Wednesday, February 13, 2013

Roadblocks and diversions in the path of scientific advancement – Some examples from the history of Physics


The Context

In one of my previous blog posts [see: 32) Chandrasekhar - Fermi-Dirac and White Dwarfs (Aug 11)] I had written as follows under ‘Science and Truth’ by way of a summation:

Authority, dogma, faith, belief, superstition, etc., are human traits found all too commonly in almost all walks of everyday life.  However, one doesn't expect to encounter them in the world of science which is characterized precisely by their absence.  But, since science cannot always be separated from what scientists do, it is not uncommon to find these traits in the day to day affairs and actions of scientists.  The Eddington affair narrated here is a classic example of this.  The history of science is replete with such episodes that have had an immediate negative impact on the march of scientific progress*.  However, the damage has always been temporary; science in its relentless pursuit of truth has always bounced back and triumphed in the end.  Even Eddington's influence could not negate the white dwarf star theory for too long.  The scientist advocating the theory may have suffered, but not science itself.  This amazing proclivity is what sets science apart from other human pursuits.

I had also gone on to add parenthetically, “*This is far too important for just a casual reference like this and I intend to expand on the theme in a future blog post.”

It is now time for me to follow up on this promise, taking a few glaring examples from the history of physics to drive home my point, in addition to the Eddington-Chandrasekhar episode discussed earlier.  These examples are discussed not so much to highlight an immediate negative impact on the march of science as in the Eddington episode, but as major roadblocks and diversions in the path of scientific progress and for their historic importance.  My choice of examples has been dictated largely by my professional background, which is mainly physics, and I am sure such examples abound in other branches of science as well.  However, I hasten to add that I have endeavored to communicate my ideas in a non-technical language and with their essence understandable to all categories of readers.
   
Aristotelian Legacy and the Copernican Revolution

Following in the footsteps of his illustrious predecessors Socrates and Plato, and belonging to the golden era of Greek civilization, the very cradle of human civilizations, Aristotle (384 BC – 322 BC) was perhaps the greatest contributor to original knowledge the world has ever known.  His work and writings in  philosophy, science, mathematics, metaphysics, art, poetry, politics, logic, rhetoric, morality and a host of other disciplines made him a sort of all-in-one walking encyclopedia, something that was possible only in such early times in the history of civilization.

In the realm of science, while Aristotle’s contributions to what may be broadly called biology stood the test of time to a considerable extent, most of his contributions to what later came to be termed physics were only like castles in the air, without firm foundations.  They were founded largely on the process of reasoning rather than experimentation, the hallmark of true science as was to be demonstrated by Galileo nearly two thousand years later.

Such an aura of reputation was built around Aristotle that he came to represent all that was authoritarian, revered and dogmatic as much in science as in other disciplines, stifling its growth for a very long time to come. The Aristotelian legacy was to do more harm than good, especially in the hands of the powerful Roman Catholic Church which ruled and controlled the minds of people based on such authoritarian precepts.
 
One such legacy was the geo-centric world view that placed earth at the centre of everything in the universe and would not tolerate any arguments or even evidence to the contrary.  The observed motions of heavenly bodies – planets, stars, the Sun and the Moon – were all artificially made to fit into a geocentric system through some tortuously complex mechanisms conceived by Ptolemy and others just to preserve appearances and essentially to conform to church dictates.

The geocentric system had met a feeble challenge from people like Aristarchus even in ancient times but it was only in the mid sixteenth century that it was confronted with a formidable and eventually victorious rival in the form of the heliocentric (sun-centered) model proposed by Nicolaus Copernicus, a Polish monk who summoned enough courage to publish his arguments towards the end of his life knowing he would not live to see their acceptance.  Based largely on observational evidence he effectively dethroned the earth from its central pedestal and showed how a sun-centered system accounts for the observations elegantly without all the complexities devised by Ptolemy and others.  It took nearly a hundred years more for its universal acceptance through systematic mathematical analysis by Johannes Kepler and the subsequent clinching observational evidence provided by the great Galileo to the consternation of the church.  The rest is history.


