4,994
edits
Changes
Jump to navigation
Jump to search
Line 141:
Line 141: + + + + + + + + + + + + + + + +
→Galileo's experiments dropping objects?
: I believe that the story about Galileo dropping rocks from the leaning tower of Pisa is now regarded as false. I don't know why everyone attacks Aristotle so much on this point, because heavier objects really do fall faster when air resistance is considered. [[User:RSchlafly|RSchlafly]] 17:57, 5 May 2007 (EDT)
: I believe that the story about Galileo dropping rocks from the leaning tower of Pisa is now regarded as false. I don't know why everyone attacks Aristotle so much on this point, because heavier objects really do fall faster when air resistance is considered. [[User:RSchlafly|RSchlafly]] 17:57, 5 May 2007 (EDT)
::Galileo attacks Aristotle by saying that, if you drop two objects, one weighing a hundred times as much as the other, a hundred cubits, Aristotle predicts the heavy object will win by 99 cubits, Galileo predicts a tie, and the actual experiment show the heavy object wins by the breadth of two fingers. "You would not hide behind these two fingers the ninety-nine cubits of Aristotle." And that's fair. Galileo's physical model is a good approximation, Aristotle's isn't even close.
::I don't think it's that "everyone" attacks Aristotle. I think generations of oversimplified textbooks copying from each other have repeated Galileo's attack on Aristotle, who was simply wrong on this point. Galileo himself slightly messed up the square-cube relationship in his bone illustration, by the way... What most people think about this point is probably based on a few sentences from a junior-high-school science book, or maybe a teacher who was overdramatizing. It's sort of like "Columbus thought the world was round when everyone else thought it was flat."
::The story that the leaning tower of Pisa ''was the location'' is apocryphal. The question is, what's known about Galileo's actual experiments?
::If you read the text at the link above, it's clear that Aristotle couldn't have done any experiments or even been a very good observer.
::Aristotle's model seems to be one in which there is no inertia, objects experience a force of gravity in proportion to their size--they have ''weight,'' but no ''mass,'' and the speed of fall is governed by the interplay of weight and air resistance. This is seen clearly in the passage beginning "The second reason is this: all movement is either compulsory or according to nature...", "the medium causes a difference because it impedes the moving thing," "Similarly the void can bear no ratio to the full, and therefore neither can movement through the one to movement through the other, but if a thing moves through the thickest medium such and such a distance in such and such a time, it moves through the void with a speed beyond any ratio."
::Mind you, I don't really follow, but I think Aristotle is saying that there cannot be a vacuum, because if there were everything in it would move with infinite speed. Or perhaps he's saying everything in it would move with ''equal'' speed.
::Of course, it probably doesn't help that the translation of Aristotle I'm looking at seems to be literal, while the translation of Galileo is readable and may well be unconsciously informed by a modern understanding of physics.
::In any case, Galileo's writing shows a very good understanding of how air resistance fits in. Both of them are theorizing on what would happen in a vacuum. Galileo says everything would fall at the same, uniformly accelerated speed. Aristotle says everything would fall at infinite speed. Galileo "got'' inertia, Aristotle didn't. [[User:Dpbsmith|Dpbsmith]] 19:41, 5 May 2007 (EDT)
Hmmm, well, maybe scientists just like to get their formula's right before they go derive things from them?
Hmmm, well, maybe scientists just like to get their formula's right before they go derive things from them?
[[User:Middle Man|Middle Man]]
[[User:Middle Man|Middle Man]]