Galileo's "falling bodies" experiment re-created at Pisa

[uracistbastard]

Galileo's "falling bodies" experiment re-created at Pisa - 23,000 views

Chinese girl on the right - 6,423,086 view

Not ironic at all

[WeaselWJ]

Good video!

[danfalkscience]

@HK379: That's right: The earth pulls more strongly on the big one, bit the big one is harder to accelerate because of its larger mass. Neglecting air resistance, they fall at the same rate. The heavier one does more damage when it hits the ground because kinetic energy depends on mass -- the larger the mass, the more kinetic energy.

[HK379]

ok . so the land puuls the heavier stronger ... but  the heavier is is more hard to pull because of greater inercia ... ???

I dont get it ...

1.if you drop`em in whater , the heavier sinks faster ...right ?

2.how come when it hits the grownd a havier object does more damage than ?

[insirtusernamehere]

@HK379 An object in space will accelerate towards another object because of gravity. On Earth this is about 9.8 meters per second, but if Earth was heavier. So say you jump out of a plane. You might think 20 seconds later you would be going nearly 196 meters per second, but due to air resistance you will go slower. You accelerate towards Earth at 9.8 meters per second, but if you are air resistant, like a parachute, you will accelerate slower and your max rate of descent will be lower.

[BOBandJOE4ever]

Science makes my fingers feel tingly!!!!!!

[BOBandJOE4ever]

Science makes my fingers feel tingly!!!!!!

[marcusaureliooze]

Air was an element, and different events meant there was a different balance in the elements. Earth (the planet) ends at the crust, and the rest is aether (all the way to the end of the universe). Smoke moves up because it contains just too much ether, so it tends to repel Earth, while a rock has little ether and much more earth in it. This was the consensus in classical Greece.

Also note that every phenomenon is the result of four (later five) basic interactions, not unlike modern physics.

[insirtusernamehere]

@marcusaureliooze In my science textbook the Earth includes the different air levels that extend up miles above the Earth's surface. It does not really matter though.

[jursamaj]

See, for all there smarts, this demonstrates the problem with Aristotle, Plato, and their ilk. They tended to make proclamations of "fact" after thinking about something, and felt doing an experiment to prove it wasn't necessary. :P

[marcusaureliooze]

@jursamaj Your hindsight is 20/20.

[jursamaj]

@marcusaureliooze

Hindsight? How about common sense? If I sit in my room and come up with an idea, the next step is to check if I'm right. These philosophers felt that experimenting was "beneath them", so their proclamation was sufficient. It doesn't take hindsight to know that's foolish.

[marcusaureliooze]

@jursamaj Actually it was empirical evidence that led to the misconception herein examined. Drop a feather and a hammer and you'll see.

[jursamaj]

@marcusaureliooze

If you read up on it, Aristotle *thought* about it, and decided, without doing any empirical tests. He simply didn't bother.

A feather and a hammer are very different objects, in many ways than just their weights. Proper experimenting controls for those differences.

Aristotle didn't just say they would fall differently, but in proportion to their weights. Drop 1 and 2 pound balls (same diameter) 20 feet, and the difference should be significant. It isn't.

[marcusaureliooze]

@jursamaj It may seem obvious now, but atmospheric friction was unheard of back then. Someone told you about it in school, but Aristotle wasn't as lucky.

[jursamaj]

@marcusaureliooze

Nonsense. Look at a flag, sail, tree, hair, etc. Look at dust and sand blowing across the ground. Hold your hand in front of your mouth and blow.

Blow on a feather, then on a cannonball.

Don't tell me the ancients had no knowledge of atmospheric friction!

[insirtusernamehere]

@jursamaj They knew about it, but they didn't really define it or give a reason for it. It's like being taught a concept and not understanding it. You can say when it works and how to use it, but can't you say how it works. They knew about the wind, as they showed through their knowledge of sails, but they didn't know why it worked like that.

[jursamaj]

@insirtusernamehere

marcusaureliooze said that atmospheric friction was unheard of back then. As I said, and you've admitted, it wasn't. They were well aware of it. Whether they had it precisely defined & quantified is irrelevant.

[FreyaBichon]

Why not use two identical bottles with different contents, then the air resistance problem is solved for the bottles, rather than have one three times the size? The bottles hit the ground at the same time (as far as could be seen) but if they did and there was more resistance on the bigger bottle, surely you could draw the conclusion that heavier items fall faster the speed being directly proportional to the affect of air resistance..

[danfalkscience]

@cljohnston108: True! If I didn't put this video together in such a hurry, I would have included a snippet from that. Still impressive, all these years later!

[cljohnston108]

The most perfect demonstration of this was made by Dave Scott, commander of Apollo 15, when he dropped a hammer and a feather simultaneously on the Moon's surface! Just search YouTube for "apollo 15 hammer and feather".

[danfalkscience]

@jfuite: Yes indeed. I think many people are surprised to learn that the concept of "inertia" is still, to some extent, mysterious. In Einstein's general relativity, it is presumed that intertial mass and gravitational mass are the same; but so far it just seems to be an empirical fact that they are, rather than something we can "explain" or "prove" in some other way.

[jfuite]

Regarding the equations at the end, danfalkscience states, "the two effects cancel each other out, that's why the rate of fall is independent of the mass".

It's interesting that the two effects actually DO cancel each other out, considering mass is involved with seemingly very different phenomena: gravity and inertia (a concept defined independent from gravity).

[danfalkscience]

A physicist friend has pointed out that what I say about air resistance is not quite correct, because there is a link between speed and the amount of air resistance. Because of this -- and I admit I glossed over this -- the bolwling ball would in fact hit the ground ahead of the volleyball.

But, at least the large and small water bottles fell at the same rate! :)

[awuma]

More relevant is that SIZE determines air resistance. If the balls have the same size but different masses, at the same speed the air resistance force is the same, but the less massive ball has less inertia and so slows down more. Despite the air resistance increasing with the square of the speed, the less massive ball slows down more. One has to make air resistance proportional to mass, like gravity, for this to work. Similarly shaped but variously sized bottles of water are good.

[danfalkscience]

Thanks, folks!

[cspinx5photon]

Good video! Galileo's falling object experiment never gets old! Did it really take 1500 years for someone to test Aristotle with a couple of rocks? Cool stuff, Dan!

[Roddy1965]

Let me see if I get this right. So if the lighter object falls faster, she is a witch?  ; ) Nice work Dan. Very professional.

[vonhasselbach]

Thanks Dan!