A constant speed of light in all reference frames? Surely you can't be serious. [Physics]

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From: Peter Webb on 3 Mar 2010 07:30

"Ste" <ste_rose0(a)hotmail.com> wrote in message
news:a04e3531-34b5-43af-822a-d5e86de1b51b(a)z11g2000yqz.googlegroups.com...
> On 3 Mar, 02:02, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au>
> wrote:
>> "Ste" <ste_ro...(a)hotmail.com> wrote in message
>>
>> news:c122829f-64e2-4568-a3c8-56796b4c6895(a)g11g2000yqe.googlegroups.com...
>>
>> > On 2 Mar, 09:15, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au>
>> > wrote:
>> >> And hence, when I say I want to discuss things instead
>> >> of just going off and reading a book, it's not because I'm being
>> >> awkward or just want to sound off cranky ideas to an audience, but
>> >> because I genuinely apprehend that the interactive discussion is
>> >> necessary for the questions at hand.
>>
>> >> _____________________________
>> >> That is obviously not true. You don't ask questions trying to learn.
>> >> You
>> >> state your open disbelief that SR is true,
>>
>> > Peter, I can only put you to the proof of showing where I said I
>> > disbelieved SR.
>>
>> That is incoherent.
>
> What on Earth is incoherent about saying "I do not accept that I said
> what you claim I have said, therefore I put you to the proof of
> showing *where* I said what you claim I have said"?
>
>

The incoherent bit is the stuff between "I do not accept .." and "... I have
said." (The second time you say it)

>
>> You say you are here to learn about SR.
>
> I am here to learn more about the *conceptual basis* of SR.
>

Minkowksi space time?

>
>
>> Do you believe SR is true?
>
> I accept it's mathematical form has some obvious truth, yes.
>

Do you believe that it correctly predicts the results of every experiment
that it claims to? That clocks run slower, and 80 foot ladders can fit
through 40 feet barns, and that the speed of light is measured the same in
every intertial frame of reference and this speed is independent of the
speed of the emitter, receiver, and underlying medium of transmission?

If you believe all of those things, then you are saying more than "SR has
some obvious truths in its mathematical form" you are saying it is an
accurate portrayal of reality - ie, what happens when you conduct those
experiments, what physically and actually happens, is exactly as predicted
by Relativity.

If, on the other hand, you do not believe in the twin "paradox" actually
happening, you don't believe in SR. If you do believe the predictions of SR
that one twin is older, then you believe that time dilation is more than
some mathematical fiction, its what actually happens in the real world.

So, when relativity predicts that one twin will age more than the other, is
this just some mathematical truth, or is it what really happens as well?

>
>
>> >> you criticise science as a whole when you are
>> >> pretending to try and learn it,
>>
>> > I have only "criticised" science in the sense of objecting to the
>> > patent inaccuracies, or even mendacities, that are perpetuated by some
>> > who claim to follow science.
>>
>> That is not true. That is not the only criticism,
>
> It really depends on what you perceive as a criticism.

Being called "mendacious" ?

So, do you believe that SR is correct in its prediction (for example) that
if one twin were to be sent off into space at 0.9c for 10 years they would
have aged less on their return than the twin that stayed at home?

Do you agree its correct when it says that an 80 foot ladder could fit
inside a 40 foot barn?

You seem to agree they are "mathematical truths". Do you also agree those
equations correctly predict the outcomes of real world experiments, which
means they are far more than simply "mathematical truths"?

From: Peter Webb on 3 Mar 2010 07:40

"Ste" <ste_rose0(a)hotmail.com> wrote in message
news:899e0123-23bd-47d9-b8d6-d32f3a59e32b(a)g10g2000yqh.googlegroups.com...
> On 3 Mar, 02:15, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au>
> wrote:
>> Next, what is the fundamental cause (confining ourselves to SR) of
>> this non-simultaneity? As I say, as far as I can tell, it's a simple
>> function of the finite speed of propagation. But I'm told that it
>> isn't, so I need to know on what grounds a simple propagation
>> explanation does not suffice.
>>
>> ________________________________
>> Hey! You asked a question about SR ! Far out!
>>
>> The ultimate reason (or, more accurately "an" ultimate reason) is that
>> the
>> speed of light is the same in all inertial reference frames, and does not
>> depend on the speeds of two different observers. This makes the
>> propagation
>> delay a function of the frame of reference you pick, and not a function
>> of
>> the underlying dynamics.
>
> I won't pretend to understand how this is supposedly not a function of
> the speed of propagation.

Try and express your question more clearly.

What is it that you don't understand? You can't understand why what exactly
is not a function of the speed of propagation of what, exactly?

