In a blanket denial of a century of progress toward understanding the universe, Donald Hamilton, possessor and author of "The Mind of Mankind" states:

A photon has no mass so it will not be effected (sic!) by gravity (even though most scientists think it will).

I'm glad that I have the mind of a gadfly, which is not affected by his nonsense!

And I won't go into why he is wrong about the principle of equivalence. That has been beaten to death on other Science Blog threads.

This bite of realism brought to you by "Gadfly."

It doesn't make any difference what particle gravity acts on. If it has inertial mass, gravity will influence it. i.e. - A photon has no mass so it will not be effected by gravity (even though most scientists think it will). Protons, neutrons, electrons make up ordinary matter, so these are the ones I choose.

The "bodies" in Newton's law of gravity are these nucleons rather then the whole body. In comparing the free fall acceleration of a electron and a proton (whose mass is about 2000 times more then the electron); while a proton falls at the normal rate - according to Millikan's experiment, "an electron falls slowly and steadly under the influence of gravity, quickly reaching its terminal velocity, also in the Stanford experiment they stated that "the gravity acceleration of the electron in a metal tube was close to zero". These are two possible examples of "bodies falling at different rates of acceleration under the force gravity. To bad the astronaut couldn't have dropped a ball of electrons and a ball of protons on the moon - that would have settled the argument.

As far as Einstein's "principle of equivalence" is concerned, it is possible to distinguish - locally - gravity from acceleration. As I said before: if you drop two balls from different heights in Einstein's room resting on Earth - they will fall at slightly different rates due to there different distances from the center of the Earth whereas in the room of an accelerating rocket they will fall to the floor at exactly the same rate.

Therefore Einstein's "principle of equivalence" is not quite correct - Inertia and gravity are not identical in nature. Inertia is a requirement that a force must be exerted on a body for it to accelerate and gravity is just one of these forces. So much for the Einstein's, General Theory of Gravitation.

Don Hamilton
Ref: The Mind of Mankind Pub.1996
http://novan.com/mind.htm

Mr. Hamilton declares:

If gravity acts on the more fundamental - quarks or leptons - it is they that will be accelerated, all at the same rate since they are being held tightly together by forces inside the proton.

I reply because of another HUGE misunderstanding:
Leptons are electrons, muons, taus, and their corresponding neutrinos. They are not "inside" protons. In fact, they are not subject to the strong nuclear force that holds quarks together as protons, neutrons, and various other baryons as well as mesons. (Those other baryons and mesons are not part of nuclei or atoms--except for virtual pions. Mr. Hamilton does not seem to understand or address the fact that not all matter is atomic or nuclear matter.)

And Mr. Hamilton still didn't address the comment about the previous nonsensical statement that ignored Newton's law of gravity.

My replies are getting shorter as the Hamiltonian nonsense piles deeper.

Fred Bortz -- Science and technology books for young readers (www.fredbortz.com) and Science book reviews (www.scienceshelf.com)

If gravity acts on the more fundamental - quarks or leptons - it is they that will be accelerated, all at the same rate since they are being held tightly together by forces inside the proton.

The weightless body will feel nothing as it falls. Only when an ordinary secondary force (such as the surface of earth) is exerted against the body will the sensation of "weight" be created. The sensation of "weight" will also be created in an "accelerating" rocket because, inertia requires a force be exerted on a body for it to accelerate, and the accelerating floor of the rocket is pushing against (accelerating) the astronaut.

A body lying on the surface of the earth is in a state of "restrained" acceleration rather then being in a "state of rest". It is analogous to a boat with it's motor running pushing against the dock as opposed to the boat just resting against the dock. If the dock was removed, the boat pushing against the dock would began to accelerate, just as a body, if the surface of the earth was removed, would began to accelerate (fall).

In both cases, the surface of the earth or the accelerating rocket, the sensation of "weight" is created when a secondary force is exerted on the body. For gravity it is the surface of the earth restraining the body's acceleration, - for the accelerating rocket it is the floor of the rocket pushing against the body. Gravity and acceleration are not equivalent, they only produce the same effect of "weight" when a secondary force is exerted on the bodies.

For more go to: http://novan.com/weight.htm

Don Hamilton

I promised only one response, but this sentence is too far wrong for me not to point out how little Mr. Hamilton understands about basic physics.

These other nucleons may have different inertial masses and would accelerate at different rates if they weren't under the influence of the protons.

Consider Newton's formula for the gravitational attraction between two masses. It states that the gravitational force F on a body is proportional to its mass m. Rewriting Newton's second law F=ma as a=F/m, it is apparent that gravitational acceleration a is therefore independent of m. (By the way, this conclusion is unchanged by a relativistic interpretation.)

The assertion about nucleons also flies in the face of the modern understanding of the standard model of particle physics, which includes many particles that are not found in association with protons. It also leaves out the fact that the mass of a composite particle (such as a proton, neutron, nucleus, or atom) is not simply the sum of the masses of its fundamental components (quarks and leptons) but also includes the mass contribution of the binding energy.

