• C++
• Math
• Physics
• Music
• Videos
• Misc

Time seems to be a simple thing that we think we understand perfectly. We spent the 20th century believing that time has started with the big bang, without really having an explanation to what existed BEFORE time. From a religious point of view, there simply is NO time before, since God is outside of it and has created it. From a more philosophical point, it is illogical that from nothingness, time and matter were created. It was only until recently that scientists were able to put forward theories that would satisfy the philosophers.

Newton was the first to describe the first fundamental force in nature, the gravitational force, in a mathematical language. Although his laws predict the velocity and acceleration of a falling object, the radial velocity of planets and planet positions, Newton never really explained what gravitation really is. Gravitation remained unexplained while scientists defined the laws that govern the second fundamental force: electromagnetism. Einstein was able to combine those two forces, seemingly unrelated, in one theory: the theory of relativity. Einstein also gave a more complete explanation of the gravitation.

He defined gravity as the distortion of space and time. Suppose space is a stretchable fabric. When you place a mass, the fabric stretches and a curvature is created around the mass. Now, suppose an object that was going in a straight line before the curvature. When this object crosses the stretched section of the fabric, it has a tendency to fall on the mass that was initially placed and that caused the curvature. But this object will not fall on the central mass because of its initial velocity (that is IF the initial velocity can outcome the centripetal force, otherwise this object will crash on the central mass). This means that Earth an object that had an initial velocity that was enough to outcome its “falling” centripetal force towards the sun. Basically, we are continuously falling on the sun, and the moon is continuously falling on us!

Einstein managed to beautifully combine the gravitational and electromagnetic forces together and describe phenomenon of astronomic scales (like gravitational lenses), but his theory did not apply to atomic-scale objects and did not include the two other forces discovered at the beginning of the 20th century: the weak and strong nuclear forces. During almost a century, scientists tried to come up with one single theory for objects of all scales.

Just like Einstein’s theory perfectly matched observations, quantum mechanics, developed in the early 20th century described phenomenon of atomic-scale objects. In fact, it is a very weird world of chances and probabilities. For example, there is a chance that you could be in different places at once, or have a chance of passing right through the wall. Of course, the chances are much, much smaller than winning the 6/49 lottery, but they theoretically exist.

To combine Quantum mechanics with Einstein’s theories, physicists proposed the Strings Theory in the 60s, but it seemed so strange that no serious work was done except a few scientists. During almost 20 years, those physicists came up with five versions of those theories. They all involved strings, some closed strings, some with two fixed endpoints, some spiral shaped, moving in different manners and directions. Edward Witten combined those five versions into one Mother Theory, called the M-Theory. He achieved this by adding six extra dimensions to the four known dimensions: left-right, back-front, up-down and time.

The idea is that the strings move freely in those dimensions, and the reason there was five different versions of the same theory was because they were viewed from or were in different dimensions. According to string theory, everything in the universe is made of tiny vibrating strings. Depending on the vibration frequency and shape of the strings, each string behaves differently making up the fundamental particles discovered earlier by particle physicists: Quarks, muons, etc.

The M-Theory is by far the most elegant theory of physics. It describes the universe like a harmonious symphony of strings. Something interesting about the strings is that they suppose a time before the big bang. Here’s how it works. Say you have a violin string. You can play different notes, which means different frequencies (higher frequencies being associated with higher kinetic energies), by sliding your finger on the string, thus changing the length of the string. Now imagine you cut the string in half and double the frequency. You continue cutting the string in half indefinitely, and notice that you end up in infinite kinetic energies. Here’s where the beauty of string theory comes in. There is a limit upon which you cannot reduce an object. So the string that you were cutting will grow longer when you reach this limit. Strange, indeed, but elegant.

As you may already know, there are two kinds of energy: Kinetic and potential. For example, by going up a hill on a bike, you lose speed, which is kinetic energy, and gain potential energy, which is the height, and when you go down, you transform your potential energy into speed without any effort because you have “stored” (potential) energy. Besides vibrating, a string can turn as a whole around the cylinder (which is the space) or wind around it one or several times like a rubber band around a rolled-up poster.

The required energy to perform these movements depends on the circumference of the cylinder. The energy of winding is directly proportional to the radius: larger cylinders require the string to stretch more, thus more energy to wind up. The energy associated with moving around the circle, on the other hand, is inversely proportional to the radius: larger cylinders allow longer wavelengths, thus lower frequencies and energy. Since we perceive a three-dimensional world, we only see the TOTAL of the energies, which is equal for a small and a large cylinder (thus symmetrical). The new size limit and the symmetry of the strings set limits and avoids the problems faced by the “old” physics in which some quantities increase indefinitely while others decrease to infinitesimal values when time is played backwards until big-bang.

String theory supposes that there is symmetry before and after the big-bang: the expansion rate 4 seconds after the big-bang is equal to the collapse rate 4 seconds before, and that our universe would hit a maximum value allowed by string theory by some point, and shrink again only to repeat the same cycle. In other words, the big bang was not the beginning of the universe, but only a transition from acceleration to deceleration.

According to this scenario, our universe was almost empty and infinitely big eternally long ago. All four forces of nature were incredibly feeble and there were almost no interactions between particles. As time went on, the forces gained in strength and pulled matter together. This created regions with densities high enough to form black holes. The matter inside the black holes continued to grow in density and temperature, until it reached the maximum valued allowed by string theory. The quantities then bounced and started to decrease, and the moment of the reversal is called the big-bang. The center of one of those black holes became our universe.

Obviously, the string theory has a very elegant explanation of the universe, but the main objection to this theory is that it is mainly philosophy because none of the string theories can be directly observed. There are some ways to verify the theories though. For example, string theory supposes that physical constants such as Newton’s and Coulomb’s do not have arbitrary values. They may take different values in different cosmological epochs or in remote regions of space, and a finding of those variations would be a big proof in favor of the harmonious theory.

There is also another problem with this theory: the extra-dimensional space. There is of course no way to visualize an 11 dimension space. There is also the big mathematical problem of the reference in the dimensions. If we are stuck in these dimensions, we might not be able to observe it completely. The only way to avoid this problem is to be OUT of these 11 dimensions, which is obviously impossible. We can only be amazed by the beauty of the string theory, but there is still a lot of work to be done before it can be accepted as real science. This, of course, does not mean that it is a useless theory. In fact, I think that this will lead us to unprecedented breakthroughs in the physics world.