Are Planck Units the Ultimate Limit for Measurements?

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    Planck Units
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Discussion Overview

The discussion centers on the interpretation and implications of Planck units, specifically Planck length, Planck mass, and Planck time. Participants explore whether these units represent ultimate limits for measurements and how they relate to physical quantities and dimensional analysis.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions if the smallest distance that can be moved is one Planck length, suggesting that there may be no such thing as moving half a Planck length.
  • Another participant asserts that Planck units are useful for making equations clearer and are related to dimensional analysis, which can provide insights into problems like renormalization in quantum field theory.
  • A participant expresses uncertainty about the renormalization problem and summarizes their understanding of Planck units as being derived from natural phenomena, not necessarily indicating the smallest measurable units.
  • Another participant confirms the accuracy of the summary regarding Planck units and downplays the relevance of the renormalization issue.
  • Further numerical comparisons are made between the mass of a proton and the Planck mass, highlighting the significant difference in scale.

Areas of Agreement / Disagreement

Participants generally agree on the nature of Planck units as derived from natural phenomena, but there is no consensus on whether they represent ultimate limits for measurements. Some participants express uncertainty and differing interpretations regarding the implications of these units.

Contextual Notes

Participants note limitations in current measurement capabilities regarding Planck units, suggesting that many are too large or small for present instruments to accurately probe. There is also an acknowledgment of the complexity surrounding the renormalization problem without a resolution provided.

Tclack
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So, the three very small quantities:

Planck length
Planck mass
Planck time

Does the physical interpretation actually mean for example that when something moves, the smallest distance it can move is one Planck length, that there's no such thing as moving half a Planck length?
And further that all other lengths, masses and times are just integer multiples of their associated Planck units?

Am I understanding this correctly?

And if that interpretation is correct, this is proven? (i.e. tried through rigorous and exhaustive experimentation)
 
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Check out:
http://en.wikipedia.org/wiki/Planck_units

Its just units that make our equations cleaner an clearer.

It is however closely related to dimensional analysis which can tell us some profound insights.

The most profound I know of (it's just what I know of - others may know stuff that's even more profound) is the insight it gives to the renormalization problem and associated infinities that plagued QFT for quite a while until Wilson and others sorted it out:
http://arxiv.org/pdf/hep-th/0212049.pdf

It turns out the cause is a dimensional mismatch and a cutoff needed to be introduced to avoid it.

Thanks
Bill
 
Last edited:
I don't quite understand the paper about the renormalization problem.

From the wiki article, I've arrived at the following:

1. These Planck units are just units that are physically derived from small natural hapenstances. i.e. are not plagued by earthly or human units, like the light-year, kg, and second

2. This DOESN'T necessarily imply that it's the SMALLEST unit of x,y or z.

3. Most of these Planck units are either too large or small for present instruments to accurately probe to.

Is this accurate?
 
Tclack said:
Is this accurate?

Yea - looks about right.

Don't worry about the renormalisation thing - it was just an aside on how useful dimensional analysis is.

Thanks
Bill
 
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Further research (numbers obtained from wiki, take that as you wish)

Mass of a Proton 1.67262178 × 10-27 kg
Planck mass 2.17651(13)×10−8 kg

Clearly, the proton is much less massive than the Planck mass...

Thank you Bill for clarifying this for me. Too bad, it was a cool idea originally. But, I'm glad that I'm not going to go around spreading misinformation eventually looking like a fool in front of an actual expert.
 

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