SR/GR use absolute time to synchronize the GPS clocks with the ground clock.
in [Physics]
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From: Michael Moroney on 3 May 2010 18:54 PD <thedraperfamily(a)gmail.com> writes: >On May 3, 12:51=A0pm, kenseto <kens...(a)erinet.com> wrote: >> In fact the GPS refute the mutual >> time dilation concept: from the ground clock point of view the SR >> effect on the GPS clock is 7 us/day running slow....and from the GPS >> point of view the SR effect on the ground clock is ~7us/day rinng >> fast. >I've already told you, Ken, that the GPS satellite is not a case of >relative *inertial* motion (within experimental precision), and so one >does not expect mutual time dilation to apply. You seem to forget this >within hours of it being told to you. Again. And again. To be fair to Ken, here he's only mentioning the SR effects (~7us/day) and not the gravitational effects. He still gets it wrong, however, by claiming the satellite sees the clock on the ground station as running fast due to SR when in fact it'll see it as running slow. It's the gravitational well effects (~45uS/day) that reverse like that, not the relative motion effects. Net effect: Ground clock sees satellite running ~45uS fast due to gravity but ~7uS slow due to motion = ~38uS/day fast. Satellite sees ground clock running ~45uS slow due to gravity and ~7uS slow due to motion = ~52uS/day slow.
From: kenseto on 4 May 2010 09:30 On May 3, 6:54 pm, moro...(a)world.std.spaamtrap.com (Michael Moroney) wrote: > PD <thedraperfam...(a)gmail.com> writes: > >On May 3, 12:51=A0pm, kenseto <kens...(a)erinet.com> wrote: > >> In fact the GPS refute the mutual > >> time dilation concept: from the ground clock point of view the SR > >> effect on the GPS clock is 7 us/day running slow....and from the GPS > >> point of view the SR effect on the ground clock is ~7us/day rinng > >> fast. > >I've already told you, Ken, that the GPS satellite is not a case of > >relative *inertial* motion (within experimental precision), and so one > >does not expect mutual time dilation to apply. You seem to forget this > >within hours of it being told to you. Again. And again. > > To be fair to Ken, here he's only mentioning the SR effects (~7us/day) > and not the gravitational effects. He still gets it wrong, however, > by claiming the satellite sees the clock on the ground station as > running fast due to SR when in fact it'll see it as running slow. > > It's the gravitational well effects (~45uS/day) that reverse like that, > not the relative motion effects. > > Net effect: Ground clock sees satellite running ~45uS fast due to gravity > but ~7uS slow due to motion = ~38uS/day fast. > > Satellite sees ground clock running ~45uS slow due to gravity > and ~7uS slow due to motion = ~52uS/day slow. This is wrong and it has been explained to you many times. If the GPS clock sees the ground clock ~ 52 us/day slow then the GPS clock is not in synch with the ground clock. Ken Seto
From: Michael Moroney on 4 May 2010 17:03 kenseto <kenseto(a)erinet.com> writes: >On May 3, 6:54 pm, moro...(a)world.std.spaamtrap.com (Michael Moroney) >wrote: >> PD <thedraperfam...(a)gmail.com> writes: >> >On May 3, 12:51 pm, kenseto <kens...(a)erinet.com> wrote: >> >> In fact the GPS refute the mutual >> >> time dilation concept: from the ground clock point of view the SR >> >> effect on the GPS clock is 7 us/day running slow....and from the GPS >> >> point of view the SR effect on the ground clock is ~7us/day rinng >> >> fast. >> >I've already told you, Ken, that the GPS satellite is not a case of >> >relative *inertial* motion (within experimental precision), and so one >> >does not expect mutual time dilation to apply. You seem to forget this >> >within hours of it being told to you. Again. And again. >> >> To be fair to Ken, here he's only mentioning the SR effects (~7us/day) >> and not the gravitational effects. He still gets it wrong, however, >> by claiming the satellite sees the clock on the ground station as >> running fast