PHYSICS
A satellite screw-up reaffirms Einstein’s theory of gravity
Incorrect orbits let scientists test how clocks change speed in a gravitational field一颗卫星的故障再次证实了爱因斯坦的引力理论
不正确的轨道可以让科学家测试钟在引力场中如何改变速度
BY EMILY CONOVER 6:00AM, DECEMBER 10, 2018
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SATELLITE SNAFU Two satellites of the European Galileo network (one illustrated) were launched in incorrect orbits, a mistake that allowed scientists to test Einstein’s theory of gravity.欧洲伽利略网络(Galileo network)的两颗卫星(如图所示)发射的轨道不正确，这一错误让科学家得以检验爱因斯坦的引力理论。
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An orbital oopsie has led to new proof of Albert Einstein’s physics prowess.一颗轨道望远镜为爱因斯坦的物理能力提供了新的证据。
In 2014, two satellites intended for Europe’s Galileo network, the equivalent of the United States’ GPS network, were placed into orbit incorrectly, causing them to travel around Earth in ellipses rather than circles. 2014年，两颗原计划用于欧洲伽利略网络(Galileo network)的卫星(相当于美国的GPS网络)被错误地放置在轨道上，导致它们以椭圆形而不是圆形绕地球运行。That wasn’t ideal for the satellites’ originally intended navigational use, but scientists realized the wayward satellites were perfect for another purpose: testing Einstein’s theory of gravity, the general theory of relativity.这就是广义相对论
According to general relativity, gravity affects not just space, but also time. The deeper within a gravitational field you are, the slower time passes引力场越深，时间过得越慢 (SN: 10/17/15, p. 16). So a clock at a higher altitude will tick faster than one closer to Earth’s surface, where Earth’s gravity is stronger. The satellites’ orbital mishap allowed the most precise test yet of this effect, known as gravitational redshift, two teams of scientists report in a pair of papers in the Dec. 7 Physical Review Letters.两组科学家在12月7日的《物理评论快报》(Physical Review Letters)上发表的两篇论文中称，卫星轨道上的意外事故让迄今为止对这种效应最精确的测试成为可能，即引力红移。
As the two misplaced satellites move in their elliptical orbits, their distance from Earth periodically increases and decreases by about 8,500 kilometers. Using the precise atomic clocks on the satellites, the scientists studied how that altitude change affected the flow of time. The clocks sped up and slowed down by tiny fractions of a second as expected, agreeing with the predictions of general relativity within a few thousandths of a percent, the teams report.时钟像预期的那样，以极微小的几分之一秒的速度加速和减速，这与广义相对论在千分之几个百分点内的预测是一致的
Citations
S. Herrmann et al. Test of the Gravitational Redshift with Galileo Satellites in an Eccentric Orbit. Physical Review Letters. Vol. 121, December 7, 2018, p. 231102. doi: 10.1103/PhysRevLett.121.231102.
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