If it is the speed of the underlying medium, observer or sender, in another
thread I gave quite a long explanation to you of how this comes about from
Maxwell's equations, using no mathematics at all. You may recall that the
form of equation of water and sound wave has the wave exchanging energy with
their medium; this is not true of the equations in Maxwell where the E and M
vectors exchange energy between themselves and not the medium in which they
travel.

This would also answer another question you asked. Recently you asked for
evidence of your inability to learn; I gave some at the time, of course, but
lets add this as another excellent example. You asked the same question
yesterday, the answer was explained to you, but you do not appear to have
learned anything at all.

There you go!

From: Bruce Richmond on 3 Mar 2010 07:42

On Mar 3, 1:55 am, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au>
wrote:
> > > Assuming that SR is wrong is a stupid starting place for somebody with
> > > your
> > > obviously modest understanding of physics.
>
> > There is a difference between requesting clarification/derivation and
> > saying something is wrong. I wrote, "Actually when I personally
> > started studying relativity I did not start by believing it was
> > false. I assumed that since so many great men of
> > science considered it to be correct that it probably was. But at the
> > same time I expected a clear, understandable explaination of how it
> > works. Never got one. And the more people insisted that it's just
> > the way nature works, the more it drove me away."
>
> > Nowhere in there did I say that I assumed SR to be wrong. What quite
> > often happens though is that when someone asks a question they are
> > jumped on for not accepting SR as gospel without question. After all,
> > look at all the much smarter people that have accepted it ;)
>
> > _______________________________
> > OK, your position is that SR is correct, but you don't understand it?
>
> Nope. I didn't understand it at one time, but that was some time
> ago. How long have you had problems reading?
>
> ______________________
> I don't.

You don't understand SR? Well there are folks around here that do
that might be willing to help you, if you read what they write.

BTW, are you ever going to learn to quote properly?

> Just to clarify your position:
>
> 1. You agree SR is correct.
> 2. You feel you understand why it is correct.
>
> Jolly good, and three cheers for you!- Hide quoted text -
>
> - Show quoted text -

From: Peter Webb on 3 Mar 2010 07:51

I'm not gloating because some here were proved wrong. I'm gloating
because some people so emphatically charged me with "idiocy" and
"ignorance", "a slave to my intuitions", etc.

_________________________
But hold it. You are an idiot, ignorant, and a slave to your intuitions.

Well, you think you know more about SR than real life physicists; that makes
you an idiot. You are ignorant (in the context of this thread) because you
know almost nothing about SR, including apparently any of the maths; and you
have repeatedly claimed that you would trust your intuitions over the
predictions of SR.

Incidentally, I have a question for you.

Two twins are separated. One is sent to a star 10 light years away and back
at 0.9c each way, for a total trip time of about 22 years.

The twins meet up again.

What does your intuition tell you? That they will still be the same age?
What do you think actually happens?

From: Jerry on 3 Mar 2010 08:29

On Mar 3, 6:28 am, Bruce Richmond <bsr3...(a)my-deja.com> wrote:

> I understand it and think it is correct.
>
> My position is that far more people would understand it if it was
> explained differently.

It is generally accepted by most legitimate posters on these
newsgroups that Einstein's original two-postulates axiomatic
approach to the development of relativity is somewhat archaic and
difficult to follow, to judge by the numerous crackpots who
stumble at the very first steps in his derivation.

You prefer Bondi's presentation of Milne's derivation, which
goes "backwards" starting with the Doppler effect. I also like
Bondi's approach which is quite intuitive, but after rederiving
all of Einstein's famous results, the reader is left somewhat
dangling. How does one proceed from there? Bondi's approach is
still, at its core, a classic geometric development of the
subject.

By analogy: One does not design a skyscraper using Euclid's
Elements, and one does not get to General Relativity through
either Einstein's original or Milne's "inverted" axiomatic
development of relativity. It's just too cumbersome a way to
get there.

Proceeding forward means presenting Minkowski spacetime. The
Minkowski spacetime approach to relativity in essence replaces
the two postulates with a single assertion: "The geometry of the
universe is accurately described (in low gravity fields) by a
four dimensional manifold with properties as follows..."

Taylor and Wheeler, which I like and you hate, start with this
single "postulate" and spend the rest of the book familiarizing
the reader with the implications of this visualization of the
universe. If the reader is diligent, by the time they finish the
book, Minkowski spacetime will have gone beyond mere mathematical
manipulation, but will have become a coherent, consistent, and
best of all, highly intuitive mental construct by which the
reader apprehends relativity.

Your main objection seems to be that Taylor and Wheeler don't
bother trying to justify relativity. T&W just want the reader
to accept that the battle has been won. Relativity works, so
the reader should just get on with learning the most efficient
way to work with it, et cetera.

You obviously don't like that attitude.

Jerry