The year
2005 has been named the 'World Year of Physics' in recognition of the 100th anniversary of
Albert Einstein's "
Miracle Year," in which he published four landmark papers, and the subsequent advances in the field of
physics.
History
Physics has been the basis for understanding the physical world and nature as a whole. The applications of physics are the basis for much of today's technology. In order to both raise the worldwide awareness of physics and celebrate the major advances made in the field, the
International Union of Pure and Applied Physics resolved that 2005 should be commemorated as the World Year of Physics. This has subsequently been endorsed by both the
United Nations and the
United States Congress [1].
Annus Mirabilis
:''Main article:
Annus Mirabilis Papers''
The year 2005 is significant primarily because of the changes that have occurred in the philosophy of physics over the past 100 years. These changes began in
1905 with the publication of four papers by Einstein that: explained
Brownian motion, introduced the
special theory of relativity, and described how the
photoelectric effect could be explained by the
quantization of light, which helped launch
quantum mechanics, and developed ''E = mc''
2. These papers are commonly called his
Annus Mirabilis Papers because they later defined 1905 as a ''miracle year'' for physics.
Most physicists agree that the first three of those papers deserved
Nobel Prizes, but only the paper on the photoelectric effect would win one. What makes these papers remarkable is that, in each case, Einstein boldly took an idea from theoretical physics to its logical consequences and managed to explain experimental results that had baffled scientists for decades.
Photoelectric effect
The first paper proposed the idea of "
energy quanta" and showed how it could be used to explain such phenomena as the
photoelectric effect. The idea of energy quanta was motivated by
Max Planck's earlier derivation of the law of
black-body radiation by assuming that
luminous energy could only be absorbed or emitted in discrete amounts, called ''quanta''. Einstein showed that, by assuming that
light actually ''consisted'' of discrete packets, he could explain the mysterious photoelectric effect.
The idea of light quanta contradicted the wave theory of light that followed naturally from
James Clerk Maxwell's
equations for
electromagnetic behavior and, more generally, the assumption of
infinite divisibility of energy in physical systems. Even after experiments showed that Einstein's equations for the photoelectric effect were accurate, his explanation was not universally accepted. However, by
1921, when he was awarded the Nobel Prize and his work on photoelectricity was mentioned by name in the award citation, most physicists thought that light quanta were possible. A complete picture of the photoelectric effect was only obtained after the maturity of quantum mechanics.
Brownian motion
His second article that year delineated a
stochastic model of
Brownian motion. Brownian motion generates expressions for the
root mean square displacement of particles. Using the then-controversial kinetic theory of fluids, it established that the phenomenon, which still lacked a satisfactory explanation decades after it was first observed, provided empirical evidence for the reality of
atoms. It also lent credence to
statistical mechanics, which was also controversial at the time.
Before this paper, atoms were recognized as a useful concept, but physicists and chemists hotly debated whether atoms were real entities. Einstein's statistical discussion of atomic behavior gave experimentalists a way to count atoms by looking through an ordinary microscope.
Wilhelm Ostwald, one of the leaders of the anti-atom school, later told
Arnold Sommerfeld that he had been converted to a belief in atoms by Einstein's complete explanation of Brownian motion.
Special relativity
Einstein's third paper that year was a highly self-contained work, hardly making reference to other works which may have led to its development. This paper introduced a theory of time, distance, mass and energy which was consistent with
electromagnetism, but omitted the force of
gravity.
Special relativity avoids the problem in science that was present after the
Michelson-Morley experiment failed to measure a speed difference between perpendicular light beams, by postulating that the
speed of light is ''not'' relative to some medium and is the same for all observers irrespective of their relative velocities. This is unlike all other known
waves, which require a medium (such as
water or
air) to propagate.
Einstein's explanation arises from two postulates: The first is
Galileo's idea that the
laws of nature are the same for all observers that move with constant velocity relative to each other. The second was that the
speed of light is the same for every observer.
Special relativity has several striking consequences, because the concepts of absolute time and space are incompatible with an absolute speed of light. The theory abounds with
paradoxes and appeared to make little sense, landing Einstein substantial ridicule, but he eventually managed to work out the apparent contradictions and solve the problems.
Consequences
Einstein's special theory of relativity heralded a new kind of physics, one that digressed from the classical mechanics that had been derived from
Newton's
calculus. Although his 1905 paper on the photoelectric effect helped spur the development of quantum mechanics, Einstein himself considered quantum theory, which introduced the concept of
uncertainty into the laws of the physical world, incomplete. His deterministic view is illustrated in the famous quote "I am convinced that He (God) does not play
dice." Einstein viewed quantum mechanics as a means simply to the end of a
unified field theory, which would unite the disparate theories of
quantum field theory,
general relativity, and
electromagnetism. However, he never denied that quantum mechanics was very successful in explaining and predicting physical phenomena.
The quest for a unified field theory is continuing with work into
quantum mechanics,
string theory, and
superconductivity. The year recognizes the fundamental shift in
natural philosophy from a theory of the absolute to that of the uncertainty and relativity spurred by Einstein's 1905 work.
Selected celebrations
★ In the
United States, the
University of Maryland sponsored several activities in cooperation with the
Smithsonian Institute and
NASA's
Goddard Space Flight Center, including various lecture series and resident programs.
University of Maryland Celebration.
★ In
Berlin, sixteen large, red ''E''
's have been erected along a section of the famous
Unter den Linden boulevard. Called the "Einstein Mile", the ''E''
's, which has been in place from April to September 2005 displaying information on the theories and life of Albert Einstein.
★ In
Egypt, the
Library of Alexandria organized the
Einstein Symposium.
★
San Marino issued a
€2 commemorative coin.
★ The
Kirwitzer Day 2005 in
Kadaň, the
Czech Republic, was dedicated to Einstein's theories.
★ The
Perimeter Institute for Theoretical Physics,
Waterloo, Ontario,
Canada, hosted 'Einstein Fest' from
September 30 to
October 23 [2].
★
Beyond Einstein World Wide Webcast, organized by
CERN, was held on
December 1,
2005.
External links
★
World Year of Physics 2005
★
Einstein Year 2005
★
Listing of US events planned to commemorate World Year of Physics
★
Einstein@Home
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