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Old 4th March 2019, 08:04 AM   #1
Robin
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Setting the record straight on Aristotle

It is a common myth that Galileo refuted Aristotle's claim that heavier things fall faster than lighter things. In fact the words the Galileo attributes to Aristotle are nowhere to be found in Aristotle's works.

Physicist Carlo Rovelli published a paper rehabilitating the physics of Aristotle which can be found here https://arxiv.org/pdf/1312.4057.pdf
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The bad reputation of Aristotle’s physics is undeserved, and leads to widespread ignorance: think for a moment, do you really believe that bodies of different weight fall at the same speed? Why don’t you just try: take a coin and piece of paper and let them fall. Do they fall at the same speed? Aristotle never claimed that bodies fall at different speed “if we take away the air”. He was interested in the speed of real bodies falling in our real world, where air or water is present. It is curious to read everywhere “Why didn’t Aristotle do the actual experiment?”. I would retort:
“Those writing this, why don’t they do the actual experiment?”. They would find Aristotle right.
In case you think he is being overly generous to Aristotle, here is part of "On the Heavens" where Aristotle is explicit that he is talking about an object going through a medium:
Quote:
But since here are two factors, the force responsible for the downward motion of the heavy body and the disruption-resisting force of the continuous surface, there must be some ratio between the two. For in proportion as the force applied by the heavy thing towards disruption and division exceeds that which resides in the continuum, the quicker will it force its way down;
Aristotle also mentions the shape as being a factor - that a round or needle shaped object will fall or sink faster than a flat object.

Still, Galileo did refute another claim of Aristotle, that of some objects possessing absolute levity, even proposing an experiment that Aristotle could have done. That is not so well known, possibly because it is a little more difficult to explain.
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Old 4th March 2019, 11:47 AM   #2
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'Robin':

Sorry but I am not really sure what you are driving at, because Aristotelian Physics did teach that if two objects were identically shaped, and both of them were falling through the same medium, then the heavier object would travel faster than the lighter object (see below).

However, Galileo showed that this thinking was quite incorrect.

https://en.wikipedia.org/wiki/Aristotelian_physics

Aristotelian physics

...

Aristotle proposed that the speed at which two identically shaped objects sink or fall is directly proportional to their weights and inversely proportional to the density of the medium through which they move. ...
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Old 4th March 2019, 12:14 PM   #3
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Quote:
Still, Galileo did refute another claim of Aristotle, that of some objects possessing absolute levity...

Like whoopee cushions?
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Old 4th March 2019, 12:57 PM   #4
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Actually, Aristotle was wrong all around. It's not that he isn't interested in what happens in a vacuum, it's that he actually makes several arguments against vacuum, one of them based on that flawed equation. Because it was inversely proportional to the density of the medium, in a vacuum things would fall infinitely fast, hence a vacuum is impossible. It seems to me like he was very much interested in a vacuum if he spent time disproving it.

It seems to me like pretty dumb revisionism to argue that, oh noes, he just wasn't interested in what happens in a void.

Anyway, let's look at what Aristotle himself wrote, as, you know, the definitive source of what he did write: http://www.filosofia.unimi.it/zucchi...%20Physics.pdf

Specifically, Book 4, chapter 8, which even starts with setting out to disprove the vacuum, and does exactly the argument I mentioned above.
We see the same weight or body moving faster than another for two reasons, either because there is a difference in what it moves through, as between water, air, and earth, or because, other things being equal, the moving body differs from the other owing to excess of weight or of lightness.
It take some mind contortions to NOT interpret the above as saying plainly that heavier things fall faster.
Let the speed have the same ratio to the speed, then, that air has to water. Then if air is twice as thin, the body will traverse B in twice the time that it does D, and the time C will be twice the time E.
That is flat out wrong.

But it gets better:
We see that bodies which have a greater impulse either of weight or of lightness, if they area like in other respects, move faster over an equal space, and in the ratio which their magnitudes bear to each other. Therefore, they will also move through the void with this ratio of speed.
This one EXPLICITLY not just says flat out that heavier things move faster than lighter things, but he tells you that the speeds are in the same ratio as the weights. It also spells it out that the same would apply in a void.

So, again, stating that oh noes, he just wasn't interested in what happens in a void, is just flat out wrong.

Etc.

