https://www.researchgate.net/post/Is_Newtons_Third_Law_a_misconception_A_metaphysical_dogma
Hello all,
Not as a first answer but to help set a possible direction in this thread.
taking a contrary view, instead of talking about what is wrong with Newton's third law, one can explore a suggestion of what might be right, and the discussion would attempt to validate that, or deny it.
For example, the conservation laws for Energy and Linear/Angular Momentum are just as inevitable from Newton's law, including or not the third law?
Cheers, Ed Gerck
Nothing's wrong with it. Newton's third law simply describes certain ways in which the coordinate transformations lead to transformations of derived quantities that can describe, in particular, energy and momentum conservation, that's all.
The conservation laws simply state, in other terms, Newton's first and third laws. Different ways of expressing the same thing, so it doesn't matter which one is used.
The same as with the 2nd. Funny notions of material point, position, momentum and force.
Hello Stam and Igor,
The third law contradicts itself when the coriolis force found by Newton's laws has no reaction pair. There are many cases where forces are called "fictitious", even within the system that is supposed to be calculating them, so it is not consistent, you cannot trust what is calculated. And, well put, a material point does not exist in this world, so the concept must lead to contradictions and misconceptions in this world.
Cheers, Ed Gerck
Of course there's no contradiction. The Coriolis force is just a way of describing certain properties of non-inertial reference frames, that's all. And it can be dispensed with altogether by working with a non-trivial spacetime metric, incidentally (as can any mention of a force, as well). It doesn't matter what formalism one uses, only the end results matter.
Material points exist insofar as their mathematical description is consistent, which can be checked to be the case. And it is equally straightforward to check when the approximation of describing experiments in terms of material points is valid and when it breaks down.
Hello Stam,
No. Coriolis forces are defined in non-inertial frames, where Newton's laws are not valid, an one has to admit the existence of ad hoc, "fictious forces" to account for what is or is not calculated. Also Corolis forces do no work, which is another exception. The case is similar to Newton's centrifugal and centripetal forces, that do not exist at all in circular motion, as the following example of the stone shows:
https://www.researchgate.net/post/Is_Newtons_Third_Law_a_misconception_A_metaphysical_dogma#view=5ab66dc5dc332d8dff017060
So, Newton's laws do not apply even in our macroscopic world, they apply in a world of their own, different from ours. Our world does not have material points or inertial reference frames. Contradictions appear, so it matters what formalism to use.
Conservation laws have no such problem, and Newton's laws with so-called "ficticious forces" do not have to be used. I welcome any counterxamples, but one can prove that there are none; it is so well-known to physicists that it is not publishable any more
Cheers, Ed Gerck
Come now, Ed. You keep insisting that Newton's laws don't work, when they work just fine. Yes, this includes Coriolis forces. You simply have to go beyond the most simple of models, even in classical mechanics, but there's no make-believe, no metaphysics, no religion involved..
F = mv2/r is the centrifugal force, of a mass rotating at tangential speed v, a radius r from where it is tethered. This is verifiable. It results from the fact that the direction of motion of that mass continuously changes, such that it's momentum, which tries to keep the mass moving in a straight line, has to be opposed. So, some sort of tether has to be used, to force rotation. A continuous counter-force, to keep the mass rotating. Action, equal and opposite reaction.
See the attached link to a well-done derivation. In particular, look at Method B. It derives quite nicely, I'd say.
Or measure it. Use a calibrated spring in the tether. Measure the expansion of the spring, at a constant rate of rotation. That spring's extension proves that indeed, a force is involved here. Nothing metaphysical.
I would not object if you simply asserted that Hamiltonians are more elegant, or what have you. But you keep overstating your case, time and time again.
Hello Albert,
The metaphysics enters in Newton's third law, but that is history, so it does not have a say today in physics. Surprisingly, it could have been right, and many of the ideas in science do come from metaphysics and were not explicitly acknowledged, mostly to avoid opposition. But is not right, that is what matters, nature is the arbiter.
You are welcome to keep your views, but the stone will not go off radially, even with some or all of the rope's length attached to it, not following a false centrifugal force, as you can try yourself: https://www.researchgate.net/post/Is_Newtons_Third_Law_a_misconception_A_metaphysical_dogma#view=5ab66dc5dc332d8dff017060
This is not a matter of opinion. Do the experiment and see. Do not believe me, if you have a doubt, try it out. It is a simple experiment, even at your desk.There is a nottion of right and wrong, in nature.
Btw, the Hamiltonian is not only more elegant but will not give you the wrong aswer, which is a benefit.
Cheers, Ed Gerck
Dear Ed,
You write: "Conservation laws have no such problem, and Newton's laws with so-called "ficticious forces" do not have to be used. I welcome any counterxamples, but one can prove that there are none; it is so well-known to physicists that it is not publishable any more"
There are issues with the conservation laws.
