The Flat Earth Society

Flat Earth Discussion Boards => Flat Earth Q&A => Topic started by: Max Fagin on December 22, 2006, 03:51:25 PM

Title: Proof of Gravity and the Cavendish Experiment
Post by: Max Fagin on December 22, 2006, 03:51:25 PM
So it turns out I was wrong.

On the Infidel Guy radio show about a week ago, Reginald Finely suggested that the existence of gravity as a force could be proven by suspending a very massive object and measuring it's gravitational pull with a nearby detector.  I then implied that I didn't think that was possible because gravity was such a weak force.

Well it turns out I was wrong.  After the show, I got an E-mail form William Jefferys, a professor of astronomy and statistics at The University of Texas.  He told me about an experiment called the Cavendish experiment.

http://en.wikipedia.org/wiki/Cavendish_experiment

Apparently, the Cavendish experiment has been used to measure the gravitational pull of small objects since the 1800's.

The set up is a bit more sophisticated then a ball on a string, but not by much.

It involves taking a rod with an iron ball on each end, and suspending it from a very thin string.  Then placing two larger iron spheres nearby, and measuring how much the apparatus rotates.

At very least, this allows you to demonstrate the existence of gravity as a force, and if you assume the Earth to be round, it lets you calculate the value of the gravitational constant, G, if you replace the string with a wire with known torsion properties.

I had always believed that the gravitational constant was measured from celestial observations, but this turns out to be a better (Although still imprecise) way of doing it.

This is a difficult experiment, but not one that is beyond reach of a well-stocked high school lab.  I think this is the most clinching proof I have seen so far that gravity exists, and FE is erroneous.

Response FE'ers?
Title: Re: Proof of Gravity and the Cavendish Experiment (I'm seri
Post by: Username on December 22, 2006, 04:02:38 PM
Quote from: "Max Fagin"
So it turns out I was wrong.

On the Infidel Guy radio show about a week ago, Reginald Finely suggested that the existence of gravity as a force could be proven by suspending a very massive object and measuring it's gravitational pull with a nearby detector.  I then implied that I didn't think that was possible because gravity was such a weak force.

Well it turns out I was wrong.  After the show, I got an E-mail form William Jefferys, a professor of astronomy and statistics at The University of Texas.  He told me about an experiment called the Cavendish experiment.

http://en.wikipedia.org/wiki/Cavendish_experiment

Apparently, the Cavendish experiment has been used to measure the gravitational pull of small objects since the 1800's.

The set up is a bit more sophisticated then a ball on a string, but not by much.

It involves taking a rod with an iron ball on each end, and suspending it from a very thin string.  Then placing two larger iron spheres nearby, and measuring how much the apparatus rotates.

At very least, this allows you to demonstrate the existence of gravity as a force, and if you assume the Earth to be round, it lets you calculate the value of the gravitational constant, G, if you replace the string with a wire with known torsion properties.

I had always believed that the gravitational constant was measured from celestial observations, but this turns out to be a better (Although still imprecise) way of doing it.

This is a difficult experiment, but not one that is beyond reach of a well-stocked high school lab.  I think this is the most clinching proof I have seen so far that gravity exists, and FE is erroneous.

Response FE'ers?


Well, my impression of FE theory was that gravity existed, but it just didn't apply to earth - OR to be more reasonable that the vast majority of earths "gravity" effects were caused by acceleration and a small remaining amount from whatever mass the flat earth is made from.
Title: Proof of Gravity and the Cavendish Experiment
Post by: ArmyJonHall on December 22, 2006, 06:24:12 PM
I'm listening to your podcast right now- and I have to say, the fact that none of the FE'ers even decided to appear makes the whole thing (the flat Earth thing, this is) hilarious.

I think I can predict the FE response-

"Max is part of the conspiracy. So was Cavendish. And anyone else to helped him."