Science had fought a long hard battle lasting many centuries, unparalleled in the history of human thought, before triumphing over authoritarian religious dogma that had tried to stifle the quest for objective truth.

Ironically, thanks to the power of mathematics coupled with the speed of number crunching operations with computers, it is indeed irrelevant whether we adopt a heliocentric or geocentric or any other world view today.  Nevertheless, the Copernican revolution uprooting the Aristotelian legacy was a major milestone in the history of scientific advancement.

Falling Bodies

A popular ‘prediction’ of Aristotelian arm-chair logic was that a heavier object would fall faster than a lighter one if dropped from the same height on earth.  Like the emperor’s invisible clothes unveiled by an innocent child, it took a simple demonstration by Galileo centuries later to unravel the fallacy of this.  Contrary to popular belief, there is no conclusive evidence that Galileo actually employed the leaning tower of Pisa to demonstrate that bodies of different weights took the same time to hit the ground when dropped simultaneously from the same height.  However, he certainly delivered a death blow to the myth.  A convincing explanation as to why this is so had to await Newton, Galileo’s worthy successor in the scientific firmament.  Using Newton’s (universal) law of gravitation, coupled with his second law of motion, it can be shown that different masses acquire the same acceleration under the earth’s pull of gravity.

If there were any doubters, the Apollo 15 astronauts demonstrated this live with a hammer and a feather on the airless surface of the Moon for all TV viewers to see.  However, there are some people who doubt that astronauts ever went to the Moon!  There is no question of convincing them of anything!

Aristotle’s authoritarian influence was so strong that it had occurred to no one to put his argument to a simple observational test.  The idea that observational/experimental evidence and not arm-chair logic would be the final arbiter in any dispute was virtually unknown.  From the perspective of scientific pursuit today it is absolutely astonishing that this remained so for centuries until the advent of Galileo on the scene.  No wonder science historians consider Galileo as the true father of modern science.

Nature of Light

Few things in everyday life are more familiar to us than light that enables us to see things around us.  Incidentally, we can only see objects that reflect/scatter or emit light, but not see light itself.  One of the most fascinating questions about the world around us concerns the nature of light itself – What is it?  What is it made of it?  How does it travel?  At what speed?  Etc.

It has long been recognized that light carries energy and travels at a finite, though enormously high, speed.  It was Newton who first proposed the corpuscular theory of light according to which it consists of corpuscles (particles) travelling in straight lines and can be reflected off material surfaces like bullets or pierce through transparent materials similarly.  On the face of it, this was an elegant and viable theory of light, accounting for some well-known properties, including reflection and refraction (bending when passing from one medium to another).  It held sway for a long time but eventually ran into serious trouble.

Newton himself had discovered a property of light that led to the formation of colored fringes when white light was reflected off very thin material.  We often see this when oil from a truck has leaked and spilled over a smooth road coated with a thin layer of rain.  Called interference, this phenomenon defied explanation under the corpuscular theory.  Also, Newton’s theory predicted that the speed of light should decrease when it refracted from a dense medium like glass into a rarer medium like air, but actual observations later showed just the opposite.  Another phenomenon that defied explanation was diffraction, the observed bending of light and formation of fringes when it passes through very narrow obstacles or at straight thin edges like a razor blade.  Yet another property of light called polarization fell totally outside the scope of the particle theory.

All these phenomena posed an insurmountable challenge to Newton’s theory much to his mounting annoyance when he realized that a rival theory proposed in 1678 by Dutch physicist Christian Huygens threatened to overthrow his own pet theory.


Huygens realized the need for a better theory of light considering that some of its properties were akin to those of mechanical waves on the calm surface of water in a pond, generated and propagated when an object is dropped or dipped into it.  He visualized every point in a medium through which light passed as a secondary source of spherical wavelets, propagating at constant speed and carrying energy in the direction of motion of the light ray.  Each of these wavelets gave rise to others in turn, thus setting up an expanding wave form much like the two dimensional waves we observe on the surface of water when disturbed.  With such a model he was able to explain practically all the phenomena where Newton’s corpuscular theory had failed.
 
