# What happens to a force too small to interact with anything? **URL:** \ **Category:** Factual Questions\ **Created:** [December 10, 2021, 7:27pm UTC](https://boards.straightdope.com/t/what-happens-to-a-force-too-small-to-interact-with-anything/955849 "2021-12-10T19:27:10Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [December 10, 2021, 7:27pm UTC](https://boards.straightdope.com/t/what-happens-to-a-force-too-small-to-interact-with-anything/955849/1 "2021-12-10T19:27:10Z")
Gravity’s simplified mathematical formula would seem to indicate as long as the distance between the 2 bodies is finite, there will be some force from gravity. What happens if those distances get very far apart, is there a point where units like plank length/time make any force still acting so small it becomes impossible to act. ---
**Author:** ![Babale](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/babale/32/15666_2.png) [@Babale](https://boards.straightdope.com/u/Babale)\ **Post date:** [December 10, 2021, 8:10pm UTC](https://boards.straightdope.com/t/what-happens-to-a-force-too-small-to-interact-with-anything/955849/2 "2021-12-10T20:10:01Z")
At some point the expansion of the universe is pushing the two objects apart faster than gravity can pull them together, but I’m not sure if that’s what you’re asking about. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [December 10, 2021, 9:45pm UTC](https://boards.straightdope.com/t/what-happens-to-a-force-too-small-to-interact-with-anything/955849/3 "2021-12-10T21:45:40Z")
The answer to any question involving Planck lengths is “We don’t know”. Everything anyone’s ever told you about the Planck length is a guess. For starters, it’s not known to be the smallest possible distance. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [December 10, 2021, 10:59pm UTC](https://boards.straightdope.com/t/what-happens-to-a-force-too-small-to-interact-with-anything/955849/4 "2021-12-10T22:59:19Z")
Most physicists _presume_ that gravity must be quantized like other forces, and that quantum field theory must somehow be extended to encompass gravitation, i.e. the realm of (classical) General Relativity. [Quantum gravity - Wikipedia](https://en.wikipedia.org/wiki/Quantum_gravity) The big problem is that gravity is not amenable to experiment. The gravitational force is very weak, and where it does reaches such extremes that classical General Relativity might break down, it’s hidden from us inside black holes. So not only do we not yet have a coherent theory, we don’t yet have any idea what testable predictions such a theory could make. So far as I’m aware, we cannot yet even prove that gravity _is_ quantized, but there are some ideas in this article. [https://www.quantamagazine.org/physicists-find-a-way-to-see-the-grin-of-quantum-gravity-20180306/](https://www.quantamagazine.org/physicists-find-a-way-to-see-the-grin-of-quantum-gravity-20180306/) > The proposed experiment will determine whether two objects — Bose’s group plans to use a pair of microdiamonds — can become quantum-mechanically entangled with each other through their mutual gravitational attraction…The authors argue that the two objects in their proposed experiment can become entangled with each other in this way only if the force that acts between them — in this case, gravity — is a quantum interaction, mediated by gravitons that can maintain quantum superpositions. “If you can do the experiment and you get entanglement, then according to those papers, you have to conclude that gravity is quantized”… The article also mentions some famous names who dissent from the consensus that gravity is quantized, including Dyson & Penrose. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [December 11, 2021, 12:28am UTC](https://boards.straightdope.com/t/what-happens-to-a-force-too-small-to-interact-with-anything/955849/5 "2021-12-11T00:28:55Z")
> [@Chronos](#): > > For starters, it’s not known to be the smallest possible distance. Does that mean it is [turtles all the way down?](https://en.wikipedia.org/wiki/Turtles_all_the_way_down) ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [December 11, 2021, 8:30pm UTC](https://boards.straightdope.com/t/what-happens-to-a-force-too-small-to-interact-with-anything/955849/6 "2021-12-11T20:30:04Z")
I’ve posted this before, but… Our best theories of gravity and our best theories of quantum mechanics are inconsistent. We can’t get away with saying that they apply in different regimes, because situations could exist where both are relevant (a very small black hole, for instance). So clearly, at least one of our best theories of gravity or our best theories of quantum mechanics (or, quite possibly, both) must be incomplete. One possible extension would be for gravity to be quantized. Most physicists strongly suspect that this is true, but we can’t be sure. If gravity is quantized, then it might mean that spacetime is also quantized. Or maybe not., because we have almost no idea about how it’s quantized. If spacetime is quantized, then it might be quantized in such a way that there exists a smallest possible distance, and/or a smallest possible time. But there are forms of quantization which don’t involve minimum possible quantities. If spacetime has a minimum possible distance and/or time, then that distance or time is smaller than anything we’ve been able to experimentally probe, but we don’t know any further than that what it might be. If one were to guess at the minimum distance and/or time, one might guess that that minimum might be somewhere in the vicinity of the Planck quantities, as those are derived from physical constants relevant to gravity and quantum mechanics. Even if there exists a minimum distance and it is in the vicinity of the Planck distance, nobody would be at all surprised if it turned out to be half the Planck distance, or pi times the Planck distance, or something like that. There are an awful lot of "if"s before you get to the statement “The Planck distance is the smallest possible distance”. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [December 11, 2021, 8:45pm UTC](https://boards.straightdope.com/t/what-happens-to-a-force-too-small-to-interact-with-anything/955849/7 "2021-12-11T20:45:06Z")
Oh, one other point: One can define a “Planck acceleration”, just as one can for any other dimension of quantity. But the Planck acceleration would be absolutely ludicrously mind-bogglingly huge. So we can’t just say “but what about forces so weak that they can’t even produce a Planck acceleration”, because all forces are that weak. Planck distance: Really, really small. Maybe (or maybe not) the smallest distance possible. Planck time: Really, really small. Maybe (or maybe not) the smallest time possible. Planck speed: Very large, but well-understood. According to all of our theories, the largest speed possible. Also known as the speed of light. Planck acceleration: Ludicrously large, and likely not relevant to anything. Planck mass: Very big by the standards of fundamental particles, but very small by human standards. About the mass of a bacterium. Planck momentum: Reasonable by human standards, but very very big by the standards of fundamental particles. About the momentum of a running housecat. Planck energy: Reasonable by human standards, but very very big by the standards of fundamental particles. About the energy content of a car’s gas tank. Planck temperature: Very, very large by any standard. Maybe (or maybe not) the highest temperature possible. ---
**Author:** ![Novelty\_Bobble](https://avatars.discourse-cdn.com/v4/letter/n/a3d4f5/32.png) [@Novelty\_Bobble](https://boards.straightdope.com/u/Novelty_Bobble)\ **Post date:** [December 11, 2021, 10:29pm UTC](https://boards.straightdope.com/t/what-happens-to-a-force-too-small-to-interact-with-anything/955849/8 "2021-12-11T22:29:43Z")
If it doesn’t interract with _anything_ in what way is it a force at all? ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [December 12, 2021, 8:07am UTC](https://boards.straightdope.com/t/what-happens-to-a-force-too-small-to-interact-with-anything/955849/9 "2021-12-12T08:07:19Z")
Isn’t the Planck length based on the speed of light and isn’t the speed of light a fundamental constant in our universe? How do you get smaller than that without pure conjecture? (as in, breaking the speed of light) ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [December 12, 2021, 10:22am UTC](https://boards.straightdope.com/t/what-happens-to-a-force-too-small-to-interact-with-anything/955849/10 "2021-12-12T10:22:12Z")
Speed of light, gravitational constant and Plank’s constant al go into the Plank Length. Sure, they are all fundamental constants, but why does the derivation of a length from them instantly get you a smallest possible length. As **Chronos** points out above, many of the other Plank values have values all over the place. If my house critter running for his dinner is the Plank momentum, there is nothing to suggest that this is a fundamental limit in any manner. The speed of causality is a fundamental thing, as relativity suggests that we travel through spacetime at c, and that never changes. There are no other speeds. Just different worldlines in spacetime. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [December 12, 2021, 2:22pm UTC](https://boards.straightdope.com/t/what-happens-to-a-force-too-small-to-interact-with-anything/955849/11 "2021-12-12T14:22:03Z")
> [@Novelty\_Bobble](#): > > If it doesn’t interract with _anything_ in what way is it a force at all? IDK. Perhaps probability would come in that if it’s impossible for this force to move this object due to the limit of distances, it still many have a probability of moving it, quantum theory and the like. Or, more likely, I’m totally off base here. Either way I guess I’m right 🙂 ---
**Author:** ![Novelty\_Bobble](https://avatars.discourse-cdn.com/v4/letter/n/a3d4f5/32.png) [@Novelty\_Bobble](https://boards.straightdope.com/u/Novelty_Bobble)\ **Post date:** [December 12, 2021, 2:41pm UTC](https://boards.straightdope.com/t/what-happens-to-a-force-too-small-to-interact-with-anything/955849/12 "2021-12-12T14:41:34Z")
> [@kanicbird](#): > > IDK. Perhaps probability would come in that if it’s impossible for this force to move this object due to the limit of distances, it still many have a probability of moving it, quantum theory and the like. Or, more likely, I’m totally off base here. Either way I guess I’m right 🙂 I guess I wondering how you define a force unless it is with respect to its interaction with something else. So if it is no able to do so, then does it actually exist.