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Thread: Special Relativity, the Moon and other space probes

  1. #1
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    Special Relativity, the Moon and other space probes

    A while ago I saw on a TV show that as a consequence of the Special Theory of Relativity, (SR), the clocks in the GPS satellites run faster and a special US Air force base has been constructed to resynchronise their clocks or else the GPS will drift.

    I also saw a story that a particular astronaut on the ISS is classes a a time traveller as he has been deemed to travell a fraction of a second into the future.

    I remember yet another programme said how time near a black hole slows down, again related to SR and it's high gravity. Now the Moon is at one sixth Earth Gravity.

    If people were able to return to the Moon and build a permanent Moon Base, would time, therefore run quicker on that base, due to SR. If it did would it be noticeable at just the level of atomic clocks. Would Earth have to send synchronisation signals, like it does for the GPS satellites?

    Has this idea ever been discussed as an issue for a Moon Base or even a base on Mars or deep space missions.

    What about our space probes to the out reaches like Voyager or New Horizons? Does SR ever cause issues with ground control?

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    Quote Originally Posted by Sticks View Post
    A while ago I saw on a TV show that as a consequence of the Special Theory of Relativity, (SR), the clocks in the GPS satellites run faster and a special US Air force base has been constructed to resynchronise their clocks or else the GPS will drift.

    I also saw a story that a particular astronaut on the ISS is classes a a time traveller as he has been deemed to travell a fraction of a second into the future.

    I remember yet another programme said how time near a black hole slows down, again related to SR and it's high gravity. Now the Moon is at one sixth Earth Gravity.

    If people were able to return to the Moon and build a permanent Moon Base, would time, therefore run quicker on that base, due to SR. If it did would it be noticeable at just the level of atomic clocks. Would Earth have to send synchronisation signals, like it does for the GPS satellites?

    Has this idea ever been discussed as an issue for a Moon Base or even a base on Mars or deep space missions.

    What about our space probes to the out reaches like Voyager or New Horizons? Does SR ever cause issues with ground control?
    I think you mean General Relativity, dealing with gravity. SR deals a lot with speed. I have read that GPS satellites have to be tweeked from time to time because of GR. I would suppose when we have a permanent base on the moon and precision time keeping is needed, the clocks would also need to be tweeked.
    I read somewhere, that Eugene Cernan, who traveled to the moon twice, Apollo 10 & 17, was something like a millionth of a second younger than if he had stayed on Earth..

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    Sorry I kept thinking that GR was just how space was bent by matter which then had to pass through bent space, explaining how gravity worked. (Matter tells space how to bend, space tells matter how to move etc..)

    I had read or heard somewhere that Acceleration due to gravity had an equivalence to speed, hence why I was using SR.

    I am ready to stand corrected by a better person at physics than I

    BTW do we ever have to tweak the space probes we sent out, like New Horizons or Messenger or even Curiosity?

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    Quote Originally Posted by Sticks View Post
    A while ago I saw on a TV show that as a consequence of the Special Theory of Relativity, (SR), the clocks in the GPS satellites run faster and a special US Air force base has been constructed to resynchronise their clocks or else the GPS will drift.

    I also saw a story that a particular astronaut on the ISS is classes a a time traveller as he has been deemed to travell a fraction of a second into the future.

    I remember yet another programme said how time near a black hole slows down, again related to SR and it's high gravity. Now the Moon is at one sixth Earth Gravity.

    If people were able to return to the Moon and build a permanent Moon Base, would time, therefore run quicker on that base, due to SR. If it did would it be noticeable at just the level of atomic clocks. Would Earth have to send synchronisation signals, like it does for the GPS satellites?

    Has this idea ever been discussed as an issue for a Moon Base or even a base on Mars or deep space missions.

    What about our space probes to the out reaches like Voyager or New Horizons? Does SR ever cause issues with ground control?
    GPS corrections for SR are done by the GPS receivers because SR depends on the speed of the GPS satellite and they have different speeds depending on their orbit and where they are in that orbit.
    GPS corrections for GR are done by having the atomic clock(s) on the GPS satellite run at a slower frequency than ground reference clocks. That is set before launch but I suspect that it can be updated during the lifetime of a GPS satellite.
    ISS astronauts age faster at a rate of some microseconds per day relative to clocks on Earth which we do not usually count as time travel.

    If a Lunar atomic clock needs to read quite close to one on the Earth then SR and GR can be applied. Or it could be a synchronization process.

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    Quote Originally Posted by Sticks View Post
    What about our space probes to the out reaches like Voyager or New Horizons? Does SR ever cause issues with ground control?
    I do recall news about one probe that had some unexpected (tiny!) timing issue while it did an Earth gravitational assist or fly-by. IIRC the issue went away when GR was included in the orbit calculation, but can't remember the details. I think there was a thread about it here, or it was mentioned in some 'anomaly' thread.
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    I saw an edition of "How the Universe Works" last night about Space Time on Discovery Channel on Demand, featuring Bad Astronomer (Phil Plait himself )

    And yes GR is involved in time dilation near gravitational fields. Like I said earlier I thought that was just in SR.

    Even more worrying as I live on the 7th floor of a tower block, (8th floor is you are in the US), I am ageing faster than my neighbours on the ground floor

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    Quote Originally Posted by Sticks View Post
    I saw an edition of "How the Universe Works" last night about Space Time on Discovery Channel on Demand, featuring Bad Astronomer (Phil Plait himself )

    And yes GR is involved in time dilation near gravitational fields. Like I said earlier I thought that was just in SR.

    Even more worrying as I live on the 7th floor of a tower block, (8th floor is you are in the US), I am ageing faster than my neighbours on the ground floor
    But the good news is that you weigh less on that floor!

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