I The Lorentz factor gamma and proper time

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The discussion centers on the concept of proper time along light-like curves in the context of special relativity, specifically addressing the Lorentz factor, gamma (γ). It is established that proper time is zero along light-like paths, as the calculation of proper time involves the term √(1 - v²/c²), which equals zero when v equals the speed of light (c). The infinities associated with γ as v approaches c are attributed to its mathematical structure rather than any fundamental issue with proper time itself. The conversation emphasizes that while proper time is undefined for massless particles like photons, this definition is useful for maintaining clarity in physics. Ultimately, the key takeaway is that proper time along a light-like curve is zero, and this understanding does not alter the underlying physics.
  • #31
Trysse said:
What is the distinction between "not experiencing time" and "experiencing ZERO time"? Does it not amount to the same?
Worrying about that isn't physics.
 
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  • #32
Trysse said:
What is the distinction between "not experiencing time" and "experiencing ZERO time"? Does it not amount to the same?
I don't know. It's a question of semantics, not physics.

The important distinction here is that for anything traveling at speed ##c## the passage of time is not defined. That is very different from saying that the passage of time is zero.

In the parlance of physics you have three types of intervals: timelike, lightlike, and spacelike. The passage of proper time is defined, and makes sense, only for timelike intervals. For a lightlike (as well as a spacelike) interval it is not possible to define the notion of proper time. It is therefore a sloppy use of terminology to say that no time passes for something traveling at light speed. Moreover, that sloppy use of terminology can lead to misconceptions.
 

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