THE WONDERS OF QUANTUM MECHANICS

    The story of science begins from the days of the early human civilizations. We have Babylonians and Egyptians who made remarkable contributions in the fields of mathematics and engineering. Modern humans are not sure how the hell the Egyptian laborers managed to pull stones of such magnificent weight and then ascended them up to such astounding height. There is a meme which says: Just because the white men didn't construct pyramids, it doesn't mean aliens made it. Indian work on astronomy (astrology, in fact), mathematics (see: Aryabhata) and ethics (Kamasutra) still holds a great value. But the most important contributors to science were the Greek philosophers and mathematicians.

    Thales of Miletus is considered by many as the world's first true philosopher, pure mathematician and actual physicist. After him, there came several Greek philosophers. They all discussed many aspects of the universe. Four Greek philosophers (Thales, Anaximenes, Heraclitus and Anaximander) considered that the world was made of water, air, fire or something infinite respectively. Afterwards, Empedocles combined the four classical elements as the basic constituents of our world. But now we know these four elements are further composed of the real elements. There are 118 of them in total. You can locate them easily on a Periodic Table. 

Bohr's simplistic atomic model

    Democritus' theory of atom was one of the most amazing hypotheses of the world history. Then mankind made other discoveries in the field of what they called natural philosophy. This is what we came to know as science. It was later divided into several sub-sciences such as physics, biology, chemistry etc. Arabs translated the works of the Greco-Roman authors and passed them down to the present-day Europeans. The books of Avicenna (on medicine) and Averroes (on Aristotelian philosophy) were taught in European universities for centuries. Philosophy, surgical biology, optical physics and mathematics were the main fields of Muslim research. There we fast-forward to Newton and Galileo.

"We recognize the lion by its paw"

- Bernoulli

    Newton was a prodigy. He is doubtlessly the greatest physicist in human history. Classical physics was established mainly by his diligence. He described the laws of motion and presented the concept of gravity. Galileo supported the heliocentric model of the universe and his confidence became a beacon of light for the future generations of scientists who considered Galileo as an emblem against the church-organized oppression of science. [PS: Galileo died in the year Newton was born?]

    Newton's death in the eighteenth century CE created a gap in physics that was to be filled by his spiritual successor Einstein (I have called latter the former's successor because both men are celebrated as the greatest physicists in the history). Newton's physics was linear and non-relativistic. Newtonian world was based on the concept that electrons (and other sub-atomic particles) acted like particles and light acted like a continuous wave. But, in the twentieth century, it was proved that electrons had dual nature i.e. they acted like both waves and particles (see: de Broglie's thesis). It was shown too that light traveled in packets. You can call light's movement digital instead of in Newtonian analogous motion. These packets of light were named by Planck as quanta (singular is quantum) of light.

Double-Split Experiment involving electrons instead of photons

      De Broglie was the first person to postulate a dual nature for electrons. Why did we do so? For that, we have to go into 1920s. By the way, he was just a graduation student when he proposed such a ground-breaking theory.

    Ever heard of Young's double-split experiment? Well, you place a light-beam projector and try to illuminate a screen. But there is a wall separating the screen and the projector. The wall has multiple slits in it so that light can only be passed through them and be projected on the screen. You see a pattern that resembles a barcode. Now, take off the projector and replace it with an electron-beam one. You realize what we are going to do? We will hit the screen with electrons instead of light particles. What happens now? One will predict that we will see the same pattern on the screen. But an amazing thing occurs instead. The entire screen gets hit upon by the electrons! How the hell do the electrons manage to pass through a wall that was placed there for the sole purpose of hindering their penetration through it? But you have to wait for the explanation as the story doesn't end here. The physicists put two detectors between the wall and the screen. When the detector are turned off, the electrons displayed their bizarre pattern. But the moment you turn them on, electrons began acting like normal particles and you get your usual light-like pattern of a barcode.

    This unique observation led scientists to discuss what could possibly alter the way electrons behave. Max Born came up with the Copenhagen interpretation of this phenomenon. He explained that, as the electrons acted both as waves and particles at the same time, it depended over the observation being made which pattern would be followed by electrons for the moment of observation. Mystics described that creepy behavior of electrons as if they were aware when humans observed them i.e. they sensed that they were being watched so they switched to particle-like pattern but, the second turn away your gaze, they started to act like a wave. Shudders!

