5 ms·

I may be missing something here, but there's a conceptual leap from "the acceleration produced by gravitational force" to "gravity as a form of acceleration".

• red_trumpet 4y ago
  Well, thinking of gravity as a force is Newtonian mechanics, which was also not available to da Vinci.
  • globuous 4y ago
    Which was in itself the genius of this newton guy. It’s one thing to realise that objects falling accelerate. It’s another to realise that F=ma, and that this can model objects falling as well as a bunch of other things. Surely da Vinci wasn’t lucky enough to have an apple fall on his head ? :)
• codethief 4y ago
  > "gravity as a form of acceleration". […] The latter was Einstein's great insight. […] equating gravity and acceleration in the way Einstein did This sounds like a gross misinterpretation of what Einstein said. Einstein's great insight was that gravity defines inertial (i.e. non-accelerated) frames of reference. Put differently, in free fall you are not in an accelerated frame, despite what an outside observer on the surface of Earth might say. This is commonly abbreviated by "All massive bodies follow the same (inertial) trajectories in the presence of gravity, irrespective of their constitution", which is the Equivalence Principle. What you are maybe referring to is what an observer experiences who stands still on the surface of a massive body: They can't free-fall, and so they're not in an inertial frame (= the thing defined by gravity) and thus actually accelerate upwards from the point of view of spacetime.
  • n4r9 4y ago
    I'm probably missing some of the nuances, but I'm referring generally to the Equivalence Principle, described by Einstein as: > we ... assume the complete physical equivalence of a gravitational field and a corresponding acceleration of the reference system
    • codethief 4y ago
      I see. Personally, the way I have always interpreted that quote is that here, in this particular case, "gravitational field" is supposed to mean "someone standing on the surface of Earth, experiencing gravity" or, more generally, "an observer in a spacetime who's not in free fall / not moving along a geodesic" (but e.g. standing on the surface of a massive body). Otherwise, as outlined in my previous comment, it does not make any sense.
• coldtea 4y ago
  >I don't see much in the article to persuade me that da Vinci was equating gravity and acceleration in the way Einstein did Thinking of the effect on speed of things falling down as acceleration (as opposed to constant), and even coming up with a formula, is already a bridge between these two things.
  • Gregaros 4y ago
    No, it is not at all a bridge to Einstein’s ‘gravity and acceleration are equal’, which is "the gravitational force is physically indistinguishable from any acceleration", which has to do with changing to relatively accelerating reference frames. The insight of da Vinci’s here is anticipating Newton, not Einstein. And yes, this is already an accomplishment, but not the outlandish one the article would imply.
    • coldtea 4y ago
      Hence "a bridge". It's not Einstein's result, but it's moving towards Netwon (and eventually that) from older ideas about the behavior of things "falling" (such as proportional to their weight and constant speed).
• mannykannot 4y ago
  Indeed; this seems to be an extreme example of what might be called the "whig history of science", which interprets the past in the light of what we know today, attributing, to historical figures, modern concepts which they surely never even conceived of, and which would undoubtedly baffle them until they had been brought up-to-date with current knowledge. https://en.wikipedia.org/wiki/Whig_history https://en.wikipedia.org/wiki/Whig_history
  • vhasus 4y ago
    TIL: thank you
  • valvar 4y ago
    > attributing, to historical figures, modern concepts which they surely never even conceived of, and which would undoubtedly baffle them until they had been brought up-to-date with current knowledge. I don't think that's quite what Whig history is. The Wikipedia article doesn't seem to imply that, either. If there was a "Tory history", I think this case would be more like that, as it presents a past figure as being more enlightened (while Whig history typically does the opposite in order to extol progress).
    • poiuyt098 4y ago
      https://en.wikipedia.org/wiki/Precursorism https://en.wikipedia.org/wiki/Precursorism states it more clearly "... a characteristic of that kind of historical writing in which the author seeks antecedents of present-day institutions or ideas in earlier historical periods. This kind of anachronism is considered to be a form of Whig history ..."
      • dragonwriter 4y ago
        Except in the rare case where a new idea emerges and is introduced fully formed in its final stage, there are precursors of present-day institutions and ideas in earlier historical periods so seeking them would just be normal history.
• photochemsyn 4y ago
  Someone has already incorporated this into the wiki entry for historical development of gravitational theory, which may or may not be entirely justified: https://en.wikipedia.org/wiki/History_of_gravitational_theory https://en.wikipedia.org/wiki/History_of_gravitational_theor... That's an interesting article, including some challenges to Aristotle's views and gravity-related concepts introduced by Indian and Islamic scholars of the 6th - 12th century eras or so.
  • wolverine876 4y ago
    > Someone has already incorporated this into the wiki entry for historical development of gravitational theory, which may or may not be entirely justified: > https://en.wikipedia.org/wiki/History_of_gravitational_theor https://en.wikipedia.org/wiki/History_of_gravitational_theor... Isn't that a core problem with Wikipedia? I don't understand why its reputation on HN improved, a few years ago, from 'infotainment but a symbol of mis-/disinformation' to 'source of truth'.
• razor_router 4y ago
  agreed, there's no evidence is there that suggests Da Vinci was equating gravity and acceleration in a similar way to Einstein
• hummus_bae 4y ago
  Early on in my physics career, my supervisor asked me to keep in mind “it’s about speed, not velocity” when doing calculations. In general a force is a change in momentum, i.e. a change in speed. Acceleration is a change in speed relative to some frame. It’s quite possible that da Vinci may unknowingly have seen gravity as an acceleration (as in my example above) and taken the next step to seeing it as a change in speed.
• lamontcg 4y ago
  Yeah, this is just high school Newtonian physics where we should have all learned the concept of gravitational acceleration.