Theory of Everything
To be curious is part of human evolution. When we were kids, we always had to explore things to learn about what’s in them and continue to explore something new daily. Once Einstien said: “The important thing is not to stop questioning. Curiosity has its own reason for existence.” String theory is one brainchild of several Curious minds trying to understand the origin of this universe.
As this universe is everything, from the tiniest particles to the giant galaxies, to the very existence of space-time and life, the question is, how did it all begin? The universe’s origin is the beginning of everything. Several scientific theories and creation myths worldwide have tried explaining its mysterious genesis. However, the Big Bang theory is the most widely accepted theory for the origin of this universe. The big bang theory state that the universe started as a hot and infinitely dense point – only a few millimeters wide, it was identical to a supercharged black hole.
About 14.7 billion years ago, this tiny singularity violently exploded, and within fractions of a second, the universe started expanding. In the first few minutes, atoms were created, all the matter and antimatter were annihilated, and only one matter particle survived. After one billion years, the universe cooled down and clumped to form celestial objects like stars, planets, galaxies, and eventually, living beings like humans because most of the atoms in our bodies are from cosmic matter.
Before the recent advancement, we believed that everything was made of the atom, so the atom was assumed to be the building block of the universe. Two thousand years ago, the greek philosopher Aristotle believed that matter could be divided infinitely without changing its properties. Democritus, a scientist of that time, disagreed. He thought that matter could only be divided until you got to the tiniest particle, which he called the atom, coming from the greek word called atomos, meaning indivisible, so the question is, who was right? Aristotle was very convincing and did many experiments using scientific methods, so more people believed him. It wasn’t till around 2000 years later, in the early 1800s, that John Dalton came along and disapproved of Aristotle’s idea.
John Dalton believed that matter is made of tiny particles called atoms, and these atoms cannot be further divided into smaller particles and can never be destroyed. Therefore, all atoms of the same elements will be the same, and that atom of different elements can be combined to form various new compounds.
Now let’s fast forward to the late 1800s when JJ. Thomson discovered the electrons. He used what we called a cathode ray tube or electron gun. He used this tube with a magnet and found that the green beam produced was made of negatively charged material. He performed several experiments and found that the mass of one of these particles was almost 2000 times lighter than a hydrogen atom. From this experiment, he decided that these particles must have come from somewhere within the atom and that Dalton was incorrect about the statement that the atom cannot be divided into smaller particles. Then Thomson got some steps further and determined that these negatively charged electrons needed something positive to balance them out, so he identified that they were surrounded by positively charged material and this became known as the “plum pudding” model of an atom, that negatively charged plums are surrounded by positively charged pudding.
A few years later, earnest Rutherford, one of Thomson’s students, did some tests on Thomson’s plum pudding model. He bombarded alpha particles on 0.00004cm thick gold foil, and he used alpha particles because alpha particles had high energy and were heavy as well, so if we say that atom is like the pudding of positively charged particles with electron embedded in it, then the particles will pass through it, this is obvious because the heavier particles will pierce through the lighter pudding structures of the atom and pass through it, this is what Rutherford thought. For this reason, their greater mass and energy than the protons made him choose alpha particles for the experiment. When he bombarded the particles on gold foil, he got astonishing results. He found that most fast-moving particles passed straight through the foil and hit the detector; however, some particles got deflected by small angles. Lastly, to his astonishment, a few alpha particles rebounded. These results made Rutherford think that the plum pudding model was not correct based on the results he got, so he put forward a new hypothesis explaining the structure of the atom that most of the space inside the atom is empty this is because
- Most of the alpha particles could easily pass through the atom.
- The second result was that the positive charge occupies a small space inside an atom, and that point is so hard that some of the alpha particles completely bounced back, and that’s what he called the nucleus of an atom and the
- The Third result was that electrons revolve around the nucleus in circular paths, and the size of the nucleus is very small compared to the size of the atom.
Then there were shortcomings of rutherford’s atomic model, which Bohor corrected later. Bohor discovered that electrons revolve around the nucleus in a circular orbit of fixed energy, an electron doesn’t continuously lose or gain energy. They lose energy only when they jump from a higher orbit to a lower orbit in the form of photons and gain energy when they jump from a lower orbit to a higher orbit, which was the most accepted model of that time.
The story doesn’t end here; these electrons, protons, and neutrons were not the universe’s building blocks. Later in 1964, George Zweig came up with the idea of quarks. Instantly it was Murray Gell Mann who came up with the name of quarks. Then in 1968, at Stanford linear accelerator, scientists bombarded protons with very high energy electrons and measured the energies and angles of scattered electrons. Their findings matched the model of three quarks. Somehow after too many hypotheses and experiments, they came up with the fact that when we magnify the nucleus, there exists positively charged protons and neutrons, which are always neutral. Still, when they further zoomed neutron, they came to know that neutron is made up of two down quarks and one up quark, and the proton is made up of two up quarks and one down quark.
