Twenty-six year old German-born Albert Einstein, while holding down a full time job as a patent clerk (third class) in Switzerland in 1905, set the physics world on its ear with the publication of no fewer than five breakthrough papers in physics. While he won the Nobel prize in 1921 for his explanation of the photoelectric effect, perhaps his most famous (and most controversial) work dealt with special relativity. The "special" in special relativity deals exclusively with those cases when objects move with uniform speed in straight lines.
He explained the nature of accelerated objects and gravity in his general theory published in 1915. The ten-year lapse in publication was probably due in part to: 1) the distraction caused by the acclaim he received from his early work; 2) the fact that he moved back to Germany; 3) the outbreak of WWI; and 4) some serious domestic discord which led to estrangement and divorce from Mrs. Einstein.

The interested student will be well-rewarded for reading one of the several biographies available describing the life and thoughts of this scientist-turned-icon.

The consequences of the special theory alter our concept of space and time by predicting that

• moving clocks run slow
• moving lengths are contracted in a direction parallel to their motion
• two events that occur simultaneously to one observer do not occur simultaneously to a second with respect to whom the events are moving.
• relative velocities of moving objects do not add as expected
• moving objects experience an increase in mass
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  Common sense is the collection of prejudices acquired by age 18. A.Einstein

The special theory of relativity is predicated on the validity of two postulates. If experimental evidence finds a discrepancy in either of these principles, then the conclusions derived from these principles will have to be changed. Despite all the challenges that have been mounted over the last 100 years, the two postulates stand as published in 1905.

POSTULATE ONE - THE PRINCIPLE OF RELATIVITY

• One cannot tell by experiment whether one is at rest or moving uniformly.
• The laws of nature are the same in a laboratory at rest as they are in any moving laboratory.
• If two experiments are done under identical conditions except that one is done in a laboratory at rest and the other in a uniformly moving laboratory, the two experiments will lead to exactly the same conclusions.
• Anybody moving uniformly with respect to somebody at rest is entitled to consider him/herself at rest and the other person to be moving uniformly.
• A system moving uniformly with respect to an inertial system is also an inertial system.

POSTULATE TWO - THE PRINCIPLE OF THE CONSTANCY OF THE VELOCITY OF LIGHT

• · The speed of light has the same value c for any inertial observer.
• · Anything that moves past an inertial observer with a speed c moves past any other inertial observer with the same speed

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  What follows is a series of lecture notes prepared by Michael Fowler of the University of Virginia.
  On waves and the Michelson-Morley experiment
• http://galileo.phys.virginia.edu/classes/109N/lectures/michelson.html
  
  Here is a bridge between Galileo and Einstein
• http://galileo.phys.virginia.edu/classes/109N/lectures/spec_rel.html
  
  Time dilation is now revealed
• http://galileo.phys.virginia.edu/classes/109N/lectures/srelwhat.html
  
• On the relativity of simultanaeity
• http://galileo.phys.virginia.edu/classes/109N/lectures/synchronizing.html
  
• More on time dilation
• http://galileo.phys.virginia.edu/classes/109N/lectures/time_dil.html
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• The twin paradox
• http://galileo.phys.virginia.edu/classes/109N/lectures/sreltwins.html
  
• Mass increases
• http://galileo.phys.virginia.edu/classes/109N/lectures/momentum.html

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• See also
  http://www.umsl.edu/~fraundor/twoclock.html
  http://physics.syr.edu/courses/modules/LIGHTCONE/java/TwinParadox.html

http://www.pay.ntnu.edu.tw/~hwang/relativity/relativity.html

http://monet.physik.unibas.ch/~schatzer/space-time.html

http://www.phys.vt.edu/~astrophy/faq/sr.html

http://www.physics.brown.edu/physics/userpages/students/Matthew_Hirsch/Time/relbomb.html
to and in http://math.ucr.edu/home/baez/physics/Relativity/SR/TwinParadox/twin_paradox.html

TIME DILATION: an experiment with mu-mesons this classic film documents an experiment done in 1963 the results of which can only be explained when one accepts the consequence that moving clocks run slow. This phenomenon is known as time dilation. The timekeeping device is the mu-mesona, a subatomic particle with origins away from the Earth moving at relativistic speed. What follows here is an explanation of the experiment described in that film. Many mu-messons rain down every hour on the Earth from sources outside of the Earth. The mu-messons are radioactive and they decay into other particles. The mu-messons are detected by a scintillation chamber which emits a flash of light whenever a particle enters the chamber or decays in it. Experimenters used photomultiplier tubes to detect light flashes and an oscilloscope measure the time between an entering flash and a decay flash. Using a 4.5 feet thick pile of iron bars, experimenters are able to stop the mu-mesons in the detection chamber. Mu-mesons travel at .99c which translates to 1000 feet per microsecond. Mt Washington where this experiment takes place, is 6300 feet above sea level. The crux of the experiment is: how many mu-mesons will survive a trip from an altitude of 6300 feet to sea level. Of a sample of 568 mu-mesons arriviing at the top of Mt Washington only 27 live longer than 6.3 µs. That means, if they repeat the experiment at sea level 27 or about 27 mu-mesons should reach a laboratory at sea level. When this experiment was repeated at sea level, 412 mu-mesonss made it to the chamber. This was many times more than 27 that they expected. The only conclusion that they could draw was that mu0mesons measured time differently because they were moving. What does this look like to an observer sitting on the mu-meson? This Observer expects a short lifetime of this particle.He sees Mt. Washington, known to be 6300 feet high, pass by at only 700 feet high, still high enough for the particle to travel a short distance in the short amount of time that it has

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