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This is a place to share greentexts and witness the confounding life of Anon. If you're new to the Greentext community, think of it as a sort of zoo with Anon as the main attraction.

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Anon is often crazy.
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Anon frequently shares thoughts that are immature, offensive, or incomprehensible.

If you find yourself getting angry (or god forbid, agreeing) with something Anon has said, you might be doing it wrong.

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Anon is a physicist (sh.itjust.works)

submitted 7 months ago by [email protected] to c/[email protected]

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[–] [email protected] 78 points 7 months ago* (last edited 7 months ago) (1 children)

Lucretius, writing in 50 BCE:

Whatever falls through water or thin air, the rate Of speed at which it falls must be related to its weight, Because the substance of water and the nature of thin air Do not resist all objects equally, but give way faster To heavier objects, overcome, while on the other hand Empty void cannot at any part or time withstand Any object, but it must continually heed Its nature and give way, so all things fall at equal speed, Even though of differing weights, through the still void.

De Rerum Natura book 2 lines 230-239

I was literally just writing about him nailing survival of the fittest too.

[–] [email protected] 17 points 7 months ago (1 children)

He's still arguing that heavy objects would fall faster when dropped anywhere on Earth, though, specifically bringing up air resistance as the reason. His argument is that they would fall at the same rate in a vacuum.

[–] [email protected] 29 points 7 months ago (1 children)

But that's true, isn't it? Putting aside volume and shape.

[–] [email protected] -5 points 7 months ago* (last edited 7 months ago) (4 children)

He's close, but not quite there. Air resistance slows things, and in a vacuum all things will fall at the same rate, yes. But, weight has zero impact on the rate an object falls through the atmosphere. Air resistance affects things based on their shape and permeability. He's still saying that a heavier object will fall faster in atmosphere, all other things being equal, which is false.

He clearly knows air resistance is a thing, he just doesn't understand how it works.

[–] [email protected] 31 points 7 months ago* (last edited 7 months ago)

Hi. Physicist here. You are absolutely wrong. The mass of an object does not affect the magnitude of force of air resistance which acts upon a falling object. But the acceleration that object will have is given by Newton's second law as Force divided by mass. So a heavy and a light ball with the same shape will experience the same air resistance, but the heavy ball will "care less" and thus fall faster.

[–] [email protected] 18 points 7 months ago

But it does affect the downward force acting on the object. Given two objects of the same shape but with different masses, one will indeed fall slower than the other. This is because the ratio of weight to surface area differs a lot between the two. Here's a calculator from NASA you can play with, and a relevant passage from the same page:

If we have two objects with the same area and drag coefficient, like two identically sized spheres, the lighter object falls slower. This seems to contradict the findings of Galileo that all free-falling objects fall at the same rate with equal air resistance. But Galileo’s principle only applies in a vacuum, where there is NO air resistance and drag is equal to zero.

https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/termvel/

[–] [email protected] 8 points 7 months ago (1 children)

A ping-pong ball sized lead shot and a ping-pong ball both fall at the same rate though air?

That doesn't sound right.

[–] [email protected] 1 points 7 months ago

I don't think he's talking about air resistance but about density, which is pretty close to the notion of weight and also affect fall speed. He probably came to this conclusion by looking at how things fall (or not) through water.