Advanced science, Bangladesh, Environmental, International, Life as it is, Technical

Cyclone Fani and global climate change

The temperature of the Earth changes over geologic time. During periods of glaciation, it was about five degrees Celsius cooler and in the interglacial period about five degrees warmer. The last glaciation period was 100,000 years ago. Since then, there have been fluctuations of a few degrees, the period of 1430 to 1850 being one of particularly low temperatures in Europe. Although there were fluctuations from year to year, it seems evident that there has been a steady increase in average global temperature since the Industrial Revolution. According to the World Meteorological Organization, average global temperatures will reach a new milestone this year—one whole degree higher than temperatures before industrialisation.

In the early 1990s, when concern about climate change caused by the rise in temperature became widespread, the “signal” of anthropogenic effects hadn’t unambiguously emerged from the “noise” of natural climate variability. However, we now know that most of the climate-related changes observed over the past 50 years is attributable to human activities. In fact, by burning prodigious amounts of fossil fuels that emit carbon dioxide, which is the principal greenhouse gas, we humans have taken Earth’s atmosphere in general and global temperature in particular into a regime that our planet hasn’t seen for millions of years.

Although the interplay between carbon dioxide and temperatures is complex and not necessarily 100 percent predictive, nevertheless, the obvious correlation between the two variables suggests that we might expect a significant adverse climatic response to the industrial-era surge in fossil fuel derived atmospheric carbon dioxide. Undeniably, the effects of this interplay are manifested in the increase in the ferocity of storms, floods of biblical proportions, spike in the number of unusually hot days, melting of the glaciers, drought, desertification and deforestation, polar vortex, uncontrollable forest fires, degradation of the coral reefs, habitat loss and rise in the sea level, to mention a few.

Today, because of global warming, intense storms are occurring in many parts of the world. If they form in the Atlantic or Caribbean, they are known as hurricanes, and in the Pacific or China Sea as typhoons. If they develop off the coast of Indian Ocean or the Bay of Bengal, we call them cyclones. These storms are one of the most awe-inspiring displays of the raw power of nature. They are also among the deadliest and costliest natural disasters we have to contend with routinely.

After churning through the Bay of Bengal for several days, gathering immense amount of energy along the way, cyclone Fani roared through Bangladesh on May 4, 2019, leaving behind a massive trail of destruction—killing more than a dozen people, knocking out power, shredding roofs and leaving hundreds of thousands homeless. Classified by meteorologists as the equivalent of a Category 4 hurricane, it was one of the most intense cyclones in 20 years in the region.

Cyclones batter Bangladesh at regular intervals, mainly in April/May or October/November, when weather conditions align in a manner most favourable for storm origination and sustenance. As examples, cyclones Aila struck southern Bangladesh on May 27, 2009 and Sidr made landfall on November 14, 2007. The occurrence of these and other cyclones in close succession is a reminder of the country’s extreme vulnerability to the devastating effects of human-induced climate change.

The 1970 cyclone that hit Bangladesh on November 12 and raged the strongest on November 13 was the worst natural disaster we have witnessed so far. The resulting storm surge, more than 20 feet high and topped by huge tidal waves, washed over offshore islands and carried water from the sea many miles inland. The cyclone and flood destroyed the entire infrastructure of the country’s southern coast and killed an estimated half a million people, though some researchers estimate that the death count was close to a million. The failure of the Pakistani government to respond quickly to the crisis, among other things, contributed to the political turmoil that led to an independent Bangladesh in 1971.

Tropical cyclones are influenced by many factors, but the role of warm sea-surface temperatures is the primary source of energy for cyclones. In particular, a cyclone gets most of its energy from the latent heat of condensation and the moisture generated from the sea. Thus, for the genesis of cyclones, temperature of water near the surface of the sea must be higher than 27 degrees to a depth of at least 150 feet. Additionally, heat from the sea and Earth’s counter-clockwise rotation conspire to create the cyclone’s spin and propulsion. Furthermore, rising sea levels mean that surges produced by cyclones are much more powerful, thereby increasing the risk of inland flooding.

Moreover, cyclones need to be at least 300 miles from the equator, where a deflective force known as Coriolis force resulting from Earth’s rotation begins to take effect. When cyclones reach land, or cooler water, they lose energy as the conditions necessary to reinforce them are no longer present.

