Friday, June 15, 2012

Virtual Aristotelian Physics


I spent several hours the other day looking up some sort of reference to a computer simulation of Aristotelian physics.

The thought came to me in connection to fantasy worlds.  Good fantasy authors will create their own fictional worlds with different histories, cultures, languages, and religions, similar to Tolkien's Lord of the Rings.  Lately authors have started going kind of crazy, and have been experimenting with alternative physics, like flat earths and sentient quanta.

I was thinking, why not Aristotelian physics?  Is it that impossible?  A professor of an old friend of mine, remarking to a room of Thomistic philosophy students, asked why they were so enamored with Aristotle when you couldn't make your car run on Aristotelian physics.  Maybe not their cars, but any car?  Can a car run in a world of Aristotelian physics?
Aristotle with impetus



The basic and most central idea in Aristotle's conception of physics is that he was an ancient Greek philosopher completely removed from my modern view of mathematical science and more interested in teleology and such.  But then after that point, another almost as central is that the speed of an object is proportional to the force acting on it.

This means that when you stop applying a force to something, it stops moving.  (Of course it does! I just did this with a coffee mug on my desk!)

Another principle is that objects can only have one "kind" of motion at a time - that is, in straight lines.

To explain projectile motion (i.e. arrows and cannonballs) Aristotle proposed a sort of reverse-air-resistance, where the air that the arrow is moving through passes over it and then closes in on the back of the arrow, pushing it forward, until it will eventually just stop.  Once this reverse-air-resistance stops, the object will just drop straight to the ground.
Impetus, and "Mixt" motion

Later thinkers amended this with the "theory of impetus", where the object itself "contained" the means of its continued movement, which is opposed by air resistance, until it stops and falls.  At first this made a trajectory like a triangle, but later it was fixed to include exponential portions, as in the drawing.

I ramble.

Believe it or not, most video games don't simulate actual physical physics, usually to conserve computations.  Like Mario might fall at a constant speed instead of constant acceleration, or Link's strike might impart more force to the moblin than to Link's arm.  So a non-Newtonian framework in video game physics is nothing new.  I was hoping to find a video or something of simulated video game-type  characters interacting with a virtual physics engine that simulates Aristotelian physics, really just to see how different the world would be.

Near as I can tell, after hours and countless searches on Google and in academic literature, there is nothing like this in existence.  The main thing I was able to find were faculty site after faculty site disproving Aristotle's physics and detailing its historical debunking by Galileo.

The search results weren't entirely useless, though.

I learned that repeated testing seemingly in every decade shows that Aristotle's understanding of physics is "more intuitive"; that is, most people when asked a question on physics will naturally go with the same explanation as Aristotle.  Some people will continue to believe Aristotle, even after taking physics courses at the collegiate level.  Aristotle's physics somehow accords more deeply with the human mind than does real physics.  I find that odd.

I learned one proposal to remedy this was virtual reality simulations of Aristotelian physics (though no actual simulations seem to exist anywhere on the internet).  By having students interact with a virtual world that actually behaves the way they think it should, students can see that their ideas of how it "should" behave are not in accordance with reality.  That certainly sounds interesting, and suggests an intriguing sort of pedagogy.

I found one academic paper that simulated 2D "rag doll" dynamics in an Aristotelian framework, and that apparently Aristotle's physics corresponds to Newtonian physics in a perfectly viscous fluid (or limit of zero Reynold's number).

One of the closest things I found was a cannon someone rigged up in Second Life that is supposed to fire projectiles that obey Aristotelian trajectories.  This was pretty cool.  It was limited to a single object on a third of the screen, but was a relief to finally find after the fifth dozen of faculty pages debunking Aristotle.

But I didn't find what I was looking actually for; that is, a virtual game-like simulation of a world obeying Aristotle's ideas of physics.

I tried later a search for someone - anyone - who had translated Aristotle's qualitative philosophy into quantitative equations such as we have in modern mathematical physics.  From what I can tell, the idea of doing this has never even occurred to anyone else, or is just so impossible that no one has done it.

I get that Aristotle's physics doesn't accurately describe how real objects really behave.  I know it doesn't.  I can prove it.  I don't think that means that Aristotle's physics "doesn't matter".  For the natural scientist, it really doesn't matter except as a historical footnote.  But just for the sake of general human curiosity, I think it is important to ask about.

Why do Aristotle's explanations seem to be "pre-programmed" in to us, whereas Newton's explanations take many semesters and complicated math to understand?

Why don't objects actually obey Aristotle's laws?

Are Aristotle's laws logically coherent and consistent with themselves?

Could it be possible, in some hypothetical Thoughtland, for creatures in some hypothetical third dimension to experience physical laws that obey the ideas of Aristotle?  What does this question even mean, and how could we even answer it?

Why is the world the way it is, and not some other way?

Maybe one day I might have the smarts to understand these questions.

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