   Now, let's divert our attention towards what Einstein accomplished. Modern Physics is made up of two subjects i.e. relativity and quantum mechanics. The strange behavior of electrons is studied under quantum mechanics. Relativity studies how time, length and speed varies from observer to observer.

Pillars of Creation

     Einstein presented his Special and General Theory of Relativity in the beginning of the twentieth century. The concept of relativity first occurred in his mind while he worked in a Swiss patent office as a junior clerk. His famous mass-energy equation [E=m(c*c)] was just one of his multiple contributions to physics which science-fiction authors turned into some sort of voodoo physics. His other major accomplishment is the explanation of the photoelectric effect. Relativity states basically that light is the fastest thing in the universe and it's impossible for an object to even travel equal with speed equal to that (denoted as "c") of light (3 raised to the 8th power of 10 m/s). Remember, light can travel 186 thousand miles in one second. Thus, it takes sunlight to reach us in about 8 minutes. If an object ventures to equalize its speed with "c", time slows down for it (time dilation) and the object shortens in length (length contraction). Einstein also stated that time will flow differently for a stationary observer and an observer in motion.

    The concept of relativity was not a difficult one to grasp. Physicists initially opposed it because it seemed quite mystical (and that's the very reason why Einstein opposed quantum mechanics i.e. it was more mystical than even relativity) and also because of Einstein's Jewish heritage. Then, when Einstein migrated to United States, he was already very famous. His theory gained popularity and became one of the standard theories in the field of science. So, according to relativity, when we look up into the sky, we are actually looking into the past (time travel). Whatever we see, light carries it to our vision. If it takes light 8 minutes to travel from sun to earth, when we look at the sun, we are actually looking at how the sun looked like 8 minutes ago. What the sun looks like in the present, we will see it 8 minutes later. This is the beauty of relativity! So, if a star is one light year away from earth, what we are looking at is an one-year-old picture of that star. Thus, those galaxies which are billions of light years away from us, we only know how they looked like in distant past. Are they still there? Are they inhabited? We will know this after billions of years lest mankind finds a way to travel faster than the speed of light. You can search for the Pillars of Creation on Google. These gigantic inter-galactic structures existed 5000 years ago. They don't exist in the present but we can still see them because the vision of their destruction is still being carried by light particles to us. Once that vision reaches the earth, we can see them being destroyed.

    As mentioned above, Einstein initially opposed quantum mechanics (see: EPR paradox). It was because, according to quantum mechanics, everything in the universe is undefined and uncertain until an observer observes the universe. So, if I look at object A, I can't be sure that A is still there when I look away. Heisenberg's Uncertainty Principle was also important in shaping these thoughts. According to the Uncertainty Principle, if you wish to calculate the speed of an electron, you can't pin-point its exact position. Then, if you try to first calculate its position, you can't make out exactly how fast this electron is revolving around its nucleus. It happens because these subatomic particles exist in such a dimension that they can act both as waves and particles.

Einstein's famous quote on quantum mechanics

     The dual and uncertain nature of these particles was quite wonderful and dangerous as well. Because all living and non-living things in this world are made up of matter, and matter consists of electrons. In other words, if we can't be sure about the nature of these electrons, how can we be sure about this entire planet which is made of electrons? To understand the Doppler Effect, you must learn that, as per Planck, energy is equal to the product of Plank's Constant ("h") and frequency. Frequency is inversely proportional to wavelength hence frequency decreases when wavelength is longer.

 

    Then what are the views of the quantum physicists about this universe? Well, ever heard of the Doppler's Effect? It states that if an observer A is standing at some place and another object B is traveling towards him, the frequency of B will keep increasing with sound waves of shorter length. Once the B has passed in front of him and begins to increase the distance between A and B, the frequency of B will keep decreasing with sound waves of longer length. Apply this effect on light, again. You will see that is B is going away from A, you will see red light emerging from it, called red-shift. If B is moving towards A, you will see blue light, called blue shift. Use this knowledge to study the galaxies and you will see that they emit red light. Hence, Hubble deduced (actually, a Christian priest did that before Hubble) that the universe is expanding. If universe is expanding, was it not doing so at some point in time? The answer is that the universe began to expand somewhere in history. We call it the Big Bang.

