The Discovery of Dynamics

What Hacker News says

1. MisterOctoberJun 2019
   Julian Barbour has what I consider to be a pretty well-reasoned notion a timeless universe composed of a large number of mathematical configuration spaces he calls "nows" -- i.e., it contains many states, but no objective notion of time -- outlined in his pop-sci book "The End of Time" [1999] and his website http://platonia.com/

   p.s. for the record, Barbour is no clown, but a serious cat -- he is also the guy that wrote "Absolute or Relative Motion / the Discovery of Dynamics" which is a bedrock treatise on Machian ideas in physics

   Show morethread
2. abecedariusOct 2018
   > Kepler first formulated his hypothesis: planets had elliptical orbits with two foci, and then set out to prove it mathematically.

   He didn't start with that hypothesis, he came to it after multiple tries at fitting other models like an equant (an offset circle with angular speed controlled from the opposite offset, which is actually a good first-order approximation to the Kepler-law motion at small eccentricity).

   > Only after repeating his procedures 70 times did he offset his computational errors. With a little less patience, he wouldn’t have proved his theory, and elliptical orbits would have eluded us for longer.

   I skimmed the paper, and it seems to be about Kepler fitting an equant instead of an ellipse. Apparently he used an iterative method, stopping after 70 iterations? And his numerical errors seem to be responsible for it not converging faster. That makes more sense to me than my misunderstanding that you were saying he ran through the whole calculation from the start 70 times. I jumped to a conclusion about that part, and I'm sorry.

   Julian Barbour's The Discovery of Dynamics explains what Kepler did in detail (it's not the whole topic of the book, but a big chunk of it). A great book -- I didn't really appreciate Kepler before reading it. Both brilliant and very human.

   Show morethread
3. abecedariusJan 2016
   Julian Barbour's The Discovery of Dynamics goes into great detail on absolute vs. relative pre-Einstein. His The End of Time reviews the ideas at a more popular level and continues the story into the 20th C.
   thread
4. abecedariusNov 2015
   The Discovery of Dynamics by Julian Barbour explains Kepler's work on Mars with enough technical detail and historical context that it made me think: holy crap, Kepler was a genius, or very lucky in some of his inspirations, like the guess that led to the equal-area law (it was meant at first to be an easier-to-compute approximation to another idea); along with the mathematical talent he worked really hard and earned that luck; and nobody else seemed to be thinking about the problems in the same way leading to Kepler's laws. I'd guess they'd have taken decades more without him, and appeared in stages.

   Of course his work was not done in a vacuum.

   Show morethread
5. MisterOctoberMay 2018
   A couple things I note :

   1) Lightman's description of his hallucinationish experience at the age of nine, wherein he perceived all time in one instant [or had the sensation of doing so], reminds me of Julian Barbour ["The Discovery of Dynamics"] and his hypothesis that all spacetime exists simultaneously -- not in a Minkowski-eque 'loaf,' but in a static collection of mathematical configuration spaces, each of which represent a "now" [which word, coincidentally, concludes Lightman's article].

   2) I can relate to Lightman's notion of 'Nothingness' as it relates to quantum field theory -- when I first cracked Tony Zee's "QFT in a Nutshell," I'm pretty sure I experienced the same feeling of complete inconsequentiality described by Lightman, though for totally different reasons.

   Show morethread