Advanced science, Astrophysics, Cultural, International, Life as it is, Religious, Technical

Isn’t black hole a black mystery?

A black hole – hitherto an invisible celestial body – was in cosmological vocabulary even before Einstein’s theory of relativity in 1915. But when the relativity theory predicted with full scientific rigour that a massive stellar body can have such a strong gravitational pull that nothing, no object, not even electromagnetic radiation such as light, can escape from it, the concept of a black hole became firmly established in scientific parlance. But it remained at that time only a mathematical curiosity, as no scientific evidence or mechanism of formation of a black hole was put forward. However, it became a realistic possibility after the detection of pulsars some decades later.   

The detection of pulsars (rotating neutron stars) by Jocelyn Bell Burnell, a research student at the University of Cambridge in 1967, gave renewed spurt to the concept of gravitational collapse and the formation of black holes. A normal star, when it comes to the end of its life due to lack of fusion fuel, collapses under its own gravity and becomes a neutron star. It may be mentioned that an atom consists of neutrons (neutral in charge) and positively charged protons and negatively charged electrons. If gravity becomes too strong, protons and electrons are pulled together to merge with each other, neutralise their charges and become neutrons and the whole star becomes a neutron star. (For the detection of neutron star, which was considered as “one of the most significant scientific achievements of the 20th century” by the Nobel Committee, her supervisor and another astronomer were awarded Nobel prize in Physics in 1974, but Jocelyn Bell was not even mentioned in the citation. However, years later, in 2018, she was awarded the Special Breakthrough Prize in Fundamental Physics. She donated the whole of the £2.3 million prize money to the Institute of Physics in the UK to help female, minority, and refugee students become physics researchers.

Not all stars eventually become neutron stars. If the mass of a star is less than 2.6 times the mass of the Sun, the gravity would not be strong enough to turn it into a neutron star. The gravitational pull in a neutron star ultimately becomes so strong that all its mass and its nearby matters are pulled to a small volume and the star becomes a black hole. A black hole can merge with another black hole to become a bigger and stronger black hole.

It is speculated that there are black holes of various sizes in most of the galaxies and in some galaxies, there are supermassive black holes at their centres. The nearest black hole from Earth is quite a few thousand light-years away; but they exert no influence on this planet. The supermassive black hole in our galaxy (the Milky Way) is about 26,000 light-years away.

Despite the name, a black hole is not all black. The gas and dust trapped around the edges of the black hole are compacted so densely and heated up so enormously that there are literally gigantic cauldrons of fire around the periphery of a black hole. The temperatures can be around billions of degrees!

The first direct visual evidence of a black hole had been produced on 10 April 2019 by a team of over 200 international experts working in a number of countries. The Event Horizon Telescope (EHT) was used to detect the existence of a colossal black hole in M87 galaxy, in the Virgo galaxy cluster. The computer simulation from data collected in the EHT is shown below. This black hole is located some 55 million light-years from the Earth and its estimated mass is 6.5 billion times that of the Sun! So, this black hole is truly a monster of a black hole.

Computer simulation of black hole from real data

Although it is a monstrous black hole, its size is quite small and it is enormously far away (520 million million million kilometres away) from Earth. To observe directly that elusive black body that far away, astronomers require a telescope with an angular resolution so sharp that it would be like spotting an apple on the surface of Moon from Earth and the aerial dish that would be required for such a detection would be around the size of Earth! Obviously, that is not possible.

Instead, the international team of experts devised a Very Long Baseline Interferometry (VLBI) technique, which involves picking up radio signals (wavelength 1.3 mm) by a network of radio telescopes scattered around the globe. The locations of these eight radio-telescopes are shown below. When radio signals from these radio-telescopes are joined up, taking into account their geographical locations, lapsed times for signal detection etc, and processed in a supercomputer, an image can gradually be built up of the bright part of the periphery of the black hole.

