Are Planck Units the Ultimate Limit for Measurements?

In summary, the Planck length, mass, and time are very small quantities that are derived from natural happenings and not affected by human units. They do not necessarily represent the smallest unit of length, mass, or time, and are currently too small for accurate measurement. The idea of using these units for all other lengths, masses, and times is proven through dimensional analysis, and has helped to solve the renormalization problem in quantum field theory. However, further research shows that the Planck mass is much larger than the mass of a proton, debunking the idea of it being the smallest unit of mass.
  • #1
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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  • #2
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:
  • #3
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?
 
  • #4
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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  • #5
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.
 

FAQ: Are Planck Units the Ultimate Limit for Measurements?

What are Planck units?

Planck units are a set of fundamental units of measurement used in physics. They are based on universal physical constants, such as the speed of light, the gravitational constant, and the reduced Planck constant.

Why are Planck units important?

Planck units are important because they allow scientists to express physical quantities in terms of fundamental constants, making it easier to compare and understand different physical phenomena. They also play a crucial role in theories of quantum gravity.

How were Planck units derived?

Planck units were derived by the German physicist Max Planck in 1899 as a way to connect classical mechanics with quantum mechanics. They are based on the principle that any physical quantity can be expressed as a combination of fundamental constants.

What are some common uses of Planck units?

Planck units are commonly used in theoretical physics and cosmology, particularly in studies related to black holes, quantum mechanics, and the early universe. They are also used in string theory and other areas of research involving quantum gravity.

Are Planck units universally accepted?

While Planck units are widely used in theoretical physics, they are not universally accepted by all scientists. Some argue that they are too arbitrary and lack a physical basis, while others see them as a useful tool for simplifying calculations and understanding the fundamental nature of the universe.

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