World Year of Physics 2005: Difference between revisions

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The year 2005 has been named the '''World Year of Physics''' in recognition of the 100th anniversary of [[Albert Einstein]]'s "[[Annus Mirabilis Papers|Miracle Year]]," in which he published four landmark papers, and the subsequent advances in the field of [[physics]].

[[Image:WYP2005 logo.png|right|200px]]

[[Image:E equals m plus c square at Taipei101.jpg|thumb|right|The mass–energy equivalence formula was displayed on [[Taipei 101]] during the eventofthe '''World Year of Physics 2005'''.]]

[[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 [[IUPAP|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]] [http://www.theithacajournal.com/news/stories/20050514/localnews/2136011.html].

===Annus Mirabilis===

{{main|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 (physics)|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 Prize]]s, 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 "[[photon|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 [[radiant energy|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 [[Maxwell equations|equations]] for [[electromagnetism|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 quantun 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 (vector)|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 [[atom]]s. 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]].

[[Image:light cone.png|thumb|right|The logo is meant to represent the [[light cone]] diagram used in [[special relativity]] to show locations that are in [[causality (physics)|causal contact]] and those that are not.]]

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 [[wave]]s, which require a medium (such as [[water]] or [[air]]) to propagate.

Einstein's explanation arises from two postulates: The first is [[Galileo Galilei|Galileo]]'s idea that the [[physical law]]s 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 [[paradox]]es 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 [[Isaac Newton|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 principle|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.

[[File:EinsteinE.JPG|thumb|right|One of 16 Einstein ''E'''s on [[Berlin]]'s [[Unter den Linden]]]]

[[File:Einstein sculpture at Questacon in April 2008.jpg|thumb|right|Statue at [[Questacon]], [[Canberra, Australian Capital Territory]], 2005]]

* In the [[United States]], the [[University of Maryland, College Park|University of Maryland]] sponsored several activities in cooperation with the [[Smithsonian Institution]] and [[NASA]]'s [[Goddard Space Flight Center]], including various lecture series and resident programs. [http://www.physics.umd.edu/events/spevents/Physics2005/index.html University of Maryland Celebration].

* In [[Berlin]], sixteen large, red ''E''<nowiki>'s</nowiki> have been erected along a section of the famous [[Unter den Linden]] boulevard. Called the "Einstein Mile", the ''E''<nowiki>'s</nowiki>, which has been in place from April to September 2005 displaying information on the theories and life of Albert Einstein.

* The [[Perimeter Institute for Theoretical Physics]], [[Waterloo, Ontario]], [[Canada]], hosted '''Einstein Fest''' from September 30 to October 23 [http://www.perimeterinstitute.ca/activities/community/einsteinfest/].

* [[Beyond Einstein World Wide Webcast]], organized by [[CERN]], was held on December 1, 2005.

* [http://www.wyp2005.org/ World Year of Physics 2005]

* [http://www.einsteinyear.org/ Einstein Year 2005]

* [http://www.physics2005.org/events/ Listing of US events planned to commemorate World Year of Physics]

* [http://einstein.phys.uwm.edu/ Einstein@Home]

* http://www.ulakaththamizh.org/JOTSArticle.aspx?id=561

[[Category:United Nations observances|Physics 2005, World Year of]]