Re: Space-time interval (2)

Le 15/08/2024 à 15:02, gharnagel a écrit :

On Thu, 15 Aug 2024 12:10:55 +0000, Richard Hachel wrote:

>
But now that we have a synchronization based on M and validated
for M, we can make A and B beep simultaneously, and M will always
receive the beeps simultaneously. This is the universal present
for M. But ONLY for M.

 Breathe, blow, yourself, Richard.
 

If I place myself at A, A will look at B with astonishment, and
will say B is out of tune, the present moment with which he beeps,
reaches me late, or rather EXISTS for me late. He beeps in my
future, and not at my present moment, because when I beep, his
beep does not exist FOR me, it will only exist in t=AB/c.

 Breathe, blow, Richard.  Scientists and engineers are smarter than
you, Richard.  They can use their brains.  They have used Einstein
synchronization, so they know the distance between A and B.  They
can use a quaint method called mathematics to calculate when the
signal from B was launched.
 

This is what we call universal anisochrony.

 It's simply time-of-flight delay.  This isn't something that requires
a new moniker or to go in a tizzy about.  Your countryman, Poincare
understood it, so did Einstein, and much better than you.
 

Are you finally starting to understand?

 We have always understood it.  We also have brains that understand
that it is a trivial matter.
 

....
And so on for all the watches of the universe.

 You always seem to want to go to extremes.  No one wants to synchronize
all the watches in the universe.
 

The solution is therefore to create a universal abstract time, and to
agree on this point, ideally placed at the same universal distance from
all the world capitals (and even that of the moon), this is what we call
universal time.
>
It is this time that is used today, and which "simulates" a global
present time which, by nature, does not exist, and has never existed
in the whole universe.

 But ... it doesn't defeat the "problem" you imagined:  if city A sends
a signal at time T to city B, it will not arrive at time T.
 

The speed of light is not a photon moving at speed c in a universal
present moment. It is for the observer an instantaneous transaction FOR
HIM in his own present moment, the two events (the supernova bursts, I
see the supernova bursting) being part of his own present.
>
What we consider a universal present is a useful abstract work. But
abstract. It does not exist.
>
Like the ancient notion of a flat earth.
>
R.H.

 Richard, you're worrying too much.  Breath, blow.  Everyone understands
this, they just can't understand why you're freaking out about it.
 Look, people have understood the concept for centuries.  If a runner
brought message to the government of an event from City A and another
runner brought a message to the government from City B that was related
to the event in City A, the potentate could consider the runners' speeds
and determine whether the events happened at the same time.  Sherlock
Holmes could do this.  Henri Poirot could do it. 

Hercule Poirot, no? Anyway, our country doctor is definitely not the
sharpest knife in the drawer.