   Now let's resume our study of quantum mechanics. Schrodinger's Cat was a thought experiment to show how one cannot be sure about the nature of an object without observing it. Quite idealistic, isn't it? He further proposed the Many Worlds Theory or the Multiverse Theory. This theory was just initiated by Schrodinger but there many other physicists who explained it in the terms I'm going to describe it. Just take the example of the same two objects A and B. A wants to decide whether it wants to move towards B or away from it. The Multiverse Theory states that A will move both towards B and away from it but in alternate realities. In one reality, A will move towards B. In other reality, A will move away from B. A's simple decision broke the universe into two parts. So, whenever we are subjected to select one of two different options, we go with both of them. You can see this theory being used in many movies and cartoons about how the main protagonist visits his alternate self who is more successful than the version we are following. So, there also may be a world where Columbus actually made it to India, Genghis died as a child, Japan remained non-Western, Gandhi succeeded in persuading Jinnah against the creation of Pakistan, Jews rule Europe, Russia is still communist, Hitler is a famous painter or cancer treatment has been discovered.

   Remember how Einstein boasted nothing could go faster than light? This is contradicted by quantum entanglement. It shows that two particles may be co-related in such a way that changing the characteristics of one results in spontaneous variation in those of the other even if their mutual distance is more than light is able to conquer. So, they communicate with each other faster than light. Though, practically, quantum entanglement has failed to proves its practicability. We can use this phenomenon for teleportation. But some argue that teleportation will only become cloning one object and then erasing the original. So, if a person is cloned to a different place and the original one is deleted (killed?), will it be counted as a moral act?

    Then you have quantum computing. Computers work on binary number system. Binary numbers system used only two digits i.e. 0 and 1. In digital electronics, there are just two states i.e. off and on. Off is represented by 0 and on is represented by 1. A computer uses binary and hexadecimal numbers to operate. In hexadecimal number system, you have 16 digits i.e. 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F. Now, a computer only has a circuit called full-adder which is uses to solve mathematical sums. There are basically three logic i.e. AND, OR and NOT. AND is logical multiplication and OR is logical addition. In AND, your system turns on when both states are 1. In OR, you system turns off when both states are 0. NOT simply means reversal of the current system position i.e. if your system is turned on and undergoes NOT, it turns off. Full-adder adds two numbers. For subtraction, you just add the first number in the negative of the second number. For multiplication, if you have to multiply 2 with 3, you just do this sum: 2+2+2. For division, the procedure is a little bit complicated. Suppose a computer has to divide 7 by 2. You subtract 2 from 7 and get 5. You subtract 2 from 5 and get 3. You get subtract 2 from 3 and get 1. As we have subtracted 2 a number of 3 times and the remainder is 1. That's how a full-adder solves division.

    Now, in quantum mechanics, you can have 0 and 1 at the same time. Thus, the computing becomes quicker and more efficient. Quantum computers are in their baby stages and it will take them some time to become more popular.

   The achievements of quantum mechanics also include the entire table of subatomic particles. We have found out approximately all the bosons and fermions. We found the Higgs' Boson in 2012 CE. Now, the real battle is between the String Theory and Loop Quantum Gravity. For example, we have to find out whether gravity is the result of bending of the space-time continuum or it is caused by a particle called graviton. We have discovered that the universe is 4% matter and 96% non-matter. More than 2/3rd of universe is made of dark energy and other portion consists of dark matter.

    What are dark matter and dark energy? Astronomers knew that the galaxies are heavier than its apparent mass should be. So, they deduced that most of the mass of the galaxies is composed of invisible matter which doesn't interact with normal matter. We call it dark matter. Now, we know about gravity. Gravity is the power of attraction. Then why is the universe still expanding? It led scientists to review Einstein's cosmological constant which he'd described as his greatest blunder. They found out that Einstein had correctly identified the presence of a weird and mysterious force that was mightier than gravity. This force made the galaxies repulse from each other. We call it dark energy. It is so powerful that more than two-third of the universe is filled with it.

    Quantum mechanics is the most important field in physics today. But we human beings cannot claim that we've succeeded in understanding the entire universe. There are still problems with out model of the galaxies. No matter how much we try to solve these secrets, the universe tends to get more and more mysterious. But a real physicist never gets tired of these mysteries. For him, it's like solving a puzzle. You don't need to solve it completely to have fun. You just need to be sure that you gave it your best.