Re: Simple question about relativity and space time
- From: Tom Roberts <tjroberts137@xxxxxxxxxxxxx>
- Date: Tue, 05 Feb 2008 18:20:27 GMT
Paul Cardinale wrote:
On Feb 5, 5:09 am, "N:dlzc D:aol T:com \(dlzc\)" <dl...@xxxxxxx>
wrote:
<reginald.lo...@xxxxxxxxx> wrote in message
news:d65ce8ab-80ff-40ce-a602-07133033ec49@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
time run slowerYes, these orbitting clocks have a few extra "ticks" in each
in the surface of the earth than higher in the sky
(where for example GPS satellite are). For this
reason, they must regularly sync these GPS
satellite clock with the time in earth or else, we
would see a drif of several kilometer per days in
our driving direction.
second, and they are adjusted periodically to keep the same time
as down here on Earth.
Not exactly. The adjustments are not made periodically, but on an as-
needed basis (typically about every few month) due to drift in the
clocks.
All three of you are wrong in the details.
On earth, a Cs atomic clock ticks 9,192,631,770 times per second. The GPS satellite Cs clocks are constructed with a slightly larger divider, to account for the satellite's altitude and orbital velocity. This "adjustment" is made in the factory, before launch [#]. Operational GPS clocks, on satellites or on the ground, are NEVER "adjusted". But once per day the satellites are uploaded with correction factors to account for minor drifts -- the RECEIVERS receive these corrections from the satellite and apply them in their computations [@] [%]. For satellite clocks this is correction usually dwarfed by similar adjustments to the orbital parameters. For all clocks this adjustment is typically a few nanoseconds.
[#] the first few satellites had the option to select
between the standard and the modified divider; it was
empirically found that the modified divided is necessary,
as predicted by GR.
[@] It was designed this way because it is a better
engineering design (putting the complexity in the receiver
rather than in the satellite); there might be some
applications which use the uncorrected clock values.
[%] The computation of these correction values is a
major fraction of the overall complexity of the GPS.
Tom Roberts
.
- Follow-Ups:
- Re: Simple question about relativity and space time
- From: Martin Hogbin
- Re: Simple question about relativity and space time
- References:
- Simple question about relativity and space time
- From: reginald . louis
- Re: Simple question about relativity and space time
- From: N:dlzc D:aol T:com \(dlzc\)
- Re: Simple question about relativity and space time
- From: Paul Cardinale
- Simple question about relativity and space time
- Prev by Date: Anomalous geniuses of physcis
- Next by Date: Re: Anomalous geniuses of physcis
- Previous by thread: Re: Simple question about relativity and space time
- Next by thread: Re: Simple question about relativity and space time
- Index(es):
Relevant Pages
|
