Miraculous Year (1905)

Poincaré & Einstein
Ref: "EINSTEIN 1905", John S. Rigden, Harvard University Press

  In his 1902 book "La Science et l'Hypothèse", the
  mathematical physicist Henri Poincaré identified three
  fundamental yet unresolved problems [in physics]. 

  One problem concerned the mysterious way ultraviolet light
  ejects electrons from the surface of a metal; 

  the second problem was the zig-zagging perpetual motion of
  pollen particles suspended in a liquid; 

  the third problem was the failure of experiments to detect
  Earth's motion through the aether.

  In 1904, Einstein read Poincaré's book. He had also been
  thinking about these problems, independently of Poincaré.
  For Einstein, they were clearly part of God's thoughts. One
  year later, in 1905, he solved all three.


Adapted from "Five papers that shook the world"
by Matthew Chalmers 
January 2005

  Most physicists would be happy to make one discovery that is
  important enough to be taught to future generations of
  physics students. Only a very small number manage this in
  their lifetime, and even fewer make two appearances in the

  But Einstein was different. In little more than eight months
  in 1905 he completed five papers that would change the world
  for ever. Spanning three quite distinct topics - relativity,
  the photoelectric effect and Brownian motion - Einstein
  overturned our view of space and time, showed that it is
  insufficient to describe light purely as a wave, and laid
  the foundations for the discovery of atoms.

  Genius at work

  Perhaps even more remarkably, Einstein's 1905 papers were
  based neither on hard experimental evidence nor
  sophisticated mathematics. Instead, he presented elegant
  arguments and conclusions based on physical intuition. 

  "Einstein's work stands out not because it was difficult but
  because nobody at that time had been thinking the way he
  did," says Gerard 't Hooft of the University of Utrecht, who
  shared the 1999 Nobel Prize for Physics for his work in
  quantum theory.

  "Dirac, Fermi, Feynman and others also made multiple
  contributions to physics, but Einstein made the world
  realize, for the first time, that pure thought can change
  our understanding of nature."

  And just in case the enormity of Einstein's achievement is
  in any doubt, we have to remember that he did all of this in
  his "spare time".

  Statistical revelations

  In 1905 Einstein was married with a one-year-old son and
  working as a patent examiner in Bern in Switzerland. His
  passion was physics, but he had been unable to find an
  academic position after graduating from the ETH in Zurich in

  Nevertheless, he had managed to publish five papers in the
  leading German journal Annalen der Physik between 1900 and
  1904, and had also submitted an unsolicited thesis on
  molecular forces to the University of Zurich, which was

  Most of these early papers were concerned with the reality
  of atoms and molecules, something that was far from certain
  at the time. But on 17 March in 1905 - three days after his
  26th birthday - Einstein submitted a paper titled "A
  heuristic point of view concerning the production and
  transformation of light" to Annalen der Physik.

  Einstein suggested that, from a thermodynamic perspective,
  light can be described as if it consists of independent
  quanta of energy (Ann. Phys., Lpz 17 132-148). 

  This hypothesis, which had been tentatively proposed by Max
  Planck a few years earlier, directly challenged the deeply
  ingrained wave picture of light. However, Einstein was able
  to use the idea to explain certain puzzles about the way
  that light or other electromagnetic radiation ejected
  electrons from a metal via the photoelectric effect.

  Maxwell's electrodynamics could not, for example, explain
  why the energy of the ejected photoelectrons depended only
  on the frequency of the incident light and not on the
  intensity. However, this phenomenon was easy to understand
  if light of a certain frequency actually consisted of
  discrete packets or photons all with the same energy. 

  Einstein would go on to receive the 1921 Nobel Prize for
  Physics for this work, although the official citation stated
  that the prize was also awarded "for his services to
  theoretical physics".

  "The arguments Einstein used in the photoelectric and
  subsequent radiation theory are staggering in their boldness
  and beauty," says Frank Wilczek, a theorist at the
  Massachusetts Institute of Technology who shared the 2004
  Nobel Prize for Physics. 

  "He put forward revolutionary ideas that both inspired
  decisive experimental work and helped launch quantum
  theory." Although not fully appreciated at the time,
  Einstein's work on the quantum nature of light was the first
  step towards establishing the wave-particle duality of
  quantum particles.

  On 30 April, one month before his paper on the photoelectric
  effect appeared in print, Einstein completed his second 1905
  paper, in which he showed how to calculate Avogadro's number
  and the size of molecules by studying their motion in a

  This article was accepted as a doctoral thesis by the
  University of Zurich in July, and published in a slightly
  altered form in Annalen der Physik in January 1906. 

