Is velocity incremental when measured precisely?

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Discussion Overview

The discussion revolves around the nature of velocity in the context of precise measurements, particularly in quantum physics. Participants explore whether velocity becomes incremental or quantized at very small scales, considering concepts like the uncertainty principle, Planck length, and energy quantization.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that many values in quantum physics become incremental at precise measurements, questioning if velocity follows this trend.
  • One participant argues that mathematically, velocity is a continuous function, implying it is not incremental and that the uncertainty principle does not apply to velocities.
  • Another participant raises the idea that if the Planck length is the minimum distance, then speed would have to be incremental in those units.
  • A different viewpoint states that there is no evidence supporting the quantization of distances at the Planck length, suggesting that if distance is continuous, then velocity must also be continuous.
  • Some participants mention that while energy is quantized, this does not necessarily imply that motion must also be quantized, especially for free particles.
  • One participant highlights that the quantization of energy applies primarily to bound states, complicating the discussion of motion in those contexts.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the nature of velocity and its relationship to quantization, with no consensus reached on whether velocity is incremental or continuous.

Contextual Notes

There are unresolved assumptions regarding the implications of the uncertainty principle, the nature of quantization in different contexts (bound vs. free states), and the interpretation of the Planck length.

golmschenk
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I know many values become incremental when you go into very precise measurements in quantum physics and whatnot. Angular momentum, spin, etc. When measured very precisely does velocity become incremental? I wouldn't think that would make much sense intuitively, but then again, neither does spin. Or does the uncertainty principle get in the way somehow? Just a random thought. I know it may be a very strange question with a simple explanation, but let me know. Thanks.
 
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golmschenk said:
I know many values become incremental when you go into very precise measurements in quantum physics and whatnot. Angular momentum, spin, etc. When measured very precisely does velocity become incremental? I wouldn't think that would make much sense intuitively, but then again, neither does spin. Or does the uncertainty principle get in the way somehow? Just a random thought. I know it may be a very strange question with a simple explanation, but let me know. Thanks.

Mathematically, velocity is a continuous function. For this reason, velocity is not 'incremental' (discreet), but always continuous. As far as I understand, the HUP does not apply to velocities. The HUP does not apply to accelerations (derivative of velocity), thus it must not necessarily apply to velocities.
 
I have no education, so I might be way off-base here. Isn't the Planck length considered the minimum distance that something can move? If so, then speed would have to be incremental in those units. :confused:
 
Planck length - Wikipedia said:
Contrary to statements sometimes found in the popular press, there is no evidence to suggest that distances in space are quantized in units of the Planck length.

Sorry about quoting Wikipedia, but this seems to suggest that distance is not quantized at the Planck length. Heck, "seems to suggest"? The article explicitly states it.

So, if a function, such as distance, is necessarily continuous (and differentiable), than its derivative (velocity here) is also continuous.

I think.
 
No education here either...but, if not distance, then at least energy is quantisized. Since the motion of an object can be translated into its energy, and energy is quantisized, it follows that its motion must be quantisized, or incremental, as well.
 
Lsos said:
No education here either...but, if not distance, then at least energy is quantisized. Since the motion of an object can be translated into its energy, and energy is quantisized, it follows that its motion must be quantisized, or incremental, as well.
I think there is a general misunderstanding of quantization of energy. The quantization of energy only applies to bound states. The energy of a free particle is, in general, not quantized.

Since the energy of a bound state is quantized then I guess you could say something to the effect that the "motion" of a bound state is quantized, but it is hard to speak meaningfully about motion in a bound state anyway. On the scale of a bound state wavefunction it is not as though you have a little billiard ball whipping around with some well defined velocity and position.
 

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