As in the case of Aristotle and his geocentric world view, Newton’s exceptional fame and authority was to thwart the acceptance and use of Huygens’ wave theory for quite a long time, to which Newton’s own attitude and opposition contributed in no small measure.  Eventually, it received its due recognition and Newton’s theory was duly consigned to the dustbin of history.
 
Rather curiously, Newton’s particulate picture of light underwent a sort of revival when Einstein came up with his photon theory of light in early twentieth century to explain certain phenomena that had been freshly discovered and had defied explanation by the wave theory itself.  However, the photons that Einstein visualized were packets of energy whose magnitude depended on the wavelength of the light in question and bore only a superficial resemblance to Newton’s corpuscles.

The wave theory itself underwent a metamorphosis in mid nineteenth century in the hands of Maxwell who bestowed on it an ‘electromagnetic’ character and a vastly expanded scope.  Also, the electromagnetic wave theory and the photon theory were both found to be perfectly valid descriptions of nature in their respective domains of applicability and the ‘duality principle’ associated with them became a fundamental attribute of nature.

The Enigmatic Aether

Historically, an inescapable implication of the wave theory of light, either the classical or the electromagnetic version, was that light waves required a medium to pass through just like mechanical waves (two common examples of which are longitudinal sound waves through air and transverse waves on the surface of water).  The fact that light from the Sun and stars are found to travel vast distances of empty space posed an obvious contradiction.  Since physicists in those days found it impossible to conceive of light without an associated medium, they decided to bestow such a material property to empty space itself and called this hypothetical medium the aether!(often also spelt as ether).  However idiosyncratic the idea may sound today, it was looked upon as perfectly sensible, indeed very essential, in those times.
 
When a systematic study was made of the properties that such an all pervasive medium ought to possess, it was deduced that the luminiferous aether should have, as one writer put it, “… some fairly impressive physical properties.  It was simultaneously a fluid (in order to fill space) but also more rigid than steel (to support the high-frequency oscillations of light waves).  Aether could have neither mass nor viscosity, otherwise it would affect the motions of the planets.  Finally it had to be non-dispersive, transparent, incompressible, and continuous at a very small scale.”  Apart from such absurdly impossible properties the aether would also provide, according to Newton’s ideas on space and time, “a universal frame of reference, and all other motion (like that of the Earth around the Sun) occurred relative to this frame, moving through the aether.”

Even as the notion of the aether clung to the body of physics like a leech, American physicists Michelson and Morley came out with the findings of a historic and super-sensitive experiment that settled the question once for all – the aether could not exist; otherwise their experiment would have easily detected its presence!    This ‘cognitive dissonance’ between theory and observation wouldn’t go away easily until Einstein came up with his revolutionary theory of relativity that totally dispensed with the need for the existence of any exotic medium like the aether.  Sanity was finally restored, but the progress of physics had suffered considerably because of its conservatism.

The N-Ray Episode

In 1903, Rene Blondlot, a well-known French physicist working in the University of Nancy, announced the discovery of a new form of radiation analogous to X-rays and named it N-Rays.  This followed a spate of publications about the supposed properties of these novel radiations, with over a hundred scientists involved.  These rays were supposed to be emitted by most substances, including the human body.  This ‘discovery’ excited international interest and a fair amount of skepticism as well by people who couldn’t reproduce the effect, including Lord Kelvin and William Crookes in England.
 
The noted American physicist Robert W Wood, also known to be something of a prankster and debunker of nonsense, was one of those welcomed by Blondlot to his laboratory to see a first-hand demonstration.  Wood smelled a rat and stealthily removed a prism used as an essential piece of equipment in the darkened room and the experimenters still claimed the ‘detection’ of the N-rays.  He similarly replaced the object supposed to be emitting the rays with a dry piece of wood (no pun intended), and with the same result.  He duly reported his findings and the N-ray related publications declined exponentially and soon died away.  The episode became an example of what Irving Langmuir called pathological science.