And that's not Wikipedia or Galileo getting it wrong, it's the actual translation of what Aristotle wrote. If in doubt, go to the primary source and all that.


But basically on the whole I'm not impressed.

The best that can be said is that I can see how Aristotle would come to that conclusion, based on his everyday experiences and intuition. But that's literally in the same sense as I could see how Pixie Of Key would reject GR based on his everyday intuitions and half-understanding. It doesn't actually mean either are right.

But that's not the same as saying that Aristotle is vindicated. Understanding how he would come to a false conclusion is not the same as saying that he was right.

Physicists and generally nerds love to do this nonsense, in which they say stuff like that Democritus was vindicated, or Plato was vindicated, or Aristotle was vindicated, because they find one bit out of context in which their theories were kinda sorta less wrong than competing theories at the time. Or because they kinda sorta had one good observation in the heap of nonsense they wrote.

But it's important to note that at the end of the day all those were still wrong according to modern physics. They were less wrong than some other contemporary philosopher, but at the end of the day less wrong is still wrong.
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Old 4th March 2019, 01:13 PM   #5
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Galileo evolved evolved our knowledge of physics beyond that of Aristotle. That's how things go. Does it matter exactly how details were? The important difference is that Galileo based his deductions on experimental evidence. That is what showed the path to modern science.

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Old 4th March 2019, 07:03 PM   #6
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Originally Posted by Robin View Post
It is a common myth that Galileo refuted Aristotle's claim that heavier things fall faster than lighter things. In fact the words the Galileo attributes to Aristotle are nowhere to be found in Aristotle's works.

Physicist Carlo Rovelli published a paper rehabilitating the physics of Aristotle which can be found here https://arxiv.org/pdf/1312.4057.pdf

In case you think he is being overly generous to Aristotle, here is part of "On the Heavens" where Aristotle is explicit that he is talking about an object going through a medium:

Aristotle also mentions the shape as being a factor - that a round or needle shaped object will fall or sink faster than a flat object.

Still, Galileo did refute another claim of Aristotle, that of some objects possessing absolute levity, even proposing an experiment that Aristotle could have done. That is not so well known, possibly because it is a little more difficult to explain.

I think Rovelli is severely underestimating the larger philosophical and theological component involved (largely considered immutable) used by Aristotle to back his conclusions (for example he seem to have thought that bigger stones contain more of the element Earth than smaller ones, thus descending faster toward the 'natural place' and so on). It's indeed how he said, Aristotle's physics was rightly criticized by some even in ancient times, but what assured the long life of his views for so many years was primarily the large acceptation of many of the ‘background’ philosophical and theological tenets laden with his conclusions. Or in the words of Gerard Holton:

Quote:
By the end of the sixteenth century, Aristotle's theory of motion had been strongly criticized by a number of eminent scientists, and it was perfectly clear that it could not hope to provide quantitative agreement with the results of the simplest experiments. Yet the theory was still firmly entrenched in the learned world.
.................................................. .................................................. .......................……..……………………………………………………...

According to Aristotle, a theory that merely describes and predicts the facts of observation, no matter how accurately, is not good enough: It must also give them meaning in a wider sense, by showing that the facts are in accord with the general postulates of the whole philosophical system. To the Aristotelian of the late sixteenth century, the postulates concerning elements and tendencies (like the postulates about circular motions in astronomy), and all conclusions from them, were true ( "philosophically true " ) , clear, and certain, because they were also part of a larger, important, and satisfying scheme, reaching into theology and other fields.

The postulates could not be given up just because the detailed motion of two weights dropped from a tower contradicted one of their many conclusions. He would give "philosophic truth" precedence over contradictory "scientific truth"-although the latter did not yet exist as a distinct concept. His physics was the investigation of the nature of things in a context so large that the preoccupation of later science-for example, with detailed measurement of falling bodies-would seem to him like a small, artificial, incomplete subject with little significance by itself.

In sum, even in ancient times it was quite clear to some scholars that Aristotle's physics was not that strongly anchored in experiment (contradicting some). Thus, I’d say that Aristotle’s physics cannot be regarded as valid on its 'domain of definition' (apart maybe during Aristotle's life and some time after), in spite of some apparent support. One can add here that most of the ‘background baggage’ (philosophical, teleological, theological etc) used by Aristotle and his later supporters to back his conclusion was proved conclusively either wrong or at least as being severely ‘degenerative' (starting well before Galileo). When both the main body of a theory and the auxiliary hypotheses are under strong doubt (the situation around and after Galileo's time) I’d say that we deal with a falsified theory….
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Old 5th March 2019, 01:26 AM   #7
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I have an iron ball and a polystyrene ball of the same size.