As a result of global warming, temperature near the surface of the Bay of Bengal varies from 27 degrees in January to more than 31 degrees in May. The unusually warm water, together with geographical and environmental factors, make the Bay of Bengal a hot spot for cyclonic activity.

Can changes in frequency and intensity of cyclones observed so far be attributed solely to anthropogenic global warming as against long-term periodic natural variations? Cyclones are affected by natural fluctuations too, driven by external factors, such as solar variability and volcanic eruptions, natural internal variations of the complex physical, chemical, and biological systems of Earth.

Additionally, research has shown that urbanisation significantly contributes to the amount of rainfall dumped, as evidenced by over 130 centimetres of rain that fell on the Houston region during hurricane Harvey in 2017. This is because the “roughness” of the city—as in the buildings and infrastructure—creates a drag on the storm system, causing it to slow down, resulting in more rain over the city area.

Climate models predict that global warming could spawn more bizarre and violent weather, notably cyclones and severe floods in the future. Indeed, while people are trying to come to grips with the effects of Fani, meteorologists have warned that Bangladesh is likely going to experience another cyclonic storm called Vayu some time later this month.

The models also predict that by the end of this century, global warming effects could increase a cyclone’s intensity by about 20 percent, making them more destructive than ever. The amount of rainfall would also increase substantially. Other estimates predict that a doubling of carbon dioxide concentration would result in a 40-50 percent increase in destructive cyclones.

So, what should we do to keep our planet in the so-called Goldilocks zone of the solar system? We have to make a concerted effort to end our dependence on fossil fuels. We have to replace them with non-polluting, renewable sources of energy. We have to develop more carbon-free energy technologies. We have to sequester carbon dioxide emissions using the available technology. More importantly, we have to shun the “business as usual” attitude. In short, we will have to build a sustainable future. Otherwise, climate change will cause our civilisation to collapse.

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

Advanced science, Astrophysics, Cultural, International, Technical

Mysterious dark matter and dark energy

Physics is traditionally viewed as a hard subject requiring a great deal of mathematical prowess, devotion and perseverance to muster the subject matter. To a large extent, it is definitely true. But it does also offer, in its turn, a great deal of satisfaction, excitement and sense of achievement.

The 21st century physics, spanning from quantum computing to super-thin layer material called graphene to ultra-efficient LED bulbs to efficient harnessing of renewable energies to black holes to dark matter and dark energy, the range of topics is endless and it will disappoint no one with its vast challenges and ensuing excitement.

In our day-to-day lives, we encounter matter comprising protons and neutrons bundled together at the centre, called nucleus, of an atom and electrons whizzing around the nucleus. Some decades ago, these protons, neutrons and electrons were thought to be the fundamental particles of all matter; but not anymore. Now, quarks (six types) are thought to be the fundamental matter particles, which are glued together by force particles to form protons and neutrons.

These atoms and molecules making up matter here on earth are what we are accustomed to. The laws of physics, or for that matter of natural sciences, were developed to explain the natural processes as we encounter in our lives.

The basic physical principles are like these: a body has a definite size comprising length, breadth and height; it has a mass and weight; it is visible when there is sufficient light. If we push a body, we impart momentum, which is the product of mass and velocity. As it has the mass, it has gravity, meaning it attracts every other body and every other body attracts this body. These are the basic properties of a body as described in classical physics.

But there is no reason to be dogmatic about these basic principles. These principles can change here on earth or in our galaxy or somewhere outside our galaxy. When they do change, we would feel that things have gone topsy-turvy.

We live on a very tiny planet, called Earth, which revolves round the star, called Sun. There are eight other planets, thousands of satellites, comets and asteroids, all held together by the gravity of the Sun. The Sun, though extremely bright and overwhelmingly powerful to us, is a small star in our galaxy, called the Milky Way. It is estimated that there are over a billion, yes, 1,000,000,000 stars, many of them are much bigger than the Sun, in our galaxy. Now our galaxy is by no means the biggest or dominant galaxy in the universe. Cosmologists estimate that there are around one billion galaxies in our universe! Some of these galaxies are hundreds or even thousands of times bigger or massive than our galaxy. There are massive black holes at the centres of most of the galaxies, exerting gravitational pull to keep the galaxy together. Some of these black holes are millions of times bigger than the Sun. Now we can have a feel of how big our universe is!