This is where the conventional idea stopped, and String Theory came along and suggested that these sub-atomic particles, like quarks, are further made of a little string-like filament that vibrates at a different frequency. Strings are more like strings on a musical instrument that can vibrate at different frequencies, creating various musical notes. Similarly, the Strings within the quark can vibrate at different frequencies, creating different sub-atomic particles like protons, neutrons, electrons, etc.
So in every matter, deep inside, there is nothing but a dancing vibrating cosmic symphony of strings, and that’s the basic idea of string theory.
String theory is the unified theory of all four forces working in nature.
1) Weak force:
The weak force is responsible for the radioactive decay of elements and acts at very tiny distances. Without it, the sun would not shine, we would not be able to get elements like radium or plutonium, and we would also not get carbon 14 dating because all of this transformation requires one particle to turn into another particle through radioactive decay. So let’s look at how weak force changes quarks’ flavors.
Quarks have different flavors like up, down, charm, strange, top, and bottom; similar to how an electron has a negative charge and a proton has a positive charge, quarks have flavors.
Except for up and down Quark, all other four flavors of Quarks decay so fast and turn into up and down quarks, so when the quarks decay, the whole composition changes, the protons convert into electrons, and so on, and that’s how the weak force works.
2) Strong force:
The next one is a strong force which is awesomely strong and not only holds atoms together, in fact, it holds protons and neutrons in the nucleus together from separating apart. Inside the nucleus, the quarks are held together by gluons forming hadrons such as protons and neutrons.
Although we cannot observe quarks directly as they are unstable and decay very fast, we can observe them indirectly by measuring the particles emitted during the decay. Moreover, Quars don’t have mass on their own, but when Quarks interact with the Higgs field, they get their mass. Bosons are the particles that give all the particles their mass.
The Higgs boson is the fundamental particle associated with the Higgs field that gives mass to other fundamental particles, such as quarks. A particle’s mass determines how much it resists changing its speed or position when it encounters a force.
3) Electromagnetic force
The third force on the quantum level is electromagnetic force which acts on the charged particles. Like electric charges repel each other and, unlike charges, attract each other. If we take a magnet and hold them closer, the north and south poles will attract each other. The bigger the magnet, the greater the force will be. All this attraction and repulsion is just because of electromagnetism. So, let’s get back to the point that string theory combines these three fundamental forces with Einstein’s general theory of relativity, which involves the fourth fundamental force called gravity.
According to Newtonian physics, gravity is a force that attracts objects. Newton gave the precise value of gravity, but he could never explain how gravity works. Later Einstein, at the age of 26, made an incredible discovery about the speed of light and said that “The velocity of light is kind of speed limit, and nothing can move faster than the speed of light, it’s the ultimate standard for speed.”
Einstein said that not even gravity can exceed the speed of light and gave a reasonable answer to different questions like what if the sun disappears from the solar system and what would happen to the planets revolving around it? According to newton, if the sun disappeared, the planets would instantly leave their orbit and start floating freely into space, but according to Einstein’s definition of gravity, space is a fabric of space-time. Gravity is experienced due to the curvature of the space-time fabric. So, if the sun disappeared, it would take several minutes before the planet would start floating freely into space due to the loss of gravity. Just like a ripple produced in water, the planet will not feel any disturbance until it catches the effect of that ripple.
Checkout my video of what happens when the Sun disappears from our solar system
After ten years of wrecking his brain, Einstein realized that space and time can’t be separated and are bound together in a single fabric of space-time. In fact, Einstein claimed that time is the 4th dimension. Einstein explained gravity with the 4-dimensional fabric of space and time. He also realized that the fabric could be stretched and wrapped but could not be ripped at the same time. So Einstien called this new picture of gravity in the universe “the general relativity.”
So let’s look at what string theory says about the unification of all the fundamental forces in nature. The most significant criticism about string theory is that it never made testable predictions. The space of possible versions of this theory is so vast that nothing can be calculated with certainty, and hence the string theory can neither be verified nor ruled out, it’s unfalsifiable.
String theorists say that string theory predicts the existence of gravity, but when we look at the mathematics of string theory, gravity appears like magic. So we don’t need to fight gravity into the string theory. In fact, it will be difficult to remove it, and the quantum gravity of string theory is immune to the main difficulty in uniting general relativity with quantum mechanics.
String Theory doesn’t give tiny black holes when we try to explain gravity on smaller scales. Let’s start with a point like a particle. When a particle moves in space, it draws a line on a space-time diagram, time versus one dimension of space, this is called its world line. In quantum mechanics, the gravitational force is carried by the particle called the graviton, when a graviton particle acts on another particle, it exerts its effects at an intersection in their world lines over some distance, but in very strong gravitational interaction, that intersection itself, becomes denser and energy at that point becomes infinite. More technically, you run away from Infinite feedback effects between the gravitons and their own field.
