Rationality Quotes: October 2009

Eliezer Yudkowsky

A monthly thread for posting rationality-related quotes you've seen recently (or had stored in your quotesfile for ages).

Please post all quotes separately, so that they can be voted up/down separately. (If they are strongly related, reply to your own comments. If strongly ordered, then fine, post them together.)
Do not quote yourself.
Do not quote comments/posts on LW/OB.
No more than 5 quotes per person per monthly thread, please.

A monthly thread for posting rationality-related quotes you've seen recently (or had stored in your quotesfile for ages).

Please post all quotes separately, so that they can be voted up/down separately. (If they are strongly related, reply to your own comments. If strongly ordered, then fine, post them together.)
Do not quote yourself.
Do not quote comments/posts on LW/OB.
No more than 5 quotes per person per monthly thread, please.

I checked Aristotle's 'On the Heavens' and 'Physics'. Nowhere could I find him saying that a heavy object falls faster than a light one. Aren't it the Aristotelian scholars who said that and who are to blame? Aristotle distinguished relative weight (our mass) and absolute weight (our mass density) and gives practical examples to check that denser objects move faster downwards in water than less dense objects, if the objects have the same shape.

Aristotle really said it, in Heavens 4.2:

For any two portions of fire, small or great, will exhibit the same ratio of solid to void, but the upward movement of the greater is quicker than that of the less, just as the downward movement of a mass of gold or lead, or of any other body endowed with weight, is quicker in proportion to its size.

Note that he take the extreme position that heavier objects fall faster, not just denser! This claim is robust against translation errors since he is keeping the material fixed. I have not been able to find the passa... (read more)

5gwern17y

It's also worth noting that when you do Galileo's Tower of Pisa experiment, the heavier object does land first. (You think you release them at the same time, but you don't - your muscles let the heavier object go first.) I find sometimes we here denigrate our distant predecessors too much; I have heard well-educated people call the Greeks fools for rejecting heliocentrism, despite the fact that the Greeks had powerful arguments against heliocentrism like the lack of stellar parallax, or we mock them for the 5 elements, despite the incredible feat of devising atomism just by considering basic logical paradoxes caused by alternative ontologies.

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