For example, from Newton's mechanics, the rotating motion of massive bodies is deemed conservative, but this ignores the fact that any rotating macroscopic body is made of submicroscopic massive and charged particles that are captive on perfectly circular orbits about the macroscopic body's rotation axis, and that each of them constantly changes direction in their circular motion. Being massive, their constant change in direction, according to the 2nd principle of thermo, cannot occur without an expenditure of energy (work).
We even have physical proof of this problem with the constant rotation axial slow down observed of both Pioneer 10 and 11 spacecrafts specifically, but also of all other spacecrafts that need to be rotated to keep antena alignment with the Earth.
Best Regards
André
Hello André.
Thank you. My original phrase could be interpreted in two ways, which was not intended and will disambiguate later. It may have caused your note. To wit:
1. conservation laws are meant as usual, not as derived from Newton's laws -- which is, logically, independent. For example, it is well-known that Newton's Corilolis force does no work, which is against conservation of energy, and has no reaction force, which is against the third Newton's law.
2. mass can move without expenditure of energy in linear motion (Gallileo law, later cited by Newton inappropriately as his first law); when moving in a geodesic then can move in circular motion without using energy; an electron can move without expenditure of an energy when in the orbit picture of QM. These occur experimentally, even though the objects are massive.
3. Newton's laws disobey experiments in circular motion, where a stone that is released form a central pivot shows absolutely NO motion radially, with zero work F.dr, but movement tangentially as expected from Galileo law. This is reported above.
4. No violation of conservation laws are reported for closed sytems, usually the fault is that the system itself is not closed. Then, the conservation laws apply for an expanded system that is closed.
Cheers, Ed Gerck
Dear Ed,
1. I agree with you that what we refer to as Coriolis forces do no work, and can do no work in fact, since it is more an "observed relative effect" rather than an actual force, that in itself induces no motion nor energy in bodies.
2. I think however that there are subtleties to be taken account of with masses in linear motion. From the classical/relativistic mechanics perspective at our macroscopic level, the conservation laws have proven to be applicable with sufficient precision to be workable.
But from the electromagnetic perspective, due to the fact that all elementary massive particles making up macroscopic bodies are charged, it simply is impossible that any type of motion would not involve an adiabatic change in energy levels of moving bodies in physical reality.
Just to take the example you mention of an electron moving in circular motion, it was demonstrated by John Blewett in the 1940's in the GE Betatron that it was not possible to keep individual electrons on a stable perfectly circular orbit in the Betatron without constantly feeding more energy to keep it on the same orbit, with no radiation emission being detected.
The case was considered closed in 1947 after it was pointed out by Schwinger that the emission spectrum should peak at a higher harmonic of the orbit frequency, since the power in the range that Blewett observed had to be negligible, and that a direct observation of radiation was made the following year at the G.E. 70 MeV synchrotron.
But it so happens that the Betatron configuration is the only type of accelerator that allows "perfect circular orbits" of individual electrons, and that the synchrotron from which the settling conclusion was made, by very design is unable to provide such a perfectly circular orbit, which can only cause synchrotron radiation at each transverse oscillation of the beam caused by the accelerating magnets.
So the Blewett observation still needs to be tested in a Betatron, the only design that would allow settling the issue.
Until this experiment is carried out, it seems that an electron on a perfectly circular orbit does loose energy without radiating it (work), which is conform to the 2nd principle of thermodynamics.
3. As with the Coriolis effect, these are observed relative effects.
4. No violation of conservation laws are reported for closed systems in "natural least action equilibrium systems", precisely because they are least action states, in which any energy expended as work is replenished by the Coulomb force acting on the charged particles making up these bodies, but it seems to me that such violations are constantly reported for closed systems that are artificially established, such as all spacecrafts sent on orbits that are not "natural least action orbits", which is all of them.
Best Regards
André
Hello André,
Your case on the electron orbit is not experimentally possible because, among other causes, (1) the electron is actually not a particle, (2) a ""perfect circular" orbit is not unforced, it has to be a geodesic.
As to the Coriolis effect, it is experimentally observed and accounts for the fact that the Amazon forest is not the "lungs of the world". The winds from North and South separate strongly at the Equator because of the work done by the Coriolis force, Newton's laws notwithstanding, and this has been confirmed for more than 40 years, experimentally and theoretically, when using the correct theory. You can also see the Coriolis force with a simple pendulum, just long enough, as done long ago.
Cheers, Ed Gerck
Dear Ed,
We know that electrons are physically localized particles because they can be scattered against each other. In fact, proof of physical existence is precisely the fact that traces of their deflected trajectories can be recorded by various means. A fact ever since bubble chambers have been introduced more than 100 years ago. Constantly used in all high energy accelerators as "bullets" to collide with other particles.
If you were to study the mechanics of betatron accelerators, you would understand that perfectly circular orbits for individual electrons are possible with this design when the beam is sufficiently thinned out, as was done by Blewett.
Best Regards
André
- Badges
- Science topic
- Similar topics
- Force