5 ms·

In university I coded an N-body simulator and visualizer. This was back before when we had so many games that exist now. It taught me a lot about orbital mechan

by LASR 3y ago

In university I coded an N-body simulator and visualizer. This was back before when we had so many games that exist now. It taught me a lot about orbital mechanics. One realization I had was how orbits were fragile and how easily you could shift them with influence from very far away. Another realization- gravity is weak, but it decreases over a huge distance compared to other forces we normally experience in human scale.

jvanderbot 3y ago
Does gravity decrease more slowly than other forces, or is it so weak that the gravity sources we feel are enormous and therefore have long radii of non-negligible effect, or is it something else?
- o11c 3y ago
  Gravity doesn't cancel like the electromagnetic force, despite otherwise decreasing at the same rate. I've never heard an explanation of the strong or weak forces that I actually "get" enough to understand their distance effects.
  - mikeInAlaska 3y ago
    >I've never heard an explanation of the strong > or weak forces that I actually "get" I thought this was excellent (in all ways) but particularly for your question: https://www.youtube.com/watch?v=UYW1lKNVI90 https://www.youtube.com/watch?v=UYW1lKNVI90
    - o11c 3y ago
      In case anyone else wants to watch: the weak force isn't mentioned until just after the 45-minute mark. I haven't got to the strong force yet but it presumably follows. Edit: so for weak, I think I understand that "photons are massless, so are only subject to the inverse-square law; weak bosons have mass, so are also subject to decay". But that doesn't explain to this dummy how the strong force works, since gluons are also massless (... though mesons are not? but they're not fundamental).
- pdonis 3y ago
  Gravity and electromagnetism both obey inverse square laws, but electromagnetism is negligible on astronomical scales because positive and negative charges cancel so astronomical objects are electrically neutral (or close enough to it that electromagnetic effects are negligible). The strong and weak interactions are only significant on very short distance scales; from the standpoint of "force laws" you can think of them as having an exponential decay with distance that makes them drop off to essentially nothing by the time you get to distances much larger than the size of an atomic nucleus. (That's an oversimplification, but it's enough to see why you can ignore them on astronomical scales.)
  - zmgsabst 3y ago
    Is there somewhere that assesses the EM impact of things? As I understand it, planetary magnetic fields influence solar winds; stellar ones structures in the galaxy; etc. I’d really like to learn more (preferably, with numbers).
    - angiosperm 3y ago
      Astronomers, as a rule, detest all discussion of EM, often going so far as to label people who insist on discussing it cranks. There are exceptions, but also cranks. It can be hard for the public to tell them apart. Astronomers do not assist, perhaps for fear of being labeled cranks themselves.
      - zmgsabst 3y ago
        This has been a large frustration of mine: I know from talks that filaments[0], galactic lobes[1], structure of arms[2], etc relate to EM — but finding anything at the layperson level is basically impossible. Just short blog posts, but no real explanation of how this all relates or what drives it. Harumph, I say! [0] - https://www.livescience.com/radio-filaments-milky-way-center https://www.livescience.com/radio-filaments-milky-way-center [1] - https://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=10918 https://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=10918 [2] - https://blogs.nasa.gov/sofia/2022/04/05/make-no-bones-about-it-sofia-maps-the-first-magnetic-fields-of-a-galactic-bone-in-their-entirety/ https://blogs.nasa.gov/sofia/2022/04/05/make-no-bones-about-...

by LASR 3y ago

jvanderbot 3y ago

Does gravity decrease more slowly than other forces, or is it so weak that the gravity sources we feel are enormous and therefore have long radii of non-negligible effect, or is it something else?

o11c 3y ago
Gravity doesn't cancel like the electromagnetic force, despite otherwise decreasing at the same rate. I've never heard an explanation of the strong or weak forces that I actually "get" enough to understand their distance effects.
- mikeInAlaska 3y ago
  >I've never heard an explanation of the strong > or weak forces that I actually "get" I thought this was excellent (in all ways) but particularly for your question: https://www.youtube.com/watch?v=UYW1lKNVI90 https://www.youtube.com/watch?v=UYW1lKNVI90
  - o11c 3y ago
    In case anyone else wants to watch: the weak force isn't mentioned until just after the 45-minute mark. I haven't got to the strong force yet but it presumably follows. Edit: so for weak, I think I understand that "photons are massless, so are only subject to the inverse-square law; weak bosons have mass, so are also subject to decay". But that doesn't explain to this dummy how the strong force works, since gluons are also massless (... though mesons are not? but they're not fundamental).
pdonis 3y ago
Gravity and electromagnetism both obey inverse square laws, but electromagnetism is negligible on astronomical scales because positive and negative charges cancel so astronomical objects are electrically neutral (or close enough to it that electromagnetic effects are negligible). The strong and weak interactions are only significant on very short distance scales; from the standpoint of "force laws" you can think of them as having an exponential decay with distance that makes them drop off to essentially nothing by the time you get to distances much larger than the size of an atomic nucleus. (That's an oversimplification, but it's enough to see why you can ignore them on astronomical scales.)
- zmgsabst 3y ago
  Is there somewhere that assesses the EM impact of things? As I understand it, planetary magnetic fields influence solar winds; stellar ones structures in the galaxy; etc. I’d really like to learn more (preferably, with numbers).
  - angiosperm 3y ago
    Astronomers, as a rule, detest all discussion of EM, often going so far as to label people who insist on discussing it cranks. There are exceptions, but also cranks. It can be hard for the public to tell them apart. Astronomers do not assist, perhaps for fear of being labeled cranks themselves.
    - zmgsabst 3y ago
      This has been a large frustration of mine: I know from talks that filaments[0], galactic lobes[1], structure of arms[2], etc relate to EM — but finding anything at the layperson level is basically impossible. Just short blog posts, but no real explanation of how this all relates or what drives it. Harumph, I say! [0] - https://www.livescience.com/radio-filaments-milky-way-center https://www.livescience.com/radio-filaments-milky-way-center [1] - https://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=10918 https://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=10918 [2] - https://blogs.nasa.gov/sofia/2022/04/05/make-no-bones-about-it-sofia-maps-the-first-magnetic-fields-of-a-galactic-bone-in-their-entirety/ https://blogs.nasa.gov/sofia/2022/04/05/make-no-bones-about-...