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Physics noob question: is there any physical framework that does away with the concept of "force"? I know a bit about how it is reconceptualized as space-time

Physics noob question: is there any physical framework that does away with the concept of "force"? I know a bit about how it is reconceptualized as space-time deformation in the context of general relativity, but that's about it. It just seems like one of those inherently anthropocentric concepts that (potentially) holds us back from exploring something different?

outworlder 6y ago
> It just seems like one of those inherently anthropocentric concepts that (potentially) holds us back from exploring something different? This is something I struggle with. I know that physics originated from an experimental framework. We observe phenomena, then we try to come up with explanations for said phenomena, formulate hypothesis, then test them. That is fine. But this breaks down when the 'fundamental forces' are involved. What _is_ a force? All the explanations I've ever seen (apart from gravity) seem to treat a 'force' as an atomic concept. They will describe what a force 'does', but not what it 'is'. Maybe that's something unknowable, but it bothers me. F* magnets, how do they work.
- l33tman 6y ago
  At its essence, in the modern understanding, a force is an emergent phenomena arising out of the fact that a world (a spacetime filled with your particles) where two particles of opposite charge seem to move towards each other is more probable than a world where they don't. This sounds silly but it's exactly the root cause in the current understanding and shoehorning in the word "force" in "force-carrying particles" is a stretch and causes this confusion. It's true that there would be no electromagnetic force without the photons. But photons and their likes are not the only way a "force" arises. For example, the Pauli exclusion principle can be seen as a "force" and it arises without photons with just electrons.
- alexlarsson 6y ago
  From feynman: https://www.youtube.com/watch?v=MO0r930Sn_8 https://www.youtube.com/watch?v=MO0r930Sn_8
BlueTemplar 6y ago
Somewhat tangential, but Newton has been made fun of because he suggested the apparently "magical" idea that forces could act at a distance...
ajkjk 6y ago
Yes, very much so. Forces are not really a thing in the Standard Model. There are symmetry groups attached to spacetime which lead to exchanges of gauge bosons which 'create' forces.
- dogma1138 6y ago
  Aren’t forces in the standard model just fields which their quanta is gauge bosons (force carrying particles)?
  - ajkjk 6y ago
    Well yes. I would say it as: forces correspond to the bosonic fields (except perhaps the Higgs, not sure if that can be regarded as a force), which do not 'take up space' as fermionic fields do. But the point I was making is just that modern physics has already done away with the concept of Force, as in, things pushing each other from afar. It is quite a bit more complicated (and yet more elegant) than that.
BlueTemplar 6y ago
I'd have to brush up on my quantum mechanics, but IIRC they don't have the concept of "force" ? (F=ma being replaced by Schrodinger's equation.)
dkersten 6y ago
Isn't quantum field theory kinda like that in that "forces" are actually just the effects of the fields interacting? (Not a physicist, so...)
dogma1138 6y ago
Gravity isn’t a force in general relativity. However other forces such as the strong nuclear and the electroweak are forces in theories such as the standard model. Grand Unification theories often are trying to turn gravity into a force this is where mediating particles such as the graviton come into play but these aren’t very successful yet. It may be that gravity isn’t a force at all and is just an emergent phenomenon from the geometric properties of space time, or it could be both basically two distinct phenomena that cause attraction between massive objects where on a larger scale it’s primarily dominated by the geometry of space time and on the quantum scales by a mediated force with its own field and quanta (particles).
- jessermeyer 6y ago
  > Gravity isn’t a force in general relativity. More importantly, GR has nothing to say about forces at all.
chriswarbo 6y ago
Lagrangian mechanics is equivalent to Newtonian mechanics, but doesn't involve force https://en.wikipedia.org/wiki/Lagrangian_mechanics https://en.wikipedia.org/wiki/Lagrangian_mechanics The idea of replacing a 'gravitational force' with spacetime curvature gave us General Relativity; extending this same idea to electromagnetism gives us Kaluza-Klein theory https://en.wikipedia.org/wiki/Kaluza%E2%80%93Klein_theory https://en.wikipedia.org/wiki/Kaluza%E2%80%93Klein_theory The current state of the art is Quantum Field Theory (of which the Standard Model is an example) https://en.wikipedia.org/wiki/Quantum_field_theory https://en.wikipedia.org/wiki/Quantum_field_theory In QFT, "particles" and "forces" are emergent phenomena (waves of excitation in the underlying fields, and the couplings/interactions/symmetries of those fields). QFT tends to be modelled using Lagrangian mechanics too.
- hinkley 6y ago
  I still need someone to ELI5 to me how space curvature model explains the attraction between two bodies that have a delta-v of 0.
  - zcrackerz 6y ago
    Think of your velocity vector as having a time component. The magnitude of this vector is c, so when you are at rest, you're moving full speed through time. When you accelerate, you shift some of this speed into the spatial dimensions. This is also why time passes more slowly for moving objects. Gravity also has this effect because not only is space curved, but space-time is curved. This means what would normally be a straight path through time is partially warped into the spatial dimensions when you encounter such a curvature.
  - stan_rogers 6y ago
    They don't. You're only thinking in three (spatial) dimensions. Time is more fundamental than you think.
  - Andrew_nenakhov 6y ago
    Imagine a 2d sheet that is weiged by steel balls. It'll be curved because of weights. Now, put a sand on it and it'll start rolling according to sheet's curvature. That's attraction between bodies for you.
fctorial 6y ago
string theory?
alephu5 6y ago
It's a good question. One thing you find in modern physics is that ideas are often named according to some mathematical analogue to classical physics. You start thinking about forces by imagining a ball being kicked, and after boiling away the conceptual baggage you realise it's all about the exchange of energy. It turns out that energy exchange is one of the most fundamental mechanisms that drives nature so it makes sense that this same mathematics appears in deeper theories. Unlike classical physics the symbols in quantum equations don't represent simple numbers, they're usually quite complicated and subtle actually but remarkably these equations share many properties with their classical counterparts. To be fair this could just be that phenomena that differ completely from classical physics are incomprehensible to us. So an electron "spin", at least mathematically, is governed by equations that are remarkable similar to classical equations of angular momentum and so on. Force is in the same category and really just means "fundamental interaction".
andi999 6y ago
Why is it an anthropocentric concept, did you never place anything on a scale? Or have a wire rip from a weight hanging on it?
- davidivadavid 6y ago
  Of course. The point is that interpreting that as a "force" is anthropomorphization ("this physical thing is "pushing"/"pulling" this").