So the general consensus here is that if I drop them both from 10 metres up they will both reach the ground at exactly the same time. Yes?

I haven't tried it yet, but I just wanted to be clear that this is what people here are saying. Is it?

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Old 5th March 2019, 01:39 AM   #8
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Originally Posted by Robin View Post
I have an iron ball and a polystyrene ball of the same size.

So the general consensus here is that if I drop them both from 10 metres up they will both reach the ground at exactly the same time. Yes?

I haven't tried it yet, but I just wanted to be clear that this is what people here are saying. Is it?

No.
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Old 5th March 2019, 01:55 AM   #9
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Originally Posted by Robin View Post
I have an iron ball and a polystyrene ball of the same size.

So the general consensus here is that if I drop them both from 10 metres up they will both reach the ground at exactly the same time. Yes?

I haven't tried it yet, but I just wanted to be clear that this is what people here are saying. Is it?

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What I am saying is that your above scenario is not what Aristotle was saying.

What I'm also saying is that what you call a "myth" in the OP, I just showed to be verbatim in Book 4 Chapter 8 of his Physics. As calling myths goes, that's an epic fail. READ what he wrote before lecturing on what he did and didn't write.

What I'm also saying is that even in the scenario you write above, Aristotle was wrong and trivially so. In fact,

A) the density of iron is 7.874 g/cm3. The density of... well, let's not take styrofoam, let's take wood, which existed in Aristotle's time, so he could have done the experiment if he weren't an idiot. The density of normal cedar wood (12% wet, which is about right unless you oven-dry it), which was amply available and used in their boats, is about 370 g/cm3.

Iron is 21 times denser than cedar wood. It doesn't fall 21 times faster.

B) according to his formula, how fast something falls is simply the ratio between its weight and the density of the medium. He even EXPLICITLY uses air and water as examples where if air is half as dense as water, stuff falls twice as fast in air as in water.

BUT that cedar wood sphere doesn't just fall slower in water, like Aristotle's prediction goes, it FLOATS.

And it's not even something he needed to do an experiment to find out. He was in a civilization which used wood extensively in both quite the trade network and in naval battles. He just needed to notice that a beam of wood falls in air, but floats in water. Something any of the thousands of people who had been in a shipwreck could have told him.


And THAT is the fundamental failing of Aristotle. Not one specific formula or another, but generally. He wasn't even remotely interested in checking if his nonsense is even remotely related to reality. Even when it was trivial to check, like that wood doesn't just sink slower than iron in water, or his idiocy that women have less teeth than men. All he had to do was tell the missus "honey, come here and open your mouth... no, you don't have to kneel this time"

But no, if he just thought real hard and pulled some postulates out of the ass as premises, then it must be right. THAT is the fundamental problem of Aristotle.
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Old 5th March 2019, 02:15 AM   #10
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It is just what he was saying in the part I quoted [i]verbatim[/]. (did you miss that I was quoting Aristotle verbatim)

And one of the parts you quoted wasn't even about falling objects and so is irrelevant to the case.

And in fact, when you don't quote it out of context, it is more or less correct. I could propose an experiment to demonstrate that too.

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Old 5th March 2019, 02:35 AM   #11
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Originally Posted by Mojo View Post
No.
Which would hit the ground first and why?

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Old 5th March 2019, 02:49 AM   #12
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Originally Posted by Robin View Post
It is just what he was saying in the part I quoted [i]verbatim[/]. (did you miss that I was quoting Aristotle verbatim)

And one of the parts you quoted wasn't even about falling objects and so is irrelevant to the case.

And in fact, when you don't quote it out of context, it is
Really? When the whole chapter is about falling objects, exactly what do you think he was talking about?
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Old 5th March 2019, 02:54 AM   #13
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Originally Posted by HansMustermann View Post
Really? When the whole chapter is about falling objects, exactly what do you think he was talking about?
You are talking about book IV, part 8? No. The whole chapter is not about falling objects. Anyone can take a look for themselves.

And the part from "On the Heavens" that I quoted was about falling or sinking objects.

