The programme examines one of the most direct consequences of special relativity, that of time dilation. It includes a thought experiment with a light clock, an experiment involving a sub-atomic pa...rticle (muon) round a ring of magnets linked to the European particle accelerator and a hypothetical space journey at near the speed of light.
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|S354, Understanding space and time
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|Julian Schwinger; Russell Stannard
|BBC Open University
|Atomic particles; Bullet; Light clock; Light velocity; Muon; Satellite; Special relativity; Time dilation
|Julian Schwinger, Nobel Laureate, University of California, introduces the programme. Schwinger, with the aid of animations, outline a thought experiment in which he demonstrates that a perfect clock will beat time more slowly when in motion that when at rest. He explains how to calculate time dilation of a clock moving at a constant velocity relative to an observer. Leading up to a physical verification of the thought experiment above, Russell Stannard explains how half life of radioactive substances is determined. He uses a geiger counter and a graph as visual aids. Using animations and looking at a spark chamber at CERN, Switzerland, Russ Stannard outlines the experiment which, by measuring the half life of fast moving muons created by the interaction of cosmic rays with the upper atmosphere confirmed the concept of time dilation. Russ Stannard, still at CERN, explains how physicists there have verified the above results by accelerating muons to nearly the speed of light and then measuring their half life at this velocity. Animations help to illustrate his point. Stannard explains the experimental procedure each step of the way. Julian Schwinger, with the aid of NASA film showing a spacecraft taking off and landing, plans an imaginery interstellar space voyage to the star Vega which ought to be possible for biological organisms due to the time dilation effect. Over shots of newspaper headlines announcing a manned inter-stellar journey and shots of the simulated journey, commentary explains what effect time dilation would have on an astronaut as compared with his brother left on earth. Russell Stannard at CERN explains how the essential conclusions of the above imaginary space voyage can be verified using particle accelerators in the laboratory.
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