C = 299 792 458 m/s and uncertainty

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Discussion Overview

The discussion centers on the speed of light, denoted as c = 299,792,458 m/s, and its relationship to uncertainty, particularly in the context of the Heisenberg uncertainty principle and the definition of the meter. Participants explore whether this value can be considered exact or if it is subject to measurement uncertainty.

Discussion Character

  • Debate/contested, Conceptual clarification, Technical explanation

Main Points Raised

  • One participant questions whether c can be considered without uncertainty, referencing the Heisenberg uncertainty principle as it applies to photons.
  • Another participant argues that the distances involved in measuring c are large enough that quantum fluctuations can be ignored, suggesting that the speed of light is effectively defined rather than measured.
  • A different viewpoint emphasizes that while the meter is defined by the distance light travels in a certain time, there remains a need to measure the time it takes for light to cross that distance, implying potential variability in c.
  • One participant reiterates that the meter's definition is based on the distance light travels in a specified time, asserting that this makes the speed of light exact.

Areas of Agreement / Disagreement

Participants express differing views on whether the speed of light can be considered exact or if it is subject to measurement uncertainty, indicating that multiple competing views remain unresolved.

Contextual Notes

Participants highlight the dependence on definitions and the implications of measurement in the context of the speed of light, but do not resolve the underlying uncertainties or assumptions involved.

DonnieD
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c is 299 792 458 m/s without uncertainty? doesn't work the Heisenberg uncertainty principle for fotons?
 
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The distances typically involved in measuring c are sufficently big that quantum fluctuations are ignored.

Also, the length of 1m is defined by the distance light travels in a certain amount of time. Because of this definition, we're effectively defining light's speed, not measuring it, so it is exact.
 
AlphaNumeric said:
Also, the length of 1m is defined by the distance light travels in a certain amount of time. Because of this definition, we're effectively defining light's speed, not measuring it, so it is exact.
we define 1m, but we must still measure in how much time light crosses 1m; we measured c but it can be less or more, right?
 

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