Does gravity change with the seasons?
来源：未知 作者：贺疱 时间：2019-03-14 10:06:03
By Marcus Chown EVERYONE has heard of Newton’s apple. He watched it drop to the ground in the autumn of 1666, prompting him to ask a series of questions. “Why should that apple always descend perpendicularly to the ground?” Newton wondered. “Why should it not go sideways or upwards, but constantly to the Earth’s centre?” One question Newton didn’t ask is whether apples or oranges fall differently. Or whether an apple would fall differently in the spring. They might seem peculiar concerns, but Alan Kostelecký, a physicist based at Indiana University in Bloomington, thinks they are important. He and his graduate student Jay Tasson have found that such flagrant violations of our best theory of gravity could easily have evaded detection for centuries. What’s more, in a paper published in Physical Review Letters (vol 102, p 10402), the pair have shown that investigating such unlikely-seeming possibilities could help us work out what makes the universe tick. “We have made a surprising and delightful discovery,” Kostelecký says. “We might just catch a glimpse of the ultimate theory that underpins our universe.” We might just catch a glimpse of the ultimate theory that underpins our universe This is the culmination of 20 years’ work for Kostelecký. In 1989, he began to think about how to find a glitch in our best understanding of how the universe works, as provided by two great theories. The first is general relativity, Einstein’s theory of how gravity works. The other is the standard model of particle physics, a quantum description of the matter around us and of all forces other than gravity. At the moment,