outworlder 6y ago

> It just seems like one of those inherently anthropocentric concepts that (potentially) holds us back from exploring something different? This is something I struggle with. I know that physics originated from an experimental framework. We observe phenomena, then we try to come up with explanations for said phenomena, formulate hypothesis, then test them. That is fine. But this breaks down when the 'fundamental forces' are involved. What _is_ a force? All the explanations I've ever seen (apart from gravity) seem to treat a 'force' as an atomic concept. They will describe what a force 'does', but not what it 'is'. Maybe that's something unknowable, but it bothers me. F* magnets, how do they work.

l33tman 6y ago
At its essence, in the modern understanding, a force is an emergent phenomena arising out of the fact that a world (a spacetime filled with your particles) where two particles of opposite charge seem to move towards each other is more probable than a world where they don't. This sounds silly but it's exactly the root cause in the current understanding and shoehorning in the word "force" in "force-carrying particles" is a stretch and causes this confusion. It's true that there would be no electromagnetic force without the photons. But photons and their likes are not the only way a "force" arises. For example, the Pauli exclusion principle can be seen as a "force" and it arises without photons with just electrons.
alexlarsson 6y ago
From feynman: https://www.youtube.com/watch?v=MO0r930Sn_8 https://www.youtube.com/watch?v=MO0r930Sn_8

BlueTemplar 6y ago

Somewhat tangential, but Newton has been made fun of because he suggested the apparently "magical" idea that forces could act at a distance...

ajkjk 6y ago

Yes, very much so. Forces are not really a thing in the Standard Model. There are symmetry groups attached to spacetime which lead to exchanges of gauge bosons which 'create' forces.

dogma1138 6y ago
Aren’t forces in the standard model just fields which their quanta is gauge bosons (force carrying particles)?
- ajkjk 6y ago
  Well yes. I would say it as: forces correspond to the bosonic fields (except perhaps the Higgs, not sure if that can be regarded as a force), which do not 'take up space' as fermionic fields do. But the point I was making is just that modern physics has already done away with the concept of Force, as in, things pushing each other from afar. It is quite a bit more complicated (and yet more elegant) than that.

