Why are the 'Fixed Stars' so FIXED?

On 16 Feb 2007 13:38:35 -0800, "PD" wrote:

On Feb 16, 2:12 pm, HW@....(Henri Wilson) wrote:
On Fri, 16 Feb 2007 12:24:16 +0100, "Paul B. Andersen"

Henri Wilson wrote:
On Sat, 10 Feb 2007 09:11:59 GMT, (Paul Schlyter) wrote:
False! Remember that c + any velocity equals c in relativity.
No theat's not relativity. That's a WIlsonian example of circular logic:

Let w always = c, by postulate.

Therefore
w = c(c+v)/(c+v)
= (c+v)/(1+v/c)
= (c+v)/(1+vc/c^2)
The speed-transformation equation u + w = (u + w)/(1 + uw/c^2)
is a consequence of the postulates of SR.
Would you please explain what's circular about that?

In the case of light, the postulate say its speed wrt an observer is always c
even if the source is moving at v.

The addition equation say if an object moves at u wrt a frame that is moving at
v wrt another frame then the object moves at w = (u + v)/(1 + uv/c^2) wrt the
second frame.

In the case of light, the postulate claims w = c ALWAYS.
So replace u with c and you get w = c = (v+c)/(1+vc/c^2)

I showed that this can be achieved by merely using a trivial circular maths
trick.

How pathetic....

Your stupidities have finally ceased to amaze me.
They are as can be expected from an imbecile.

Tell me what is wrong with my derivation...


Nothing is wrong with your derivation. Your conclusion that it implies
circularity is what's wrong.

The rule for combining velocities is not, nor was it ever, used to
assert that the speed of light is constant regardless of reference
frame. The only claim that is made is that the frame independence of
the speed of light is *consistent with* the rule for combining
velocities. Moreover, the experimental evidence in support of the rule
for combining velocities has nothing to do with measuring the speed of
light, but in fact measuring the speed of other particles in different
reference frames -- and it is there that measurements are completely
consistent with the velocity combination rule.

The frame-independence of the speed of light is taken as an unproven
*postulate* in special relativity. It is not necessary in science to
experimentally prove a postulate. One determines the implications of a
postulate (and just as you derived it, the velocity addition rule is
an example of an implication of this postulate) and then tests those
implications against experiment. If the implications match experiment,
and if the postulate is able to generate more successful implications
that match up to experiment than competing postulates, then this is
taken in science to be sufficient grounds for belief in the truth of
that postulate.

In this particular case, the postulate is the frame-independence of
the speed of light. One implication (of numerous implications) is the
rule for combining velocities. The rule for combining velocities has
been tested experimentally in a wide variety of circumstances (without
needing a direct test of the frame-independence of the speed of
light). And because this, and so many other implications, match
experiment so well, we take stock in the truth of the frame-
independence of the speed of light.

I hope this clears things up for you, Henri. At least a little.

You can stay in cuckoo land as long as you like as far as I'm concerned.


PD