Locations of Event Horizon Telescopes (EHT)

The key feature of a black hole is its event horizon – the boundary at which even light cannot escape its gravitational pull. The size of the event horizon depends on the mass of the black hole. Once an object crosses the boundary of the event horizon, there is absolutely no chance of coming back. A lead astronomer from MIT working on this EHT team said, “Black hole is a one-way door out of this universe.”

The general theory of relativity also predicted that a black hole will have a “shadow” around it, which may be around three times larger than the event horizon size. This shadow is caused by gravitational bending of light by the black hole. If something gets nearer the shadow, it can possibly escape the gravitational pull of the black hole, if its speed is sufficiently high (comparable to the speed of light).

It is postulated that the “shadow” comprises a number of rings around the event horizon. The nearer a ring is to the event horizon, the more rigorous and compact it is with extreme pressure-temperature conditions. 

If, hypothetically, an unfortunate human being falls even into the outer ring of a “shadow”, he will be pulled towards the black hole initially slowly and then progressively strongly – his leg will be pulled more vigorously than his upper part and consequently, his body will be deformed into a long thin strip like a spaghetti. And when that spaghetti shape crosses the event horizon, it will be stretched so much that it will become a very thin and very long string of atoms!

Is wormhole the link between a black hole and a white hole?

The general perception of a black hole is that it is a monster vacuum cleaner where everything, even light, is sucked into it through a funnel and nothing, absolutely nothing, can come out. It absorbs enormous amount of matter and squashes them into tiny volumes. What happens to this gigantic amount of matter is a mystery, a black mystery.

There are two parallel streams of pure speculative thoughts. One is that when a black hole becomes too big – either by incessantly swallowing up matters from its surroundings or by merger with other black holes – a super-giant explosion, more like a big bang, may take place. So, a black hole may be the mother of a new big bang, a new generation of universe.

The other thought is that the funnel of a black hole is connected through a neck, called the wormhole, to a different spacetime and hence a different universe at the other end. All the materials that a black hole sucks up at the front end in this universe go through the wormhole to another reverse funnel where all the materials are spewed out into a different spacetime. That funnel is called the white hole. Thus, a black hole and a white hole is a conjugate pair – a connection between two universes!  But the question is, since there are billions of black holes in our universe, then there could be billions of corresponding wormholes and white holes and universes.

One universe is big enough or bad enough for human minds to contemplate, billions of universes will make humans go crazy.

Dr A Rahman is an author and a columnist

Advanced science, Life as it is, Technical

Quantum Formalism

Quantum mechanics came into existence at the turn of the twentieth century when many newly discovered experimental evidences could not be explained with classical mechanics. Max Planck initiated the concept of quantisation of light in 1900 to give a rational explanation of the black body radiation. Albert Einstein laid the concept of quantisation on a firm foundation in 1905 when he produced the theory of photoelectric effects and established photons as the entity of light quanta.

Since then quantum mechanics had gone from strength to strength and produced many laws, principles and theories to explain successfully the newly emerging scientific and technical problems that came up with advanced technologies. But at the same time there were some most bizarre and mind-boggling phenomena that defied intuitive logical explanation and challenged quantum principles right up to the limits. This write-up presents some of those bizarre inexplicable phenomena.

But, first of all, we need to define specifically the broad areas of quantum mechanics and differentiate it from classical mechanics. Quantum mechanics deals with extremely small entities, such as atoms, electrons, photons etc., which are commonly called quantum particles.

An atom as a whole is neutral in charge; which means that there are as many protons (positively charged) as there are electrons (negatively charged) in an atom. Hydrogen is the first element with just one proton and hence one electron; carbon is the sixth element with six protons and six electrons. There are more than 100 elements; each element has equal number of protons and electrons. These electrons are assumed to revolve round the nucleus of the atom. When an electron is dislodged from an atom, it is free to diffuse or drift along the material. When these electrons flow in large numbers through a conducting medium, we get electricity.

