Is The Planck Length the smallest length possible?

[VictorMedvil]

So, I was wondering is the Planck length the smallest length possible for measurement in physics? Please give as much details as to why or why not.

 

[Dale]

The Planck length is not the smallest possible length. It is just the length scale where quantum gravitational effects are expected to be large.

 

[VictorMedvil]

The Planck length is not the smallest possible length. It is just the length scale where quantum gravitational effects are expected to be large.

Ah, Okay then is there a smallest length?

 

[Nugatory]

Ah, Okay then is there a smallest length?

There might be, but no sign of such a thing has appeared in any experiment we’ve been able to perform and nothing in any of our best theories (general relativity and quantum field theory) that such a thing must exist. So... we don’t know.

also try this Insights article: https://www.physicsforums.com/insights/hand-wavy-discussion-planck-length/

 

[VictorMedvil]

There might be, but no sign of such a thing has appeared in any experiment we’ve been able to perform and nothing in any of our best theories (general relativity and quantum field theory) that such a thing must exist. So... we don’t know.

also try this Insights article: https://www.physicsforums.com/insights/hand-wavy-discussion-planck-length/

The original question posed to me was the universe infinite, so I suppose a solid answer to that question, is I don't know then if there is no confirmed smallest length of space, thanks for your input guys.

 

[Nugatory]

there is no confirmed smallest length

There is no confirmed smallest length - we can be clear about that.
But there might be one that we just don't know about - we have not confirmed that there is not one.

 

[AdvaitDhingra]

This is an occasion where physics doesn’t allow something that mathematics does. For example, think about moving faster than the speed of light. On paper you could apply a force to a mass and accelerate it up and past the speed of light, but we know that in nature that just is not physically possible because the mass of the object (and thus, the energy needed to speed it up) goes towards infinity—both keep growing without any limit. So what we can do on paper, we can’t do in reality.

 

[weirdoguy]

On paper you could apply a force to a mass and accelerate it up and past the speed of ligh

Nonsense. Not in the framework of relativity.

but we know that in nature that just is not physically possible because the mass of the object (...) goes towards infinity

No, we do not know that: https://www.physicsforums.com/insights/what-is-relativistic-mass-and-why-it-is-not-used-much/

 

[VictorMedvil]

I guess it comes down to a thought experiment do you think something like a Tipler Cylinder(https://journals.aps.org/prd/abstract/10.1103/PhysRevD.9.2203) is possible without exotic matter that causality violations can happen with a finite length? If you think that something like that is possible with a finite length then space must be finite too, I would think since there would be a shifting of the null cones into the past CTC without a infinite length(http://cds.cern.ch/record/364418/files/9809037.pdf).
Steven Hawking certainly did not think Tipler Cylinders were possible without exotic matter or an infinite length(https://arxiv.org/pdf/gr-qc/0603045.pdf).

 

[AdvaitDhingra]

Nonsense. Not in the framework of relativity.

On paper means in Mathematics.No, we do not know that: https://www.physicsforums.com/insights/what-is-relativistic-mass-and-why-it-is-not-used-much/

I am referring to the Lorentz transformation. What I am trying to say is that some things are mathematically possible but not physically.

 

[weirdoguy]

On paper means in Mathematics.

There is no force and acceleration in mathematics. These are physical terms.

I am referring to the Lorentz transformation.

No you are not, you were talking about relativistic mass.

 

[berkeman]

Thread closed temporarily for Moderation...

 

[berkeman]

I guess it comes down to a thought experiment do you think something like a Tipler Cylinder(https://journals.aps.org/prd/abstract/10.1103/PhysRevD.9.2203) is possible without exotic matter that causality violations can happen with a finite length? If you think that something like that is possible with a finite length then space must be finite too, I would think since there would be a shifting of the null cones into the past CTC without a infinite length(http://cds.cern.ch/record/364418/files/9809037.pdf).
Steven Hawking certainly did not think Tipler Cylinders were possible without exotic matter or an infinite length(https://arxiv.org/pdf/gr-qc/0603045.pdf).

@VictorMedvil -- It's great that you are curious and want to learn. Please keep in mind that here at PF we are happy to answer questions and make suggestions of reading to do to learn more, but we do not allow personal speculation. So when asking questions, please be careful to avoid speculating and just ask questions to help you understand your reading better. Thanks.

Your original questions have been answered, so this thread will remain closed.

@AdvaitDhingra -- I've copied your New Member Introduction post here for the others to better understand your passion for learning. Keep up the good work!

How did you find PF?: I Googled "Physics Forums" and voilà!

Hi, my name is Advait Dhingra and I'm a 15-year-old high schooler from Germany.

I have been interested in Physics since I was 4 and I particularly like Quantum Physics, String Theory and Cosmology. I also like to code physics simulations and visualisations.

I've made a Muon simulation in C++, a Schrödinger Wavefunction and Amplitude visualizer and much more!

I plan on studying Physics and becoming a Physicist, if all goes well.

Feel free to contact me if you have any further questions!