3 ms·

Isn’t Navier-Stokes smoothness just a reframing of the three-body problem? Karl Sundman solved that one in 1909, and n-body was generalized in 1990 by Qiudong W

Isn’t Navier-Stokes smoothness just a reframing of the three-body problem? Karl Sundman solved that one in 1909, and n-body was generalized in 1990 by Qiudong Wang. Edit- to answer my own question: http://www.scholarpedia.org/article/N-body_simulations_(gravitational)#Mean_Field_Approach:_analogies_and_differences_with_fluid_dynamics http://www.scholarpedia.org/article/N-body_simulations_(grav...

qubex 9y ago
I'm sorry if it seems I am persecuting you and putting all your ideas down, but I really don't see how this can be true either. The 3- or N-body problem is about point-particles interacting gravitationally at nonzero distance according to an inverse square law. Navier-Stokes is, at root and in the limit, about elastic collisions about infinitesimal corpuscles that transfer momentum between each other. Again, I can see the analogy “lots of things interacting”, but they have quite little in common beyond that.
- throwwit 9y ago
  Just the inverse n-vectors applied (regardless of space and field strength or possibly just instantaneous field strength). Always good to be called out tho.
  - qubex 9y ago
    I don't understand what the first sentence of your reply is supposed to mean, but the second sentence is a very mature response and belies your wisdom: yes, science and rational thinking is all about putting ideas out there and rejoicing when somebody helps you etch away at those that are not compatible with reality, so that only plausible ones remain.
    - throwwit 9y ago
      Well what I meant was shrinking the n body system to a point then extending that to a field. But it’s beyond me how the math works to invert those same force vectors to an impulse.
      - throwwit 9y ago
        Apologies if I’m cargo-culting math... just positing.
        qubex 9y ago
        https://xkcd.com/451/ https://xkcd.com/451/ ;)
      - qubex 9y ago
        Fluid dynamics and gravitation are not about the things that are interacting (of which there can be many in both cases) but in the forces that arise between these things, and the forces are profoundly different in both cases.

qubex 9y ago

I'm sorry if it seems I am persecuting you and putting all your ideas down, but I really don't see how this can be true either. The 3- or N-body problem is about point-particles interacting gravitationally at nonzero distance according to an inverse square law. Navier-Stokes is, at root and in the limit, about elastic collisions about infinitesimal corpuscles that transfer momentum between each other. Again, I can see the analogy “lots of things interacting”, but they have quite little in common beyond that.

throwwit 9y ago
Just the inverse n-vectors applied (regardless of space and field strength or possibly just instantaneous field strength). Always good to be called out tho.
- qubex 9y ago
  I don't understand what the first sentence of your reply is supposed to mean, but the second sentence is a very mature response and belies your wisdom: yes, science and rational thinking is all about putting ideas out there and rejoicing when somebody helps you etch away at those that are not compatible with reality, so that only plausible ones remain.
  - throwwit 9y ago
    Well what I meant was shrinking the n body system to a point then extending that to a field. But it’s beyond me how the math works to invert those same force vectors to an impulse.
    - throwwit 9y ago
      Apologies if I’m cargo-culting math... just positing.
      - qubex 9y ago
        https://xkcd.com/451/ https://xkcd.com/451/ ;)
    - qubex 9y ago
      Fluid dynamics and gravitation are not about the things that are interacting (of which there can be many in both cases) but in the forces that arise between these things, and the forces are profoundly different in both cases.