Now the technical question that can be posed, is an electron a particle like a miniature ball or a wave like a photon? Quantum mechanics asserts that it can be either – a wave or a particle – depending on the circumstance. In fact, one of the major planks of quantum mechanics is the wave-particle duality. Louis de Broglie in his Ph.D. dissertation in 1924 postulated that if light waves i.e. electromagnetic waves could behave like particles, then particles such as electrons could also exhibit wave properties. Indeed, they do and Louise de Broglie received a Nobel Prize in 1929 for his ground-breaking contribution of wave-particle duality.

Electromagnetic waves propagate through space like waves, as water waves do on the surface of water having crests and troughs. When two waves merge together in harmony, the crests and troughs join together and become larger (the amplitudes of two crests or two troughs add together); this is called the constructive interference. On the other have, if two waves merge in opposition i.e. in anti-phase, the crests and troughs cancel each other and there will be no ripple and that is called the destructive interference.

Double-slit experiment with a light source

If a light source is placed in front of a double-slit barrier and the light is allowed to fall on a screen behind the barrier, the constructive and destructive interferences would show as interference fringes of bright and dark bands, as shown above. So, interference fringe is a definitive proof of wave nature of light – light diffracting through the double-slits. (Of course, light can also have particulate nature, as shown in Einstein’s photoelectric effects.)

Double-slit experiment with an electron source

Now let us get back to the question of electrons. If electrons are fired from a source towards a screen and there is a double-slit barrier between the source and the screen, the screen should show the images of two slits on the screen. That is expected and perfectly normal, as the electrons are behaving like particles going through the slits and then striking the screen. Now if the slits are sufficiently narrowed down and the rest of the arrangement remains same, what is then seen on the screen is a band of bright and dark bands, as if the electrons are behaving like waves producing interference patterns! Now remembering de Broglie’s wave-particle duality, this outcome would not be too surprising or outrageous!

Now let us make an arrangement when just one electron is fired at a time and let that electron have sufficient transit time to go through the slit and reach the screen. The electron can go through either of the slits and one would expect that images of the slits would be produced on the screen, if sufficiently large number of electrons are fired. But amazingly, an interference pattern appears on the screen!

This is bizarre. Remember that just one electron was fired at a time. Even if the electron behaved like a wave, then that electron-wave would just melt away as it reached the screen. It surely could not wait on the screen for the next electron-wave to come through and interfere with it!

Now, could that be that an electron somehow goes through both the slits simultaneously to produce an interference pattern on the screen? Then what on earth is the physical mechanism to have one electron going through two slits at the same time? The other possible picture could be that half of an electron goes through one slit and the other half through the other slit and they produce the interference pattern. But then what is the mechanism of splitting an electron into two halves to make an interference pattern? The whole thing becomes surreal, but the interference pattern is real.

Then the experimenter became more curious and thought that it would be worthwhile to find out exactly which way the electrons are going? Is an electron going through both the slits simultaneously? A detector was placed very discreetly away from the path of the electrons behind one of the slits. As an electron is negatively charged, the flow of the electron would produce current and that current would produce a magnetic field. The detector that had been designed to detect the magnetic field. Thus, a detector placed behind one of the slits would not disturb the electron path and its flow.

The experiment was then conducted with the same setup, but with a detector placed discreetly behind one of the slits. What had been found on the screen? The interference pattern just disappeared completely! Yes, no bright and dark bands; only images of the slits on the screen! It is, as if, the electrons found out that they had been spied on and they decided not to behave like waves any more. Take the detector away, interference pattern return! Science becomes supernatural!

These strange behaviours of electrons were so puzzling that even more than hundred years later (since these experimental evidences) nobody could give a rational explanation. Quantum mechanics came into existence and flourished since then, but even quantum mechanics could not give any sensible explanation of the bizarre electron behaviour. But, nonetheless, quantum mechanics had produced an abstract mathematical formalism to explain this evidence.  

