Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: benm on 29/03/2019 10:37:26
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Jörg has a timely question:
Einstein told us time passes more slowly at higher altitudes and with faster speed. Modern clocks can measure the difference in time passing in a valley compared to on a mountain, and in a jet compared to a point on the ground. The effect is too subtle for our unaided senses to appreciate. What effect does time have on our distant Voyager and New Horizon space probes? Will they function appreciably longer due to time distortion as they leave behind the mass of earth and the solar system at high speed?
Can anybody help out?
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Not in any way we could measure with these spacecraft.
The lifetime of these spacecraft is limited by the electricity generated by their radioactive generators, and their communications capacity is limited by the size of their transmitters and antennas.
If they had a highly accurate atomic clock onboard, we would be able to measure a difference in the way they experience time. But they don't have such clocks - it wasn't a priority for their mission.
To detect these small relativistic effects, you would have to subtract the much larger non-relativistic effect of 20 hours delay each way due to the finite speed of light.
Current distance of the Voyager spacecraft: https://voyager.jpl.nasa.gov/mission/status/
But we don't need to look this far for relativistic effects - the GPS satellites do have timekeeping as a primary objective of their mission; each satellite carries several high-accuracy atomic clocks, and they are orbiting at a constant distance from the center of the Earth (reducing the non-relativistic effects). These clocks do show net relativistic effects attributable to both speed and "height" in Earth's gravitational well.
See: https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_Positioning_System#Special_and_general_relativity
And the US National Standards Lab (NIST) has non-portable atomic clocks that are so accurate that they can measure the difference in the flow of time when the table on which one of them is mounted is raised by just 1 foot (30cm).