We get nonsense black holes in the math if we even try to describe very strong gravitational interactions. Ok, so let’s switch to the string theory in which graviton is also a string and, in particular, is in the loop. When strings move on a space-time diagram, they trace out sheets or columns. You can think of a string not as a 1D surface but as a 2D sheet called a world sheet. Now, let’s describe the interaction of two strings, their vertex will no longer be point-like, it actually cannot be point-like. Even the most energetic interactions are smeared out over the string, so you avoid the danger of black holes creating infinities.
On the other hand, string theory also tries to explain the answers to some questions, which have been with us since the time of ancient greeks. Questions like “is there more than one dimension of time? And one of the strangest features of string theory is that when you study mathematics, you clearly see in the equations that the world cannot have only three familiar dimensions of space that we all know about that are right, left, up, down, top, bottom, back, forth, the three dimensions of common experience, that’s actually what we know. Still, mathematics requires additional space dimensions for the equations not to have illogical inconsistency. We believe those extra dimensions are all around us, crumpled to a tiny size so that the naked eye cannot see it so small that even other dimensions are right here. Still, we cannot see them with the most powerful magnifying glasses available today.
So let’s go some steps forward. First, the question arises: Why can time have additional dimensions similar to space? String theorists are still struggling to find the answer if there is a second or third dimension of time. However, it’s certainly worth investigating it as a possibility since the math does not rule it out.
The laws of physics as we experience them are set in the very early stages of the universe, and quantum fluctuations in everything would be responsible for another universe having slight different laws of physics than ours because the quantum fluctuations will be taken in a slightly different law of physics than our universe and this would keep going. So every universe that’s born, even if it started the same in the very first instant, a later instant when other laws of physics manifest could be slightly different, the concept of an infinite world is a very old idea discussed in the philosophy and this idea of multiple universes has reached maturity only in the time of modern physics and now in the string theory.
In 1952 Erwin Schrodinger conducted a lecture in which he told his audience that what he was about to say might seem lunatic. He stated that when his equations seemed to describe several different histories, these were not alternatives, but all happened simultaneously. This sort of duality is called superposition, a hard-core concept in and of itself. The idea of a multiverse states that these are essentially independent universes from one another and never the twain will meet. So, for example, suppose there is another universe about which we know, but we can only see that universe when the horizons of both universe overlap. To access that universe, we have to find some way to tunnel from one universe to the other, but that could be very dangerous because if the laws of physics are different, the charge on electrons would be different, and all of your biochemistry would change.
The different universes within the multiverse are called the parallel universe, alternate universes, or in technical terms, are also known as parallel dimensions, quantum realities, alternate realities, etc.
There could be universes where the laws of physics are there, but they will never allow the matter to coalesce, we will never get stars, that would be a lifeless universe, there could be another universe where you can make stars but you can’t make heavy elements that would be a universe with stars and wonderful night skies as we have now but nothing that we know and love, no planets, no life, and nothing.
String theory also predicts warm holes in space through which time travel is possible. According to Einstein, space and time can stretch and wrap, then the time travel through space is possible by wrapping the fabric of space to a particular place, and we can travel through the ripped fabric of space-time called warm holes that’s what the theories say, but according to Einstien, the fabric of space-time can stretch, bend, curve and wrap but it cannot be ripped, and another complication about traveling through warm hole is that warm holes could be so small and narrower that a person cannot pass through it, and if we try to, then it will just get destroyed in no time, and for that purpose, we need to make an exotic matter.
Warm holes need negative energy to maintain their stability. Negative energy helps to stabilize a warm hole by pushing on the walls of the throat of the warm hole keeping the warm hole from collapsing in on itself. So how do we obtain negative energy? The answer is exotic matter, a kind of matter which is not made by subatomic particles like protons and neutrons. Baryonic matter is made of exotic matter with negative energy, but how would it work mathematically? According to Einstein’s equation E=mc^2, which is that mass and energy are interchangeable, so if we need negative energy like (-E=mc^2), it means mass will also be negative, and according to Einstein’s theory of relativity, this isn’t possible as the theory of relativity only allows for antigravity fields with reasonable states of matter. So the scientists made some modifications to the negative mass theory and then realized that if negative mass existed in liquid form instead of solid form, it wouldn’t conflict with the theory of relativity, although the issue of where exactly we can find the exotic matter is still unanswered however some interesting ideas have popped up, for example, Dr. Jamie Farnes at oxford university claims that dark matter and energy could be a single unified fluid of negative mass and has even gone as far as to propose modifications to the theory of relativity.
So there are a lot of gaps in this theory of everything, and it predicts that this universe or may be so-called “multiverse” can be more strange than any of us has ever thought. And if this theory gets positive results, then we can study everything in only this one theory, but we don’t know how much time is needed to prove this, so let’s hope for the best.