In quantum mechanics, particles or waves are treated wave functions (Schrodinger’s wave equation). When there are two slits, two wave functions go through and interfere and that process is called quantum superposition. That superposition of waves produces interference pattern. Even one wave function – a mathematical formalism – can go through two slits and have superposition and produce an interference pattern.

Niels Bohr, the high priest of quantum mechanics, and his group of fellow quantum physicists produced, what is known as Copenhagen Interpretation of quantum mechanics.  This Interpretation advanced the idea that sheer act of observation of quantum particles disturbed the character of electron-wave flow and that caused the waves to collapse into particles.

Quantum mechanics gives an abstract mathematical formalism of a system. It can predict quite accurately the correct outcome (such as electron fringes), but it does not or cannot give the physical picture of the path of the electron. In fact, the Copenhagen Interpretation insists that asking to know the path of the electron is superfluous and irrelevant. What is relevant is what happens when electrons reach the destination and quantum mechanics has the answer for that. That is the strength of quantum mechanics.    

  • Dr A Rahman is an author and a columnist

Advanced science, Astrophysics, Life as it is, Technical

From Newton’s Gravitational Law to Einstein’s Gravitational waves

Visualisation of Newton’s gravitational attraction

Summer 1666, a young Cambridge University physics student by the name Isaac Newton was sitting under an apple tree in his mother’s garden at Woolsthorpe Manor in Lincolnshire, England. An apple fell from the tree on the ground and that triggered him to think: why did the apple come down straight to earth, not go sideways or upwards? That question led him to delve deeper into the mystery of attraction between two bodies and to come up with the law of gravity. He published his research work in “The Principia Mathematica” in 1687, where he described, among other things, this seminal work on the law of universal gravitation.  

This law of gravitation tells us that two bodies attract each other with a force which is proportional to the product of the masses of the bodies and inversely proportional to the square of the distance between them. This simple empirical formula was astonishingly successful in calculating the force of attraction between two bodies on earth. This law was also applied to calculate the attractive force between the earth and the moon and to the orbital motion of the moon round the earth. The law was quite accurate in defining the orbits of many other celestial bodies, although in few cases the law was somewhat inaccurate.

This law was and still is the centre piece of what is now known as the ‘classical physics’ or ‘Newtonian Physics’. We all studied this law, Newton’s laws of motion, properties of matter, electricity and magnetism, heat and thermodynamics, optics etc in our schools and they gave the grounding for advanced physics.

For nearly 300 years this law was supreme and explained how the force of gravity controls the motions of all celestial bodies. However, the law did not say anything about the nature of this force or how the force is propagated through space; it just stated that the force diffuses through space without leaving any trace. As the predictions of the law were right in most of the cases, nobody bothered too much about these minor details or even ignored some minor discrepancies.    

At the turn of the 20th century, a patent clerk by the name Albert Einstein was working on patent submissions of electrical devices in Bern, Switzerland as a ‘Technical Expert, Third Class’ and in his spare time he was working on gravitational problems. The Patent Office work took up 48 hours of his time per week over six days. Einstein described his work load subsequently as, it left him with ‘eight hours for fooling around each day and then there is also Sunday!’.

In 1905 he published a technical paper outlining the Special Theory of Relativity giving revolutionary scientific ideas and concepts. In this paper, he introduced two fundamental concepts: the principle of relativity and the constancy of speed of light. The speed of light was stated to be independent of the speed of the observer. In other words, whether the observer moves in the direction of light or opposite to it, he would see the speed of light always remaining constant (c= 3*108 m/s). (It may be mentioned that in 1905, Albert Einstein produced three more monumental papers of enormous significance: (i) the mass-energy equivalence (E=mc2), (ii) Brownian motion of small particles, and (iii) photoelectric effects. For his work on photoelectric effects showing the particulate nature of light, which laid the foundation for quantum mechanics, he was awarded Nobel prize in 1921. As mentioned above, the year 1905 was extremely productive for Albert Einstein.

