Re: "Time" vs "physical time"

On 2024-08-11 17:33:20 +0000, Paul.B.Andersen said:

Den 10.08.2024 23:35, skrev Richard Hachel:

Le 10/08/2024 à 21:48, "Paul.B.Andersen" a écrit :

Den 08.08.2024 19:55, skrev Richard Hachel:

Can you reformulate your question using a vast underground tunnel between Paris and Oslo, in which we could launch particles at high speed from Paris to Oslo and vice versa?
 We assume that the length of the tunnel would be 1320 kms.

 

OK, let's assume that the length of the tunnel is exactly 1320 km.
We are using two clocks showing UTC+2h. But they have to be
more precisely synchronised than the clocks on the airports
which can not be expected to be synchronous to much better than
within a second.

Well, I've been to both airports, but never at the same time, so I haven't the chance to compare their clocks.

 So we will use two atomic clocks which are synchronised
by GPS to show UTC+2h to within 1 ns.
 The particle we will use is a photon.
 A photon is sent from Oslo at the time 12.00.000000000 ± 1ns
and is detected in Paris at the time   12.00.004403046 ± 1ns
The measured speed of the photon is 299792461 ± 68 m/s
 A photon is sent from Paris at the time 13.00.000000000 ± 1ns
and is detected in Oslo at the time     13.00.004403046 ± 1ns
The measured speed of the photon is 299792461 ± 68 m/s
 Any problem with this?

 

 No.
 Absolutely not.
 All you said is correct.
 R.H.
 

 OK. So you have realised that it is possible to synchronise
a clock in Oslo and a clock in Paris to within 1 ns if
we use the GPS.
 But have you realised that the clocks on the wall in
Oslo Airport and Paris Airport are synchronous to within
few seconds (probably better)?
 Please answer the question below, and don't flee yet again.
 Clocks in Oslo and Paris are showing the time UTC+2h.
 I leave Oslo Airport (Gardemoen Airport) when the watch on the airport
shows 12.00.00
I arrive at Paris Airport (Charles De Gaulle Airport) when the watch
on the airport shows 13.30.32.
 The difference is T = 1h 30m 32s
 Question #1:
============
Is it possible to calculate the duration of the journey (measured
in the ground frame) by comparing the reading of the clock in Oslo
at the departure and the reading of the clock in Paris at arrival?
 Yes or no, please.
  The distance in the ground frame between the airports is L = 1358.03 km.
 Question #2:
============
Is the real speed of the plane in the ground frame v = L/T = 900 km/h,
or is it impossible to know the real speed of the plane because
of the universal anisochrony?
 Yes or no, please.

--
Athel -- French and British, living in Marseilles for 37 years; mainly in England until 1987.