Word: per
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Dates: during 1990-1999
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...leading causes of death, rate per...
...Number of servings of Coca-Cola sold per...
Einstein's conclusions became known as the special theory of relativity. No matter how fast one is moving toward or away from a source of light, the speed of that light beam will appear the same, a constant 186,000 miles per second. But space and time will appear relative. As a train accelerates to near the speed of light, time on the train will slow down from the perspective of a stationary observer, and the train will get shorter and heavier. O.K., it's not obvious, but that's why we're no Einstein...
...With each advance in subsistence technology, survival grew more secure, hastening population growth; and as population grew, the advances came more quickly. By the Mesolithic Age, around 10,000 B.C., with the neuronal population up to around 4 million, the rate of advance had moved from one major innovation per 20,000 years to a sizzling one per 200--including such gifts to posterity as combs and beer...
...calories an hour - an initially meager loss that could nevertheless manifest itself as a more significant 11 pounds a year. Of course, that's only if the chewing is constant over the course of the day, which is defined distressingly as "every waking hour," or about 12 hours per day. Study participants were timed with a metronome in order to establish a uniform chewing rate. "Every little bit helps, I guess," says TIME senior science reporter Alice Park. "But probably the most important weight-loss aspect of gum chewing is that you have something in your mouth all the time...