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Enter the Relativity Challenge
An anonymous reader writes "Any slashdotters wanna pick up a lazy 25,000 Euros? All you have to do is explain Einstein's theory of relativity in a five minute multimedia presentation. The Pirelli Group have laid down this 'Relativity Challenge' to anyone as part of the International Year of Physics. Entries close on 31 March 2005."
OK, let's see if I can help.
Maxwell's equations of electro-magnetic theory show the speed of light in a medium to be determined by 2 properties of that medium. For vacuum, those two properties are fundimental constants - thus the speed of light is fixed.
Now, if I take a squirt gun with a fixed exit velocity and squirt it at you, the water will be moving slower if I am backing away from you and quicker if I am running at you. That fits with our day-to-day experience.
But for light in a vacuum that does not happen - if I now use a light-gun, you will measure the speed of all three beams of light (me backing away, me standing still relative to you, me running at you) as the same.
And curiously, so will I - I will measure the speed of light leaving my light-gun as the same, no matter what.
Now, the ONLY way you can get both my measurements and yours to agree is if things like length, mass, and time change based upon my motion relative to you - hence the need for the Lorentz transformation.
Then, you get into the "twins paradox" - Take 2 twins. Kick one of them up to nearly the speed of light. Wait till the other one has aged 10 years. Bring the high-speed twin back.
From the stationary twin's perspective, the high speed twin slowed down. From the high speed twin's perspective, the stationary twin (who wasn't stationary from the high speed twin's perspective) slowed down. Yet both cannot be true.
So Einstein reasoned out that the ONLY difference between the twins was who felt the acceleration - that twin would slow down.
But if I lock you in a box, you cannot tell if you are setting on a planet or in free space being accelerated - so gravity must be like acceleration.
That's GR in a nutshel.
www.eFax.com are spammers
I'll take that challenge:
Light goes the same speed
For everyone everywhere
Funkiness ensues
When you are courting a nice girl an hour seems like a second. When you sit on a red-hot cinder a second seems like an hour. That's relativity. -Einstein
I don't think it can be said much better.