Visualisation of Einstein’s spacetime construct

Einstein developed his relativity concept even further and produced the General Theory of Relativity in 1915. In this General Theory of Relativity, he advanced the principle of spacetime, not space and time. He stipulated that the three dimensions of space (such as X, Y and Z dimensions of cartesian coordinates) and one dimension of time are not independent of each other, but intricately linked to form a single four-dimensional spacetime continuum.

This concept of spacetime continuum was revolutionary at that time and even now they make human beings baffled. The relativistic consideration has produced what is now called the time dilation. The passage of time is relative and so it depends on the motion of an observer relative to a stationary observer. Also, the passage of time depends on the location in a gravitational field. For example, a clock attached to an observer in a spaceship will tick slower than that of a clock attached to an observer in a stationary position. Also, a clock in a higher gravitational field, such as at the surface of earth, will tick slower than that of a clock in lower gravitational field such as the top of a mountain.

Let’s take an example. There were three men in the UK, all of them exactly of the same age, say, 25 years. They decided to offer themselves as guinea pigs for a research on gravity. One was asked to stay in Lincolnshire, England (not too far from Newton’s famous apple tree), the other was told to go and live high up in the Himalayan mountains and the third, most adventurer of the lot, got the opportunity to have a space travel in a superfast spaceship. The spaceship travelled fast and so his clock was ticking slowly. Let’s say his spaceship was so fast that one year in the spaceship clock was equal to five earth years and the mountain man clocked 10 minutes more than the Lincolnshire man in five years. When after five years they met on earth, they found that the mountain man was 10 minutes older than 30 years, Lincolnshire man was 30 years of earth age and the spaceship man was whopping four years younger than 30 years! To the spaceship man, it would look like he had come back four years in the future!     

Einstein stipulated that the gravitational field creates space and the bodies with masses bend and warp space; more like massive bodies create curvature in a trampoline. All less massive bodies fall into the curvature in the trampoline created by the massive bodies. When there are a large number of bodies warping the space, the space becomes jagged and celestial bodies move around in tortuous paths. There is no force of gravity pulling objects towards each other; just the bodies move around the jagged curved space along the path of least resistance.

Space, like any other force field, is discreet, quantised and granular. The quantum of space is dubbed as graviton, similar to the term photon in electromagnetic field, and it is so small that we cannot feel its discreteness, as we cannot feel the discreteness of photons of light or discreteness of atoms in a solid body.

Exactly hundred years after Einstein’s General Theory of Relativity, experimental evidence of gravitational field and gravitational wave have been produced by the LIGO (Laser Interferometer Gravitational-wave Observatory) experiment and shown that space is modulated by the gravitational field. A monochromatic laser beam of light was split and sent at right angles to each other along two arms, each of 4 km long. These beams were reflected back along the same path and allowed to interfere back at source. If there is no distortion or modulation of the path lengths, the two beams would interfere in anti-phases and there would be no interference patterns.

When two super massive black holes some 1.3 billion light years away merged and produced a gigantic massive black hole, an enormous amount of energy, equal to three solar masses, was produced and sent out as gravitational energy. It rippled through the whole universe in the form of gravitational wave at the speed of light and deformed the spacetime fabric. That deformation in spacetime was detected by the LIGO experiment in the form of interference pattern and that proves that gravitational waves modulates the space. 

The implication of Einstein’s spacetime is that at the very beginning when even the ‘Big Bang’ did not take place, there was no spacetime. Spacetime came into existence following that ‘Big Bang’, when gravity came into play along with other forces such as electrical force, strong nuclear force and weak nuclear force. If at the end, as Physics predicts, the whole universe starts to collapse, there would be what is called the ‘Big Crunch’ and the spacetime would collapse too and disappear. There will be nothing, no material, no space and no time. These are the predictions of scientific theories as exist today.

In 1930 when Einstein came to London as the guest of honour at a fundraising dinner to help the East European Jews, George Bernard Shaw, the chief guest, said humourously, “Ptolemy made a universe which lasted for 1400 years. Newton made a universe which lasted for 300 years. Einstein has made a universe, and I can’t tell you how long that will last.” The audience laughed loudly, but none louder than Einstein.

