Freedom of Science

9 Responses to “Cavendish experiment 2”  

1. 1 Kea Oct 17th, 2007 at 9:32 pm

   Most physicists agree that Force does not exist, since GR introduces the idea of gravity as geometry. You can argue with the Cavendish experiment, but I would like to hear your gripes with the use of F=ma in a limit of Einstein’s equations, which you must be suggesting need modifying so that both sides are made of marble. While I might agree, I feel I must point out that a resolution of this problem is unbelievably more subtle than the considerations that you appear, to date, to be undertaking.

2. 2 Pioneer1 Oct 18th, 2007 at 9:24 pm

   Thanks for this thoughtful comment.

   Most physicists agree that Force does not exist, since GR introduces the idea of gravity as geometry.

   I think that when physicists agree that force does not exist that always comes with the qualification that force does not exist in the context of general relativity but it does exist in the context of Newtonian physics.

   I don’t know if you agree with this.

   I can try to support it with the documents written by physicists where they claim that Newtonian force emanating from a lead ball sets the Cavendish pendulum in motion.

   Some examples:

   
   [Force equation] describes the attractive force between the two masses m and M separated by distance r.

   Newton’s law of gravitation, F=GmM/r^2, describes the attraction between any two masses in the universe.

   The law states that every body attracts every other body with a force whose magnitude is given by equation 1.

   By measuring the amount of twist, you can determine the strength of the force of gravity, and if you know the masses involved and the distance between them, you can determine the value of Newton’s gravitational constant G.

   The experiment claiming to measure the official value of G assumes Newtonian force and attraction.

   In the context of the Cavendish experiment physicists believe that there is a measurable quantity called Newton’s force and this thing as occult as it is sets the pendulum in motion and physicists measure it and find the exact value of the unit of this force.

   I am trying to narrow the question to what physicists call “classical physics.” In this domain physicists claim that Newtonian force is a measurable quantity and it was first measured by Cavendish.

   Did Cavendish pendulum move under the influence of the Newtonian force?

   Do you think the answer to this question involves General Relativity?

   I found in my Cavendish page this paper by Dieter Brill who writes that “… there exists “anti-Cavendish” solutions of Einstein field equation describing slabs that do not attract each other.” Brill then derives a “Cavendish” solution. Apparently, General Relativity can be tweaked to give a solution supporting Cavendish experiment and not.

   But I only look at the equation of motion of the Cavendish experiment. This is the standard pendulum equation with an additional term representing force.

   I believe that F=ma is not used in the analysis of the experiment and it is not a part of the equation of motion or the experiment.

   So I don’t understand how the occultness of the Newtonian force disappears if Einstein equations reduces to it in some limit.

   I am ready to call this whole Cavendish experiment thing off and move on with my life if I can convince myself that physicists really measure the occult in an experiment.

   Do you think that the equation of motion that I’ve been using is a GR equation and does not represent the Newtonian force?

   …I would like to hear your gripes with the use of F=ma…

   I didn’t exactly understand your comment about F=ma. In the context of Cavendish experiment F=ma doesn’t need to be modified because it does not enter the equation of motion.

   More generally, I believe that F=ma is one of the non-working parts of Kepler’s rule. When both sides are united F cancels. F is not used in computation of orbits. But I hope that I’m wrong on this too. For instance, I once wrote to the astronomer Michael E. Brown who wrote that he used “equations used by Isaac Newton to figure out the mass of Jupiter, we can now tell that Eris has a mass 27 per cent higher than that of Pluto.”

   But in his paper in Science about the same topic, he wrote “from the period and semimajor axis of the orbit of Dysnomia, we can use Kepler’s laws to calculate a mass for the Eris-Dysnomia system….”

   I asked him why “Newton’s laws were needed,” I believe that he replied that Newton’s laws are needed to get better precision. But I didn’t follow up after that. I don’t know how he used Newton’s laws or what he calls Newton’s laws.

   Thanks again for your comment.

3. 3 Kea Oct 18th, 2007 at 9:55 pm

   Thanks for the Brill reference re using Cavendish to measure extremal charge for a given mass. What he says does suggest that GR is needed to understand G, but note that the non-Cavendish solutions use exotic matter. Anyway, the fact remains that the ‘occult’ is used everyday in practical applications. My students can happily draw force vectors, and the concept helps them solve problems, so even if it is only a ’spurious limit’ of a more complete theory, I believe it has its uses.

