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From: Thomas Heger <ttt_heg@web.de>
Newsgroups: sci.physics.relativity
Subject: Re: Approximately 300,000 km/s With Respect To What?
Date: Mon, 15 Jul 2024 08:26:42 +0200
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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.

This is possible, if all inertial reference frames are of equal rights.

I can therefore use this setting, because it makes some sense and is 
allowed.

BUT: if the observer does not move, how could he possibly reach v=c???

So I turned the 'twin paradox' upside down and applied it to the point 
of origin (e.g. the Earth if a spacecraft starts from there).

....


TH