Word: light
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Dates: during 2000-2000
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...unknown has to do with inflation--the theory that the universe began as a bubble of empty space that initially expanded at a velocity much faster than that of light (see "Will We Discover Another Universe?", in this issue). Cosmologists take inflation seriously because it resolves problems that bedeviled older versions of the Big Bang, but inflation also has implications for the study of cosmic destiny. Among them is that the force that drove the inflationary spasm, sometimes tagged with the Greek letter lambda after its designation in Einstein's general-relativity equations, might not have subsided altogether back when...
Consider the billions of tons of carbon dioxide that are emitted every year in the course of our daily life. Driving a car, switching on a light, working in a factory, fertilizing a field all contribute to the atmosphere's growing burden of heat-trapping gases. Unless we start to control emissions of CO2 and similar compounds, global mean temperatures will probably rise somewhere between 2[degrees]F and 7[degrees]F by the end of the next century; even the low end of that spectrum could set the stage for a lot of meteorological mischief. Among other things...
...fraction of a second, to make a round trip to the sun in just over a quarter of an hour, to go to Neptune and back in a workday. Modern life is too busy to waste time getting from here to there, and flitting around at the speed of light--about 186,000 miles per second--would take a lot of the drudgery out of travel...
Forget it, though. You'll never go that fast. Albert Einstein said so. His special theory of relativity had at its heart an astonishing claim: the speed of light in a vacuum is always the same, for all observers. Shine a flashlight out into space and the light goes at 186,000 m.p.s. Jump into a spaceship and chase the beam at 185,000 m.p.s. and it recedes from you not at 1,000 m.p.s. but at 186,000 m.p.s. If you head in the opposite direction at 185,000 m.p.s., the light beam still moves away at...you guessed...
...even stranger consequences, including the fact that as an object goes faster, its mass increases (the reasons are dizzyingly complex, but it's been verified in particle accelerators). The faster you go, the harder it is to get yourself going faster still. As you near the speed of light, your weight heads for infinity, which makes it infinitely hard to go faster. So while we might reach 99% of light-speed, or even 99.99999%, the last little bit will forever lie just beyond our grasp...