Also, are you serious that you think that Aristotle didn't know about floating?
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Old 5th March 2019, 03:17 AM   #14
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Originally Posted by HansMustermann View Post
He wasn't even remotely interested in checking if his nonsense is even remotely related to reality.
Sure. He dissected birds eggs at various states if development faithfully describing the growing embryo at each stage because he wasn't interested in checking. Very plausible

Quote:
or his idiocy that women have less teeth than men. All he had to do was tell the missus "honey, come here and open your mouth... no, you don't have to kneel this time"
You haven't read what Aristotle said about teeth in males and females, have you?

But then again, neither did Bertrand Russell apparently. It never occurred to him to check.

Quote:
But no, if he just thought real hard and pulled some postulates out of the ass as premises, then it must be right.
On the contrary he had other people do the observations for him. They got it wrong, he believed the data. It happens to scientist all the time. But he explicitly says that there are more observations to be done about the number of teeth in males and females.
Quote:
THAT is the fundamental problem of Aristotle.
No, that is another myth about Aristotle. In fact Aristotle is very explicit that you can't get knowledge about the world using a deductive process on postulates. He say explicitly that you have to use an inductive process on empirical data. If you don't believe me I will find you the part when I am back on my computer.


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Old 5th March 2019, 03:17 AM   #15
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Yet you accuse me of taking it out of context, and say that "And one of the parts you quoted wasn't even about falling objects and so is irrelevant to the case."

Yet all three quotes are from Book IV, chapter 8. Which now you say, "The whole chapter is not about falling objects."

So please explain how a quote from that chapter can be not even about falling objects.
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Old 5th March 2019, 03:26 AM   #16
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Here is the part about teeth.
Quote:
”Males have more teeth than females in the case of men, sheep, goats, and swine; in the case of other animals observations have not yet been made.”

On the Parts of Animals. Book III
See, no postulates. He got the observations wrong. It happens. But note "observations have not yet been made", indicating that there is further checking to do.

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Old 5th March 2019, 03:32 AM   #17
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Did he even make any observation? Because for all 4 species he mentions, it's just flat out wrong. It's hard to imagine anyone actually counting teeth for 4 different species and managing to be wrong every single time.

Seems to me like a case of talking out the ass and claiming it to be an observation.
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Old 5th March 2019, 03:47 AM   #18
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Originally Posted by HansMustermann View Post
Did he even make any observation?
In this case probably nor, as I said he had people to do the observations for him. So he got some of that wrong. Just as your assumption that he tried to derive this from postulates was wrong. People get stuff wrong.

In other cases, such as the dissection of birds eggs he appears to have done that himself.

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Old 5th March 2019, 03:54 AM   #19
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Originally Posted by HansMustermann View Post
Yet you accuse me of taking it out of context, and say that "And one of the parts you quoted wasn't even about falling objects and so is irrelevant to the case."

Yet all three quotes are from Book IV, chapter 8. Which now you say, "The whole chapter is not about falling objects."

So please explain how a quote from that chapter can be not even about falling objects.
Others can go and check it out for themselves. It is not about falling objects. You are basing your criticism of Aristotle on an inaccurate interpretation of what he said.

According to Aristotle's physics, cedar in water doesn't have weight at all, it has relative levity in water and relative weight in air.

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Old 5th March 2019, 04:02 AM   #20
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Originally Posted by HansMustermann View Post
Did he even make any observation? Because for all 4 species he mentions, it's just flat out wrong. It's hard to imagine anyone actually counting teeth for 4 different species and managing to be wrong every single time.

Seems to me like a case of talking out the ass and claiming it to be an observation.
The first example is correct, though that's probably a result of flawed translation rather than the intention of the author. There are vastly more male men than female ones.
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Old 5th March 2019, 04:33 AM   #21
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No-one has answered my question.

I have an iron ball and a polystyrene ball of the same size. I go to a 10 metre high balcony and drop them at the same time.

Will they reach the ground together?

Or will one get there first? Which one? Why?

