Re: A funny kind of rectilinearity
- From: Tom Roberts <tjroberts@xxxxxxxxxx>
- Date: Sun, 31 Jul 2005 00:42:42 GMT
msadkins04@xxxxxxxxx wrote:
In SR, light propagates in a vacuum in a straight line and does not
share the velocity of the source (i.e., additive velocities do not
apply to c regardless of the motion of the source).
Not quite. The light always propagates with SPEED c in any inertial frame, but its direction in any frame clearly depends on the orientation of the source in that frame.
But clearly it does share the velocity -- at least, the directional component of the velocity vector. And the angle of this "straight line" is something different for every frame.
Sure -- because the light source has in general a different orientation in different frames.
BTW this is true in Newtonian physics for light or any object with finite speed, such as cannonballs -- drive past a cannon firing vertically, and in the frame of your car the cannon is not aimed straight up (where "aimed" is defined by where the cannonball goes, not necessarily the orientation of the cannon itself).
Since the path of the light as assumed by S is longer than the path assumed by S', then assuming (as both do) that the scalar component of c is absolute regardless of the velocity of the source, light must take longer to cover the path assumed by S than to cover the path assumed by S'. Hence the time light takes to cross this path will be asserted by S' to have a value less than that asserted by S.
Sure.
However, each frame's assumptions about the path light takes (and they
are just that, assumptions)
No, they are MEASUREMENTS. That is, in S' when one measures the distance from source (at emission time) to detector (at detection time) one gets a smaller value than when S measures the distance from source (at emission time) to detector (at detection time). This is just simple Euclidean geometry plus the fact that in S the source and detector are moving.
Thus, it can be seen that the "dilation" is really an artifact of different assumptions about the length of the path light takes when S' synchronizes his clocks.
With "assumptions" => "measurements" this is sort-of correct; there is an aditional contibution from "time dilation" (but that, too, is related to your basic point).
If the principle of the relativity of simultaneity were applied universally in SR, S would have to conclude that S' mis-synchronized his clocks,
There is no "principle of the relativity of simultaneity".
S concludes that S' uses a different method to synchronize clocks that are at rest in S' than S uses for clocks at rest in S. This is manifestly so, of course.
it isn't the
mechanical prowess of S' that is at issue, but his *assumptions* about
the length of the path taken by light traveling between his clocks
during his synchronization procedure.
No, it is MEASUREMENTS, not assumptions.
Why S should be free to insist
on the validity of his own observations with respect to every other
event other than the clock synchronization procedure of S', but not in
the latter case, is a mystery whose answer is not to be found in the
literature of SR.
Your question does not make sense, once you realize the mistakes pointed out above. S' uses a different synchronization procedure than S, so of course S' gets different answers for measurements in which synchronization is important. Nothing strange or unexpected there....
Tom Roberts tjroberts@xxxxxxxxxx .
- Follow-Ups:
- Re: A funny kind of rectilinearity
- From: msadkins04
- Re: A funny kind of rectilinearity
- References:
- A funny kind of rectilinearity
- From: msadkins04
- A funny kind of rectilinearity
- Prev by Date: Re: Wrong physics
- Next by Date: Re: Space-time curvature
- Previous by thread: Re: A funny kind of rectilinearity
- Next by thread: Re: A funny kind of rectilinearity
- Index(es):
Relevant Pages
|