4. 4 Pioneer1 Oct 20th, 2007 at 10:22 pm

   The ‘occult’ is used everyday in practical applications.

   I don’t understand this. You may be referring to pedagogical applications. That’s different. Are you for instance saying that the occult paranormal force advocated by Uri Geller who uses it to bend spoons is a real force? This force too can be represented by vectors, does this make it a scientific quantity?

   Do you think that the occult force of Newton set the Cavendish pendulum in motion? I believe that this is not possible. Occult is not a scientific quantity. The fact that your students call an arrow “force” and use it to solve problems does not make occult real.

   Occult is not a “spurious limit” of a more complete theory. As far as I know there is no scientific theory that predicts the existance of the occult.

   Thanks.

5. 5 Kea Oct 23rd, 2007 at 2:29 pm

   Yes, I just meant pedagogical applications. I really do agree that the concept of Force has led theoretical physics very astray, but it still has its place in the discipline.

6. 6 Pioneer1 Oct 24th, 2007 at 9:20 pm

   I agree with you that force has led physics astray. But in what sense do you mean this? To me it is serious business if force led theoretical physics astray and it is still used as the fundamental assumption of physics. If true, this is an important obstacle for the progress of foundational research.

   What are your objections for the removal of force from physics? It is not used in half of physics, namely, General Relativity. In the other half it is used in mechanics to solve mechanics problems. In mechanics it is used as pressure or contact force. In that sense I have no objection to its use. May I assume that you mean this when you say force has its place in physics? But in astronomy force is not a contact force, it is occult. As a result, in astronomy force cancels and it is not needed.

   Thanks.

7. 7 Kea Oct 25th, 2007 at 1:55 pm

   What are your objections for the removal of force from physics?

   I think Newtonian mechanics is an excellent way to introduce rigorous methods to first year students, and teach them about vector quantities and conservation of energy (a concept that postdates Newton). In second year, students are still struggling with basic techniques. Force only begins to be a problem in third year physics, when students begin to be indoctrinated in GR and QFT courses (if they even do this in third year these days!) I think there needs to be a broader education at the third year level, and higher, and I agree with you that the problem would be less severe if the students started out with a better appreciation for history and philosophy.

8. 8 Pioneer1 Oct 28th, 2007 at 8:50 pm

   I think Newtonian mechanics is an excellent way to introduce rigorous methods to first year students, and teach them about vector quantities and conservation of energy (a concept that postdates Newton).

   You touch on several topics that I am interested in. Below are some thoughts inspired by your comment. I will post this later as an article as well.

   Newtonian mechanics and Education

   In your comment you emphasize physics education and I agree that this is important but, since I am more interested in the content of Newtonian Mechanics than teaching of it, I would like to separate Newtonian Mechanics from teaching Newtonian Mechanics.

   Mechanics

   The word mechanics is a rubric. It is the name of a wide range of topics about the study of change in all its aspects (as you know). So every observation, rule, problem, or solution that is related to motion is classified under the rubric “mechanics.”

   I believe that the science of mechanics, or study of motion, can be divided into two main sections:

   1. Mechanics based on Kepler’s rule
   2. Mechanics not based on Kepler’s rule

   Projectile motion, free fall, orbits, collisions, what is called energy conservation, among others, are explained by Kepler’s rule (R3T2).

   Physics and Kepler’s Rule

   As part of their professional tradition, physicists call R3T2 Newton’s laws. They compute with R3T2 but praise Newton.

   For instance, Cavendish experiment is a computation of mean density of the Earth by applying Kepler’s Rule to the constants of the pendulum. I am always amazed to the length physicists would go to deny Kepler’s Rule in order to save Newton’s authority.

   R3T2 is fundamental not Newtonian mechanics.

   If so, why do we need Kepler’s Rule with Newton’s labels? If the labels cancel we don’t need them.

   I believe that it is a fundamentally important to call Kepler’s Rule Kepler’s Rule and not Newton’s law. This is not just a matter of labeling. R3T2 does not include an occult force. Newtonian R3T2 has occult force in it.