Note that Aristotle does not say that if A is ten times heavier than B then it will fall or sink 10 times as fast.
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Old 5th March 2019, 05:11 AM   #22
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I just gave you an exact quote, and the link to the translation to check it, where he says EXACTLY that it's in proportion to their weight. Also quite explicitly that the same would apply in a void. Denial is not the same thing as having an argument.
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Old 5th March 2019, 05:16 AM   #23
Robin
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OK, how about this:
Originally Posted by HansMustermann View Post
But it gets better:
We see that bodies which have a greater impulse either of weight or of lightness, if they area like in other respects, move faster over an equal space, and in the ratio which their magnitudes bear to each other. Therefore, they will also move through the void with this ratio of speed.
This one EXPLICITLY not just says flat out that heavier things move faster than lighter things, but he tells you that the speeds are in the same ratio as the weights. It also spells it out that the same would apply in a void.
Does he?

We had better have the full quote:
Quote:
These are the consequences that result from a difference in the media; the following depend upon an excess of one moving body over another. We see that bodies which have a greater impulse either of weight or of lightness, if they are alike in other respects, move faster over an equal space, and in the ratio which their magnitudes bear to each other. Therefore they will also move through the void with this ratio of speed. But that is impossible; for why should one move faster? (In moving through plena it must be so; for the greater divides them faster by its force. For a moving thing cleaves the medium either by its shape, or by the impulse which the body that is carried along or is projected possesses.)
So, no. he is saying the opposite. That it wouldn't apply in a void. He is being specific that the reason has to do with the medium: "](In moving through plena it must be so; for the greater divides them faster by its force. For a moving thing cleaves the medium either by its shape, or by the impulse which the body that is carried along or is projected possesses.)"
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Old 5th March 2019, 05:50 AM   #24
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More myths.

No, Aristotle didn't say that things accelerated as they fell because they grew more jubilant as they approached their place of rest. It is not even the kind of thing he says.

Hawking and Mlodinov claim that Aristotle thought this. I guess they got it from BF Skinner, who in turn got it from H Butterfield in "The Origins of Modern Science". I don't know where he got it from.

Apparently none of them bothered to check.

And Aristotle did not think that a real rabbit was an approximation of an ideal Platonic rabbit. Aristotle rejected the theory of Platonic Forms.

Again, it did not seem to occur to Richard Dawkins to check if this was true.
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Old 5th March 2019, 06:05 AM   #25
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Originally Posted by Robin View Post
No-one has answered my question.

I have an iron ball and a polystyrene ball of the same size. I go to a 10 metre high balcony and drop them at the same time.

Will they reach the ground together?

Or will one get there first? Which one? Why?

Note that Aristotle does not say that if A is ten times heavier than B then it will fall or sink 10 times as fast.
Provided that the dropping can be done in vacuum in order to negate the effects of air resistance, then 'Yes' both of the balls would contact the ground at the same time.

Note: there was a popular experiment that was done in the 1700's called a 'Guinea Tube' where a gold coin called a Guinea and a feather were put into an air tight glass tube.

http://physics.kenyon.edu/EarlyAppar...ther_Tube.html

When the tube was inverted, then the gold coin would always be the first object to contact the other side of the tube.

But when the air was pumped out of the tube and then the tube was inverted, then both the coin and the feather would contact the other side of the tube at the same moment.

This demonstrated showed two things:

One, that gravity causes all objects to accelerate at the same rate.

Two, the effects of air resistance can be considerable.

Finally, a similar experiment was done during one of the Apollo Moon landings.

I hope this helps.
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Old 5th March 2019, 11:23 AM   #26
HansMustermann
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Originally Posted by Robin View Post
OK, how about this:

Does he?

We had better have the full quote:

So, no. he is saying the opposite. That it wouldn't apply in a void.
Dude, exactly what kind of mental contortions do you need for that kind of silly reading? He's explicitly saying that the same would apply to a void, he just doesn't think a void can exist. In fact, if he didn't think the same applies in a void, then the whole ad absurdum argument he makes against the existence of the void wouldn't even work.

Because yeah, the part you bolded? That's part of the ad-absurdum, silly. But you'd need to actually read and understand, to figure that out, not just quote mine for your delusional CT against Aristotle BS

Originally Posted by Robin View Post
He is being specific that the reason has to do with the medium: "](In moving through plena it must be so; for the greater divides them faster by its force. For a moving thing cleaves the medium either by its shape, or by the impulse which the body that is carried along or is projected possesses.)"
And that still doesn't negate the fact that he said that it will be proportional to the weight or "lightness", nor with the fact that he explicitly writes that the same would apply in a void, if a void were possible. Again, it's part of an ad absurdum argument that wouldn't even work if things were different in a void.
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Old 5th March 2019, 01:41 PM   #27
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Originally Posted by Robin View Post
Which would hit the ground first and why?

