Re: The velocity of light going pass a moving train.
- From: bz <bz+spr@xxxxxxxxxxxxxxxxxxxx>
- Date: Wed, 11 Jul 2007 12:22:31 +0000 (UTC)
G <gehan_ameresekere@xxxxxxxxxxx> wrote in
news:1184128142.012393.189630@xxxxxxxxxxxxxxxxxxxxxxxxxxxx:
On Jul 9, 2:48 am, bz <bz+...@xxxxxxxxxxxxxxxxxxxx> wrote:
G <gehan_ameresek...@xxxxxxxxxxx> wrote inBUT see Jeckyl's post where he says velocity IS dependent..
news:1183856648.047299.264950 @e16g2000pri.googlegroups.com:
....
inertial Frames of Reference.
There is one thing which I would like to know ( Hi, 275 posts
later...)
*** Is the velocity of light dependent on the velocity of the
source? ****
Not according to Einstein and to experimental data.
I have stopped reading Jeckyl and Dono.
I may start again when they stop quarrelling with each other and start to
rationally discuss physics.
OK
If you answer yes, then does that not contradict the 2nd postulate of
SRT?
It would if I had answered yes. I did not.SO this is AE's postulate, OK
If you answer no, then why should light emitted from a source on a
movingtrain(relative to you, on the tracks) move along with the
train, "carried along with thetrain"? This can only be if you assume
that light travels at a constant velocity to the source on thetrain.
Light travels with a constant velocity, as seen by ANY observer in ANY
iFoR, including the observer riding on thetrainwith the source and
mirror.
AE's postulate. Others have reached same conclusion via other math with
other postulates, ab-initio.
Consistent with observations to date.
In the double star -type of experiments : whether the star ismoving
towards the earth or away, the velocity of light relative to an
( assumed) stationary observer (stationary , on the earth, wrt to the
centre of orbits) is c, that is constant. Once again, it is AS IF
THERE IS AN ETHER in the observers reference frame,
It is as if there is an Ether in the iFoR of ANY observer. Except the
ether has NO useful property except to make those who demand a
'physical carrier' of light 'more comfortable'.
Exactly. I cannot find any evidence of Ether - but then I have not
done the experiments :}
I don't have to stand on a train track until a train comes by in order to
believe someone when they publish data on the damage done by car-train
collisions.
I am able to read what has been published, check the calculations, talk to
those who have done similar experiments and reach a conclusion about the
veracity of the author.
And an ether that travels along with each and every observer is
indistiguishable from no ether at all.
Exactly..
Which is what AE said in 1905.
that makes sure
that any light emitted travels at a constant velocity c WRT the
observers FoR, like air ensures that sounds are carried at velocity
330m/s WRT observer who is in still air relative to him. I think you
all agreed on this.
The geometric explanation is better than the ether that follows each
observer around.
Geometric - like the train and tracks experiment?
Like raising minks to get rich quick in minkowski space.
Like looking at how motion effects what we can see when we look at things
in 'space-time'.
.....
If the beam is vertical and the source is stationary in the tracks iFoR
then the horizontal component of the light's velocity, v is zero in the
tracks iFoR.
OK. But if the source is moving, then is it not as if it was
momentaritly stationary, emitted the light directly upwards , and then
moved on?
NO. Do the headlights on your car become momentarily stationary every time
they emit a photon? Last time my headlights became stationary while the car
was in motion, it took a body shop and a lot of money to repair the
damages.
If the source is moving, it is moving. It is NOT stopping.
If the target (the mirror) is ALSO moving [in the track iFoR] then the
light MUST follow a path that will take it to the same place it is OBSERVED
to go in the trains iFoR, which is the center of the mirror.
The trackside observer is the one that concludes that the light must follow
a slanting path in order to go from the laser to the mirror. It MUST follow
that path because it DOES follow that path. It does go from the laser to
the center of the mirror. The guy on the train SEES that it does this.
There is no question because he has aimed the mirror and the laser so that
the beam hits the mirror dead center.
Time dilation does not change this fact. There is no time dilation
for an observer in the FoR of the tracks, in his own FoR.
That is correct.
Oh I agree.
I see you are a scientist.
What is (the) truth?
In science, the truth is that we can not distinguish between 'any
theory that is consistent with all known data' and it is useless to
argue about which is right. If you want to know which one to spend your
time testing, you test the one that is easiest to test, which is
usually the 'simpler one'
I try to think like one. I don't play one on TV.
I have worked with and been considered such by some scientists, over the
years.
In this case, SR/GR is easier to test and is being tested many times a
day in laboratories around the world as people try to find a way to
earn a nobel prize by disproving the currently 'accepted' theories.
OK, however will people be allowed to disprove accepted theories and
once proven will the proof be allowed? It may take a litte time, like
100 years of relativity.
In science, a theory is never proven. Science does not seek to prove
things.
ONE (1) reproducable experiment is ALWAYS sufficient to DISPROVE any
theory, no matter how firmly entrenched. Once a theory is DISPROVEN, it may
be revised or replaced by an entirely new theory. It will PROBABLY be
revised because any new theory must explain everything that the old theory
explained AND explain the results of the new experiment too.
G
But why? What if the train was still and the platform moving? ThenI suppose you could also say that if (x,y,z,t)1 and (x,y,z,t)2 have
identical values
you mean magintude of x y z?
No, I mean the position of event 1 in space-time is (x,y,z,t) and the
position of event 2 is (x,y,z,t) where x,y,z and t have some specific
values, like 10 ft,0 ft,10 ft,10 sec.
Thetrainhas moved 10 feet from it's original position, (the x value).
The light has moved 10 feet from it's original position along the x
axis
would the light move ?
In the iFoR of the train, the train IS still and the platform IS moving.
When I was a kid and we were driving across country, I used to imagine that
there was a rope connecting our car to the sun and that the earth was
moving underneath the car. [of course, I didn't realize that the relative
velocity was much too small, the rope would have to stretch because the
car, moving at 60 mph was much too slow to keep up with the sun.]
and 10 feet from its original position on the z axis)(it started atI suppose, is it another form of the equivalence principle?
(0,0,0,0) and moved to (10,0,10,10), where it intercepted the mirror.
The mirror has moved 10 feet from it's original position along the x
axis and stayed at 10 feet on the z axis (it started at (0,0,10,0) and
moved to (10,0,10,10)
NO. The equivalence principle from General Relativity says that we can't
tell the difference between gravity and acceleration [without looking
outside the box] so they are equivalent.
The principle I stated above just says that things equal to the same thing
are equal to each other. If the space time coordinates of two events are
equal, then the two events happen at the same place and same time and are,
in effect, [part of] the same event.
for x,y,z and t (two events occur at the same place and
time) then (x',y',z',t')1 and (x',y',z',t')2 MUST also have
identical values for x', y', z' and t', no matter what inertial
frame of reference views events 1 and 2.
--
bz
please pardon my infinite ignorance, the set-of-things-I-do-not-know is
an infinite set.
I suppose that is true of us all- That's a heck of a thing to base all
our theories on : a finite subset of an infinite set of facts.
Yep. It helps me keep things in perspective. It reminds me that every
single human being knows things that I do not know and can teach me
something.
It also reminds me that no matter how much I think I know, it ain't a drop
in the bucket.
--
bz
please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.
bz+spr@xxxxxxxxxxxxxxxxxxxx remove ch100-5 to avoid spam trap
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