  • Dr A Rahman is an author and a columnist

Advanced science, Bangladesh, Economic, Environmental, International, Political, Technical

Welcome to the age of climate change

Our planet is under tremendous stress now. During the last week of January, major cities in the US Midwest and Northeast were colder than some regions in Antarctica. Temperature in Minneapolis dipped as low as negative 32 degrees Celsius, with the wind chill reaching negative 47. Grand Forks in North Dakota has seen the lowest wind chill at negative 54 degrees. As many as 21 cold-related deaths have been reported so far.

Temperatures during the first week of February rose on average by a whopping 40-50 degrees. However, the reprieve is going to be short-lived as the frigid temperatures are expected to return later this month.

Although the scientifically challenged US president wants global warming to “come back fast”, someone should whisper into his ears that extreme cold spells in the Northern Hemisphere are caused, at least in part, by global warming. Under normal circumstances, cold air mass sits above the poles in an area called the polar vortex. Emerging research suggests that a warming Arctic distorts the vortex in the North Pole, so that instead of staying where it belongs in winter, closer to the Arctic Circle, the air moves down south into continental United States. Hence, the brutal cold spells. With the rapid warming of the Arctic, the effects of the polar vortex could become more frequent and severe, bringing about more intense periods of cold snaps and storms.

While we are trying to stay warm, down under, Australians are getting baked by record-breaking heat. Over two days in November, temperatures exceeding 40 degrees in Australia’s north wiped out almost one-third of the nation’s fruit bats, also known as spectacled flying foxes. Scores of brumbies—Australian wild horses—in the Northern Territory have fallen victim to the January heatwave, which soared to a high of 47 degrees. They died from starvation and dehydration. More than a million fish have perished in a river in New South Wales as the water temperature surpassed their tolerance limit.

Last summer, many nuclear power plants in Europe halted operation because overheated river water could no longer cool down the reactors. And like many Asian megalopolises, Bangkok is choking on air pollution. Water cannons are used to alleviate the smog that has shrouded the city for weeks.

A series of droughts with little recovery time in the intervals has pushed millions to the edge of survival in the Horn of Africa. Bangladesh is staring at an unprecedented migration problem as hundreds of thousands face a stark choice between inundated coastal areas and urban slums.

California saw its most ruinous wildfires ever in 2018, claiming more than 100 lives and burning down nearly 1.6 million acres. There have even been freak blazes in Lapland and elsewhere in the Arctic Circle. There is ample data to suggest that climate change is the biggest driver of out-of-control wildfires. In colder regions, an unusually warmer climate leads to earlier snowmelt and, consequently, spring arrives earlier. An early spring causes soils to be drier for a longer period of time. Drier conditions and higher temperatures increase not only the likelihood of a wildfire to occur, but also affect its severity and duration.

Typhoon Mangkhut with maximum sustained winds of 120 miles per hour roared across the Philippines and China in September 2018, triggering landslides, extensive flooding and killing some 100 people. The ferocity of the typhoon matched that of Hurricane Florence on the other side of the globe that pummelled the Mid-Atlantic Coast of the United States just four days earlier. The wind speed was 130 miles per hour and the hurricane claimed 36 lives.

Cutting-edge research by climate scientists indicates that the intensity of hurricanes and typhoons is closely connected to global warming. Higher sea levels due to melting of glaciers and Greenland’s ice sheets and warm water give coastal storm surges a higher starting point. Additionally, because hurricanes and tropical storms gain energy from water, their destructive power intensifies. Moreover, as the Earth has warmed, the probability of a storm with high precipitation levels is much higher than it was at the end of the twentieth century.

Besides raising the sea level, climate change is also modifying oceans in different ways. According to a study published in Nature Communications in January 2019, as climate change gradually heats oceans around the globe, it is also making the ocean waves stronger and more deadly.