Well done on the show too. Thoroughly enjoyable.
Title: Proof of Gravity and the Cavendish Experiment
Post by: Wolfwood on December 22, 2006, 08:56:12 PM
Wouldn't Iron be effected by magnetics?
Title: Proof of Gravity and the Cavendish Experiment
Post by: ArmyJonHall on December 22, 2006, 10:12:17 PM
Quote from: "Wolfwood"
Wouldn't Iron be effected by magnetics?

They were lead spheres, not iron, and lead is non-ferrous (not magnetic)
Title: Proof of Gravity and the Cavendish Experiment
Post by: coddy on December 23, 2006, 05:23:21 AM
Quote from: "ArmyJonHall"
Quote from: "Wolfwood"
Wouldn't Iron be effected by magnetics?

They were lead spheres, not iron, and lead is non-ferrous (not magnetic)


A metal does not have to be ferous to be magnetic...nickel and cobalt are also magnetic...
Title: Re: Proof of Gravity and the Cavendish Experiment (I'm seri
Post by: Wolfwood on December 23, 2006, 07:34:58 AM
Quote from: "Max Fagin"
So it turns out I was wrong.

On the Infidel Guy radio show about a week ago, Reginald Finely suggested that the existence of gravity as a force could be proven by suspending a very massive object and measuring it's gravitational pull with a nearby detector.  I then implied that I didn't think that was possible because gravity was such a weak force.

Well it turns out I was wrong.  After the show, I got an E-mail form William Jefferys, a professor of astronomy and statistics at The University of Texas.  He told me about an experiment called the Cavendish experiment.

http://en.wikipedia.org/wiki/Cavendish_experiment

Apparently, the Cavendish experiment has been used to measure the gravitational pull of small objects since the 1800's.

The set up is a bit more sophisticated then a ball on a string, but not by much.

It involves taking a rod with an iron ball on each end, and suspending it from a very thin string.  Then placing two larger iron spheres nearby, and measuring how much the apparatus rotates.

At very least, this allows you to demonstrate the existence of gravity as a force, and if you assume the Earth to be round, it lets you calculate the value of the gravitational constant, G, if you replace the string with a wire with known torsion properties.

I had always believed that the gravitational constant was measured from celestial observations, but this turns out to be a better (Although still imprecise) way of doing it.

This is a difficult experiment, but not one that is beyond reach of a well-stocked high school lab.  I think this is the most clinching proof I have seen so far that gravity exists, and FE is erroneous.

Response FE'ers?


He quite clearly said Iron there...
Title: Re: Proof of Gravity and the Cavendish Experiment (I'm seri
Post by: Max Fagin on December 23, 2006, 10:29:58 AM
Quote from: "Wolfwood"
He quite clearly said Iron there...


My mistake.  I just assumed it was iron.  But it seems like the experiment was done with lead.
Title: Proof of Gravity and the Cavendish Experiment
Post by: Erasmus on December 24, 2006, 12:11:09 AM
Sorry dude, but, from: http://theflatearthsociety.org/forums/viewtopic.php?p=8562&highlight=torsion+balance#8562

Quote from: "I"
Yeah, that experiment is pretty stunning. Somebody (maybe you; I don't remember) recently posted a link on this forum to a website about a do-it-yourself torsion balance experiment, in two versions: one with modern materials, and one with materials available to, say, Archimedes. There are videos! The videos are *awesome*. I don't remember what thread it was in, but the link is http://www.fourmilab.ch/gravitation/foobar/

-Erasmus
Title: Proof of Gravity and the Cavendish Experiment
Post by: beast on December 24, 2006, 12:54:07 AM
Quote from: "ArmyJonHall"
I'm listening to your podcast right now- and I have to say, the fact that none of the FE'ers even decided to appear makes the whole thing (the flat Earth thing, this is) hilarious.

I think I can predict the FE response-

"Max is part of the conspiracy. So was Cavendish. And anyone else to helped him."

Well done on the show too. Thoroughly enjoyable.