Blondlot’s claim was not really a hoax as many such claims actually are, but illustrates the lack of unbiased objectivity and illusionary tendencies that sometimes haunts even scientific investigations.  The episode illustrates how even hardened scientists can sometimes become highly subjective and claim findings that matched their a priori expectations.  It is very frequently cited as a classic example of the dangers inherent in experimenter bias, the very antithesis of good science.  The history of science is replete with many examples not only of such delusional discoveries, but also outright hoaxes and plain cheating.  I would like to reserve them for separate treatment in a later blog.  But the bottom line is that science has always bounced back from such setbacks and triumphed in the end.

The ‘Martians’

Extraterrestrial life has been an eternal fascination for all mankind.  This is also the dominant theme of all science fiction.  But till date there is no evidence of the actual existence of advanced life forms anywhere outside our mother planet.  While this has never bothered fiction writers from conjuring up their tales, hard headed scientists have also occasionally fallen prey to the temptation of interpreting highly questionable observations as evidence in favour of extraterrestrial life.

Giovanni Schiaparelli, a reputed Italian astronomer, made numerous telescopic observations of planet Mars during its opposition in 1877 and observed a dense network of linear structures on its surface, which he called ‘canali’ in Italian but was loosely translated into ‘canals’ in English, and drew worldwide attention as representative of the handiwork of intelligent life on the planet.  Questionable observations mingling with unquestionably wild speculation led to the hypothesis of the ‘Martians’ and a fancy folklore and colorful fiction grew up around it.

Adding fuel to the fire was the role of the American astronomer Percival Lowell who became a strong votary for the existence of intelligent life on Mars based on his own ‘supportive’ observations and interpretations.  Though it was soon conclusively established that what these two astronomers and their supporters had observed was just some optical illusion, compounded by poor quality optics, the hysteria didn’t die away easily.  As recently as 1938, Orson Welles was successful in frightening vast radio audiences out of their wits through a fake ‘live’ broadcast of  an attack on Earth from these ‘Martians’.


It was not until the early sixties of the last century that all speculation about unusual features and happenings on the surface of Mars were fully dispelled through close-up pictures and studies of the planet by NASA’s Mariner space crafts.

In recent months, Curiosity the NASA automated Mars Science Laboratory roaming on the surface of the red planet has made some tantalizing discoveries, but no evidence of any form of life has emerged as yet, nor is any really expected to turn up in this mission.

The Elusive Neutrino

Radioactivity is the process of emission of ionizing radiation by unstable atomic nuclei.  Three such processes are common, involving the emissions of what came to be called alpha rays, beta rays, and gamma rays respectively.  When an alpha particle (stable nucleus of helium) is emitted the unstable parent nucleus decays into a more stable daughter nucleus of a different element.  When a beta particle (an electron) is emitted the parent nucleus decays into another nucleus in which one neutron will have changed into a proton.  When a gamma ray (a high energy photon) is emitted the unstable nucleus loses some of its excess energy and drop down to a lower, more stable, state without undergoing any elemental transformation.

In all the transformations involving radioactive decay and other nuclear processes, the fundamental principles of conservation of energy, linear momentum, and angular momentum (spin) are inviolable.  But beta decay had raised grave questions about the validity of one of them and driven physics into a major crisis before being resolved in a manner that marks one of the greatest triumphs of the scientific method.

In beta decay, the parent nucleus emits an electron (or a positron) and changes to another nucleus as in the following example: 6C14 -> 7N14 + (-1)e0.  The root of the trouble with beta decay was that the sum of the energies of the decay products was invariably less than the energy of the parent, though not always by the same amount.  The beta energies exhibited an unexpected continuous spectrum up to a maximum value and this was another puzzle.  Even the momentum was not fully accounted for.  These anomalies prompted a series of very sensitive and precise measurements, thereby giving a boost to experimental techniques, but could not be resolved.  The community of nuclear physicists the world over faced such a serious situation that some of them were even prepared to abandon the cherished energy conservation principle, at least in the beta decay process.

