Time Travel Research Center
© 2005 Cetin BAL - GSM:+90 05366063183 - Turkey / Denizli
This Week in Phys 203/204 -- January 13 1997 --
Study, study, study, ...
Let's begin with a few hints on
doing well in this course.
Albert Einstein, one of the most brilliant and famous physicists of the 20th century, was born in 1879 in Germany. While working at the patent office in Bern Germany in 1905, he published three classic physics papers. One describing special relativity, one explaining the photoelectric effect by proposing that light is quantized, and one on statistical physics. Later in the same year he extended the special theory of relativity to include the equivalence of mass and energy, E=mc^2. Einstein won the Nobel Prize in 1921 for his work on the photoelectric effect. He died in 1955 in the United States while working unsuccessfully on a grand unification theory.
For a detailed biography with references, see the History of Mathematics Archive. Every scientist has the benefit of the work of his or her predecessors and contemporaries. The same site describes the contributions of other mathematicians and physicists to the special theory of relativity and to the general theory of relativity
A spear 10 meters long is thrown at a relativistic speed through a pipe that is 10 meters long. Both these dimensions are measured when each is at rest. When the spear passes through the pipe, which of the following statements best describes what is observed? (and why?)
Sort of makes you want to say "Hmmmm.......", doesn't it?
Well, the warmup question is relatively straightforward, but there are several famous relativistic 'paradoxes' to really make you scratch your head! A discussion can be found here.
Star Trek and General Relativity
"But I canna change the laws of physics, Captain!"
One interesting way to study Einstein's general theory of relativity is to watch Star Trek, though you must watch carefully because fact, speculations, and error often occur in the same episode!
This discussion is largely based on a superb book, The Physics of Star Trek, by Lawrence M. Krauss published by HarperCollins Publishers in 1995. (ISBN 0-465-00559-4) Readable and highly recommended!
Let's begin with the propulsion system. Speed is given in terms of a warp
factor and the engines are refered to as the warp drive. What is meant by 'warp
But why the term 'warp'?
In warped or curved space, the shortest path between two points may differ from the shortest path in flat space. For example, in flat space the shortest path between A and B is along the diameter rather than around the circle. But, if space is warped into a funnel then the shortest path is around the circle.
There are several practical problems to warp speed travel.
Both of these can be solved using a creative new solution to the equations of general relativity by Miguel Alcubierre, a physicist at the University of Wales. He was able to show that it is possible to design a solution which allows travel between any two points in space in as short a time as you like while the ship itself travels at speeds much less than the speed of light so that the occupants are not significantly effected by time dilation and clocks stay synchronized. Alcubierre's solution is simple to imagine: space compresses in front of the ship and stretches behind the ship while doing neither beneath the ship. If the compression is big enough, then a far away galaxy will be brought close so the ship thinks it travels only a short distance. The ship 'surfs' on the warped space. (This picture, due to Alcubierre, conveys the idea; however, we cannot really draw the actual situation since spacetime is four dimensional.) Note that we never address what would happen to a planet that was located within the warped space; you probably wouldn't want to live there!
So, why don't we build a warp drive?
Faster than Light Travel
There once was a lady named Bright, Who traveled much faster than light. She departed one day, in a relative way, And returned on the previous night! -Anonymous
Wow, if time dilation is extended to speeds beyond the speed of light,
wouldn't that mean that time would have to run backwards?
Never the less, theoreticians have speculated about the existence of particles called tachyons which might travel faster than the speed of light. (See for example Bilaniuk and Sudarshan, Physics Today 22,43 (1969)) Such particles would have very unusual properties; for example, they would speed up as they lost energy. Needless to say, no such particles have ever been found and they currently exist only in the imagination of theoretical physicists and science fiction writers.
Physics Limerick Contest (Deadline Jan 15)
The American Physical Society is looking for original physics limericks. Please keep them clean...
Limericks selected will be printed in APS News and authors awarded a dunking bird, arguably the best physics toy ever invented. Author of the best limerick will win a flock. Submit entries to: "firstname.lastname@example.org", or mail to: Limerick Contest, APS News, The American Physical Society, College Park, MD 20740.
Mail suggestions and complaints regarding subject material to "email@example.com".
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The Time Machine Project © 2005 Cetin BAL - GSM:+90 05366063183 -Turkiye/Denizli