Unlocking the mysteries of force
Syed Fattahul Alim | Saturday, 19 July 2008
On a par with the advancement of human knowledge about the structure of matter, the technological civilisation made great strides. And when one talks about structure, the concept of force automatically comes in. For how is it possible to conceive of a structure without some force to keep its constituent parts together or push them apart? The idea of force itself has an aura of mystery around it and is not yet understood why man instinctively invokes the idea of force in an attempt to comprehend the cause that makes things to move. Newton, however, drew the line between the concept of physical force and the more informal aspect of the idea that people unconsciously use to explain any kind of motion.
Magnet was the source of a kind of attractive force people have been aware of since antiquity. Similarly, they also knew of static electricity that is produced as a result of friction between certain substances and has the power to attract things. However, the exact relation between the two was explained in the second half of the 19th century. But there were also other forces like gravitation, or the force of attraction between constituent parts of the atomic core.
Physicists are of the view that the four fundamental forces now known to them are but the remains of the 'superforce' that was created under the condition of the extreme heat that existed a hundred billionth of a second after the birth of the universe. Robert Matthews of the Guardian tells the story of these fundamental forces in more details in the following:
Look around you: everything you see shows that The Force is with us. Or, to be more precise, its four descendants, in the form of a quartet of fundamental forces spawned moments after the big bang.
Two of the four are familiar enough: gravity, which weighs us down on the Earth, and electromagnetism, which keeps compass needles pointing north and paper sticking to charged-up balloons. The two other forces are less familiar, but no less important to shaping our world: the strong nuclear force, which binds together the nuclei of atoms, and the weak force, which causes nuclei to disintegrate.
In their present guise, each of the four appears utterly unlike any other: they each rule different domains, and have radically different strengths - the strong force living up to its name by being more than a trillion trillion trillion times stronger than gravity, the weakest of the four. Yet physicists now believe these differences mask a deeper unity, one that existed for just a fleeting but crucial instant at the birth of the universe.
Current theories predict that in the searing heat of the big bang all four forces were unified into a single "superforce" of unimaginable strength. While the superforce itself may never be recreated, its existence has been hinted at in experiments that can reach energy levels that existed in the early universe. This is possible using colossal accelerators that smash together subatomic particles at speeds close to the speed of light - thus mimicking conditions close to the big bang.
In experiments conducted with accelerators like the Large Hadron Collider on the Swiss-French border, physicists have been able to wind back the clock to one hundred-billionth of a second after the big bang, and study the behaviour of some of the fundamental forces. The results show changes in the forces of just the kind expected if they all turn into a single, unified superforce at some ultra-high energy far beyond our reach.
The era of the superforce may have long since ended, but we are still left with its shattered remains, which are now the subject of intense research.
Gravity
For all its successes, (Newton's law of gravity) does nothing to cast light on the real nature of gravity. Newton himself refused to speculate, airily declaring: "I frame no hypotheses ... to us it is enough that gravity really does exist."
Privately, Newton believed it was a manifestation of God's all-pervading spirit, which was hardly more helpful. A more concrete view of gravity emerged with the publication, in 1915, of Einstein's theory of general relativity.
According to Einstein, space and time are not a static arena in which events take place, as envisaged by Newton. Rather, they are more like some form of cosmic fabric that can be curved and warped by the presence of mass.
Einstein's theory gives a precise account of how much distortion in the fabric of space-time is produced by a given amount of mass. And it shows that what we think of as the "force" of gravity is really a kind of illusion created by this distortion in space and time. When the concentration of mass in one place is relatively low - as it is on the Earth - Einstein's theory gives results in precise agreement with Newton's famous law. But as the concentration increases, the theory shows that the fabric of space-time can curl up completely, forming what we now call a black hole, from which not even light can escape.
General relativity is more than just a more sophisticated way of describing gravity, however. Unlike Newton's theory, it accurately describes the effects of intense gravitational fields around planets, stars and black holes, and has so far survived every experimental test of its predictions. Yet even Einstein's theory reaches its limits at the big bang, giving nonsensical values for the temperature, gravitational field and density of the universe.
This has led to the search for a successor to general relativity, which includes the crucial ingredient it lacks: the laws of the subatomic world in the form of quantum theory. Marrying these two theories is the greatest challenge facing theoretical physicists. But if they succeed, the result will be the so-called theory of everything, which will encompass all from the smallest subatomic particle to the entire universe.
