Op 4/09/2023 om 9:14 schreef Luigi Fortunati:
> wugi il 03/09/2023 09:21:35 ha scritto:
>> And as always, don't forget the difference between *calculating Lorentz
>> objects* and *looking at Doppler/Einstein objects*.
>
> I really want to talk about *calculating Lorentz objects* and,
> therefore, let's leave aside what is seen (or not seen).
>
>> You should moreover keep in mind (which obviously you don't) that the length
>> contracted object is described by events (at its inner and outer extremities)
>> that are simultaneous in the observing (moving) system, but that are not
>> simultaneous in the rotating rod's (or wheel's) own system!
>
> See my animation
>
https://www.geogebra.org/m/xzsf765h
>
> There are 2 types of contraction.
Of course not.
> One is the contraction of the "space" between D and E (which is what
> you measure with your method and about which I have nothing to dispute
> about) and another is the contraction of the "body" AC, about which I
> have so much to say.
>
> The contracting space DE has no consequences, because the space between
> D and E is empty.
Space is space, it doesn't care who measures what in it, you can't
pinpoint anything in it in an absolute manner.
Contraction applies to sizes and distances of and between material objects.
> But the AC rod is not empty and if it contracts there are consequences
> (if the contraction is real).
Which it is.
> And this is exactly what I want to get to: does the AC body really
> contract or is it just an apparent contraction?
It's real, better get used to the idea.
And, bis repetita placent, you keep forgetting, or omitting, some
meaningful details, like this one:
that "your" events A and C are simultaneous in the observing (rest)
system, but they aren't in the moving system!
AB is simultaneous in both rest and moving systems, but AC isn't.
At least two other events C' and C" exist along the AC axis, in the
order A,C,C'C", so that
AC'= AB : proper lengths in *rest* system (with ABC' simultaneous in
it), and
AC = AC'/gamma(v) : length contraction in rest system;
and
AC" = AB : proper lengths in *moving* system (with ABC" simultaneous in
it), and
AC'= AC"/gamma(v) : length contraction (of rest system lengths!) in
moving system.
The contractions are real and reciprocal(!) <==> they correspond to
relativistic lengths and distances, and time intervals do the same: C,
C' and C" are different events at different times.
These are real properties of real matter distribution in space and time:
empty space and time don't *care* about units, directions etc. defined
upon them.
So you can draw three "ellipses" now, instead of only one:
ABC : ellips of length contraction of moving system in rest system
ABC' : circle of rest lengths in rest system
ABC" : elongated ellips in rest system ~ "circle of rest lengths" in
moving system.
Here you can see the three in a proper setting with proper events
defining them:
https://www.desmos.com/calculator/7h1h4jvzno?lang=nl
>> [[Mod. note -- Yes, there is another explanation: "rigid" only applies
>> in the rod's own inertial reference frame. Observers in other inertial
>> reference frames may (will) observe non-ridity, but that's an artifact
>> of their motion and doesn't affect the rod.
>
> If it is an artifact that does not affect the rod, it means that the
> non-rigidity is only an appearance.
Rigidity supposes checking lengths and times anywhere anytime. Now
what's the basic mechanism for checking and calibrating those? ... light
clocks! So then, matter ought to "distribute" its lengths and times in
accordance with light clock behaviour. It's that simple to understand
the basics of relativity, in an intuitive way at that.
Eg, light clocks and why there must be time dilation:
https://www.desmos.com/calculator/zlplep7g5k?lang=nl
And light clocks and why there must be length contraction:
https://www.desmos.com/calculator/ytyyijmgno?lang=nl
More at
https://www.wugi.be/srtinterac.html
Rigidity problems arise, as said earlier, when swapping among different
inertial states at relativistic acceleration speeds.
--
guido wugi