Re: Approximately 300,000 km/s With Respect To What?

Am Freitag000012, 12.07.2024 um 11:26 schrieb Mikko:

On 2024-07-11 19:58:02 +0000, amirjf nin said:
 

Approximately 300,000 km/s with respect to what?

 Whenever the speec of something is measured it is measured with respect
to someting else. The report should make clear what is the reference that
is considered stationary. Usually it is the instruments used in the
measurement, and usually but not always they are at rest with restpect to
Earth surface at the place of the measurement.
 

'Stationary' can be understood as 'not moving' and that as 'having velocity zero'.
But velocity would require a reference point, in respect to which the object does not move.
But what was actually Einstein's reference, in respect to which velocity v was measured.
Usually we could take 'the universe' as kind of background and Newton's absolute space as reference.
But this wasn't possible, because Einstein had explicitly excluded Newton's absolute space.
But if not that space, then what else could you take?
I suggested the following concept:
the observer always takes the own position and assumes, that would not move.
This assumption is wrong, of course.
But what else could you take???
TH