Physics, or more appropriately astrophysics, studies the processes of these vast expanse of celestial bodies. The Sun as well as our galaxy, the Milky Way having over a billion stars are not static. The stars are spinning, the galaxy is spiralling, and everything is in motion.

Strange glow from the centre of the Milky Way

It was estimated, purely on physical principles, that the stars at the edges of a galaxy should move slower than the central ones, as the force of gravity of the galaxy is weaker away from the centre. But astronomical observations show that stars orbit at more or less at the same speed regardless of their distance from the centre. That was a great surprise, indeed shock, to the astrophysicists. The way this puzzle was eventually tackled was by assuming that there are massive unseen matters that exert tremendous amount of gravitational pull to keep the outlying stars moving at nearly the same speed and that mysterious matter is called the dark matter.

There are other tell-tale signs that there is something amiss in the material accounting of the universe. A strange bright glow spread over the length of the Milky Way was thought to be due to ordinary pulsars (pulsating stars) along the length. But now it is thought that dark matter may be responsible for this glow! But how does it do that, physics does not know yet.

But is this dark matter a fudge to solve the apparent conflict of physical behaviour with observations? Not really, this is how science progresses. Well thought out ideas are advanced and those ideas are tested and cross-examined against observations and the idea or concept that passes the tests is taken as the valid scientific concept.

But how do we know dark matter is there, if we cannot see them. We cannot see them because dark matter does not interact with light or electromagnetic radiation such as visible light, infra-red, ultra violet, radio waves, gamma rays and so on. Light goes straight through the dark matter, as if it is not there.

It should, however, be pointed out that dark matter is not the same thing as black hole. A black hole is made up of everyday particles (matter particles and force particles) – electrons, protons, neutrons, atoms, molecules, photons etc. Its gravity has just become so strong (because of its mass and super-compacted size) that it pulls and crushes everything to its core and nothing can escape from its clutches, not even light! A beam of light coming close to a black hole is pulled right insight and that is the end of that light beam never to be seen again!

Dark energy expansion

Dark matter, although invisible, does exert gravitation pull and this gravitational pull that makes dark matter attractive to scientists. The Universe, although expanding, is not in danger of runaway expansion. There is something that is holding the whole thing together and that something may be the dark matter.

Immediately following the Big Bang, the then Universe expanded very rapidly, known as inflationary phase, for tens of millions of years followed by expansion for some billion years and then it stabilised for a few billion years and now it is again in the expansion phase. The present expansion is that the space itself is expanding and so every star and every galaxy is moving away from every other star or galaxy. What is giving these celestial bodies energy (repulsive in this case) to move away from each other? Scientists came up with the proposition that there must be some unknown, unseen energy, which is now called the dark energy.

On purely material and energy balance of the Universe, it is thought that our visible (and known) Universe accounts for only 4.9 percent of the total Universe, dark matter accounts for 26.8 percent and dark energy for 68.3 percent. So, we only know in the vast mind-boggling universe extending over 13.8 billion light years a meagre 5 percent and the remaining 95 percent is hidden or unknown to us!

Scientists all over the world are trying hard to find evidence of dark matter and dark energy. CERN’s Large Hadron Collider (LHC) is trying to find any remotest evidence of dark matter and energy. On theoretical basis, some scientists are proposing that dark energy may emanate from a fifth form of force, which is yet unknown. The four forces that we know are electromagnetic, weak nuclear, strong nuclear and gravitational forces. The fifth force may be a variant of gravitational force – a repulsive gravitational force – that comes into play in the vast intergalactic space.

When Einstein produced the general theory of relativity in 1915, he introduced, almost arbitrarily, a parameter, called the cosmological constant, into the theory to counter the effects of gravitational pull and make the Universe a static one. That cosmological constant effectively introduced the repulsive effects. It may be pointed out that the Universe was thought to be static at that time. But only a few years later when it was incontrovertibly shown that the Universe was, in fact, expanding, Einstein humbly admitted that it was his “biggest mistake”. Now, more than hundred years later, it is assumed that the cosmological constant may be considered to be the quantity to cater for the dark energy! Could Einstein’s “biggest mistake” be a blessing in disguise, it offers not only a correct presumption but also a saviour of modern cosmology?

  • Dr A Rahman is an author and a columnist

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