Posted on 12/07/2018 12:39:21 PM PST by ETL
Making lemonade from lemons, two teams of physicists have used data from misguided satellites to put Albert Einstein’s theory of gravity, the general theory of relativity, to an unexpected test.
The opportunistic experiment confirms to unprecedented precision a key prediction of the theory—that time ticks slower near a massive body like Earth than it does farther away.
As Einstein explained, gravity arises because massive bodies warp space-time. Free-falling objects follow the straightest possible paths in that curved space-time, which to us appear as the parabolic arc of a thrown ball or the circular or elliptical orbit of a satellite.
As part of that warping, time should tick more slowly near a massive body than it does farther away. That bizarre effect was first confirmed to low precision in 1959 in an experiment on Earth and in 1976 by Gravity Probe A, a 2-hour rocket-born experiment that compared the ticking of an atomic clock on the rocket with another on the ground.
In 2014, scientists got another chance to test the effect when two of the 26 satellites now in Europe’s Galileo global navigation system, like the one pictured above, were accidentally launched into elliptical orbits instead of circular ones. The satellites now rise and fall by 8500 kilometers on every 13-hour orbit, which should cause their ticking to speed up and slow down by about one part in 10 billion over the course of each orbit. Now, two teams of physicists have tracked the variations and have shown, to five times better precision than before, that they match the predictions of general relativity, they report 4 December in Physical Review Letters. That’s not bad, considering the satellites weren’t designed to do the experiment. However, another experiment set to be launched to the space station in 2020 aims to search for similar deviations with five times greater precision still.
:)
The music would be different on the two elevators.
Of course it works, however it is not a true zero-gravity environment.
Our satellites and the ISS are also in 'artificial' zero gravity environments. They are subject to both gravity and centrifugal force. That is not the same as being in a true zero gravity environment. I doubt that we have had anything, ever, in a true zero gravity environment. It may not even be possible to find a place where there is no gravitational pull.
The force of gravity varies depending on exactly where you are on the surface of Earth. This would infer that two atomic clocks, on the surface, but in two distinct locations should also show a 'difference' in time.
In theory. We actually don't know as we can't actually measure whether they are or not.
In theory. We actually don't know as we can't actually measure whether they are or not.
Well, since they have mass they are a source of gravity. However, compared to the other forces (normally) operating at that small scale, gravititational effects are practically zero. Now if we are talking about the very tiny region inside a black hole, the "singularity", then things are likely very much different. There you have an immense gravitational field at the atomic/quantum scale. Weird things surely must be going on there.
P.S. Since people at the equator are moving faster and the pull of gravity is reduced by centrifugal force, compared to people who live near the poles, one would think that ‘time’ would be affected and ‘different’ for those two groups.
SO... I wonder what the gravitational pull is at the exact center of a planet or star ?
Yes, but far too small to matter.
Doesn’t an atomic clock measure ‘time’ by the decay of cesium atoms (or something similar) ?
There have been theories that the decay of certain particles, which are used to do carbon dating (or the decay or radioactive particles like Uranium), have changed over the eons, likely due to a change in the environment (The Sun and it’s dance with the Earth).
So, if it could affect radiocarbon dating, couldn’t it affect these atomic clocks ?
Likely true.
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And they do!
That is why the current time standard is in orbit (the GPS constellation)
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>> “Our satellites and the ISS are also in ‘artificial’ zero gravity environments” <<
False! Due to centripetal force, they are in an accelerated environment.
Actually, they refer to it as MICROGRAVITY.
Bump to read.
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Who is “they?”
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