The Shape of Time

Based on our observations, time seems to flow. Not only does it seem to flow, it seems to flow in one direction; the future. But, contrary to popular opinion, the distinction between past, present, and future is only an illusion, however persistent. Time itself is relative, and events we think can unfold in one direction, can also unfold in reverse.

Because our perception of everything in the universe is based on what our mind tells us this is a difficult idea to grasp. Our mind is so obtuse that some smartly drawn geometric patterns are enough to completely mess it up; dependance on such a machine to understand the cosmos is the biggest blunder, and that’s why we put to test Einstein’s theory of relative spacetime through extremely advanced machines and not biological networks of our body.

Isaac Newton gave us the first mathematical model for time and space in his ‘Principia Mathematica’, published in 1687, and essentially stated that time is the same for everyone, and there is nothing we can do about it. This aligns with our intuition; however, German thinker Immanuel Kant said that Newton’s theory meant that time existed forever and if infinite time had passed, it raises a question of why the universe had not reached thermal equilibrium. Einstein obliterates Newton’s idea of space and time being independent; there is no grand cosmic clock that is the ultimate source of understanding of what time really is. In fact, time is in the eye of the beholder. He studied Maxwell’s work on electromagnetic waves and derived a conclusion that if speed of time is constant then space and time must adjust with each other to let light be constant to the eyes of the observer. Einstein found that space and time are perpendicular to each other and any object at rest is moving in time, but, every object that’s in motion, is moving through space, and, time, and thus, slower in time as compared to his stationary self; the slowing down can be briefly understood through vectors, however, Einstein’s math is much more complicated and includes geodesics and metric tensors which are not the topic of this blog.

300This theory – relativity – has been tried and tested countless times. A muon accelerated to a speed close to the speed of light, exists for a few seconds as compared to its stationary self, that self destructs in a millionth of a second. Time slows down for the muon because even though it is close to the speed of light, if the muon looks at light – obviously it won’t literally look at light, but hypothetically, if it did – it would see it move at the speed of light. Imagine how slow time must be flowing for the muon for it to observe such a phenomenon. If you were put in such an accelerator for a few seconds of ‘your time’, you would come out a few million years later.

Just how can you move in space, and, time. The fact is we do it all the time. Einstein unified space and time, and proved that they are profoundly connected; if you can move in space, why is it so difficult to digest the fact, that you can, and are, moving in time.

Past, present, and future coexist; it is unimaginably wrong to believe that the past has occurred and the future will occur, and we live in the present. We see a clock ticking, a meteor hitting the moon, a man running, at the same instant and define this as the present. However, motion affects time, and hence for every particle in the entire universe, time passes differently, and the present is different.

To understand this bizarre concept imagine an alien ten million light years away from you that is at rest just as you are – this is not possible since galaxies spin, planets orbit stars or black holes, and planets themselves spin, and all the velocity adds up to make your velocity at a point in spacetime, but assume that you are at rest with respect to each other and the universe for some time – then both of you are existing in the present. But, if the alien gets in motion then time will passes differently for it than it does for you, and hence it will no longer exist in your present. (Einstein explains this by asking the reader to think of spacetime as a loaf of bread. If you take a knife and cut it parallel to the square side you will have your ’now’ slice – your present slice – however if you get in motion, your now slice’s angle with respect to the alien’s now slice where both of you existed, will change.) Even though the angle made by the alien with our now slice is small, the distance between us is so enormous that in the alien’s present, Beethoven is finishing his fifth symphony. If the alien moves towards Earth, his now slice will point towards our future instead of the past.

Just the way you can move your telescope by a millimetre and see another star or galaxy, by gaining the smallest velocity, you can change your present slice by a copious amount and the time difference between your now slice when you were at rest and your now slice when you were in motion for an object far away from you will differ by the distance of the object from you.

Hawking proposed that if one follows our past light cone back in time, it will be bent by the matter in the early universe. The whole universe we observe is contained in a region whose boundaries shrink to zero at the Big Bang. This would be a singularity, a place where the density of matter would be infinite and classical relativity would break down, and since space had a beginning, time had a beginning.

The Theory of Everything?

In all my blogs I dumb things down to the level of a five year old. In this particular blog, I would like to present things the way they are. The way Stephen Hawking presented them in his books. I hope you understand this blog and marvel at the beauty of our reality.

Albert Einstein started the revolution in our understanding of modern physics and thus the entire universe when he proposed a simple idea about light propagating at a constant speed irrespective of the frame of reference, which is a system of geometric axes in relation to which measurements of size, position, or motion can be made. Einstein postulated that the laws of science should appear the same to all freely moving observers. Speed of light is independent of their motion and is the same in all directions. This required abandonment of the idea that there is a universal quantity called time that all clocks would measure. In essence, time depends of the velocity of an object with respect to the only static measurable quantity, the speed of light. This has been confirmed by a number of experiments including one in which two accurate clocks were flown in opposite directions around the world and returned showing very slightly different times. A simple method to explain this theory is that you imagine yourself in a spaceship travelling at 99.99999% the speed of light. This means that’s the speed you are moving at as well. If you walk in the spaceship in the direction of the spaceship, your velocity will add to the velocity the spaceship is travelling at and you will break the barrier of the speed limit. This is not possible because nothing can move faster than light. Thus, time for you will slow down and an observer in the ship will see you running in slow motion. (For those who do not understand, time gets introduced because of the formula of velocity is equivalent to displacement per unit time). This theory implied that everything is relative and there were no moral standards. 042617_EC_quantum-equivalence_main_FREE

