Clocks in space
Discussion
No, any relative movement in space, means less movement in time, so the travelled clock would be slow compared with the stationary one. The faster you move it, the less time it will experience.
Relativity, it's for this reason that photons experience no time, as all of their velocity is in the spatial dimensions, none in the temporal one. If you look at a photon through a telescope from an early galaxy that formed 10 billion years ago, that photon has not aged by a single second, even though it's been travelling for 10,000,000,000 years.
If you spend your whole life on aeroplanes you will live a few nanoseconds longer apparently (although not on EasyJet as the plane food will probably offset this).
Relativity, it's for this reason that photons experience no time, as all of their velocity is in the spatial dimensions, none in the temporal one. If you look at a photon through a telescope from an early galaxy that formed 10 billion years ago, that photon has not aged by a single second, even though it's been travelling for 10,000,000,000 years.
If you spend your whole life on aeroplanes you will live a few nanoseconds longer apparently (although not on EasyJet as the plane food will probably offset this).
OK, so if you have a clock on the ground, and put another in a geosynchronous space station (so the space station will be travelling faster in order to stay above the same bit of Earch), and then bring the space clock back down after years and years, would the clocks be out of synch?
Also, does it matter what type of clock it is (other than the fact that an atomic clock will be more accurate)? (I don't think it matters, but my workmate is insisting it does!).
Also, does it matter what type of clock it is (other than the fact that an atomic clock will be more accurate)? (I don't think it matters, but my workmate is insisting it does!).
type of clock is irrelevant for the causation of the effect but to measure it accurately on an achievable (with current technology) timescale/speed/distance travelled you need an atomic clock.
the experiment of putting such atomic on clocks on planes around the world has been done:
http://www.sciencemag.org/content/177/4044/168.abs...
The clocks do indeed show different 'elapsed times' I can send you the paper if you want.
the experiment of putting such atomic on clocks on planes around the world has been done:
http://www.sciencemag.org/content/177/4044/168.abs...
The clocks do indeed show different 'elapsed times' I can send you the paper if you want.
Mellow Matt said:
OK, so if you have a clock on the ground, and put another in a geosynchronous space station (so the space station will be travelling faster in order to stay above the same bit of Earch), and then bring the space clock back down after years and years, would the clocks be out of synch?
Yes. Indeed, the GPS system has to correct for this to work.Mellow Matt said:
Also, does it matter what type of clock it is (other than the fact that an atomic clock will be more accurate)? (I don't think it matters, but my workmate is insisting it does!).
No, if you could build a purely mechanical clock that was accurate enough it would show the same result.Edited by Mr E on Monday 20th August 13:16
Mellow Matt said:
OK, so if you have a clock on the ground, and put another in a geosynchronous space station (so the space station will be travelling faster in order to stay above the same bit of Earch), and then bring the space clock back down after years and years, would the clocks be out of synch?
Also, does it matter what type of clock it is (other than the fact that an atomic clock will be more accurate)? (I don't think it matters, but my workmate is insisting it does!).
Geostationary Orbit is ~7000Mph.Also, does it matter what type of clock it is (other than the fact that an atomic clock will be more accurate)? (I don't think it matters, but my workmate is insisting it does!).
Earth at the equator is ~1000Mph.
Yes, it's the relative velocity that affects the relative time dilation, not the position.
Yes, the effect at those velocities is very small. You're talking very small fractions of a second.
The effect is non-linear, as you approach the speed of light it becomes much more significant.
Mellow Matt said:
OK, so if you have a clock on the ground, and put another in a geosynchronous space station (so the space station will be travelling faster in order to stay above the same bit of Earch), and then bring the space clock back down after years and years, would the clocks be out of synch?
Ahh, now that is a more interesting question, they would as you had to move the clock to get it to the space station. But, if you synchronised them once the clock was up there (this gets complicated as it is precisely the time delay between satellites and terrestrial receivers that allow things like GPS to work), then I'm not so sure, I still think they would. But if that does count as a different inertial frame then just sitting the clock one on top of the other would mean they are travelling at different velocities too. Otherwise where do you draw a distinction? A hot air balloon anchored to the ground, a space probe orbiting further out than the moon with an orbital velocity of thousands of km/s? I'll get the popcorn out and wait for Gene Vincent to answer that one.Mellow Matt said:
Also, does it matter what type of clock it is (other than the fact that an atomic clock will be more accurate)? (I don't think it matters, but my workmate is insisting it does!).
No. As Use Psychology (and you) said, only for accuracy, your workmate is wrong. Ask him how many energy changes in a caesium atom there are a second, if he doesn't know it to at least four significant figures, tell him to shut up about atomic clocks. It's 9,192,631,770.Mellow Matt said:
OK, so if you have a clock on the ground, and put another in a geosynchronous space station (so the space station will be travelling faster in order to stay above the same bit of Earch), and then bring the space clock back down after years and years, would the clocks be out of synch?