   What we call R^3=T^2 defines how we perceive the world. If we call R^3=T^2 Newton’s laws and we write it with F and M, then we accept Newton’s occult force and we must believe that nature is occult. I don’t believe that nature is supernatural.

   Newtonian mechanics

   Why is there a Newtonian Mechanics? Mechanics is an old science that existed since history began. What happened in the 18th century that a new discipline called Newtonian Mechanics was created?

   I think looking at the titles of mechanics books would help.

   Up to Newton’s time, every Peripatetic Doctor was required to write a treatise called De Motu. So Galileo wrote one, Newton wrote one. De Motu was written as a commentary to Aristotelian Mechanics. Galileo realized that he was just writing yet another scholastic treatise on the Impetus theory and moved on to his independent study of motion without scholastic labels. Impetus theory was the theoretical and scholastic way of studying motion that corresponds to gravity theories of today.

   Newton also composed his De Motu as part of his Doctoral duties. This was a standard De Motu and it wasn’t even worth publishing. Newton sat on it for two decades.

   So before Newton, scholastic doctors who studied motion wrote treatises they called On Motion. They used legal labels they culled from vast literature and composed a commentary and embellished it by adding some new stuff of their own.

   What changed the status quo in scholastic mechanics was Newton’s discovery of Kepler’s Rule.

   Once he learned about Kepler’s Rule, Newton started to codify mechanics by labeling permutations and parts of Kepler’s rule with his own labels.

   Newton and Kepler’s Rule

   Newton knew that with R3T2 he had a game changing rule in his hands. So, Newton did not write yet another treatise on motion. He wrote Principles or Newton’s Laws. He wrote a book called (Newtonian) Principles to establish his doctrines about how the world must be perceived as the science of mechanics. Newton codified the old science of mechanics by stating it with his axioms, laws and rules. This is what scholasticism required. After codification, mechanics became teachable under Newton’s name and Newton’s school (Natural Philosophy) was established. Newton set the standards for mechanics that physicists still teach today.

   But Principia is Newton’s De Motu with the addition of Kepler’s Rule.

   Principia = De Motu + R3T2

   Or

   Principia = De Motu Newtonian definitions + R3T2

   I believe that we do not need Newton’s definitions and axioms (Newton’s Laws) and his scholastic De Motu and his cosmogonic speculations about space and time to study and understand motion.

   Since we know R3T2 we can derive the rest of physics (supposedly study of change and motion) from it. There is no other rule that we know connecting radius and period of an orbit, so any study of motion must be based on Kepler’s Rule. Only if we reject Newton’s authority and his laws we can go back to studying motion. Otherwise we will always end up fitting nature and motion into Newton’s laws.

   Today we have

   1. Physics based on R3T2 expressed as Newtonian Mechanics
   2. Physics not based on R3T2

   Part of physics is based on R3T2 but it is presented with Newtonian labels and it is called Newtonian mechanics. We can free this part of physics from Newtonian occult and recover R3T2.

   Rectification of Physics

   Why not simplify physics by removing legacy elements such as spurious labels and occult concepts still carried forward from the 18th century to save Newton’s authority?

   The benefits of elimination of Newtonian labels manifests itself in the concept of conservation of energy.

   Conservation of Energy

   You write that conservation of energy post-dates Newton.

   But it doesn’t. Or, if it does, it does only as a label. Once we eliminate Newton’s legacy we see that conservation of energy is nothing other than Kepler’s Rule written as R^2/T^2 = 1/R.

   Note that it took physicists about a century to label this permutation of Kepler’s Rule as “Conservation of Energy.” Physicists have been staring at Kepler’s Rule but could not see that it was Conservation of Energy. Or, more likely, they knew conservation of energy was Kepler’s Rule, but in order to save Newton’s authority they had to invent a new label.

   “Tragicomical history of thermodynamics” is a proof of how Newton’s sacred authority impedes progress.

   Once we eliminate Newton’s authority our perception of the world will change. This is what happened when Aristotelian Mechanics had been recognized as Authoritarian Mechanics. We once again ended up with an Authoritarian Mechanics, this time, under Newton’s brand.

   Thanks again for your comments.

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