The stage was set for a radical solution to the crisis proposed around 1930 by an extraordinarily brilliant Austrian theoretical physicist, Wolfgang Pauli, best known for the ‘Exclusion Principle’ named after him and a founding father of the New Quantum Mechanics.  Realizing that his idea might not be accepted for formal publication, he informally postulated in a conference of ‘radioactive’ physicists the existence of an unknown neutral, massless, and chargeless particle that carried away just the amount of unaccounted ‘missing’ energy!  Furthermore, he attributed its non-detection to its exceptionally low interaction with matter in any form!  The equation in the example cited earlier would now read:  6C14 -> 7N14 + (-1)e0 + 0n0 where n represents the new particle later called the neutrino (actually its anti-particle).  The whole idea sounded so outrageously unconventional, even ridiculous, that it met with little enthusiasm despite having come from one of the founders of the new quantum mechanics.  But not for too long!

The celebrated Italian physicist Enrico Fermi, one of the all-time greats in the history of physics, took up Pauli’s idea seriously and incorporated it into a very sound quantum-mechanical theory of beta decay that conferred virtual acceptance to the neutrino hypothesis.  But the clinching evidence came from the elaborate and successful experimental detection of the particle by Clyde Cowan and Frederick Reines in 1956, an eventual Nobel Prize winning effort.


Today the neutrino is so well known as to constitute an integral part of any fundamental theory of astro-particle physics and we even have ‘neutrino telescopes’ in operation in some parts of the earth deep underground.

Fusion, hot and cold

Even small amounts of matter can be transformed into enormous amounts of energy under certain conditions in accordance with Einstein’s famous relation between the two, E=mc2, c being the speed of light and equal to a huge 300,000 km/sec. Nuclear fusion is the process taking place all the time deep inside most stars, including of course our Sun, by which energy is generated by the fusing together of four hydrogen nuclei (protons) effectively into one helium nucleus.  Nuclear fission is the opposite process in which a heavy nucleus like uranium breaks up into smaller fragments, also releasing energy because of a net reduction in mass.

Both these forms of energy have been harnessed on earth by Man.  While fission energy has been put to use for both constructive (as in nuclear power reactors) and destructive (as in nuclear weapons) purposes, fusion energy is so far confined to destructive purposes only, with the ‘hydrogen bombs’ based on fusion deadlier than the ‘atom bomb’ based on fission.
 
Nuclear fusion requires the material (hydrogen nuclei) to be heated to temperatures of the order of tens of millions of degrees, a requirement easily fulfilled inside most stars.  In ‘hydrogen bombs’ such temperatures are uncontrollably created by the initial explosion of a fission bomb that acts as a trigger.

Because of the virtually limitless supply of hydrogen in the form of water on earth, controlled fusion energy can be a solution to all our energy needs if it can be harnessed in a controllable manner.  Till now this has been just a pipe dream because of formidable technical problems that persist in spite of huge investments in resources and efforts spread over the last 5-6 decades.
  
It is in this context that a claim in 1989 from two scientists, Martin Fleishmann in UK and Stanley Pons in USA, created worldwide interest, excitement, and even sensation.  They claimed to have produced fusion energy in small amounts in a room temperature tabletop experiment involving electrolysis of heavy water (in which the hydrogen atom of ordinary water is replaced by its heavier cousin deuterium that is made up of a proton and a neutron) on the surface of a palladium electrode.  It soon failed one of the most fundamental tests for good science and a basic tenet of the scientific method – reproducibility.

As summed up by a reviewer at that time, “Many scientists tried to replicate the experiment with the few details available.  Hopes fell with the large number of negative replications, the withdrawal of many positive replications, the discovery of flaws and sources of experimental error in the original experiment, and finally the discovery that Fleischmann and Pons had not actually detected nuclear reaction byproducts.”  Like the N-ray episode discussed earlier, in course of time this ‘Cold Fusion’ episode came to be regarded as another instance of pathological science.

The fact that many die hard experimenters still continue to pursue their cold fusion researches does not necessarily bestow any authenticity for cold fusion as opposed to hot fusion which is a demonstrated fact, though it has proved impossible to harness for peaceful purposes till now.

