The Time Travel Conundrum

Delving into one of the biggest sci-fi phenomenon.


‘Time Travel’ has always fascinated the sci-fi community and countless movies and TV Series have attempted in some way to adopt topic in a sort of fantasy-ish way. Be it one of the latest box office successes, ‘Interstellar’ or long-running franchises such as ‘Star Trek’ or ‘Back to the future’  or even one of the cult TV Series – ‘Doctor Who’, the topic has been explored many times. But, as we talk about the significance of ‘Time Travel’ in Sci-fi community, the true, complex nature of the problem remains mysterious.

It all began with again, the same, ‘Einstein’s General Theory of Relativity’.  The Theory of Relativity gave us the concept of Time Dilation. The Time moved at different rates for different individuals based on their speeds. This was further given a proof after the ‘Jet Experiment’ was done. Today, all satellites follow the theory. This gave rise to the talks that if time moved relatively to different observers, with a significant speed achieved, the time travel would be possible.

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Do Multiverses exist?

Universe, is a rather overwhelming concept. We have always studied the Universe as everything there is. There is nothing outside the Universe or rather, there is no outside to the Universe. Universe is all there is and everything that exists is in this one particular Universe. And then, we study the origin of this universe, its history, its expanse and even its future, but what if there are other Universes? And we, being minuscule parts of one of those Universes cannot even think of existence of others? But, the Scientists have thought and thus, brainstormed a rather fantasy-like Multiverse theory.

The Name gives away everything in this case. The multiple Universes that co-exist with our own universe. Since 1930s there have been plenty of attempts in explaining why this is a possibility. One of the theories suggests that the Universe made up of particles, can only have a finite number of arrangements of those particles. Even though the number is very very huge, it is not infinite. And as the Mathematics gives, there can be 10^10^122 possible arrangements. So, after these many arrangements, there must be repetitions thus giving rise to similar other universes. There can certainly be other universes which differ an arrangement of just one particle or just two particles.This can explain the possibility of Multiverse existence.

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The Big Bang Theory

It’s ironic how a TV show which was named after one of the most significant theories of Universe creation is actually more popular than the theory itself. Well, it must have to do something with a rather odd name for a scientific theory. The Name Big Bang also started a misconception that the Universe was created with a “Bang…!” which is not at all what this theory is all about.

The Big Bang theory doesn’t really tell about how the Universe was started, it is something we are yet to figure out. Yet, what it does is, it addresses almost every question after that, considering that at the start the Universe existed as a Singularity. So what is a Singularity? It is again a theoretical concept which says Singularity is a small body  with almost infinitely large mass and infinite density (Again, an assumption). These Singularities are mainly said to exist at the centers of black holes.

The Theory says that at the birth of the Universe there was a Singularity (Where it came from? We don’t know). The singularity was very small body with immense density and heat. The Heat as told by NASA could be up to 5.5 Billion degrees. At such high temperatures and pressures, the physical matter and the energy was all one and the Continue reading “The Big Bang Theory”

Black Holes

Curiosity builds up as this topic emerges. One of the most intriguing and exciting mysteries in the Universe. An Astrophysical body that practically gallops everything in its vicinity. Einstein’s General theory of relativity theoretically proved the existence of black holes. The Phenomenon was so strange that even Einstein couldn’t believe that such a body could practically exist in the Universe despite his theory proving their existence.

A Black hole is nothing but, an astrophysical body having enough mass so as to warp the space-time continuum so much that nothing in the vicinity, not even light can escape its gravitational pull. What causes them? When a Massive star, having mass  100s of times mass of the sun starts dying, the fusion reactions start the formation of heavier elements like silicon, Copper and finally Iron. Once heavy metals like iron are formed from the fusion reaction, no more energy can be radiated, only the mass of the core is increased. When the core is filled with enormous amounts of iron, the core collapses under its own gravitation pull unable to sustain its volume. This will cause the core to shrink in size increasing the density of the core enormously. This will then cause a supernova explosion disbursing the gas clouds around the core leaving away a Black Hole. The core in the center is so dense that it causes a space-time warp so deep that nothing in its vicinity can escape its pull. This dense core is called Singularity.


The Black Holes get their name because of the fact that even light is absorbed by them. So, what does this exactly mean? If you consider a light approaching black hole from a distant galaxy, the light very close to black hole will get absorbed, light with some distance from black hole will change its path when near black hole circling around it. Sounds weird? We know that gravitation can bend the light in its direction but, the gravitation field of black hole is so strong that instead of bending light a little bit and curving its path, its gravity causes light to move in circles around it. Literally, light orbits around black hole. The circling around of light causes a ring type structure around the black hole. This is called an Event Horizon. So, if you are standing at the edge of an event horizon and you look at your right, you can see yourself standing right besides you because light reflected from your face is circled back to you. Basically Event Horizon is a point near black hole from where there is no return. Once a body is moved past the event horizon, it will need to move at a speed more than speed of light to stop falling into the singularity which means nothing can escape not even light once you pass the event horizon of a black hole. If you pass the event horizon of black hole, a distant observer will never actually see you falling  inside the singularity, they will just see you become dimmer and dimmer nearing the edge of event horizon eventually vanishing.


The black holes which are formed by collapsing of a huge star are termed as stellar black holes. Scientists believe that there are another kinds of black holes called super massive black holes. These black holes have masses billions of times that of sun and volume up to millions of times that of sun. They are believed to be formed during galaxy formation. Scientists believe that every galaxy has a super massive black hole in its center.

