Re: Question about light clock and derivation of time dilation

EL a écrit : 
Just answer me this question: Is there any physical sense in a negative
frequency?
You are at noon today, if yesterday is a negative time interval and
tomorrow is a positive time interval relatively, then what is the sign
of today's time interval at your temporal position?


"yesterday" is not a negative time interval, but a negative time
instant.

An interval is defined from a pair of instants as the set of instants
between them. This pair is unordereded (did you ever see [2,1] in any
analysis text ? It could either means the empty set or [1,2] AFAIK, in
both cases we do have a better way of saying that).

Frequecy depends on duration, duration is the length of an interval,
lengthes are nonnegative.
.