The flow of time, said Einstein, is relative. The faster you move, the slower your clock ticks compared to that of a stationary observer.
His
first breakthrough paper, published in 1905, notes that if a person
took a clock around the equator, that clock would move slower than a
similar clock moving round the Earth’s poles.
Providing an example that time is relative, not absolute, Einstein made the following observation in his 1905 paper:
By “That train arrives here at 7 o’clock,” I mean something like
this: “The pointing of the small hand of my watch to 7 and the arrival
of the train are simultaneous events.”
So how did Einstein
answer his childhood question: What would happen if he could ride a
beam of light? "Nothing - for he never could" (as an animation in this
video clip depicts). At the speed of light, according to Einstein’s
theory of special relativity, length shrinks to zero and time stands
still.
His 1905 paper on the subject, which had no footnotes,
stood alone. Einstein’s thinking was totally new, and he experienced "a
miracle year."
Almost as an afterthought, he applied his special relativity theory to mass and energy. More formally, he found that E=mc2.
Succinctly put, that means the energy, contained in any object, is
equal to its mass times the speed of light squared. That translates
into enormous numbers.
If none of the energy locked inside mass
escapes, however, that energy cannot be observed. As Einstein
reportedly said: "It’s like a fabulously rich man who never spends
anything. No one can tell how rich he is."
Credits
From Einstein Revealed, starring Andrew Sachs as Einstein, part five.
