What were Galileo's balls made of?

[jberryhill]

Now I realize that the story of him dropping balls from a tower is most likely mythical.

But in his experiments involving ramps, balls and a water clock, I'm curious about the experimental setup and the scale at which one could reliably detect consistent acceleration across different masses.

Even if significant wind resistance is eliminated, there will still be rolling resistance issues that will scale with the inverse of the size, and hence the mass of his balls.

At that time in his region, he would have access to lead balls, brass balls, glass or marble balls. Were balls used for recreation, like bocce, commonly available at that time, or would he have to make his own balls?

[unblock]

1. tougher stuff than donnie's, that's for sure.

sorry... low hanging fruit

[Xipe Totec]

2. You're asking for it. You know that, don't you? nt

[TreasonousBastard]

3. Galileo thought about it but Jan Cornets de Groot actually did it in Delft around the time...

Gaileo was thinking about it. Two lead balls, one 10 times larger and heavier, and they both hit the ground at about the same time.

The only variable would be the greater amount of air resistance with the larger ball, but it's apparently not enough to affect the experiment.

I would try two spheres, one hollow, but I suspect that's been done over the years. Besides, these days dropping balls off a building gets you into Gitmo.

[jberryhill]

5. Not the tower thing. The ramp experiments.

[TreasonousBastard]

6. Bronze balls...

One bronze ball, and a wooden plank.

http://education.seattlepi.com/galileos-experiments-theory-rolling-balls-down-inclined-planes-4831.html

Again, since he was using one ball and one ramp, rolling and air resistance would be roughly the same for all trials. And the water clock he used was accurate. Kids make them now for junior science projects.

(It's getting late and I admit I didn't read your whole post)

[Warpy]

10. Lead would have been my guess

it was cheap and available at the time, used in great quantity by the church for stained glass windows and roofing material. Likely he could have gotten cast off scrap very cheaply.

Other available metals would have been more expensive and/or harder to work.

[deathrind]

4. I think it is safe to...

...to say he would have been familiar with the game:

"An Historical Look. Throwing balls toward a target is the oldest game known to mankind. As early as 5000 B.C. the Egyptians played a form of Bocce with polished rocks. Graphic representations of figures tossing a ball or polished stone have been recorded as early as 5200 B.C."

Having said that he most likely would have also made spheres out of varying materials in order to understand how/if material characteristics affected the results.

Peculiar question... but interesting. I did not realize how far back that type of entertainment went. Would have never guessed it would be that far.

[jberryhill]

7. At that time in Italy...

...would polished marble balls be hard to come by?

Various games of marbles are ancient, but they'd be too small.

Playing marbles with actual marble marbles is a different game entirely, since some are harder than others.

But I've never seen a description, or educated guess, about his actual experimental setup.

Where you say he would have played around to deal with rolling resistance, would "rolling resistance" be an obvious source of experimental error to him? We are fairly oblivious to the ubiquity of exquisitely machined or precision formed objects. His environment is one in which carts have axles made of logs.

From the moment he thinks, "I can slow down falling by rolling things down ramps" I'd think it would be easier to make a track for variously weighted wheels than say "I'll just grab some handy balls". Wheels and discs are easier to make than well rounded balls, aren't they?

[deathrind]

9. IMO...

"would polished marble balls be hard to come by?"

They were polishing glass into lens and smooth polished marble had been around for centuries by the time Galileo was born so I do not think it would have been too hard...more than likely actually.

"would "rolling resistance" be an obvious source of experimental error to him?"

I would think, Yes. He obviously understood scientific experimentation and the need to experiment under different conditions in order to get a full understanding of how variations affect outcomes.

"Wheels and discs are easier to make than well rounded balls, aren't they?"

Two dimensional objects are almost always easier to make than three dimensional object. What his preference might have been is hard to say. It would depend on the reason for the experiment to begin with and on the application of the knowledge gained. IMO he would have experimented with both as both would have had practical applications in his time.

[yellowcanine]

8. He stood up to the Pope, so I am going to say brass.

[Galileo126]

11. I refuse to comment...

[Javaman]

12. Personally, I think AC/DC said it best...