# Is there any proof to show that gravity works at the Planck length?

Is there any experimental proof which shows that the force of gravity works at planck length? Has it been verified already? Is it verifiable?

Drakkith
Staff Emeritus
Nothing at the planck length is currently observable as far as I know. So I don't think any experiments have been set up in an attempt to test anything at that scale.

mitrasoumya
Do we even have the accuracy and precision to measure the force of gravity at atomic level? I would be actually really surprised if we do.

mitrasoumya
phinds
Gold Member
Is there any experimental proof which shows that the force of gravity works at planck length? Has it been verified already? Is it verifiable?
Plank length is approximately TWENTY ORDERS OF MAGNITUDE smaller than anything we can currently measure, so no. BUT ... there is nothing special about the plank length in that regard, any more than there's anything special about the meter or the foot.

TheOldFart, Tazerfish, mitrasoumya and 1 other person
Plank length is approximately TWENTY ORDERS OF MAGNITUDE smaller than anything we can currently measure, so no. BUT ... there is nothing special about the plank length in that regard, any more than there's anything special about the meter or the foot.
But how can we say that so confidently about something we haven't been able to measure as yet.

Because there is no reason to think that planck lenght is special. If there is no reason, why should we think it is special? There are other "planck units", like planck resistance, which I read here (didn't calculate it myself) is about 30 ohms. Why should we think it's special?

mitrasoumya
Because there is no reason to think that planck lenght is special. If there is no reason, why should we think it is special? There are other "planck units", like planck resistance, which I read here (didn't calculate it myself) is about 30 ohms. Why should we think it's special?
Plank length is the shortest meaningful distance and therefore it IS special.

Drakkith
Staff Emeritus
Plank length is the shortest meaningful distance and therefore it IS special.

That's only true for certain quantum theories of gravity. All of which are hypothetical and are not currently accepted as mainstream theories.

mitrasoumya
davenn
Gold Member
Plank length is the shortest meaningful distance and therefore it IS special.

you are giving it too much importance

you really need to listen to what the others are telling you

mitrasoumya
That's only true for certain quantum theories of gravity. All of which are hypothetical and are not currently accepted as mainstream theories.
But the "mainstream" is incomplete, and therefore leaves gaps that have to be filled by some or other hypothesis. The assumption that gravity acts at Planck length is still an assumption. And all assumptions tend to limit our imagination. The "obviousness" of objects falling down, the idea of absolute space and absolute time were all assumptions that have been proved wrong by proof.

Drakkith
Staff Emeritus
But the "mainstream" is incomplete, and therefore leaves gaps that have to be filled by some or other hypothesis.

And?

assumption that gravity acts at Planck length is still an assumption.

If it doesn't act at the Planck length, then how does it act at larger distances? All known fundamental forces become stronger at shorter distances. The idea that gravity acts at all lengths is far more than an assumption in my opinion.

OnlyMe and mitrasoumya
Staff Emeritus
you really need to listen to what the others are telling you

This.

If it were me, I'd learn what physics says before complaining that physicists are doing it wrong and limiting their imagination. Just sayin;.

Last edited:
mitrasoumya
All known fundamental forces become stronger at shorter distances.
Yes. And that implies that the force would become infinite at plank length!!! Which perhaps has no observational evidence.

Drakkith
Staff Emeritus
Yes. And that implies that the force would become infinite at plank length!!!

Please show or reference some calculations supporting this.

phinds
Gold Member
Yes. And that implies that the force would become infinite at plank length!!!
That's just ridiculous. The Plank Length is not zero, you know.

@mitrasoumya you really need to study some basics and not make statements that you can't back up.

From a simple Occam's Razor perspective, one should first assume the laws apply at all scales. Because otherwise you might as well start checking whether gravity works behind your house.

TheOldFart, Drakkith and sophiecentaur
The Plank Length is not zero.
It is 0.000000000000000000000000000000000016 m

So?

phinds
Gold Member
It is 0.000000000000000000000000000000000016 m
And yet you treated it like zero. Do you not see the contradiction?

PhysicsExplorer
No, nothing is observable at this scale, but some physicists think that gravity could be significant at the Planck scale, giving rise to fluctuations and possibly wormholes. There have been many attempts to understand what physics may be going on here, something I have taken interest in investigating myself.

For instance, there is possible a non-trivial relationship called a spacetime uncertainty in natural units c=1

$$\Delta x \Delta t \geq \ell^2_P$$

This is a non-commutation relationship between space and time - and while it is written like a spacetime uncertainty, it's actually just a reinterpretation of the length in which it takes to scatter particles.

$$\Delta x \approx \frac{1}{\Delta p}$$

Both quantum loop gravity and string theory predicts the relationship. The length on the right hand side of the inequality, refers to Planck spacetime.