You're completely wrong.  I agreed to take part.  I just never heard anything more about it and was too busy to follow it up myself.  My argument would have been completely different to what you're suggesting and would have pwned all REers everywhere.
Title: Proof of Gravity and the Cavendish Experiment
Post by: ArmyJonHall on December 24, 2006, 01:23:38 AM
Quote from: "beast"
You're completely wrong.  I agreed to take part.  I just never heard anything more about it and was too busy to follow it up myself.  My argument would have been completely different to what you're suggesting and would have pwned all REers everywhere.

Whoh whoh whoh, back up on the use of the word 'wrong' there fella. You agreed to take part after the show aired. You can't hit back out at me about that now.

If you ask Reginald Finely nicely he might run another debate for ya. I'm willing to bet Max would be more than keen to do another appearance. Stop hitting out at me. Go and actually do something about it, I'd love to hear an even, moderated debate about this.
Title: Proof of Gravity and the Cavendish Experiment
Post by: beast on December 24, 2006, 01:24:50 AM
Actually I agreed to take place in the show after it was first mentioned on this forum.
Title: Proof of Gravity and the Cavendish Experiment
Post by: beast on December 24, 2006, 01:28:12 AM
http://www.theflatearthsociety.org/forums/viewtopic.php?t=6345

omg, I'm right and actually know what I'm talking about.  :shock:
Title: Proof of Gravity and the Cavendish Experiment
Post by: ArmyJonHall on December 24, 2006, 01:34:13 AM
Quote from: "beast"
http://www.theflatearthsociety.org/forums/viewtopic.php?t=6345

omg, I'm right and actually know what I'm talking about.  :shock:

... and then proceeded to make excuses as to why you didn't go on the show when you had the chance. He offered to call you, you could have contacted him through his email, chatted to him through his IRC channel, or if money weren't such a big issue for you, you could have called him. His line was open the entire time during the show.

That aside, if you're still keen on doing a debate you should contact Reginald, not whinge about it here. If he flat out refuses to do it, then you can whinge about it.
Title: Proof of Gravity and the Cavendish Experiment
Post by: beast on December 24, 2006, 01:40:35 AM
Do you honestly want me to quote my own post a couple of posts up?
Title: Proof of Gravity and the Cavendish Experiment
Post by: skeptical scientist on December 24, 2006, 01:58:37 AM
Quote from: "beast"
http://www.theflatearthsociety.org/forums/viewtopic.php?t=6345

omg, I'm right and actually know what I'm talking about.  :shock:

OMG!

I hope there's going to be a radio debate, as I think it would be really cool. I really wouldn't want to do it myself though, as I haven't been in a live debate since high school, and am much more comfortable debating via forum post as I have time to rewrite my post several times and maybe do some quick web research.
Title: Proof of Gravity and the Cavendish Experiment
Post by: ArmyJonHall on December 24, 2006, 02:10:41 AM
Quote from: "beast"
Do you honestly want me to quote my own post a couple of posts up?

NO! I want you to contact Reginald Finely, and ask him for the chance to do another debate. When he did his first broadcast about FE with Max he said  he would be more than happy to do it again with an FE'er there.
Title: Proof of Gravity and the Cavendish Experiment
Post by: ArmyJonHall on December 24, 2006, 03:01:17 AM
In case you were actually genuine on contacting Finely, here's his contact information for you in case you were too lazy to follow it up on your own-

Quote
Well.. I guess I'll give you all the information you need to listen and participate if you wish.

http://www.thedebatehour.com

The toll-free call in number for US residents is: 888-503-0802

The show will begin @ 8PM ET.