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On Earth, the iron ball would hit the ground first due to air resistance. On the Moon, OTOH....


Hans
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Old 5th March 2019, 02:03 PM   #28
HansMustermann
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Originally Posted by Robin View Post
Still, Galileo did refute another claim of Aristotle, that of some objects possessing absolute levity, even proposing an experiment that Aristotle could have done. That is not so well known, possibly because it is a little more difficult to explain.
Actually it's trivial to explain: Aristotle argues repeatedly that for some things like a rock the "natural" movement is down, i.e., towards the centre of the Earth, while for other stuff like fire, the "natural" movement is up. Movement in the other direction is apparently "unnatural" and can be only done by force. (Translated as by "violence" in the link I provided, but I think that's not entirely accurate.)
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Old 5th March 2019, 02:06 PM   #29
HansMustermann
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Originally Posted by MRC_Hans View Post
On Earth, the iron ball would hit the ground first due to air resistance. On the Moon, OTOH....


Hans
That would imply that he actually thought that things can fall towards the moon. He didn't. Up and down were for him only towards the centre of the Earth or away from it. Even when he imagined other worlds, they would have to be made only of air and fire, or they'd fall to Earth. Logic, see?

So, anyway, if you went to the Moon with an iron ball, both you and the ball would fall to Earth
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Old 5th March 2019, 02:15 PM   #30
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Originally Posted by HansMustermann View Post
That would imply that he actually thought that things can fall towards the moon. He didn't. Up and down were for him only towards the centre of the Earth or away from it. Even when he imagined other worlds, they would have to be made only of air and fire, or they'd fall to Earth. Logic, see?

So, anyway, if you went to the Moon with an iron ball, both you and the ball would fall to Earth
Oh, I thought we were talking about reality. Why would I bother what Aristotle thought.

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Old 5th March 2019, 02:22 PM   #31
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'Cause dead philosophers say the darndest things?
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Old 5th March 2019, 02:38 PM   #32
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Also because this is a thread to discuss what Aristotle thought.
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Old 5th March 2019, 04:30 PM   #33
Robin
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Originally Posted by MRC_Hans View Post
On Earth, the iron ball would hit the ground first due to air resistance. On the Moon, OTOH....


Hans
So on Earth his principle was correct, right?

The heavier ball would fall faster for just the reasons he says.

Just as the principle that a falling object accelerates at 9.8 meters per second per second only works close to the Earth's surface.
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Old 5th March 2019, 04:32 PM   #34
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Originally Posted by HansMustermann View Post
That would imply that he actually thought that things can fall towards the moon. He didn't. Up and down were for him only towards the centre of the Earth or away from it. Even when he imagined other worlds, they would have to be made only of air and fire, or they'd fall to Earth. Logic, see?

So, anyway, if you went to the Moon with an iron ball, both you and the ball would fall to Earth
So basically your criticism of Aristotle is that he didn't discover in one lifetime what it took the rest of humanity another 2,000 years to discover. Yes?
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Old 5th March 2019, 04:50 PM   #35
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Originally Posted by Crossbow View Post
Provided that the dropping can be done in vacuum in order to negate the effects of air resistance, then 'Yes' both of the balls would contact the ground at the same time.
But Aristotle is explicit that he is talking about objects passing through a medium like air or water.

So why would you test a claim about objects moving through a medium by removing that medium? That doesn't make sense.

In fact Aristotle is explicit that in a void there is no reason why the objects would move at a different speed.

So if I take my iron ball and polystyrene ball and I drop it from a height of ten metres in just the conditions described by Aristotle, ie through the medium of air, which would reach the ground first?
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Old 5th March 2019, 04:57 PM   #36
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Originally Posted by Robin View Post
I have an iron ball and a polystyrene ball of the same size.

So the general consensus here is that if I drop them both from 10 metres up they will both reach the ground at exactly the same time. Yes?

I haven't tried it yet, but I just wanted to be clear that this is what people here are saying. Is it?

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One can accept that Aristole's theory had good experimental support for some time but from here does not follow the way stronger thesis of Rovelli who sees Aristotle's physics basically as approximating at limit Galilean and Newtonian mechanics (and even modern physics). Indeed about Galileo's time the problems with the core concepts of Aristole's physics were so many (it was no more the case that the theory and its core concepts had adequate empirical support*) that non trivial changes had to be made, the fact that a few concepts survied being rather irrelevant (likewise for example the atomic theory of the greeks cannot be seen as approximating the modern atomic theory).

