Re: This about Newton's First Law


"sal" <pragmatist@xxxxxxxxxx> wrote in message
news:pan.2005.05.29.02.08.36.72685@xxxxxxxxxxxxx
> On Sun, 29 May 2005 00:10:31 +0000, Bill Hobba wrote:
>
> >
> > "sal" <pragmatist@xxxxxxxxxx> wrote in message
> > news:pan.2005.05.28.02.23.22.569115@xxxxxxxxxxxxx
> >> On Fri, 27 May 2005 22:10:41 +0000, Bill Hobba wrote:
> >>
> >>
> >> > "sal" <pragmatist@xxxxxxxxxx> wrote in message
> >> > news:pan.2005.05.27.19.04.42.402285@xxxxxxxxxxxxx
> >> >> On Fri, 27 May 2005 02:56:40 +0000, Bill Hobba wrote:
> >> >>
> >> >>
> >> >> > <geraldkelleher@xxxxxxxxxxx> wrote in message
> >> >> > news:1117129736.977597.202340@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> >> >> >
> >> >> > Mr Savain has rightly pointed out that nothing moves in the early
> > 20th
> >> >> > century relativistic concept but the same applies to Newtonian
> >> > terrestial
> >> >> > ballistics applied to planetary motion.
> >> >> >
> >> >> > Bill
> >> >> > It might be a good idea for you to explain what you mean by
nothing
> >> > moves.
> >> >>
> >> >> I can't comment on Savain's notion of reality,
> >> >
> >> > He is simply an idiot who can not even understand what a grade 8
> >> > science student can - namely Newton's first law of motion.
> >>
> >> Yeah, well, perhaps I should have said I can't comment beyond that
> >> observation which you just made.
> >
> > Ok. Form your own opinion - do not take my word for it.
>
> Hey, I already did. Didn't take reading more'n a couple of his posts.
>
>
> >> >> but the observation that
> >> >> "nothing moves" in relativity is actually pretty reasonable, I think
> >> >> ... at least from one point of view.
> >> >>
> >> >> In the 4-d representation of the universe, all events just "are".
> >> >> They have particular coordinates which don't change. Worldlines are
> >> >> sets of events, and they don't change either. In this sense, I
> >> >> think it's fair to say "nothing moves", and thinking of it that way
> >> >> can actually help with understanding it, IMHO.
> >> >
> >> > Errrrrr - Sal what would that make the v in the lorentz
> >> > transformations then?
> >>
> >> The "v" in the Lorentz transformation is the 3-velocity -- or, rather,
> >> the 3-speed, since it's a scalar, not a vector.
> >
> > It is a vector. The denominator contains v^2 which is a scalar but the
> > numerator is a different matter. Of course in standard configuration it
> > is a speed - which is what you may be considering. But in general it is
> > not the case.
>
> Come to think of it, yes, I was thinking of the standard configuration.
> Sigh -- been away from this stuff since last fall, and the rust builds up
> fast. Taking a little while to knock it off again.

No problemo.

>
> [ ... ]
>
> >> > In SR time is not
> >> > absolute which is logically equivalent (via the POR) to locality and
> >> > conversely in Newtonian mechanics time is absolute which is logically
> >> > equivalent to no limiting velocity (ie no locality ie event A can
> >> > cause event B instantaneously).
> >>
> >> Say what? Can you prove that any model which allows universal clock
> >> synchronization must also allow unlimited velocity? I rather doubt it!
> >
> > Yes it can be proved.
>
> Ah, right, so it can, if you assume the POR.
>
>
> >> Newtonian mechanics certainly includes both,
> >>
> >>
> > Come agian - Nwetonian mechanics assumes the Galelain trasformatons.
>
> Right. It includes universal time and no limiting velocity.
>
>
> >> and relativity includes
> >> neither. By itself that's no proof that the two are equivalent.
> >
> > I have no idea what you mean by the above. To me, on the face of it, it
> > does not make sense. Could you elaborate?
>
> Relativity includes neither "no limiting velocity" nor universal time.
> And yes I used a double negative there which sure didn't make it clearer,
> did it?
>
>
> >> > And that is the only difference. Both Relativistic mechanics and
> >> > Newtonian mechanics still have the POR and the PLA - the difference
> >> > is in the coordinate transformations.
> >>
> >> Um, right. But that's a big difference -- in particular, Newtonian
> >> mechanics doesn't normally use any transforms of the form
> >>
> >> (x1,y1,z1,t1) --> (x2,y2,z2,t2)
> >>
> >> save with the time mapping t1 = t2.
> >
> > I beg to differ. See a full development such as Landau - Mechanics
> > where the Galilean transformations are a central postulate.
>
> Differ how? The Galilean transformation is a linear transformation on the
> spatial coordinates, where that part of the transform includes a time
> term, and a straight t1 == t2 mapping on the time coordinate. I'm lazy;
> I'll quote from math world. In standard configuration it's (and I hope my
> posting software doesn't mutilate this):
>
> |t'| | 1 0 0 0 | |t|
> |x'| = | -v 1 0 0 | * |x|
> |y'| | 0 0 1 0 | |y|
> |z'| | 0 0 0 1 | |z|
>
> No matter how you rotate the spacial coordinates you always get t' = t,
> which is what makes the 3+1 view so natural in Newtonian mechanics.
>
> That's all I was trying to say, really. Is this at odds with Landau's
> development? (I haven't got Landau here, sad to say.)

Now you clarified it - fine. The point though is that the Galilean
transformation is exactly the same as the Lorentz transformations with c =
infinity. That is the justification for my claim absolute time implies no
limiting velocity ie c = infinity. If t = t' in the Lorentz transformations
it is easy to see c must be infinity.

Thanks
Bill

>
> [ ... ]
>
> --
> Nospam becomes physicsinsights to fix the email
> I can be also contacted through http://www.physicsinsights.org
>


.

Relevant Pages

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