What makes the study of black holes a tough task is that they are invisible. They don’t reflect light, they absorb it all so they are invisible. The Event horizon can be seen but, it requires specialized devices mounted to detect the gas clouds surrounding the event horizon. The scientists try to study the black holes by observing the effects they have on neighboring bodies like planets or stars. No one has seen a black hole. So, everything is based on theories. But, why should we believe those theories? What is the proof that actually something like a black hole can exist? Actually, there is. It all is in Newton’s law of gravitation and its formula. Newton’s formula for gravitation is:


It can be inferred from that, more the mass of the body and lesser its radius more is the gravitational force. So, if we decrease the radius of earth keeping the mass constant, it will increase its gravitational force. In other words, the escape velocity will increase. Now, if we could compress the volume of earth up to radius say, of Mumbai, it will have the escape velocity close to speed of light. Thus, we have a black hole. Any object if compressed of certain radius can give us a black hole. That certain radius is called Schwarzschild radius. Example, if Mt.Everest is compressed to a radius of basket ball, we have a black hole. If a basket ball is compressed to  radius of one atom, we have a black hole. But, of course it’s not possible to achieve that type of enormous compression as of now.


Where do we stand in all this? We Earthlings need not worry about black holes galloping earth because even the closest black hole from earth is millions of light years away. And Sun will never turn into a black hole as it does not have sufficient mass. And even if it somehow does turn into a black hole, earth will still continue to revolve around it, apart from the fact that everything will be dead frozen.

The Schrodinger’s Cat

If you follow the pop culture, you must have already heard this term at least once. For those who haven’t, Schrödinger’s cat isn’t about some pet Cat. It is a thought experiment performed (or rather, thought) by Erwin Schrödinger. The experiment later went on to become a popular term for many pop culture references, internet jokes, memes and even T-Shirts. But, what is this experiment really about? What was Erwin Schrödinger trying to prove by putting an innocent imaginary cat in a complicated situation of life and death? Let’s find out.


Before we move to the actual experiment, let’s first know why Schrodinger thought of the experiment in the first place. This has to do with the Copenhagen interpretation of quantum physics. What is it? Well, it basically says that according to Quantum Theory, all the matter exists in two forms particle and wave. Now, as for the bigger objects such as cats, the wave properties cannot be observed as their wavelengths are very negligible. But, for objects like atoms or electrons, the particle and wave duality can be observed and they do show properties of both waves and particles. The Copenhagen interpretation says that if every matter exhibits the dual nature then, any physical properties such as length, speed or even position of that object cannot be definitely determined as a wave does not have a single position but many positions along its wavelength. So, it stated that any particle exhibits in all states unless an Continue reading “The Schrodinger’s Cat”

Einstein’s General Theory of Relativity

One of the most important theories in the history of Astrophysics which has changed our views to see the universe entirely. One of the most brilliant minds the world has ever seen, Albert Einstein has proposed this theory of general relativity. The General theory of relativity and Time Dilation go hand in hand. This theory further expands the views of time dilation and combines it with space expansion. Let’s get into it. Again, this might shatter some of our preoccupied notions and might be thought as sci-fi but, it has been accepted by many scientists and its time we do too.

Let’s again start with a hypothetical experiment. We are sitting in the car which is at rest and the headlights are blinked. The speed of light emitted from headlights is measured and is recorded accurately as speed of light. Now, if the car is moved at a speed of say 80 and the headlights are again blinked, and the speed is recorded, the speed remains constant. Yes, as the speed of car is negligible as compared to that of light but still there is not even negligible increase in the speed of light when measured accurately enough. The reason for this as we know now is Time Dilation. The time moves slowly so as to keep the speed of light constant. But, Einstein says that it’s not only time that moves slowly but, the space (or in case of car ‘Distance’) expands. So, basically, we know Speed= distance(Space)/Time. Einstein says not only time slows down but also the space expands and both of them thus keep resultant speed of light constant. This led to a new revolutionary theory that space and time are not different entities at all. They are related and linked to each other. This new entity, Einstein called it as Spacetime.

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Time Dilation

One of the most ground-breaking theories in physics which led us to the understanding of universe that we know of now is Time dilation. But, before we move on to that, lets brush up with some of our basic concepts. So, we all have studied in physics about Newtonian relativity which states that the speed of any body is measured relative to the observer’s frame of reference. In simple words, If you are sitting in a moving car with your friend, your friend appears to be stationary to you as you both are moving with same speed in same direction viz, you both are in same frame of reference. But, if a guy who is standing on the road sees you he will record your speed as the speed of the car. Also, if you throw a ball from this moving car, at a speed , say 20 and car is at speed say  40. Then in ideal case, the ball will have total speed of 60 when thrown.

Now, lets apply similar logic with a slightly different scenario. You are in a stationery car, and you start its headlights and the exact speed of light is measured and recorded. Now, the car is moved at a speed of say, 80 km/hr and the headlights are blinked and again the speed is measured. Now, Newton’s theory says that the speed of light that would be measured must be addition of speed of light and speed of car (Which is of course very minute as compared to speed of light) But, the results say otherwise. The speed of light remains constant and not even minute increase in speed is recorded. This concludes that speed of light is constant irrespective of frame of reference in which it moves.

The question is, does Time depend on the frame of reference of the observer? Is time different for people in different frames of references? And surprisingly enough, the answer is Yes. The Time passes differently depending upon your frame of reference. If you are sitting at rest. The time passes normally as your speed is zero. But, if you are moving at a certain speed, the time will pass slower than it will at rest. This thing that time passing differently for each person depending on their frame of reference is called Time Dilation. So, why don’t we observe it? Because it is minute when compared to the human speeds. To observe measurable time dilation, one would have to go close to the speed of light. This theory was put forth by Albert Einstein and then was worked upon by many other physicist all of them leading to prove it right. Continue reading “Time Dilation”