The live listen LINK is here: http://www.thedebatehour.com/listen.m3u

You can interact with us via my stickam video room or my irc chat room.
Stickam room: http://www.stickam.com/profile/infidelguy

for irc participation:
http://www.infidelguy.com/cgi-bin/cgiirc/irc.cgi
Title: Proof of Gravity and the Cavendish Experiment
Post by: Dionysius on December 26, 2006, 10:20:05 AM
Quote from: "ArmyJonHall"
Quote from: "beast"
http://www.theflatearthsociety.org/forums/viewtopic.php?t=6345

omg, I'm right and actually know what I'm talking about.  :shock:

... and then proceeded to make excuses as to why you didn't go on the show when you had the chance. He offered to call you, you could have contacted him through his email, chatted to him through his IRC channel, or if money weren't such a big issue for you, you could have called him. His line was open the entire time during the show.

That aside, if you're still keen on doing a debate you should contact Reginald, not whinge about it here. If he flat out refuses to do it, then you can whinge about it.


Are you sure that you are referring to beast rather than someone else?  I do believe everyone here would like to see a debate between Max Fagin and beast.  I concur that beast should contact Finley so a debate can be scheduled.

  And it was encouraging that Max got an informative e-mail from a university professor as a result of the show.
Title: Proof of Gravity and the Cavendish Experiment
Post by: ArmyJonHall on December 26, 2006, 06:45:29 PM
So... is beast still keen on doing the debate?
Title: Proof of Gravity and the Cavendish Experiment
Post by: Dionysius on December 27, 2006, 03:50:54 AM
According to beast's posts the answer is yes.
 
It would be much appreciated if anyone (beast, Max Fagin, infidelguy, phaseshifter) who has information of an upcoming debate would post that information when they get it.  Thanks.
Title: Proof of Gravity and the Cavendish Experiment
Post by: Max Fagin on December 28, 2006, 11:27:40 AM
I still want to know how FE'ers account for this.  Isn't this evidence that Gravity exists as a force, and applies down here on Earth?
Title: Proof of Gravity and the Cavendish Experiment
Post by: PaRtZ on December 28, 2006, 02:03:11 PM
as far as I can tell, yeah lol
Title: Proof of Gravity and the Cavendish Experiment
Post by: Wolfwood on December 28, 2006, 02:04:43 PM
Quote from: "Max Fagin"
I still want to know how FE'ers account for this.  Isn't this evidence that Gravity exists as a force, and applies down here on Earth?


Except for the possibility that the lead could have been manipulated by Earth's magnetic field.
Title: Proof of Gravity and the Cavendish Experiment
Post by: Dionysius on January 05, 2007, 12:57:37 PM
Quote from: "Max Fagin"
I still want to know how FE'ers account for this.  Isn't this evidence that Gravity exists as a force, and applies down here on Earth?

I have not looked into this yet, but the magnetism was the first thing that came to mind.  The principle difference in our understanding of the concept of gravity is that I believe that heavy things go downwards while you probably believe they are pulled inwards to the centre of huge objects like the way you imagine the World to be, probably due in some way to the mass of such objects.  Your view is much older than Newton as the globularists of Ptolemy's era had already thought of it as a defense of their theory.  The following by Lactantius is a summary of how the globularist misunderstanding of gravity came into being:

------------------------------------------------------------------------------------------------------------------
  "What course of argument, therefore, led them to the idea of the antipodes? They saw the courses of the stars travelling towards the west; they saw that the sun and the moon always set towards the same quarter, and rise from the same. But since they did not perceive what contrivance regulated their courses, nor how they returned from the west to the east, but supposed that the heaven itself sloped downwards in every direction, which appearance it must present on account of its immense breadth, they thought that the world is round like a ball, and they fancied that the heaven revolves in accordance with the motion of the heavenly bodies; and thus that the stars and sun, when they have set, by the very rapidity of the motion of the world are borne back to the east. Therefore they both constructed brazen orbs, as though after the figure of the world, and engraved upon them certain monstrous images, which they said were constellations. It followed, therefore, from this rotundity of the heaven, that the earth was enclosed in the midst of its curved surface. But if this were so, the earth also itself must be like a globe; for that could not possibly be anything but round, which was held enclosed by that which was round. But if the earth also were round, it must necessarily happen that it should present the same appearance to all parts of the heaven; that is, that it should raise aloft mountains, extend plains, and have level seas. And if this were so, that last consequence also followed, that there would be no part of the earth uninhabited by men and the other animals. Thus the rotundity of the earth leads, in addition, to the invention of those suspended antipodes.  