due to SR when in fact it'll see it as running slow. >> >> It's the gravitational well effects (~45uS/day) that reverse like that, >> not the relative motion effects. >> >> Net effect: Ground clock sees satellite running ~45uS fast due to gravity >> but ~7uS slow due to motion = ~38uS/day fast. >> >> Satellite sees ground clock running ~45uS slow due to gravity >> and ~7uS slow due to motion = ~52uS/day slow. >This is wrong and it has been explained to you many times. Nope, that's correct. SR effects of motion always cause the moving clock to be seen as running slow. > If the GPS >clock sees the ground clock ~ 52 us/day slow then the GPS clock is not >in synch with the ground clock. Congratulations! That's probably the first correct thing you've said in this entire thread. The GPS clock is *not* in synch with the ground clocks, because 1) it's moving at a non-trivial rate and 2) it's in a different position in the gravity well. However, since the satellites are in a circular orbit, the altitude (position in the gravity well) and the orbital speed are both pretty much constant, so the onboard GPS clock can produce a second pseudo-second signal that runs just slightly slower than the actual second signal. This signal, when "sped up" by GR effects when it reaches Earth, will correspond exactly* to a ground-based 1 second signal. Just like the train, if the train moves at just the right speed, an A-flat whistle will be heard on the platform as a perfectly tuned "A". Same effect, different cause (Doppler vs. GR). Of course when going the other way, the gravitational and motion effects of an earth-originated signal both decrease its frequency, so the satellite will see an earth signal as ~52uS/day slow. The ground transmitter will need the same modification as the satellite one, it needs to have its clock running 52uS/day fast for the satellite to get the correct timing from it. * to within limits of measuring/setting its speed and altitude.
From: Sam Wormley on 4 May 2010 17:14 On 5/4/10 8:30 AM, kenseto wrote: > > This is wrong and it has been explained to you many times. If the GPS > clock sees the ground clock ~ 52 us/day slow then the GPS clock is not > in synch with the ground clock. > > Ken Seto http://www.facebook.com/profile.php?id=100000102086824&ref=pymk The seconds on satellites are the same as the seconds everywhere else in the universe. Gravitation and relative velocity can cause time dilation of an observer. Here is the detail of calculating the time dilation of satellite clocks: http://relativity.livingreviews.org/open?pubNo=lrr-2003-1&page=node5.html
From: jem on 5 May 2010 08:31
> On May 3, 6:54 pm, moro...(a)world.std.spaamtrap.com (Michael Moroney) > wrote: >> PD <thedraperfam...(a)gmail.com> writes: >>> On May 3, 12:51=A0pm, kenseto <kens...(a)erinet.com> wrote: >>>> In fact the GPS refute the mutual >>>> time dilation concept: from the ground clock point of view the SR >>>> effect on the GPS clock is 7 us/day running slow....and from the GPS >>>> point of view the SR effect on the ground clock is ~7us/day rinng >>>> fast. >>> I've already told you, Ken, that the GPS satellite is not a case of >>> relative *inertial* motion (within experimental precision), and so one >>> does not expect mutual time dilation to apply. You seem to forget this >>> within hours of it being told to you. Again. And again. >> To be fair to Ken, here he's only mentioning the SR effects (~7us/day) >> and not the gravitational effects. He still gets it wrong, however, >> by claiming the satellite sees the clock on the ground station as >> running fast due to SR when in fact it'll see it as running slow. >> >> It's the gravitational well effects (~45uS/day) that reverse like that, >> not the relative motion effects. >> >> Net effect: Ground clock sees satellite running ~45uS fast due to gravity >> but ~7uS slow due to motion = ~38uS/day fast. >> >> Satellite sees ground clock running ~45uS slow due to gravity >> and ~7uS slow due to motion = ~52uS/day slow. Learn before you teach. |