Re: On the observation of a moving object.

stephen_at_nomail.com
Date: 11/11/04 

Date: 11 Nov 2004 16:28:38 GMT

Harry <harald.vanlintel@epfl.ch> wrote:

: "kenneth couesbouc" <kencouesbouc@yahoo.fr> wrote in message
:> The apparent length depends on
:> proportionate speeds. Is this still optical aberration?
:> Regards, Ken

: This is certainly not optical aberration. Optical aberration refers to the
: apparent position of an object, whereby the angles to the extremes are
: approximated to be the same, and thus the lengtt is neglected.
: To the contrary, length contraction should also occur even at zero distance
: at which optical effects don't play a role at all.

: Harald

The OP is talking about an optical affect. I do not know if it
has a name. Consider an object with a length of 1 light second.
The front of the object is 4 light seconds from us, and moving
towards us at a speed of .5c. Ignoring relativity, which the
OP seems to be doing, light from the back of the object when
the back was 5 light seconds away from us will reach us at time 5. At
the same time, light from the front of the object when the object
was 3 light seconds away from us will reach us. So at the same
time, the front "appears" to be 3 lightseconds away, and the back
5 lightseconds away, so the object appears to have a length of
2 lightseconds. If it was moving away from us, the same argument
would say that the object would appear shorter. Of course
this is not how length contraction is defined in relativity.

Stephen