But if you inquire from those who defend these marvellous fictions, why all things do not fall into that lower part of the heaven, they reply that such is the nature of things, that heavy bodies are borne to the middle, and that they are all joined together towards the middle, as we see spokes in a wheel; but that the bodies which are light, as mist, smoke, and fire, are borne away from the middle, so as to seek the heaven. I am at a loss what to say respecting those who, when they have once erred, consistently persevere in their folly, and defend one vain thing by another; but that I sometimes imagine that they either discuss philosophy for the sake of a jest, or purposely and knowingly undertake to defend falsehoods, as if to exercise or display their talents on false subjects. But I should be able to prove by many arguments that it is impossible for the heaven to be lower than the earth, were is not that this book must now be concluded, and that some things still remain, which are more necessary for the present work. And since it is not the work of a single book to run over the errors of each individually, let it be sufficient to have enumerated a few, from which the nature of the others may be understood."
www.sacred-texts.com/chr/ecf/007/0070075.htm
------------------------------------------------------------------------------------------------------------------------------

  As to Cavendish, I thank you for drawing this to our attention, but you attach more weight to it than I do judging by your conclusion that the Earth is globular because of the Cavendish experiment.  I consider such a conclusion to be a hypothesis requiring multiple other specific opinions which I do not share.  And there is still the question as to whether Cavendish confirms your view of gravity which must show that the experiment works with materials such as lead (or something like plastic or anything that one would presume to have minimal magnetic draw) and then still prove that with respect to such materials their effect upon a suspended object (if they have one) is not magnetism.  

  Do you equate magnetism with gravity?
Title: Proof of Gravity and the Cavendish Experiment
Post by: Max Fagin on January 06, 2007, 12:06:10 AM
I read the above block of text from sacred-texts.com twice Dionysius, but I'm not grasping the point it is trying to make, or it's relevance to this topic.  Are you arguing in favor of Ptolemy's universe?

Quote from: "Dionysius"
...your conclusion that the Earth is globular because of the Cavendish experiment.


I wasn't saying that.  I realize that demonstrating the existence of gravity does not prove the Earth to be spherical.  What it does do however is put to rest one of the major claims of the FE'ers who believe that things fall due to an "upward" acceleration of the Earth.

As for the effects of the experiment being attributed to magnetism, let me give two reasons why magnetism can't explain what we are seeing:

1.  Lead is magnetically inert.  It does not carry any net electric charge.

2.  The Cavendish experiment provides identical results every time it is performed.  If for some reason the spheres did develop an electric change, it would have to be exactly the same amount of charge every time the experiment is performed, which is unlikely.
Title: Proof of Gravity and the Cavendish Experiment
Post by: Mr. Smammi on January 06, 2007, 01:29:05 AM
A very powerful blow to one of the major disputes here. However, I hope you to come to your full senses, Max.
Title: Proof of Gravity and the Cavendish Experiment
Post by: FastEddy on January 06, 2007, 03:00:47 AM
Quote from: "Mr. Smammi"
A very powerful blow to one of the major disputes here. However, I hope you to come to your full senses, Max.

Going on his last posts, he's already there, and waiting for the FE'ers to catch up.

