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So he says that heavier objects fall faster than light ones and size is irrelevant? (at least as far as I understand)
This brings 2 easy ways to see the error of this.

1) throw a big rock and a small one

2) thought experiment 2 weights connected by a thin piece of material the moment that thin piece of material snaps the 2 objects begin falling at half the rate they used to

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    $\begingroup$ Possible duplicate of Was Aristotle really wrong about gravity? $\endgroup$ – Conifold Sep 2 '18 at 23:41
  • $\begingroup$ The difference for rocks could be dismissed as not noticeable over short heights, tall towers weren't common and neither was staging experiments. But the difference between rock and feather was a commonplace observation. The thought experiment is due to Galileo, you are unlikely to have come up with it if you did not hear about it somewhere. It is also not clear cut, see Is Galileo's argument about falling bodies logically flawed? $\endgroup$ – Conifold Sep 2 '18 at 23:49
  • $\begingroup$ I came up with this argument by myself I don't see why it's hard seriously this seems easier than zeno's paradoxs Even holding 2 rocks at shoulder height it seems this is so obviously false so idk $\endgroup$ – Hao S Sep 3 '18 at 1:28
  • $\begingroup$ Hao, I challenge you to "prove" equal fall time from shoulder height, given a lack of ability to verify equal start (release) time or to measure impact time to sufficient accuracy and precision. Recall there were no clocks, let alone digital timers, back then. $\endgroup$ – Carl Witthoft Sep 4 '18 at 12:36
  • $\begingroup$ My understanding is that Aristotle said direct proportion? That is double weight double speed? sure I can't say exactly same speed but shoulder should give like no more than say 10% for say 4 times weight just by inspection $\endgroup$ – Hao S Sep 4 '18 at 14:59
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The assumption that people believed Aristotle’s law for so long is highly questionable.

Aristotle’s law occurs in a philosophical context. He introduces it in order to argue that there can be no such thing as an object of infinite weight. It was not intended as a starting point for quantitative science, nor did many readers take it as such. Insofar as people “believed” Aristotle’s law, they did so largely as a by-product of accepting Aristotle’s system as a whole on philosophical grounds that had next to nothing to do with quantitative science.

There is no evidence that any mathematical scientist in antiquity accepted Aristotle’s law, and quite some evidence to the contrary. Both Strato and Hipparchus wrote treatises on falling bodies that are now lost. By all indications they did not follow Aristotle’s law. Philoponus (in his commentary on Aristotle) used the experiment (1) you mention to reject Aristotle’s law of fall more than a thousand years before Galileo. Still earlier, Lucretius clearly stated that, in the absence of air resistance, all objects fall at the same speed regardless of weight (De rerum natura, II:225–239).

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  • $\begingroup$ but what was the point of Galileos experiment of dropping 2 balls then? $\endgroup$ – Hao S Sep 3 '18 at 21:35
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    $\begingroup$ @HaoSun The experiment is fine physics in itself, regardless of Aristotle. One does not need to pretend that “everybody” was wrong in order for this to be a meaningful experiment. $\endgroup$ – Viktor Blasjo Sep 4 '18 at 7:08

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