Anyways closer to our days both Arisrtotle's physics and the 'background' assumptions (philosophical, religious etc) used to back his Physics were conclusively shown as being at least severely degenerative, the mark of thoroughly falsified research programs (not the case of Newtonian physics for example which has few anomalies). I don't think that Rovelli's strong conclusion follows, I'm afraid Kuhn's account of scientific change** is a better choice (of course some may say that Lakatos' views offer a better solution, they have a point in my view).

If one adds here that Aristotle rejected rather apriori the very possibility that bodies with different weights could fall simultaneously (by rejecting the existence of the void which would otherwise create huge problems to his theory) I think it is safe to conclude that the views of most modern philosophers of science about the subject are well grounded, Aristotle's physics is barely scientific and very few of its core cncepts survived until today.


* for example it was quite clear at the time to some that a stone 10 times heavier than another one does not fall 10 times as fast (valid even today of course, even if they don't reach the soil at the same time this still definitely disconfirm Aristotle on the ''domain of definition' of his theory )

** without the 'incommensurability' thesis though which does not 'hold water'; actually Kuhn himself renounced it at some point. One can definitely reject it without needing to go in the direction suggested by Rovelli here
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Old 5th March 2019, 05:11 PM   #37
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Originally Posted by Robin View Post
So on Earth his principle was correct, right?

The heavier ball would fall faster for just the reasons he says.

Just as the principle that a falling object accelerates at 9.8 meters per second per second only works close to the Earth's surface.
Would he have been correct if you dropped a wooden spear and a metal spear?

At 10 meters neither is going to slowed much by drag in the air and they'll probably hit the ground very close to the same time. Yet Aristotle's math specifies the metal spear should fall at least 10 times as fast. This would have been an easy experiment to do, why did he get it wrong?
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Old 5th March 2019, 05:19 PM   #38
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Originally Posted by Crossbow View Post
'Robin':

Sorry but I am not really sure what you are driving at, because Aristotelian Physics did teach that if two objects were identically shaped, and both of them were falling through the same medium, then the heavier object would travel faster than the lighter object (see below).

However, Galileo showed that this thinking was quite incorrect.
The experiment I propose sets up just exactly this scenario which you claim is quite incorrect.

I take an iron ball and a polystyrene ball and drop them from a height of ten metres through the same medium (ie air), which will land first?
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Old 5th March 2019, 05:27 PM   #39
Robin
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Originally Posted by JimOfAllTrades View Post
Would he have been correct if you dropped a wooden spear and a metal spear?

At 10 meters neither is going to slowed much by drag in the air and they'll probably hit the ground very close to the same time. Yet Aristotle's math specifies the metal spear should fall at least 10 times as fast. This would have been an easy experiment to do, why did he get it wrong?
Can you quote Aristotle's maths that says this?

Remember Aristotle says there are three factors:

1. The weight of the falling object having the force to divide the medium,
2. The resistance of the medium to being divided and
3. The shape of the falling object.

Now where is the maths that says that the metal spear should fall at least 10 times as fast? Provide a reference from something Aristotle said, and not something attributed to him.

Here is where he talks specifically about falling or sinking objects in "On the Heavens"

Quote:
For in proportion as the force applied by the heavy thing towards disruption and division exceeds that which resides in the continuum, the quicker will it force its way down; only if the force of the heavy thing is the weaker, will it ride upon the surface.
ie "in proportion to the force applied by the heavy thing towards disruption and division"

Your two spears will not show much difference as they are passing through a medium which is easily divided and both have a shape which will easily divide the medium.

But they will fall at a slightly different rate.

So how exactly does that experiment contradict Aristotle?
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Old 5th March 2019, 05:45 PM   #40
Robin
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Originally Posted by JimOfAllTrades View Post
Would he have been correct if you dropped a wooden spear and a metal spear?
Or the shorter version - yes, he would have been correct. The metal spear would have fallen quicker, just as he says.

I can't see anywhere that Aristotle says that if X is A times heavier than Y then X will fall A times faster than Y. Perhaps I have missed it.

He says the heavier object will fall faster. And it will.
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