BlueTemplar 6y ago

I'd have to brush up on my quantum mechanics, but IIRC they don't have the concept of "force" ? (F=ma being replaced by Schrodinger's equation.)

dkersten 6y ago

Isn't quantum field theory kinda like that in that "forces" are actually just the effects of the fields interacting? (Not a physicist, so...)

dogma1138 6y ago

Gravity isn’t a force in general relativity. However other forces such as the strong nuclear and the electroweak are forces in theories such as the standard model. Grand Unification theories often are trying to turn gravity into a force this is where mediating particles such as the graviton come into play but these aren’t very successful yet. It may be that gravity isn’t a force at all and is just an emergent phenomenon from the geometric properties of space time, or it could be both basically two distinct phenomena that cause attraction between massive objects where on a larger scale it’s primarily dominated by the geometry of space time and on the quantum scales by a mediated force with its own field and quanta (particles).

jessermeyer 6y ago
> Gravity isn’t a force in general relativity. More importantly, GR has nothing to say about forces at all.

chriswarbo 6y ago

Lagrangian mechanics is equivalent to Newtonian mechanics, but doesn't involve force https://en.wikipedia.org/wiki/Lagrangian_mechanics https://en.wikipedia.org/wiki/Lagrangian_mechanics The idea of replacing a 'gravitational force' with spacetime curvature gave us General Relativity; extending this same idea to electromagnetism gives us Kaluza-Klein theory https://en.wikipedia.org/wiki/Kaluza%E2%80%93Klein_theory https://en.wikipedia.org/wiki/Kaluza%E2%80%93Klein_theory The current state of the art is Quantum Field Theory (of which the Standard Model is an example) https://en.wikipedia.org/wiki/Quantum_field_theory https://en.wikipedia.org/wiki/Quantum_field_theory In QFT, "particles" and "forces" are emergent phenomena (waves of excitation in the underlying fields, and the couplings/interactions/symmetries of those fields). QFT tends to be modelled using Lagrangian mechanics too.

hinkley 6y ago
I still need someone to ELI5 to me how space curvature model explains the attraction between two bodies that have a delta-v of 0.
- zcrackerz 6y ago
  Think of your velocity vector as having a time component. The magnitude of this vector is c, so when you are at rest, you're moving full speed through time. When you accelerate, you shift some of this speed into the spatial dimensions. This is also why time passes more slowly for moving objects. Gravity also has this effect because not only is space curved, but space-time is curved. This means what would normally be a straight path through time is partially warped into the spatial dimensions when you encounter such a curvature.
- stan_rogers 6y ago
  They don't. You're only thinking in three (spatial) dimensions. Time is more fundamental than you think.
- Andrew_nenakhov 6y ago
  Imagine a 2d sheet that is weiged by steel balls. It'll be curved because of weights. Now, put a sand on it and it'll start rolling according to sheet's curvature. That's attraction between bodies for you.

fctorial 6y ago

string theory?

alephu5 6y ago

It's a good question. One thing you find in modern physics is that ideas are often named according to some mathematical analogue to classical physics. You start thinking about forces by imagining a ball being kicked, and after boiling away the conceptual baggage you realise it's all about the exchange of energy. It turns out that energy exchange is one of the most fundamental mechanisms that drives nature so it makes sense that this same mathematics appears in deeper theories. Unlike classical physics the symbols in quantum equations don't represent simple numbers, they're usually quite complicated and subtle actually but remarkably these equations share many properties with their classical counterparts. To be fair this could just be that phenomena that differ completely from classical physics are incomprehensible to us. So an electron "spin", at least mathematically, is governed by equations that are remarkable similar to classical equations of angular momentum and so on. Force is in the same category and really just means "fundamental interaction".

andi999 6y ago

Why is it an anthropocentric concept, did you never place anything on a scale? Or have a wire rip from a weight hanging on it?

davidivadavid 6y ago
Of course. The point is that interpreting that as a "force" is anthropomorphization ("this physical thing is "pushing"/"pulling" this").