Also, does it matter what type of clock it is (other than the fact that an atomic clock will be more accurate)? (I don't think it matters, but my workmate is insisting it does!).
I think that the one in orbit will be slower. I vaguely remember my physics teacher explaining that reduced elapsed time experienced is due to the relative acceleration experienced by each clock. This is why the clock in the 747 (from the abovementioned experiment) is slower even though both clocks are moving at identical speeds in relation to each other.Also, does it matter what type of clock it is (other than the fact that an atomic clock will be more accurate)? (I don't think it matters, but my workmate is insisting it does!).
So, in a rotating object a = (v^2)/r which will be greater for the clock in geosynchronous orbit.
And no, it doesn't matter what type of clocks they are provided they both keep the same time when in identical conditions.
Velocity and gravitational time dilation combined-effect tests
Hafele and Keating, in 1971, flew caesium atomic clocks east and west around the earth in commercial airliners, to compare the elapsed time against that of a clock that remained at the US Naval Observatory. Two opposite effects came into play. The clocks were expected to age more quickly (show a larger elapsed time) than the reference clock, since they were in a higher (weaker) gravitational potential for most of the trip (c.f. Pound, Rebka). But also, contrastingly, the moving clocks were expected to age more slowly because of the speed of their travel. From the actual flight paths of each trip, the theory predicted that the flying clocks, compared with reference clocks at the U.S. Naval Observatory, should have lost 40±23 nanoseconds during the eastward trip and should have gained 275±21 nanoseconds during the westward trip. Relative to the atomic time scale of the U.S. Naval Observatory, the flying clocks lost 59±10 nanoseconds during the eastward trip and gained 273±7 nanoseconds during the westward trip (where the error bars represent standard deviation).[13] In 2005, the National Physical Laboratory in the United Kingdom reported their limited replication of this experiment.[14] The NPL experiment differed from the original in that the caesium clocks were sent on a shorter trip (London–Washington D.C. return), but the clocks were more accurate. The reported results are within 4% of the predictions of relativity.
The Global Positioning System can be considered a continuously operating experiment in both special and general relativity. The in-orbit clocks are corrected for both special and general relativistic time dilation effects as described above, so that (as observed from the earth's surface) they run at the same rate as clocks on the surface of the Earth.
From here:
http://en.wikipedia.org/wiki/Time_dilation
Very interesting subject, and the cause of the error leading to the FTL neutrino observations at Gran Sasso. 'Not enough relativity' essentially.
Hafele and Keating, in 1971, flew caesium atomic clocks east and west around the earth in commercial airliners, to compare the elapsed time against that of a clock that remained at the US Naval Observatory. Two opposite effects came into play. The clocks were expected to age more quickly (show a larger elapsed time) than the reference clock, since they were in a higher (weaker) gravitational potential for most of the trip (c.f. Pound, Rebka). But also, contrastingly, the moving clocks were expected to age more slowly because of the speed of their travel. From the actual flight paths of each trip, the theory predicted that the flying clocks, compared with reference clocks at the U.S. Naval Observatory, should have lost 40±23 nanoseconds during the eastward trip and should have gained 275±21 nanoseconds during the westward trip. Relative to the atomic time scale of the U.S. Naval Observatory, the flying clocks lost 59±10 nanoseconds during the eastward trip and gained 273±7 nanoseconds during the westward trip (where the error bars represent standard deviation).[13] In 2005, the National Physical Laboratory in the United Kingdom reported their limited replication of this experiment.[14] The NPL experiment differed from the original in that the caesium clocks were sent on a shorter trip (London–Washington D.C. return), but the clocks were more accurate. The reported results are within 4% of the predictions of relativity.
The Global Positioning System can be considered a continuously operating experiment in both special and general relativity. The in-orbit clocks are corrected for both special and general relativistic time dilation effects as described above, so that (as observed from the earth's surface) they run at the same rate as clocks on the surface of the Earth.
From here:
http://en.wikipedia.org/wiki/Time_dilation
Very interesting subject, and the cause of the error leading to the FTL neutrino observations at Gran Sasso. 'Not enough relativity' essentially.
Good man, should be compulsory literature in schools that book. Read Brian Greene's The Elegant Universe next. Fantastic book.
Just found this:
http://www.lightandmatter.com/html_books/genrel/ch...
So you've go the Lorentz factor for Gravitational time dilation but also the relative differences in orbital velocity relative to each other depending on the difference in altitude, which act in opposite ways. I'm not a physicist so this starts to get quite complicated and involved quite quickly.
Just found this:
http://www.lightandmatter.com/html_books/genrel/ch...
So you've go the Lorentz factor for Gravitational time dilation but also the relative differences in orbital velocity relative to each other depending on the difference in altitude, which act in opposite ways. I'm not a physicist so this starts to get quite complicated and involved quite quickly.
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