Climate change is ravaging the natural laboratory in the Galápagos Islands, one of the most pristine and isolated places in the world, where Charles Darwin saw a blueprint for the origin and natural selection of every species, including humans. Today, because of the more frequent El Niño events that have come with warming of the seas, the inhabitants of the islands are trying to cope with the whims of natural selection.

Welcome to the age of climate change! These are just a few examples of multiple weather-related extremes occurring all over the world. They beg the question: Can human beings survive the climate crisis? The answer depends on what we do in the next 10-20 years. It will determine whether our planet will remain hospitable to human life or slide down an irreversible path towards becoming uninhabitable.

At the World Economic Forum in Davos last month, the UN Secretary General Antonio Guterres said, “If what we agreed in Paris would be materialised, the temperature would rise more than three degrees.” He is finally seeing eye-to-eye with the mainstream scientists and essentially declared the 2015 Paris Accord a dead deal.

If global temperature indeed increases by more than three degrees, summer heat would become unbearable. In particular, temperatures and humidity levels in cities that are already scorching hot would rise to levels that the human body simply cannot tolerate, researchers warn. More importantly, it would trigger a positive greenhouse effect feedback that would eventually push our planet, according to Guterres, “dramatically into a runaway climate change….” Once the runaway greenhouse effect starts, then Paris-like accords, conferences of parties, rulebooks for adaptation to climate change, or going cold turkey with fossil fuels won’t be able to reverse the situation.

Runaway greenhouse effect is not a “Chinese hoax.” Several billion years ago, Venus was cooler than what it is now and had an abundance of water in oceans overlain by an oxygen-rich atmosphere. The current hellish condition on Venus where the surface temperature is a blistering 460 degrees Celsius was caused by runaway greenhouse effect.

Thus, without a significant adjustment to how we conduct our lives, the possibility of Venus syndrome is quite high. In this scenario, our planet would still keep on spinning, but as the fourth dead ball of rock devoid of life.

Quamrul Haider is a Professor of Physics at Fordham University, New York.

Advanced science, Astrophysics, Life as it is, Technical

Quantum Conundrum

The quantum concept that came into existence precisely in the year 1900 was both revolutionary in outlook and spectacular in outcome. This very concept which was put forward by Max Planck in 1900 when he tried to explain black body radiation was subsequently taken up by a luminary like Albert Einstein (as yet unknown to the world) in 1905 and gave a rational explanation to the hitherto difficult scientific problem.

The classical physics (also known as Newtonian physics) was ruling the day until about 1900 when all day-to-day physical problems could be explained by this discipline. But gradually it was running out of steam as new technically challenging phenomena came up due to invention of new instruments and reliable measurements were made.

The intractable physical processes like the black body radiation, interactions of light with particles, the puzzling behaviour of light and many more physical processes could not be explained by traditional classical mechanics. So, a new method, a new mode of thinking, a new science had to be invented that would explain all these inexplicable things.

Although Max Planck was first to venture outside the conventional concept of light being wave in nature to explain ‘black body radiation’ in 1900, it was Albert Einstein who gave scientific explanation by proposing in 1905 the ‘quantisation’ of light – a phenomenon where light was assumed to consist of discreet packets of energy – which he called quantum of light or photon. This quantum of light was advanced in order to explain the hitherto inexplicable photoelectric process, where light was allowed to fall on the surface of a metal and electrons were detected to have emitted. No matter how long or how intense one type of light was, electrons would not be emitted. Only when light of higher frequencies was allowed, electrons were emitted. Einstein showed that photons (quantum of energy in a bundle) of higher frequencies have higher energies and those higher energy photons could emit electrons. (It was like, no matter how long or how heavy the rain is, the roof would not be dented. Only when hailstorm of sufficient big sizes falls on the roof, does the roof cave in). For this quantisation theory, Einstein was awarded Nobel prize in 1921.

