Is Planck Time Truly a Proven Concept or Still Theoretical?

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Discussion Overview

The discussion centers on the status of Planck time as a concept in physics, exploring whether it is a proven fact or remains theoretical. Participants examine its relationship to quantum field theory (QFT) and general relativity (GR), as well as the evidence supporting or challenging its validity.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants assert that Planck time is still theoretical and lacks experimental evidence, as suggested by Michio Kaku.
  • Others clarify that Planck time is defined in relation to Planck length, where QFT and GR conflict, and argue that it does not require proof in the traditional sense.
  • A participant questions the evidence for QFT itself, comparing it to the established evidence for the Planck constant, and seeks clarity on the evidence for Planck time and length.
  • It is noted that Planck scale is currently beyond theoretical and experimental reach, indicating limitations in current understanding.
  • One participant describes Planck time as a natural unit derived from universal constants, emphasizing its defined nature rather than its empirical validation.

Areas of Agreement / Disagreement

Participants express differing views on the status of Planck time, with some viewing it as theoretical and others emphasizing its definitional status. There is no consensus on whether it is proven or merely a theoretical construct.

Contextual Notes

Participants highlight the limitations of current theories and experimental capabilities in addressing questions about Planck time and scale, indicating a dependence on future developments in theoretical physics.

bobsmith76
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I was watching indepth on cspan booktv with Michio Kaku and he says that the Planck time has not be proven. I thought it was a proven fact, but he says it is still theoretical and we have no evidence for it yet. Is this true?
 
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The way you put it that doesn't really make a lot of sense. Planck time is defined as the time associated with the Planck length, which is defined as a length scale where we know that QFT comes in conflict with GR. That's simply because at this length scale energy would be so concentrated that it becomes very relevant for space-time geometry as described by GR. So there's nothing to "prove" about Planck scale.

What you might be referring to is an actual theory that does work at Planck scale. There are candidates (basically the usual theories dealing with quantum gravity), but there has not been enough experimental evidence or theoretical prediction to decide which of the ideas describes nature best.

Cheers,

Jazz
 
But do we have evidence for QFT or is it just a mathematical model at this point? For example, I'm pretty sure we have evidence for the Planck constant in the equation, E = hv, but do we have evidence for the Planck time and the Planck length?
 
It's one of the natural units based on the universal constants. If anything it is a defined number. We don't know if they have any inherent value-it will depend on future theories and experiments-but they are the units derived from h, c, and G.
Planck time I believe is the time it takes a photon traveling at c to cross one Planck length.
 

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