A brief introduction to time travel

What is time ?

      Earlier, before Einstein, "time" was considered to be a constant quantity, but Einstein said that time is an illusion, it is relative, and it is different for different observers, speed, and space. He considered time as a free dimension, a fourth dimension. If we consider 3 dimensions, then they are length, width, and height. All three together define space, and the fourth dimension is time, which defines the direction to it, which is specifically only in the forward direction. So, all together, is the four-dimensional fabric known as space-time. According to Albert Einstein’s theory of relativity, time slows down or moves faster as we approach the speed of light. When a four-dimensional piece of fabric is introduced with a piece of mass, then it produces a curve or dimple or groove in it. This curve, or bending, allows the object to move in the curve. This curve represents gravity.

    Gravity plays a vital role in time. Time is inversely proportional to gravity, i.e., the stronger the gravity, the slower the time will move, and the weaker the gravity, the faster the time. So, when you stand for a minute, your head will be nearly 9.5 femtoseconds younger than your feet, as gravity is a tiny bit weaker on your head as compared to your feet. As a result, the clocks on the satellites are calibrated so that they correspond to the time on Earth. From all this, we could say gravity can slow down or move fast.

Paradoxes related to time travel

Bootstrap paradox:

     According to this, an object, person, or piece of information can be stuck in an endless loop in which its existence and origin are not possible to define. Consider this: you are working when suddenly the doorbell rings. When you open the door, you receive a mysterious packet that contains a book that explains all the possible ways by which you can travel through time, i.e., an ideal way to create a time machine. After understanding all these concepts, you start to build the time machine. It took you almost 15 years to build this. At last, after these endless trials, you can now travel back to the past or to the future. Now, what you do is grab that same book and travel back to the past on the same day when you received it, keeping the book on your doorstep. That means you were the one who gave the book to yourself. But then, from where the book originally came from, the book will now move in an endless loop, the origin of which is unknown.

                                                                                                                                                                                                                                               

  This all means that you take all the proofs and explanations of Newton's laws and go back to the past before Newton was even born and published the papers explaining these laws. At present time, Newton's laws exist and are known under the name Newton, but you published them. That means now you are Newton. This was an example of a person stuck in an endless loop.

   The example of information stuck in an endless loop can be explained by this simple example. Consider that you went to the past and explained to Albert Einstein the theory of General and Special Relativity, and then at present you learn that in your college that means the piece of information about General and Special Relativity is now stuck in an endless loop.  

Grandfather Paradox:

    It is a paradox about time travel in which inconsistencies appear due to changes in the past. In this paradox, you go to the past and make changes that affect your present. Assume you went to your past when your grandfather was young and you killed your grandfather. This resulted in your father or mother not being born. That means you are not born. That means you can’t go back to the past to kill your. As a result, your grandfather is still alive. That means you are born, you travel back in time, and this endless loop continues. Due to this paradox, many scientists have started to believe that time travel is not possible on logical grounds.

Grandfather Paradox

                            

Black holes and time travel

    Many scientists believe that black holes are the primary and major mode of time travel. The gravitational force in a black hole is very very strong. That means time travels very slowly near it. The stronger the gravitational force, the slower time moves. Assume you're in a spaceship on its way to a black hole, and your twin is on Earth. Now you rotate around the black hole for five years. As now, the gravitational force is strong and time moves slowly for you, your ageing will also slow down. When you return to earth in five years, your twin could be 10 years older than you. So, it can be a way of travelling through time using gravity.

What is a Wormhole and how it is possible to travel through time?

  A wormhole is a tunnel that connects two distinct points in space or can extend up to two universes through space-time curvature. In fact, it provides the shortest path between two points without even having to travel that distance.

Considering a wormhole, space can be visualized as a two-dimensional surface. In this case, a wormhole would appear as a hole in that surface, lead into a 3D tube (the inside surface of a cylinder), then re-emerge at another location on the 2D surface with a hole similar to the entrance. An actual wormhole would be analogous to this, but with the spatial dimensions raised by one. For example, instead of circular holes on a 2D-plane, the entry and exit points could be visualized as spheres in 3D space.