Electromagnetism
Of the four forces, electromagnetism is the best-understood - and the most important in everyday life. Unlike the others, it can be controlled and directed, which has put it at the heart of our technological world. It is also the force at the heart of all matter, binding charged particles together and thus making possible the existence of atoms, molecules and life itself.
The practical value of electromagnetism has been recognised for millennia. Archaeologists in the Middle East have found 2,200-year-old electric batteries made from electrodes immersed in vinegar, while naturally magnetic lodestone, which makes an effective navigation compass, was mentioned by the Greek scholar Thales in the 6th century BC.
Understanding electromagnetism has taken the combined genius of some of the greatest scientists of the last 200 years. Michael Faraday showed how to turn electromagnetism into motion and vice-versa through his invention of the electric motor and the dynamo - the latter still being the basis of electric power generation.
The Scottish theorist James Clerk Maxwell created a mathematical theory describing Faraday's discoveries which revealed that electricity and magnetism were different facets of a single, unified phenomenon called electromagnetism. Maxwell went on to predict the existence of invisible waves of electromagnetism able to travel even through a vacuum at the speed of light - which itself is such a wave. This astounding prediction was confirmed in 1888 by Heinrich Hertz, and now forms the basis of all telecommunications.
At a more fundamental level, theorists have combined electromagnetism with quantum theory, the laws governing the subatomic world. The result, known as quantum electrodynamics (QED), describes what happens when photons of light interact with electrons of matter, though esoteric, its predictions have proved astonishingly accurate.
Weak nuclear force
Some crystals kept in a cupboard were the unlikely stimulus for the discovery of the weak nuclear force. In the spring of 1896, the French chemist Henri Becquerel was investigating compounds that glow in the dark after exposure to sunlight. A spell of overcast weather had prevented him from studying the effect, prompting him to gather up the crystals and put them in a cupboard along with a sealed photographic plate. After a few days, he examined the plate and was puzzled to find it had fogged, as if the crystals were still emitting rays despite not being exposed to sunlight.
Becquerel had accidentally discovered radioactivity. The crystals contained uranium, whose notoriously unstable atoms disintegrate in a process called beta decay, releasing fast-moving electrons. But these electrons are not those in orbit around the nuclei of atoms; they come from the uranium nuclei themselves, the product of a conjuring trick performed by the weak force, which breaks apart neutrons and turns them into other particles - including electrons.
The particle-changing abilities of the weak nuclear force seems esoteric, but they are essential to the nuclear reactions that keep the sun and stars burning. But for theorists, the force has the distinction of being the first to be unified with one of the other fundamental interactions: electromagnetism. At first sight, the two forces have little in common; the weak force is a billion times more feeble than electromagnetism, and is confined to the atomic nucleus. Yet during the 1960s, theorists in the US and UK found deep mathematical connections between the two forces, suggesting they were different facets of a single "electroweak" force. This underlying unity was finally confirmed in particle accelerator experiments in the early 1980s.
Strong nuclear force
The strong nuclear force resolves a paradox that emerges from two basic facts about our universe. First, every atom apart from hydrogen contains at least two positively charged protons in its nucleus; and second, like charges repel. How then can these atoms exist if their protons cannot bear to be in each other's company? The answer lies in the strong nuclear force, which is 10,000 times more powerful than the electromagnetic repulsion trying to tear the protons apart.
The source of this force lies within the protons and their fellow denizens of the atomic nucleus, the charge-free neutrons. Inside each lurks three constituent particles known as quarks (rhyming with "forks"), permanently trapped within their host by force-carrying particles aptly known as gluons.
First postulated in the early 1960s to explain odd regularities in the properties of subatomic particles, the existence of quarks was once regarded as little more than a mathematical mind game. However, by the early 1970s experiments with particle accelerators revealed the existence of nugget-like objects inside protons with precisely the properties predicted for quarks.
The strong nuclear force turns out to be just a side-effect of the interactions between quarks that keeps them caged within protons and neutrons. Even so, it has a profound effect on the cosmos. Without it, atoms more complex than hydrogen couldn't exist - and nor could we. Yet while it is much stronger than electromagnetism over very short distances, it rapidly becomes weaker with distance, making large atoms relatively unstable. Their instability is exploited by nuclear reactors, where fast-moving particles are used to split unstable atoms, releasing huge amounts of energy.