This is one of the ultimate bugbears for the FE'ers. It's a consistent, repeatable exercise which produces the same result each time. It does not require overly expensive materials which the government controls (ruling out the too-oft-mentioned conspiracy theory) and any response the FE'ers put forward is easily rebutted by known, observed facts.
Title: Proof of Gravity and the Cavendish Experiment
Post by: Strader on January 06, 2007, 03:38:29 AM
There;s that or they will just throw an insult at you guys, most FE'ers on here do that, not that it will prove much, other than that they are childish and are wrong to believe in FE.
Title: Proof of Gravity and the Cavendish Experiment
Post by: EnragedPenguin on January 06, 2007, 07:13:40 AM
Quote from: "Max Fagin"

I wasn't saying that.  I realize that demonstrating the existence of gravity does not prove the Earth to be spherical.  What it does do however is put to rest one of the major claims of the FE'ers who believe that things fall due to an "upward" acceleration of the Earth.


I would say all it does is show that the two spheres you're using are gravitationally attracted. I see no reason to infer that Earth must have a gravitational field simply because two spheres of iron do. Just as I see no reason to infer that just because Magnetite is magnetically attractive, the same must be true for Granite, or Flint.
The Earth is not those two iron spheres, and thus shouldn't be expected to share the same properties.
Title: Proof of Gravity and the Cavendish Experiment
Post by: Max Fagin on January 06, 2007, 08:59:11 AM
Quote from: "Enraged Penguin"

The Earth is not those two iron spheres, and thus shouldn't be expected to share the same properties.


Why not? Even in the FE model, the Earth is composed largely of metals.

http://www.theflatearthsociety.org/forums/viewtopic.php?t=1361&highlight=magnetic+field

Edit: I know Erasmus never says "metallic magnets" in the above explanation, but I think it's a fair assumption.  I take it he isn't referring to super conductors, so the magnets must be metallic.

But even that isn't necessary. Would performing this experiment with two massive rocks (Parts of the Earth) convince you that the Earth has gravity?
Title: Proof of Gravity and the Cavendish Experiment
Post by: EnragedPenguin on January 06, 2007, 11:45:40 AM
Quote from: "Max Fagin"
Why not? Even in the FE model, the Earth is composed largely of metals.

Are you willing to test every single one of them? Otherwise the experiment only proves that iron has gravitational attraction.
Quote
But even that isn't necessary. Would performing this experiment with two massive rocks (Parts of the Earth) convince you that the Earth has gravity?

Yes. Or rather, it would show that the material making up the crust of Earth has a gravitational field.
Title: Proof of Gravity and the Cavendish Experiment
Post by: Max Fagin on January 06, 2007, 03:45:22 PM
Quote from: "EnragedPenguin"
Quote from: "Max Fagin"

Quote
But even that isn't necessary. Would performing this experiment with two massive rocks (Parts of the Earth) convince you that the Earth has gravity?

Yes. Or rather, it would show that the material making up the crust of Earth has a gravitational field.



Great.  Here is a description of an experiment that measured the gravitational atraction of several materials:

http://www.fourmilab.ch/gravitation/foobar/

and here are the timelapse videos showing the results with two chunks of rock.

http://www.fourmilab.ch/gravitation/foobar/figures/movie-3.mpg
http://www.fourmilab.ch/gravitation/foobar/figures/movie-4.mpg
Title: Proof of Gravity and the Cavendish Experiment
Post by: FastEddy on January 06, 2007, 04:18:21 PM
Check and mate!
Title: Proof of Gravity and the Cavendish Experiment
Post by: TheEngineer on January 06, 2007, 09:10:20 PM
Quote from: "Max Fagin"

Great.  Here is a description of an experiment that measured the gravitational atraction of several materials:

http://www.fourmilab.ch/gravitation/foobar/

and here are the timelapse videos showing the results with two chunks of rock.

http://www.fourmilab.ch/gravitation/foobar/figures/movie-3.mpg
http://www.fourmilab.ch/gravitation/foobar/figures/movie-4.mpg

From the link on Wiki about this experiment:
Quote
Bending Spacetime in the Basement (do-it-yourself Cavendish apparatus - appears to be seriously flawed)
Title: Proof of Gravity and the Cavendish Experiment
Post by: Erasmus on January 06, 2007, 09:45:48 PM
Quote from: "Dionysius"
And there is still the question as to whether Cavendish confirms your view of gravity which must show that the experiment works with materials such as lead (or something like plastic or anything that one would presume to have minimal magnetic draw) and then still prove that with respect to such materials their effect upon a suspended object (if they have one) is not magnetism.