Thus, light came to be viewed as both wave and particle, depending on experimental circumstances, and hence the nomenclature ‘wave-particle duality’ came into common vocabulary. If hitherto electromagnetic light can be viewed both as wave and particle, can particles (like electrons) behave like waves? Indeed, so. If electrons are allowed to go through two slits, they interfere and produce alternate bright and dark spectral lines on a screen, exactly like light waves do. The microscopic world does not distinguish between waves and particles, they are blurred into indistinguishable entities. That is the nature that quantum mechanics has produced. 

Although Einstein was the pioneer of quantisation of light, he was not at ease with the way this new concept had been taken up by ‘new lions’ under the stewardship of physicists like Niels Bohr, Wolfgang Pauli, Werner Heisenberg, Erwin Schrodinger, Max Born and many more in the early part of the last century. They collectively produced the full-blown quantum mechanics, which Einstein had difficulty in recognising.  

In quantum theory, particles like electrons revolving round the nucleus of an atom do not exist as particles. They are like strata of waves smeared round the nucleus. However, they exist, behaving like particles, when some energy is imparted to the atom or some energy is taken away from the atom resulting in those electrons moving up or down in energy levels. In other words, electrons exist only when there is an interaction or transition. Without such transitions, electrons just do not show up. However, electrons (with negative charge) are there around the nucleus, but there is no way of telling where the electrons are – only probability of their presence (wave function) can be described! No wonder, Einstein was not happy with such description, which he called incomplete.

Heisenberg produced what came to be known as ‘Heisenberg uncertainty principle’. The elementary particle like an electron cannot be measured with absolute accuracy both its position and momentum at the same time. The act of measuring the position of an electron disturbs the complementary parameter like velocity and so certain amount of uncertainty in momentum creeps in – that is the uncertainty principle. Similar uncertainty exists when measuring time and energy of the particle at the same time.

Niels Bohr, the high priest of quantum mechanics, produced from his Advanced Institute of Physics in Copenhagen, what came to be known as ‘Copenhagen Interpretation’ of quantum mechanics. This interpretation advanced the idea that elementary particles like electrons do not exist in stable or stationary conditions; they only exist in transitions and in interactions.

The ‘Copenhagen Interpretation’ further emphasised that a quantum particle can only be said to exist when it is observed, if it is not observed it does not exist. This was a revolutionary concept. Einstein could not reconcile with that idea. He retorted, “When the Moon is there in the sky, it is real; whether one observes it or not”. Thus, the great intellectual battle on the nature of reality ensued between Einstein and Bohr. Einstein firmly believed that the quantum mechanics as it existed in his life time was inconsistent and incomplete (although he withdrew the ‘inconsistent’ branding, as quantum mechanics kept explaining modern technical processes with consistency). To prove that ‘incompleteness’, he produced various ‘thought experiments’ at various times to challenge Bohr’s ‘Copenhagen Interpretation’. Bohr countered those challenges with technical explanations, but Einstein was not fully convinced.   

Einstein did not like the abstract nature of quantum mechanics. He always demanded that theory must correspond to the reality, if not, it becomes a ‘voodoo’ science.  

For his criticism, he was not very popular with the advocates of ‘Copenhagen Interpretation’. They even lamented that ‘how is it possible that Einstein who was the pioneer of quantum theory and who revolutionised gravitational concept by saying that space is warped by gravity and the gravitational field is indeed the space, now he is reluctant to accept ideas of quantum mechanics’?   

Quantum mechanics had solved many intractable problems and predicted many physical aspects which subsequently came to be true. But at the same time, it is incomprehensible, extremely abstract and devoid of ‘elements of reality’. Anybody hoping to see theory mirroring reality would be totally disappointed. Even Richard Feynman, American Nobel laureate, who contributed significantly to the development of quantum physics once retorted, “I think I can safely say that nobody understands quantum mechanics”! Nonetheless, quantum mechanics is the most advanced scientific discipline of today.

– Dr A Rahman is an author and a columnist.