Gravity's Effect on Spacetime

  • By Arlo Perez
  • Posted 05.30.18
  • NOVA

Einstein's theory showed that time itself is affected by gravity.

Running Time: 01:48


Gravity's Effect on Spacetime

Published May 30, 2018

Narrator: Today, 100 years after general relativity was first presented, new technology is allowing us to explore the most remarkable predictions of the theory: an expanding universe; black holes; ripples in space-time; and perhaps the most bizarre, the idea that not just space, but time itself is distorted by heavy objects.

To prove it, a team of physicists is carrying out a remarkable experiment. They’re using two atomic clocks that are in near perfect sync, accurate to a billionth of a second. The master clock remains at sea level while they take the second clock to the top of New Hampshire’s Mount Sunapee.

General relativity tells us that as you move away from the mass of the planet, time should speed up. After four days at the top of the mountain, the test clock is taken back to the lab for comparison. There, they compare it to the sea level master clock. Four days ago they were in ticking in unison. But what about now?

David Scherer: You guys ready? This is it, right here. The time interval counter is going to show us the time difference between these two clock ticks.

Twenty nanoseconds!

You can see the time difference between them represented here, graphically: the clock that was up at the mountain for four days and our master clock.

Narrator: Gravity, the distortion of space and time, becomes weaker as you move away from the surface of the planet, so while the test clock was up the mountain, time sped up. It’s now 20 nanoseconds, 20 billionths of a second, ahead of the sea level clock.



Digital Producer
Arlo Perez
Editorial Review
Julia Cort, Ari Daniel
© WGBH Educational Foundation 2018



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