Plank Time & Speed: Is Light C Plank Speed?

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The discussion centers on the relationship between Planck time, Planck length, and the speed of light (c). It suggests that if Planck time is defined as the time it takes for a photon to travel a Planck length, then c could be considered a form of Planck speed. However, it emphasizes that the speed of light is a physical constant defined in terms of the meter, which complicates the notion of using it as evidence for Planck time. The conversation also questions the need for "evidence" of a unit of measurement, suggesting that units like the meter and second are definitions rather than empirical evidence. Ultimately, the discussion leans towards treating c and Planck units as fundamental definitions rather than evidence of physical phenomena.
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If plank time is the time it takes a photon to travel a plank length and speed is d/t or meters/second. then is the speed of light c plank speed? is the constant speed of light evidence of plank time?
 
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Yep, I guess.

Note however, that the speed of light is a physical constant and in fact the meter is defined in terms of it. A unit like the Planck time and Plank length are also defined in terms of other fundamental constants, e.g. t_\mathrm{P} = \ell_\mathrm{P} / c where \ell_\mathrm{P} = \sqrt{\hbar G c^{-3}} is defined in terms of c and two other fundamental constants. So it's basically by construction, which I wouldn't call "evidence".
 
brianhurren said:
evidence of plank time?
What does that mean? Do you need evidence of ounces, or teaspoons? What does it mean to have evidence of a unit?
 
Meter is a definition, second is. (Teaspoons also). So it is better to set c as 1. And lp as 1.

Sincerely.
 

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