Word: light
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Dates: during 2000-2000
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...short distances. The final theory will let us answer the deepest questions of cosmology: Was there a beginning to the present expansion of the universe? What determined the conditions at the beginning? And is what we call our universe, the expanding cloud of matter and radiation extending billions of light-years in all directions, really all there is, or is it only one part of a much larger universe in which the expansion we see is just a local episode...
...early '80s, U.S. and Russian physicists (including Guth) realized that powerful energy fields dominating the cosmos when it was a fraction of a second old could have turbocharged the expansion, forcing the universe to fly apart--or "inflate"--at a rate many times faster than the speed of light. (The light barrier can't be broken by things moving through space, but space itself is exempt from this universal speed limit...
...still talking about one universe--though one vastly larger than the tiny patch, a mere 30 billion light-years across, that we can see. But then scientists, including the Russian emigre Andrei Linde, realized that this inflation was more flexible than anyone had thought. Energy fields of early-universe intensity could arise purely by chance in subatomic-size regions of even a normal cosmos...
...human--doing this trick is infinitesimal. But thanks to Albert Einstein we know that time travel of a different sort does happen in the macroscopic world. As he showed back in 1905 with his special theory of relativity, time slows down for objects moving close to the speed of light, at least from the viewpoint of a stationary observer. You want to visit the earth 1,000 years from now? Just travel to a star 500 light-years away and return, going both ways at 99.995% the speed of light. When you return, the earth will be 1,000 years...
...Earth. Clocks on Mercury tick more slowly than those on Earth because Mercury circles the sun at a faster speed (and also because Mercury is deeper in the sun's gravitational field; gravity affects clocks much as velocity does). Astronauts traveling away from Earth to a distance of 0.1 light years and returning at 1% the speed of light would arrive back 8.8 hours younger than if they hadn't gone...