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From: Mikko <mikko.levanto@iki.fi>
Newsgroups: sci.physics.relativity
Subject: Re: Approximately 300,000 km/s With Respect To What?
Date: Mon, 15 Jul 2024 12:05:13 +0300
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On 2024-07-15 06:26:42 +0000, Thomas Heger said:

> Am Sonntag000014, 14.07.2024 um 12:19 schrieb Mikko:
>> On 2024-07-13 08:08:44 +0000, Thomas Heger said:
>> 
>>> 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'.
>> 
>> Yes, that is what the word means.
>> 
>>> But velocity would require a reference point, in respect to which the 
>>> object does not move.
>> 
>> That gives you a revefernce point: the object does not move in respect to
>> itself.
>> 
> 
> Actually I have used this setting in my 'book' and declared, that all 
> observers regard themselves as non-moving.

That is possible but not always the best idea. In the real world an observer
often considers oneself as moving and someting else as stationary. Often
it is better to choose samething inertial for "statinary" when the observer
is not inertial.

-- 
Mikko