The strong force also powers the sun and stars, which crush atoms of hydrogen together so tightly that their nuclei overcome their natural repulsion and fuse together. The result is the release of a million times more energy, pound for pound, than any conventional fuel.
Magnet was the source of a kind of attractive force people have been aware of since antiquity. Similarly, they also knew of static electricity that is produced as a result of friction between certain substances and has the power to attract things. However, the exact relation between the two was explained in the second half of the 19th century. But there were also other forces like gravitation, or the force of attraction between constituent parts of the atomic core.
Physicists are of the view that the four fundamental forces now known to them are but the remains of the 'superforce' that was created under the condition of the extreme heat that existed a hundred billionth of a second after the birth of the universe. Robert Matthews of the Guardian tells the story of these fundamental forces in more details in the following:
Look around you: everything you see shows that The Force is with us. Or, to be more precise, its four descendants, in the form of a quartet of fundamental forces spawned moments after the big bang.
Two of the four are familiar enough: gravity, which weighs us down on the Earth, and electromagnetism, which keeps compass needles pointing north and paper sticking to charged-up balloons. The two other forces are less familiar, but no less important to shaping our world: the strong nuclear force, which binds together the nuclei of atoms, and the weak force, which causes nuclei to disintegrate.
In their present guise, each of the four appears utterly unlike any other: they each rule different domains, and have radically different strengths - the strong force living up to its name by being more than a trillion trillion trillion times stronger than gravity, the weakest of the four. Yet physicists now believe these differences mask a deeper unity, one that existed for just a fleeting but crucial instant at the birth of the universe.
Current theories predict that in the searing heat of the big bang all four forces were unified into a single "superforce" of unimaginable strength. While the superforce itself may never be recreated, its existence has been hinted at in experiments that can reach energy levels that existed in the early universe. This is possible using colossal accelerators that smash together subatomic particles at speeds close to the speed of light - thus mimicking conditions close to the big bang.
In experiments conducted with accelerators like the Large Hadron Collider on the Swiss-French border, physicists have been able to wind back the clock to one hundred-billionth of a second after the big bang, and study the behaviour of some of the fundamental forces. The results show changes in the forces of just the kind expected if they all turn into a single, unified superforce at some ultra-high energy far beyond our reach.
The era of the superforce may have long since ended, but we are still left with its shattered remains, which are now the subject of intense research.
Gravity
For all its successes, (Newton's law of gravity) does nothing to cast light on the real nature of gravity. Newton himself refused to speculate, airily declaring: "I frame no hypotheses ... to us it is enough that gravity really does exist."
Privately, Newton believed it was a manifestation of God's all-pervading spirit, which was hardly more helpful. A more concrete view of gravity emerged with the publication, in 1915, of Einstein's theory of general relativity.
According to Einstein, space and time are not a static arena in which events take place, as envisaged by Newton. Rather, they are more like some form of cosmic fabric that can be curved and warped by the presence of mass.
Einstein's theory gives a precise account of how much distortion in the fabric of space-time is produced by a given amount of mass. And it shows that what we think of as the "force" of gravity is really a kind of illusion created by this distortion in space and time. When the concentration of mass in one place is relatively low - as it is on the Earth - Einstein's theory gives results in precise agreement with Newton's famous law. But as the concentration increases, the theory shows that the fabric of space-time can curl up completely, forming what we now call a black hole, from which not even light can escape.
General relativity is more than just a more sophisticated way of describing gravity, however. Unlike Newton's theory, it accurately describes the effects of intense gravitational fields around planets, stars and black holes, and has so far survived every experimental test of its predictions. Yet even Einstein's theory reaches its limits at the big bang, giving nonsensical values for the temperature, gravitational field and density of the universe.
This has led to the search for a successor to general relativity, which includes the crucial ingredient it lacks: the laws of the subatomic world in the form of quantum theory. Marrying these two theories is the greatest challenge facing theoretical physicists. But if they succeed, the result will be the so-called theory of everything, which will encompass all from the smallest subatomic particle to the entire universe.
Electromagnetism
Of the four forces, electromagnetism is the best-understood - and the most important in everyday life. Unlike the others, it can be controlled and directed, which has put it at the heart of our technological world. It is also the force at the heart of all matter, binding charged particles together and thus making possible the existence of atoms, molecules and life itself.