Faster than light entities

Einstein’s Theory of Relativity sets an upper limit on the speed that anything can travel with respect to anything else.  This is the well-known speed of light whose value is close to 300,000 km/sec.  Nothing can travel faster than this under any circumstances and this is one of the most fundamental truths of nature.  Even science fiction writers seem to respect this and try to overcome the limitation in devious ways such as travelling through hypothetical worm holes in space-time to bridge the travel time gap.  Space travel to distant stars and their planets is a virtual impossibility because of the enormous span of time, a few thousand years at the very least, involved in just reaching such a place even using highly futuristic technology.

Einstein’s theories have withstood every conceivable challenge repeatedly, both theoretical and observational, and the concept of the ultimate speed inherent in them has found experimental support in innumerable ways.  For example, it is a well-established fact that the speed of a fundamental particle such as the proton doesn’t reach the speed of light (though it comes tantalizingly close to it) even when imparted the fullest possible energy employing the world’s largest particle accelerator, the Large Hadron Collider (LHC) at CERN near Geneva.  All the gargantuan energy goes to increase the mass of the particle, not its speed beyond the limit.

Not to be discouraged by nature-imposed limitations, some physicists, including the highly respected India born George Sudarshan, proposed particles called tachyons with an ‘imaginary mass’ that would always travel faster than the speed of light.  This idea has remained only as a mathematical curiosity without any application or relevance in the real world.

Against this background came the stunning news from the CERN-associated OPERA experiment in the Gran Sasso Laboratories in Italy in September 2011 that neutrinos produced at CERN travelled faster than light through the earth’s crust (nothing is impervious to neutrinos) and reached their detector about sixty nanoseconds sooner than they ought to have!  To be fair, the OPERA team announced this with caution and emphasized that the findings that had emerged over a significant period of time needed to be double-checked and replicated elsewhere though their own findings were inside the confidence level for such measurements.  Yet the news was received with a wide spectrum of reactions, ranging from contemptuous dismissal to qualified acquiescence, with the majority reaction being studied skepticism so characteristic of the method of science.  While most people were resigned to waiting for further developments there were some who jumped to a variety of speculative conclusions and started publicizing them in various media.  Novel theories accommodating faster than light entities also started cropping up without sufficient regard to their implications for existing ones.
 
One of the observations strongly against the superluminal (faster than light) neutrinos was a major astrophysical observation associated with the great supernova of 1987 that was detected in the Large Megellanic Cloud, a satellite galaxy about 168,000 light years away in the southern skies.  Two to three hours before the visible light from this supernova explosion reached the Earth, a burst of neutrinos was observed at three separate neutrino observatories.  This is due to expected neutrino emission which occurs simultaneously with the event.  If these neutrinos had been travelling as fast as the Gran Sasso neutrinos they should have arrived about four years before the light did, not just a few hours!

An undercurrent of controlled chaos prevailed in the world of physics for some time before the ICARUS study of the same type of events from the same source, also at Gran Sasso, restored the status quo once for all in favour of Einstein’s theory as could only be expected.  As a large number of observers had so strongly suspected, the earlier measurements had suffered from instrumental calibration errors.  Coming from such an internationally reputed institution this was not quite acceptable and two of the prominent people involved in the first announcement had to resign from their positions.  More importantly, sanity had been restored and science had triumphed yet again.

Summation

Ever since its quest began for objective truth and unraveling the workings of nature, the path of scientific progress has never been smooth.  It has often been strewn with roadblocks, bottlenecks, misdirections, diversions, pitfalls and other impediments and suffered the consequences.  However, because of its unique self-healing nature, science has always recovered from its setbacks and come out ultimately triumphant as the episodes narrated here demonstrate.  The work of scientists may have suffered from a whole gamut of human shortcomings – subjective judgments, misjudgments, prejudices, authoritarian influences, dogma, superstitions, bias, dissonance, professional jealousies, conservatism, a certain degree of lemming mentality, plagiarism, deceit and even cheating – but in the long run and last analysis these have not done any lasting damage to science itself.  Paradoxically perhaps, it has in fact emerged stronger.


8 comments:

Jayant Murthy said...

Cold fusion is still actively promoted in India. There was a conference at NIAS about three years ago where they were looking for funding.Abs

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