  Despite often being obscured by the fame of his papers on
  special relativity and the photoelectric effect, Einstein's
  thesis on molecular dimensions became one of his most quoted

  Indeed, it was his preoccupation with statistical mechanics
  that formed the basis of several of his breakthroughs,
  including the idea that light was quantized.

  After finishing a doctoral thesis, most physicists would be
  either celebrating or sleeping. But just 11 days later
  Einstein sent another paper to Annalen der Physik, this time
  on the subject of Brownian motion. 

  In this paper, "On the movement of small particles suspended
  in stationary liquids required by the molecular-kinetic
  theory of heat", Einstein combined kinetic theory and
  classical hydrodynamics to derive an equation that showed
  that the displacement of Brownian particles varies as the
  square root of time (Ann. Phys., Lpz 17 549-560).

  This was confirmed experimentally by Jean Perrin three years
  later, proving once and for all that atoms do exist. In
  fact, Einstein extended his theory of Brownian motion in an
  additional paper that he sent to the journal on 19 December,
  although this was not published until February 1906.

  A special discovery

  Shortly after finishing his paper on Brownian motion
  Einstein had an idea about synchronizing clocks that were
  spatially separated.

Adapted from "The Mechanical Universe"
Episode 43: Velocity and Time 

  In the 1800s Michael Faraday discovered, or I should say
  formalized, electromagnetic induction. Given a coil of wire
  and a bar magnet...

	     F = qE + qv x B

  Holding the coil stationary and moving the bar magnet
  produced an electric current in the coil. Similarly holding
  the bar magnet stationary and moving the coil also produced
  an electric current in the coil. 

  But in the language of electrodynamics of the day the two
  cases were distinct independent phenomena that had
  completely different explanations.

  When Albert Einstein saw that, he said "Look guys, you've
  just got to be kidding--Any yo-yo can see that these are the
  same thing". 

  So it was this little experiment that was really the start
  of relativity, not the Michelson-Morley Experiment--not some
  exotic experiment to detect the motion of the earth through
  the aether.

  With this simple little phenomenon, that of course everybody
  knew about, disturbed nobody else, but Albert Einstein.   

  This led him to write a paper that landed on the desks of
  Annalen der Physik on 30 June, and would go on to completely
  overhaul our understanding of space and time. Some 30 pages
  long and containing no references, his fourth 1905 paper was
  titled "On the electrodynamics of moving bodies" (Ann.
  Phys., Lpz 17 891-921).

  In the 200 or so years before 1905, physics had been built
  on Newton's laws of motion, which were known to hold equally
  well in stationary reference frames and in frames moving at
  a constant velocity in a straight line. Provided the correct
  "Galilean" rules were applied, one could therefore transform
  the laws of physics so that they did not depend on the frame
  of reference. 

  However, the theory of electrodynamics developed by Maxwell
  in the late 19th century posed a fundamental problem to this
  "principle of relativity" because it suggested that
  electromagnetic waves always travel at the same speed.

  Either electrodynamics was wrong or there had to be some
  kind of stationary "ether" through which the waves could


  I just want to read to you the first two paragraphs of
  Einsteins 4th paper...
By A. Einstein
June 30, 1905

  It is known that Maxwell's electrodynamics--as usually
  understood at the present time--when applied to moving
  bodies, leads to asymmetries which do not appear to be
  inherent in the phenomena. 

  Take, for example, the reciprocal electrodynamic action of a
  magnet and a conductor. The observable phenomenon here
  depends only on the relative motion of the conductor and the
  magnet, whereas the customary view draws a sharp distinction
  between the two cases in which either the one or the other
  of these bodies is in motion. For if the magnet is in motion
  and the conductor at rest, there arises in the neighbourhood
  of the magnet an electric field with a certain definite
  energy, producing a current at the places where parts of the
  conductor are situated. 

  But if the magnet is stationary and the conductor in motion,
  no electric field arises in the neighbourhood of the magnet.
  In the conductor, however, we find an electromotive force,
  to which in itself there is no corresponding energy, but
  which gives rise--assuming equality of relative motion in
  the two cases discussed--to electric currents of the same
  path and intensity as those produced by the electric forces
  in the former case.

  Examples of this sort, together with the unsuccessful
  attempts to discover any motion of the earth relatively to
  the "light medium," suggest that the phenomena of
  electrodynamics as well as of mechanics possess no
  properties corresponding to the idea of absolute rest. 