If it could be demonstrated that the experiment works with a variety of nonmagnetic materials, would you accept the universality of gravitation?
Title: Proof of Gravity and the Cavendish Experiment
Post by: EnragedPenguin on January 07, 2007, 11:18:23 AM
Quote from: "Max Fagin"

Great.  Here is a description of an experiment that measured the gravitational attraction of several materials:


Well the videos are, like pictures, not admissible as evidence. I'd have to be able to test it myself, and I can't use an experiment whose validity is in doubt.
Of course, anyone can edit wikipedia, so that's not reason to discount the experiment entirely. Maybe Erasmus, Engineer, or Skeptical can vouch for it?
Title: Proof of Gravity and the Cavendish Experiment
Post by: Max Fagin on January 07, 2007, 02:14:12 PM
Actually EnragedPenguin, I found this experiment so interesting, that a friend and I decided to try it out.  I'll post any videos as soon as I have them.  Are you willing to belive that I am not part of the conspiracy?
Title: Proof of Gravity and the Cavendish Experiment
Post by: Erasmus on January 07, 2007, 02:33:19 PM
Quote from: "EnragedPenguin"
Well the videos are, like pictures, not admissible as evidence. I'd have to be able to test it myself, and I can't use an experiment whose validity is in doubt.
Of course, anyone can edit wikipedia, so that's not reason to discount the experiment entirely. Maybe Erasmus, Engineer, or Skeptical can vouch for it?


The "Discussion" section on that WP article describes the flaw in the experiment.  These calculations could probably be reproduced by the people you listed.
Title: Proof of Gravity and the Cavendish Experiment
Post by: Erasmus on January 07, 2007, 06:20:29 PM
Quote from: "Erasmus"
The "Discussion" section on that WP article describes the flaw in the experiment.  These calculations could probably be reproduced by the people you listed.


After some head scratching I came up with a differential equation describing the motion of the torsion balance arm.  Assuming there is no torque from the suspending string, no atmosphere, and a massless arm, the dynamics are:

Code: [Select]
dθ     GM  (    cos θ/2            sin θ/2      )
---- = -----  ( --------------  -  ---------------- )
dt      2R  ( 1 - cos θ/2     1 + cos θ/2 )


where G is the gravitational constant, M is the mass of each fixed weight, and 2R is the distance along the balance arm at which the smaller masses are placed.

I couldn't find an analytical solution to this equation, but a numerical simulation showed that, starting from an angle of θ=10, it took just over ten minutes for the arm to complete its motion (I used values of M and R from the website).

I am running the simulation on a greater variety of initial states, and report results when I have them.  For now, however, it would appear that it is entirely possible that Bending Spacetime in the Basement could be a genuine demonstration of gravitational attraction between two small objects.
Title: Proof of Gravity and the Cavendish Experiment
Post by: Erasmus on January 07, 2007, 10:02:13 PM
Results of my wasted Sunday afternoon:

(http://i49.photobucket.com/albums/f287/PraiseOfFolly/Flat%20Earth%20Society/torsion-time.gif)

Estimate for yourself the initial angle and the time the arm took to complete the swing by watching the video, and decide whether it's plausible.
Title: Proof of Gravity and the Cavendish Experiment
Post by: TheEngineer on January 07, 2007, 10:08:02 PM
I will say, you are dedicated.
Title: Proof of Gravity and the Cavendish Experiment
Post by: TheEngineer on January 07, 2007, 10:15:53 PM
I see less than 5 minutes to swing through about 40 degrees.  By your kinematics, that should take a little over 80 minutes.