🚀 go-pugleaf

In article <1993Dec2....@rhrk.uni-kl.de>, ste...@gypsy.physik.uni-kl.de (Guido Steiner) writes:
> Not only CAN such particles travel at the speed of light, they MUST travel
> exactly at that velocity.
>
> This follows from the special theory of relativity.

Only in a vacuum.  In the presence of matter light propagates slower than
the speed of light
--Ray Cote

There's no government like no government.

Guido Steiner (ste...@gypsy.physik.uni-kl.de) wrote:

: > The correct statement is that nothing _with non-zero rest mass_ can travel
: > at exactly the speed of light. Photons have zero rest mass. Hence, no
: > problem.

: Not only CAN such particles travel at the speed of light, they MUST travel
: exactly at that velocity.

: This follows from the special theory of relativity.

Considering that the "special theory of relativity" _starts_ with the
assumption of the constancy of the speed of light, and that non-local
events can only be measured _with_ light, saying that this follows
_from_ SR is circular reasoning.

cot...@woods.uml.edu wrote:
: In article <1993Dec2....@rhrk.uni-kl.de>, ste...@gypsy.physik.uni-kl.de (Guido Steiner) writes:
: > Not only CAN such particles travel at the speed of light, they MUST travel
: > exactly at that velocity.
: >
: > This follows from the special theory of relativity.

: Only in a vacuum.  In the presence of matter light propagates slower than
: the speed of light
: --Ray Cote

The correct statement is "in the presence of matter light propagates
slower than it does in a vacuum".

Massive particles _can_ travel faster than the speed of light (in a
medium), _never_ faster than the speed of light in a vacuum.

This is the cause of Cerenkov radiation (the "blue glow" seen in e.g.
water in which is stored radioactive material).

- dc

>Only in a vacuum.  In the presence of matter light propagates slower than
>the speed of light
>  --Ray Cote

A small technicality bothers me about special relativity and the speed
of light in a medium:  What about special relativity in a medium (not
continuum mecnanics mind you)?  Should one use the velocity of light
in a medium, in place of the speed of light in vacuum, when using the
Lorentz transform in a medium?  In other words, does the "c" in the
Lorentz transformation imply general velocity in an arbitrary medium,
or does it remain fixed at so-called "c_nought" - the speed of light
en-vacuo - irrespective of the medium?

>There's no government like no government.

PS:
You seem like you might have read the Schrodinger's Cat Trilogy by
Robert Anton Wilson, or are a fan of his in some respect.  But in case
you aren't you might like this exerpt from the above work:

T.A.N.S.T.A.G.
--> There Ain't No Such Thing As Government
- Government is just a transitory phase between phases of chaos.

In article <PDELONG.93...@eden.rutgers.edu>, pde...@eden.rutgers.edu (Paul DeLong) writes:
When using the Lorentz transforms you use the velocity of light in a vacuum.

> PS:
> You seem like you might have read the Schrodinger's Cat Trilogy by
> Robert Anton Wilson, or are a fan of his in some respect.  But in case
> you aren't you might like this exerpt from the above work:
>
> T.A.N.S.T.A.G.
> --> There Ain't No Such Thing As Government
> - Government is just a transitory phase between phases of chaos.

I haven't read any of his books, but those are nice sayings.
--Ray Cote

There's no government like no government.

In article <1993Dec13....@ibr.cs.tu-bs.de>, y000...@ws.rz.tu-bs.de (Franz) writes:
> I also want to know how Cerenkov radiation fits in to relativity.  It would
> seem to me that Cerenkov radiation is analogous to a sonic boom or other
> medium-transmitted wave phenomenon, so why does it happen to electromagnetic
> waves?

I don't know much about Cerenkov radiation, but I believe it's created when
a particle travels faster than light does in a medium.  Since the particle
is not travelling faster than c there is no violation of relativity.
--Ray Cote

There's no government like no government.

In article <PDELONG.93...@eden.rutgers.edu>, pde...@eden.rutgers.edu
(Paul DeLong) writes:
|>
|> >Only in a vacuum.  In the presence of matter light propagates slower than
|> >the speed of light
|> >  --Ray Cote
|>
|> A small technicality bothers me about special relativity and the speed
|> of light in a medium:  What about special relativity in a medium (not
|> continuum mecnanics mind you)?  Should one use the velocity of light
|> in a medium, in place of the speed of light in vacuum, when using the
|> Lorentz transform in a medium?  In other words, does the "c" in the
|> Lorentz transformation imply general velocity in an arbitrary medium,
|> or does it remain fixed at so-called "c_nought" - the speed of light
|> en-vacuo - irrespective of the medium?
|>
|> >There's no government like no government.
|>
|> PS:
|> You seem like you might have read the Schrodinger's Cat Trilogy by
|> Robert Anton Wilson, or are a fan of his in some respect.  But in case
|> you aren't you might like this exerpt from the above work:
|>
|> T.A.N.S.T.A.G.
|> --> There Ain't No Such Thing As Government
|> - Government is just a transitory phase between phases of chaos.


I also want to know how Cerenkov radiation fits in to relativity.  It would
seem to me that Cerenkov radiation is analogous to a sonic boom or other
medium-transmitted wave phenomenon, so why does it happen to electromagnetic
waves?

Michael Franz
y000...@rzab0.rz.tu-bs.de
"Beware of Germans bearing Gift."

>I don't know much about Cerenkov radiation, but I believe it's created when
>a particle travels faster than light does in a medium.  Since the particle
>is not travelling faster than c there is no violation of relativity.
> --Ray Cote

Okay, I buy that.  But in the case of the electron going faster than
light in the medium, will the electron then have an apparenent mass or
effective mass(or energy) which is imaginary (analogous to the
electron's effective mass in a crystal) - similar to the case where it
would have imaginary mass if it were going faster than light in a
vacuum?  Also, I'm curious as to time dilation and space contraction,
etc., would be affected by the fact that the speed of light is
different in the medium.

> There's no government like no government.

(equal (not 'government) (not 'government))^J
t

An interesting question, and one that can be answered by considering the
amount of time that it takes to drive across Texas, alone and avoiding cities.

Assuming that your route is 650 miles long, and you can safely travel at 65
miles an hour (no radar detector), what is the first thing you notice?
The first thing you notice is that the
distance in this example is artificial.  How long does it take you to
make the drive?  It is obvious that the trip takes ten hours.  HAH, you
forgot to consider that one must consume massive quantities of caffeinated
beverage in order to stay awake.  When one does this, one must make pit
stops.  These of course lower your average speed, even though while in
the car you travl at 65mph.

For the case of a dilute texas, in which your speed driving and speed in
restrooms are uncoupled, the only remaining questions are, what do photons
drink, and are atomic restrooms clean?

Further, it is obvious that photons must drink JOLT, because nothing else
legal could make them go so fast.

Should you drive through a crystalline structure instead, more complicated
explanations are in order, although they follow the same sort of
reasoning.

-----------------
On an entirely unrelated note, is there anyone in London who has a room
to rent (no homicidal killers, please).  I start grad school in physics
in January and need a place to stay.

Thanks,
ed