Groups > sci.physics.relativity > #599795

Re: Kinetic Energy formula check - a series of short burn rockets, and see how the velocity adds up.

From	Thomas Heger <ttt_heg@web.de>
Newsgroups	sci.physics.relativity
Subject	Re: Kinetic Energy formula check - a series of short burn rockets, and see how the velocity adds up.
Date	2023-01-18 09:22 +0100
Message-ID	<k2poiiFi1jiU1@mid.individual.net> (permalink)
References	(8 earlier) <ae680a29-ddf7-44c4-a6cd-e589bb192781n@googlegroups.com> <k2hnbiFaphqU2@mid.individual.net> <1c40752b-50d6-4c70-98ea-3ad0bfde5ad0n@googlegroups.com> <k2kbehFn2nnU1@mid.individual.net> <tq6nuu$3b8ve$1@dont-email.me>

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Am 17.01.2023 um 19:04 schrieb Volney:

>> Such inertial frames require absense of gravity, which we earthlings
>> obviously cannot provide.
>
> As usual in physics, especially then, things are tested to within an
> error limit, where it can be shown the error from the existence of
> gravity or whatever is smaller than measurement errors or outcome error.
>
> Secondly, this is theoretical, it's what happens when there is no
> gravity even if such a situation is difficult or impossible to reproduce
> in real life. Just like Einstein's trains, moving at a substantial
> fraction of c, with observers able to time flashes from lightning bolts
> as a train passes an embankment aren't real.
>
>> But in such a dark and gravity free inertial frame, you have abolutely
>> nothing, which could eventually help you to measure absolute velocity.
>
> And Einstein doesn't try to use any absolute velocity. He says simply
> here's a frame where the equations of Newton's mechanics hold good. Are
> you going to complain that Einstein didn't discuss moving objects around
> and accelerating them to test Newton's mechanics?
>>
>> In that scenario you always need something, where you could base your
>> position vectors on.
>
> You, the observer, say "Here's the origin".

That would be actually correct, but was not, what Einstein said.

I personally use a concept I call 'subjectivism', which states, that all 
observers would naturally take the own position and base observations 
upon that.

But the concept of Einstein's SRT didn't do that. Instead, the 
'stationary' frame was 'defined' as one, where the equations of Newton's 
mechanics hold good.

The equations of Newton were actually not developed for such a scenario, 
because Newton lived on planet Earth, where we have gravity and all sort 
of other things, which we do not find in inertial frames of reference.

Therefore Einstein's stationary system were undefined, because he didn't 
write, in respect to what they were stationary.

He couldn't actually do, because this would require infinite regress of 
references.

In the end 'stationary' remains undefined entirely, which would also 
include velocity v and also the term 'space'.

That is quite unfortunate, because velocity plays a mayor role in SRT.

>>
>> You could place a 'buoy' somewhere as reference, but don't know its
>> velocity neither.
>
> Doesn't matter. Observer considers himself stationary and verifies
> Newton's mechanics.
>
> Remember, Einstein was writing for other physicists who understood
> perfectly what the equations of Newton's mechanics hold good means,
> there was no need for him to write another 5000 pages to explain all of
> that.

Sure.

But still 'equations of Newton hold good' would not define 'stationary'.

> You come up with some of the craziest nitpicks, no wonder you found 400+
> "errors" where there are none.


This is not 'nitpick'!

It is absolutely essential in relativity to define relations of objects 
under consideration.

It's simply not allowed to 'reference to nothing' in relativity, because 
the very word 'relative' requires a relation between at least two entities.

>> So, you need another buoy, to reference the position of the first buoy.
>
> What first buoy? Where the observer declares the origin and declares it
> to be stationary? Remember, these are user defined, frames are infinite
> in extent, and can be anywhere the observer wants.

Sure, that would be acceptable, but was not Einstein's setting.

...

TH

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