However, it was inconsistent with newton’s law of gravity that stated that if one changed the distribution of matter in one region of space, the change in the gravitational field would be instantaneously experienced everywhere in the universe. (Our galaxy is one of hundreds of billions of galaxies and is 100,000 light years long) Because of the word instantaneous in the equation, universal time must exist. Moreover, how can this information travel through the fabric of space unimaginably faster than the universal speed limit set up by Einstein’s equations. He observed that anything in free fall experiences weightlessness and thus gravity and motion must be related. Thus the theory of relativity states that spacetime is a four dimensional house differential manifold on which a metric tensor is imposed that solves his field equations, and that metric tensor gives rise to geodesics, and objects that are not experiencing any other force, will move along the geodesics described by that metric. A British astronomer’s observation in West Africa of light of nearby star bending was the first proof of relativity. But, since matter warps spacetime in such a way that all matter should fall together, there must be some force that is not letting that happen. This pressure in the universe was represented by a cosmological constant in his equations. Other scientists worked on his equations and found that the universe was expanding faster and faster and everything came from a point, the Big Bang. The density of the density in the very easy stages of the Big Bang must have been trillion trillion trillion trillion trillion trillion tons per centimetre cube and relativity would not allow such a point to expand due to tremendous gravitational pull. Time itself would distort so much that it would stop at such a point. This point, now commonly known as a singularity, is at the centre of every black hole, which is formed by the collapse of a massive star, that is at least twice the mass of our sun.



Since Einstein’s theories were not in agreement to the theory of the atomic scale, the quantum theory, a new theory of everything was required. Kaluza was looking for a theory of everything as well. He thought to himself Einstein has been able to describe gravity in terms of warps and curves in space and time, maybe I can play the same game with the other known force known as the electromagnetic force, the only known force at that time other than gravity. Kaluza said maybe there are more dimensions in space other than the traditional three. He not only found Einsteins equations of relativity by adding dimensions, he found one more equation of the one more dimension, and when he looked at that equation, it was none other than the equation scientists had long known to describe electromagnetic force. Oscar Klein suggested that since there are no more ‘big’ dimensions left after spacetime, there must be smaller dimensions. One can go forward and backward when walking on a wire but an ant can go around the wire. This suggested the possibility of smaller dimensions that the one dimension we are aware of. The math did not work and the idea was forgotten. This strange but very compelling idea of how to unify the laws of physics faded away.

1200px-Calabi_yauSuperstring theory has nothing to do at first sight, but, it resurrects this idea in a sparkling new form. It is a theory that tries to answer the question what are the basic, fundamental, indivisible, uncuttable constituents making up everything in the world around us. String theory came in the picture when we looked deep inside the atom and found proton and neutrons. When we looked deeper into the sub-atomic particles we found quarks and leptons. Scientists came up with a theory that vibrating strings are the real fundamental unit of matter. When a violin is played, the same strings make different noises. Thus same strings can make different matter when vibrating differently. However the math was not able to predict the the mass of an electron, until, the calculations were done keeping 10 dimensions in them. This is because the geometry of ten dimensions allow the strings to vibrate the way the do, they can’t be ignored during the math when all we are trying to find is the mathematical model that describes our universe. There is not much importance of understanding ten dimensions, since we can only move in three dimensions. One should not waste much time trying to understand them. An experiment by the large hadron collider where the initial energy is less than the final energy is more than enough to prove extra dimensions, since the lost energy is sent in the other dimensions. Just the way you would find much less intensity of sound if measured on a 2 dimensional plane, instead of the entire intensity of sound in three dimensions. However, time as a dimension must be understood, I will try to explain it soon. For physicists ten dimensions become important since they help explain the various forces, and more importantly, the very particular fashion in which these strings vibrate, making the matter we observe. A very important application of superstring theory is that all the infinities like the infinite energy of the universe can be cancelled out. When a string vibrates in a particular manner, another string is formed which vibrates in the exact opposite manner. What would happen if two oppositely vibrating strings would meet? They would cancel each other out and annihilate. This explains antimatter and anti-energy, or as some some, negative energy. Antimatter behaves exactly opposite to matter. If gravity attracts matter, it will repel antimatter. Another important application is the multiverse. It was interesting that the 10 dimensions lead to a number of possible geometries. 100? 200? As of today there are 10^500 geometric possibilities of the way these can be arranged. Every possibility is equally likely and every Big Bang is a small part of many big bangs that keep happening simultaneously. It is very likely that our universe is just one of the 10^500 universes that we for sure know are possible. The arrangement of the dimensions allow mass of the electron to be x and mass of a quark to be y and forces to be z, etc. If anything was changed in the slightest fashion, our universe would have either collapsed on itself, or would have been completely different than the one we live in.

You now know why there exists infinite energy in the universe and there is no need to involve god into the equation. Innovation and discovery dies when god is born. Newton died believing that gravity existed because of god. If he would have not been poisoned by this, he might have given the world much more. (Although it was impossible for newton to do Einstein’s because the mathematical tools did not exist in his time and knowledge was very limited) This is why Stephen Hawking says god must die.

Hawking’s work deals with black holes and time; theories after string theory. There was the p brane theory that said a string is a p brane. p=1 brane is a string, 2 is a membrane/ surface, and so on. Accepting that strings make our universe is unfair to the other branes, since all of them give the same solutions to our equations of super gravity. String theory is good for explaining particle physics, but, not good for explaining something as huge as the curve in spacetime. For this we need supergravity and the shape of time. But, they deserve blogs of their own.


A good note to end on at this moment is that we are very similar to monkeys, orbiting a very average star, on a very tiny planet (a picture of Earth and the Sun, from Saturn is given above to explain how tiny we really are), but, we can understand the universe, and that makes us extraordinarily special.

(This blog has been written after a thorough reading of “Universe in a Nutshell” by Dr. Stephen Hawking. Like always any corrections are welcome. Please email me at