Wormhole connects two space time

  One of the theories suggests that at the end of a black hole at the singularity, the singularity of a white hole is connected, i.e., it’s a path where the entrance is from the black hole end and the exit is through the white hole end. But, it’s all just a theory, but that could be possible.

 Finally, we know that all these concepts are still on paper only. It is still not possible in our real world, but it will not be impossible in the future. We will be able to travel through time.

Read More

Collision: Destruction or Creation

   We still know how giant and strong these black holes are. This was all for about a single black hole, but now imagine what would happen if a black hole collided with another black hole of about the same mass. What will be the result of this destruction? Will it be a very huge big bang or the creation of a new beast? So, let’s find out what will happen.

Binary black holes.

     A binary black hole system is a pair of black holes revolving around a particular point that is its epicenter. So, is the collision of all the black holes the same? The answer is no, as when different sizes of black holes collide with each other, the resultant energy released is different. That is, the collision of two stellar black holes will result in a different amount of energy being released than the collision of two supermassive black holes. So, there are different types of collisions. One type of collision is the collision of two stellar black holes formed by the revolution of the remains of two heavily dense stars revolving around a particular point. Then there is the collision of two galaxies that results in the collision of two super massive black holes. So, all these black holes before colliding revolve around each other, and this system is coined as the binary black hole system.

 Process of collision.

    Imagine two black holes of nearly 80 solar masses each. That is the mass of 80 suns densely packed together into an area that is the size of Japan. Then what would happen is the formation of a black hole. Now, imagine two black holes, the second one similar to the first one we discussed earlier, approaching each other. What will happen? Earlier, when it was not observed, it was very difficult to locate a black hole precisely where it was and how far it was from us, because the black hole does not give any signs of its existence due to its terrible gravitational force. But when two black holes collide, an immense amount of energy in the form of gravitational waves is released in the space and time whose energy has been calculated by the use of general relativity. It is said that the collision of two black holes results in the strongest and largest production of gravitational waves. These are the only quantities that remain the same in all dimensions, so it is easy to detect them. As the gravitational waves are released, the orbit of a black hole decays, and the period of the orbit also decreases. This whole phenomenon is known as an inspiral. Once it happens, the back holes start to merge into each other, and finally a single black hole is formed. In this process, as two black holes combine, the total mass of the black hole is not the same as the addition of the masses of two black holes, as at the time of collision, a huge amount of energy is released in the form of gravitational waves. So some amount of mass is converted into energy in the form of gravitational waves and released.

So, what ones happened is….

    On the 14th of September 2015, approximately 1.4 billion light-years from Earth, two black holes spiraled around each other and, after some time, collided, creating waves in the fabric of space-time. These waves, known as gravitational waves, arrived at Earth and were observed and announced by Virgo and LIGO in February 2016. The readings given by LIGO were approximately and more accurately correct and were accurate to the general relativity prediction of two massive bodies spiraling inwards towards each other, having asses approximately equal to 36 and 29 solar masses, which finally emerged into a single black hole. The signal that was detected was named GW150914, which says, Gravitational waves noticed on September 14, 2015. It was the first time an observation of the merging or collision of black holes was observed and put forward with proof. This gave a clear response that the collision of stellar black holes still occurs in this age and era. Earlier, gravitational waves had only been inferred indirectly, via their effect on the timing of pulsars in binary star systems. The news of the first direct observation was spread around the world as a remarkable achievement for many reasons. Many efforts have been made in the last fifty-five years to show the existence of such waves, and the waves are so small that Albert Einstein himself never thought that they could ever be detected. But, this gave the boost to the scientists and researchers that they needed for a long time to discover many more things about them, and the day is not so far when we could actually go near this beast.

Read More