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General relativity has readers feeling upside down

Reader feedback on the June 25, 2016, issue of Science News

3:36pm, August 10, 2016

It’s all relative

In “Earth is young at heart” (SN: 6/25/16, p. 5), Emily Conover reported that Earth’s core is more than two years younger than the planet’s surface, according to new calculations. Thanks to the effect of gravity on the passage of time, a clock placed at Earth’s core will tick fractions of a second slower than a clock at the surface. After 4.5 billion years, all of that different ticking adds up to 2.5 years.

“ ‘Earth is young at heart’ has got me feeling upside down! Wouldn’t gravity at Earth’s center be zero, not max?” asked reader Pete Caruso. “Sure, the center of the Earth is

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