The practical value of electromagnetism has been recognised for millennia. Archaeologists in the Middle East have found 2,200-year-old electric batteries made from electrodes immersed in vinegar, while naturally magnetic lodestone, which makes an effective navigation compass, was mentioned by the Greek scholar Thales in the 6th century BC.
Understanding electromagnetism has taken the combined genius of some of the greatest scientists of the last 200 years. Michael Faraday showed how to turn electromagnetism into motion and vice-versa through his invention of the electric motor and the dynamo - the latter still being the basis of electric power generation.
The Scottish theorist James Clerk Maxwell created a mathematical theory describing Faraday's discoveries which revealed that electricity and magnetism were different facets of a single, unified phenomenon called electromagnetism. Maxwell went on to predict the existence of invisible waves of electromagnetism able to travel even through a vacuum at the speed of light - which itself is such a wave. This astounding prediction was confirmed in 1888 by Heinrich Hertz, and now forms the basis of all telecommunications.
At a more fundamental level, theorists have combined electromagnetism with quantum theory, the laws governing the subatomic world. The result, known as quantum electrodynamics (QED), describes what happens when photons of light interact with electrons of matter, though esoteric, its predictions have proved astonishingly accurate.
Weak nuclear force
Some crystals kept in a cupboard were the unlikely stimulus for the discovery of the weak nuclear force. In the spring of 1896, the French chemist Henri Becquerel was investigating compounds that glow in the dark after exposure to sunlight. A spell of overcast weather had prevented him from studying the effect, prompting him to gather up the crystals and put them in a cupboard along with a sealed photographic plate. After a few days, he examined the plate and was puzzled to find it had fogged, as if the crystals were still emitting rays despite not being exposed to sunlight.
Becquerel had accidentally discovered radioactivity. The crystals contained uranium, whose notoriously unstable atoms disintegrate in a process called beta decay, releasing fast-moving electrons. But these electrons are not those in orbit around the nuclei of atoms; they come from the uranium nuclei themselves, the product of a conjuring trick performed by the weak force, which breaks apart neutrons and turns them into other particles - including electrons.
The particle-changing abilities of the weak nuclear force seems esoteric, but they are essential to the nuclear reactions that keep the sun and stars burning. But for theorists, the force has the distinction of being the first to be unified with one of the other fundamental interactions: electromagnetism. At first sight, the two forces have little in common; the weak force is a billion times more feeble than electromagnetism, and is confined to the atomic nucleus. Yet during the 1960s, theorists in the US and UK found deep mathematical connections between the two forces, suggesting they were different facets of a single "electroweak" force. This underlying unity was finally confirmed in particle accelerator experiments in the early 1980s.
Strong nuclear force
The strong nuclear force resolves a paradox that emerges from two basic facts about our universe. First, every atom apart from hydrogen contains at least two positively charged protons in its nucleus; and second, like charges repel. How then can these atoms exist if their protons cannot bear to be in each other's company? The answer lies in the strong nuclear force, which is 10,000 times more powerful than the electromagnetic repulsion trying to tear the protons apart.
The source of this force lies within the protons and their fellow denizens of the atomic nucleus, the charge-free neutrons. Inside each lurks three constituent particles known as quarks (rhyming with "forks"), permanently trapped within their host by force-carrying particles aptly known as gluons.
First postulated in the early 1960s to explain odd regularities in the properties of subatomic particles, the existence of quarks was once regarded as little more than a mathematical mind game. However, by the early 1970s experiments with particle accelerators revealed the existence of nugget-like objects inside protons with precisely the properties predicted for quarks.
The strong nuclear force turns out to be just a side-effect of the interactions between quarks that keeps them caged within protons and neutrons. Even so, it has a profound effect on the cosmos. Without it, atoms more complex than hydrogen couldn't exist - and nor could we. Yet while it is much stronger than electromagnetism over very short distances, it rapidly becomes weaker with distance, making large atoms relatively unstable. Their instability is exploited by nuclear reactors, where fast-moving particles are used to split unstable atoms, releasing huge amounts of energy.
The strong force also powers the sun and stars, which crush atoms of hydrogen together so tightly that their nuclei overcome their natural repulsion and fuse together. The result is the release of a million times more energy, pound for pound, than any conventional fuel.