possible for multiple but opposite events to occur at the same location. Now the question is, if someone looks inside the room, will he see a live and a dead cat at the same time? The answer is, no! That is, if we have different observers for the same experiment, each will see only one result. One experimenter would see the dead cat and at the same time another experimenter would see the live cat in the room. This means that two observers can see the same event from both sides, but not each other. That is, they are witnessing two different times with respect to that specific event, their observations are divided into two different timelines. Just as two parallel lines begin to run side by side but never meet at an infinite distance. That is, the mathematical probability of two different or opposite events happening at the same time at the same place points to our parallel universe!

Two different events can happen at the same place at the same time; image source: Wikipedia

String Theory String theory (later super string theory) is called the 'theory of everything'. String theory is probably the most exciting theory in physics after Einstein's space-time theory. With this, scientists have basically tried to explain the four forces of the universe (gravitational force, electromagnetic force, strong nuclear force and weak nuclear force) together. The essence of this theory is that everything in the universe is made of the vibration of some string. The question is, where are these strings located? 

If we continue to divide matter into smaller parts, we will see molecules, atoms, nuclei, electrons, protons, neutrons, quarks, etc. But modern physics says that there is another tiny part of matter after the quark. If we expand the quark, we get a force, which is like a string or wire. When someone tunes a guitar the vibrations of the guitar create the sounds. Here too the string vibrates and produces quarks. Neutrons make quarks. If we put them all back together like this, we get the original elemental atom. Everything we've discovered so far is basically some string vibrating in its own way at each step. This is the basic concept of string theory.

Now, scientists working on string theory eventually realized that to explain them, several dimensions are needed, which are even larger than our fourth-dimensional universe. That is, ten different dimensions are needed to explain the particles with this string theory. In which case these dimensions can be outside these four dimensions, and again can be inside these four dimensions. The question may arise, how is the dimension inside the dimension! Feeling a little difficult? Let's explain a little more simply!

Not holding on, I'm walking on a narrow bamboo strip. Bamboo is like a straight line to me, one dimensional. I can only walk the length of it. But to an ant, bamboo is two-dimensional. Because he can walk around the perimeter of the bamboo if he wants. In the same way, the dimensions around us may have different dimensions, dimensions that we do not have the ability to access, but others may have the ability to access. Again, when the ant enters the circular bamboo, it feels like it is inside a cylindrical three-dimensional surface. Now imagine, while moving on the two-dimensional floor of the bamboo, he cannot see me walking on the bamboo only in one-dimensional floor. That is, we did not see each other very often due to entering different dimensions. The concept of parallel universes comes from the concept of this ten-dimensional universe. It is assumed that there are other universes within our universe, but due to dimensional complexity we do not have the ability to access them.

 

image source: sciencebook.com

Another aspect of string theory also hints at the possibility of a multiverse. Scientists believe that our universe is so vast that it is possible to have multiple universes. According to scientists, other Big Bangs have occurred or are occurring outside our universe, resulting in the creation of multiple universes. That is, if we think of many small bubbles within a big bubble, then we can understand how the multiverse is created or sustained.

Multiverse; image source: forbes.com

Finally, the answer to the most important and surprising question! Is it really possible to travel to parallel universes? Answer, theoretically possible! But it requires two things. One, the ability to access different levels; Two, a journey into a parallel universe by traveling back in time through a wormhole. However, since physics has not yet been able to show us any real possibility of either of these two, I assume we are no longer able to travel to parallel universes or multiverses for now. The kind of regret the reader is having right now after reading this text, maybe a person similar to the reader is sitting in another universe at the same time, reading the same text and regretting not seeing the parallel universe!