Re: HOCUS POCUS


Randy Poe wrote:
mluttgens@xxxxxxxxxx wrote:
PD wrote:
mluttgens@xxxxxxxxxx wrote:
HOCUS POCUS

Two electrons E1 and E2 are ejected along a straight line with
opposite velocities v1 and v2 from a device stationary in S,
at t=0 according to S clock.

Assuming that v1 = -0.6 c and v2 = 0.8 c, what is the relative
velocity between E1 and E2 ?

After a time interval t measured on his clock, S will conclude
that the distance separating E1 from E2 is (0.6 + 0.8) ct = 1.4 ct,
hence that E2 is moving away from E1 at V = 1.4 c, or that E1 is
moving away from E2 at V = 1.4 c, meaning that the relative velocity
between E1 and E2 exceeds c.

Yes, and there is nothing wrong with that.


Ein Zwei Ein Stein HOCUS POCUS
E1 = S',
V = (.8 c-(-0.6c))/(1+0.8*0.6) = 1.40/1.48 c = ~.9459 c
E2 moves at 1.4/1.48 c relative to S'
E2 moves at 1.4/1.48 c relative to E1
ABRACADABRA
420000 = ~283784

By assimilating E1 to a frame S' moving away at -0.6 c from a frame S,
Srists claim that the electron E2, which had a velocity V = 1.4 c
wrt E1 measured in S, has only a velocity V' = ~0.9459 c measured in
S'.

Yes.


But the electrons don't bother about which name they are given, nor
does their relative velocity V depend on their velocity wrt the device
by which they have been emitted. Such device -the frame S according
to SRists- should be ignored after their emission, it belongs to
history.

Not at all. You seem to think that relative velocity between two
objects should be a frame-independent quantity. It's not. I don't know
why you think it should be.


I am skeptical about the physical validity of a formula (the
relativistic addition of velocities), which gives an infinity of
solutions for a same velocity V between to objects, for instance
1.4 c, measured in one frame (S in my example).

Because you have divine knowledge that separation rate
is independent of reference frame?

Well, the rest of us without divine knowledge are stuck
with describing what we see in experiment, which
is that the Lorentz transform is valid.

You cannot devise an experiment to validate the velocity addition
formula since that would require measuring the OWSL. The velocity
addition formula is a deduction from the postulate of c invariance in
inertial FoR. So talk about valid deduction, it is ok, b ut do not
bullshut people that this is experimentally verified.

Mike



There's nothing I can do about the fact that your
divine knowledge contradicts experiment, that there
is some unknowable "reality" different from my
observable universe and accessible only to you.

So I'll stick with the equations that describe life
in my universe.

Let's consider a planet inhabited by advanced ET's, situated at
x billions light-years from the Earth. Their physicists, from the
redshift of the Earth galaxy A and the Hubble constant, calculate that
the Earth is moving away from them at -0.7 c. Opposite the Earth,
they observe another galaxy B, whose velocity relative to them is
+0.7c.
They conclude, in accordance with the cosmic expansion, that such
galaxy has a velocity 1.4 c relative to the Earth.

No, they conclude that those two points are separating
IN THEIR REFERENCE FRAME at 1.4 c.

As they have mastered FTL communication, they transmit those data to
the Earth SRists, who calculate that B is in fact moving away from
them at 0.7c + 0.7c / 1 + 0.7*0.7 =~ 0.94 c, forgetting that it is
impossible to observe a galaxy moving away at 1.4 c.

On Earth, galaxy B is OBSERVED to be moving
away at 0.94c. Earth scientists easily calculate that
the two points are separating at 1.4c from the point
of view of Planet X. They also can see galaxy C
receding at 0.7c (i.e., separating from Planet X
at 1.4c IN THE EARTH FRAME). They can easily
calculate that IN PLANET X FRAME, the observers on
Planet X would see Galaxy C receding at 0.94 c.
Planet X sends a message confirming that the
redshift of Galaxy C is consistent with a relative
velocity of 0.94c.

- Randy

.

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