  They suggest rather that, as has already been shown to  (1)
  the first order of small quantities, the same laws of
  electrodynamics and optics will be valid for all frames of
  reference for which the equations of mechanics hold good. We
  will raise this conjecture (the purport of which will
  hereafter be called the ``Principle of Relativity'') to the
  status of a postulate, 

  and also introduce another postulate, which is only     (2)
  apparently irreconcilable with the former, namely, that 
  light is always propagated in empty space with a definite
  velocity c which is independent of the state of motion of
  the emitting body. 

  These two postulates suffice for the attainment of a simple
  and consistent theory of the electrodynamics of moving
  bodies based on Maxwell's theory for stationary bodies. 

  The introduction of a "luminiferous ether" will prove to be
  superfluous inasmuch as the view here to be developed will
  not require an "absolutely stationary space" provided with
  special properties, nor assign a velocity-vector to a point
  of the empty space in which electromagnetic processes take

  And, of course the paper goes on to develop the ideas and
  make his case...


  True to style, Einstein swept away the concept of the ether
  (which, in any case, had not been detected experimentally)
  in one audacious step. He postulated that no matter how fast
  you are moving, light will always appear to travel at the
  same velocity: the speed of light is a fundamental constant
  of nature that cannot be exceeded.

  Combined with the requirement that the laws of physics are
  the identical in all "inertial" (i.e. non-accelerating)
  frames, Einstein built a completely new theory of motion
  that revealed Newtonian mechanics to be an approximation
  that only holds at low, everyday speeds. 

  The theory later became known as the special theory of
  relativity - special because it applies only to
  non-accelerating frames - and led to the realization that
  space and time are intimately linked to one another.

  In order that the two postulates of special relativity are
  respected, strange things have to happen to space and time,
  which, unbeknown to Einstein, had been predicted by Lorentz
  and others the previous year. 

  For instance, the length of an object becomes shorter when
  it travels at a constant velocity, and a moving clock runs
  slower than a stationary clock.

  Effects like these have been verified in countless
  experiments over the last 100 years, but in 1905 the most
  famous prediction of Einstein's theory was still to come.

  After a short family holiday in Serbia, Einstein submitted
  his fifth and final paper of 1905 on 27 September. Just
  three pages long and titled "Does the inertia of a body
  depend on its energy content?", this paper presented an
  "afterthought" on the consequences of special relativity,
  which culminated in a simple equation that is now known as E
  = mc^2 (Ann. Phys., Lpz 18 639-641). 

  This equation, which was to become the most famous in all of
  science, was the icing on the cake.

  "The special theory of relativity, culminating in the
  prediction that mass and energy can be converted into one
  another, is one of the greatest achievements in physics - or
  anything else for that matter," says Wilczek. 

  "Einstein's work on Brownian motion would have merited a
  sound Nobel prize, the photoelectric effect a strong Nobel
  prize, but special relativity and E = mc^2 were worth a
  super-strong Nobel prize."

  However, while not doubting the scale of Einstein's
  achievements, many physicists also think that his 1905
  discoveries would have eventually been made by others. 

  "If Einstein had not lived, people would have stumbled on
  for a number of years, maybe a decade or so, before getting
  a clear conception of special relativity," says Ed Witten of
  the Institute for Advanced Study in Princeton.

  't Hooft agrees. "The more natural course of events would
  have been that Einstein's 1905 discoveries were made by
  different people, not by one and the same person," he says.
  However, most think that it would have taken much longer -
  perhaps a few decades - for Einstein's general theory of
  relativity to emerge. 

  Indeed, Wilczek points out that one consequence of general
  relativity being so far ahead of its time was that the
  subject languished for many years afterwards.

  The aftermath

  By the end of 1905 Einstein was starting to make a name for
  himself in the physics community, with Planck and Philipp
  Lenard - who won the Nobel prize that year - among his most
  famous supporters. Indeed, Planck was a member of the
  editorial board of Annalen der Physik at the time.

  Einstein was finally given the title of Herr Doktor from the
  University of Zurich in January 1906, but he remained at the
  patent office for a further two and a half years before
  taking up his first academic position at Zurich. 

  By this time his statistical interpretation of Brownian
  motion and his bold postulates of special relativity were
  becoming part of the fabric of physics, although it would
  take several more years for his paper on light quanta to
  gain wide acceptance.

  1905 was undoubtedly a great year for physics, and for
  Einstein. "You have to go back to quasi-mythical figures
  like Galileo or especially Newton to find good analogues,"
  says Wilczek. 

  "The closest in modern times might be Dirac, who, if
  magnetic monopoles had been discovered, would have given
  Einstein some real competition!" But we should not forget
  that 1905 was just the beginning of Einstein's legacy. His
  crowning achievement - the general theory of relativity -
  was still to come.