Re: Speed ​​and celerity in relativity.

Richard Hachel wrote:

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Speed ​​and celerity in relativity.
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There is a very important notion in relativity: the notion of real speed.
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Relativistic speeds can be classified into three types of speed.
- the real speeds (Vr) or celerities.
- observable, measurable, classic speeds (Vo).
- apparent speeds (Vapp)
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Physicists are used to using the last two kinds of speeds, which they denote v and v_app and which are the same thing as Vo and Vapp in Hachel notation.
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But let's return to the real speed, also called celerity,

No, it's not.  Real speed is denoted as dx/dt.  Nobody calls it "celerity"
or celery, either.

and denoted Vr by Hachel.

Most physicists denote real velocity as v.  Your a Johnny-come-lately who
muddles the waters with obfuscation.

This notion is immensely important, although little used, and the more difficult the problems become, the more we realize that we can no longer reasonably ignore it, particularly in accelerated frames of reference or rotating frames of reference.

I just use v for an inertial observer.  If I want to specify the speed of
an object, I'll use u, or w.  The important thing, however, is to DEFINE
what they refer to.  You haven't done that.

What is real speed? As its name suggests, it is the exact description of what happens in a movement between A and B, i.e. the distance traveled by the actual time taken to travel it.

Vr=x/Tr

As I said, dx/dt.

However, in our world, in our daily physics, it is not this time, and it is not this speed that we are used to using.

Maybe YOU are confused.  Physicists aren't.

But we use a deformation of things which is a difference in time measured by a clock A compared to the time (at the instant) measured by a clock B.

Not necessary.  A moving object's velocity can be determined a number of
ways, but the best two require only one clock.

We see immediately that this time is clearly biased in an anicochronous universe (our universe), and that this time is not correct, nor true, since clock A is constantly out of tune with clock B and vice versa.

No physicist uses a clock in one inertial frame for one time a clock in
a different frame for a second time in calculating a velocity.
"one should never mix together the descriptions of one phenomenon
yielded by different observers, otherwise--even in ordinary physics--
one would immediately meet contradictions" -- E. Recami

You must then use only one clock and the best clock is a single FIXED clock. Now, we see, as the excellent Jean-Pierre Python says, that the only fixed clock in this story is the mobile clock, and event A and event B occur in the same place.

With Doctor Hache, this is the only way to have true time, real time; a true speed, a real speed.

Not really.  But you must realize that the velocity you measure will always
be in the past.  No problem if it's constant.

Thus the notion of celerity is a fundamental notion,

You're misusing a term that has already be taken (celeretas) and kidnapping
it for a meaningless term.

today quite neglected, but which, with the precision of theoretical concepts
should take in the future, a preponderant place in the thinking of the relativistic physicist.
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R.H.

No one is going to do such a stupid thing, R. H.