"Reality is merely an illusion, albeit a very persistent one." (A thousand points to whoever guesses the person who said this.)
I am giving a talk on special relativity at the Harvard Student Lecture Series this Friday. Let me come up with a quick rundown of the special theory.
1. The laws of physics hold for all inertial frames.
2. The speed of light (c = 3 x 10^8 m/s) is the same for all inertial frames.
Note: An inertial frame is one that is not accelerating (moving in one, straight direction and at constant speed).
The revolutionary claim is the latter. If you are on the ground and your friend is on a moving train and shining light in the same direction, both of you will observe the light traveling at the same speed. As a consequence of these two postulates, bizarre effects result: loss of simultaneity, time dilation, length contraction, E = mc^2 and more.
One interesting application is time travel. You can travel into the future by going on a rocket moving close to the speed of light and coming back to Earth. If you travel sufficiently fast, a one-week ride can lead you a hundred years into the future or more. You can achieve this if you travel 99.9999982% of the speed of light. If the rocket is 100,000 kg, you would need 4.7 x 10^25 Joules of energy. With this amount of energy, you can sustain 10 billion people for a million years.
If I have enough time, I will write up a qualitative derivation of the results. If you are interested in this stuff, check out the lecture I will give this Friday at 8pm in the Adams Pool Theater. Alternatively, look up "special relativity" in Wikipedia.
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