Besides revisiting his Physics I textbooks, Don might benefit by reading the discussion of the many particles he is leaving out and the history of the development of the standard model of particle physics in my Physics: Decade by Decade (Facts On File, Twentieth-Century Science set, 2007).

If Don wants to display his lack of knowledge further in this thread, I promise to let him do so without further comment. He appeared to be asking for this one!

Fred Bortz -- Science and technology books for young readers (www.fredbortz.com) and Science book reviews (www.scienceshelf.com)

>What's the moon got to do with it?
>Submitted by Fred Bortz on Sun, 2008-02-03 18:35.

>Don writes:
>"For some mysterious reason gravitational mass acted >differently then inertial mass."

>Actually, gravitational mass does not "act" >differently from inertial mass. In fact, one might >say that they "act" the same way, and that is >surprising when viewed as follows.

>Inertial mass is a property that can be measured by >the acceleration produced by a net force. (Newton's >second law)

>In Newtonian terms, gravity is a force between two >bodies, and it is proportional to the inertial mass >of each interacting body. There is no a priori >reason why that should be so.

Don - "I try to explain this "mystery" by saying - "Bodies of different weights all fall at the same rate because gravity is exerting its force on the protons all of which have the same inertial mass, therefore will all accelerate at the same speed. The other nucleons (electrons, neutrons, etc.) are all bound to the protons (the main components of atoms) by the other primary forces so they will be carried along with the protons as they accelerate (fall). These other nucleons may have different inertial masses and would accelerate at different rates if they weren't under the influence of the protons."

>For example, an electrical force is proportional to >the electric charges, which are not necessarily >proportional to the inertial masses. Why couldn't >there also be a gravitational "charge" that is not >proportional to the inertial mass?
>Einstein did not address the "why" of this, but he >used the fact of it to develop his general theory of >relativity--and that led some to conclude that >gravity is not a force but a geometrical effect >produced by the presence of masses in spacetime. He >did not prove the equivalence of the two masses. He >just used the experimental evidence that the two are >equivalent.

>Newton also assumed that equivalence. In fact, as >far as I know, he never considered that there might >be a difference between the two masses.

Don - "There is no difference - gravitational mass is just a special case of inertial mass - it is simply a body that is being accelerated by gravity alone."

>Don also writes this as if the reason for dropping >the hammer and the feather on the Moon had something >to do with a test of the Einsteinian equivalence of >gravitational and inertial mass.
>That is utterly mistaken. This is a classical >mechanics demonstration, with nothing to do with >relativity.

Don - "Both theories try to explain nature's law of gravity. Newton said gravity is a force - Einstein said it is not a force - who is correct??"

>It was simply designed to demonstrate that in the >near-vacuum of the Moon's atmosphere, there is no >air resistance, so the only force acting on both >hammer and feather (in the classical use of the term >force) is gravity.

>Their falling at the same rate demonstrates that >their weight (the force of gravity on them) is >proportional to their inertial mass, something >Galileo and Newton assumed as a limiting case but >could not test in a vacuum.

Don - A falling body has no weight - it is weightless (you should know that). Gravity is acting on the inertial mass of each proton, etc. of the body, simultaneously. Since all the protons have the same inertial mass they will all accelerate at the same rate. Therefore no stress is manifested on the body - the body is weightless - it feels nothing.

Don Hamilton http://novan.com/mind.htm
http://novan.com/

Don Hamilton

Don writes:
"For some mysterious reason gravitational mass acted differently then inertial mass."

Actually, gravitational mass does not "act" differently from inertial mass. In fact, one might say that they "act" the same way, and that is surprising when viewed as follows.

Inertial mass is a property that can be measured by the acceleration produced by a net force. (Newton's second law)

In Newtonian terms, gravity is a force between two bodies, and it is proportional to the inertial mass of each interacting body. There is no a priori reason why that should be so.

For example, an electrical force is proportional to the electric charges, which are not necessarily proportional to the inertial masses. Why couldn't there also be a gravitational "charge" that is not proportional to the inertial mass?

Einstein did not address the "why" of this, but he used the fact of it to develop his general theory of relativity--and that led some to conclude that gravity is not a force but a geometrical effect produced by the presence of masses in spacetime. He did not prove the equivalence of the two masses. He just used the experimental evidence that the two are equivalent.

Newton also assumed that equivalence. In fact, as far as I know, he never considered that there might be a difference between the two masses.

Don also writes this as if the reason for dropping the hammer and the feather on the Moon had something to do with a test of the Einsteinian equivalence of gravitational and inertial mass.

That is utterly mistaken. This is a classical mechanics demonstration, with nothing to do with relativity.

It was simply designed to demonstrate that in the near-vacuum of the Moon's atmosphere, there is no air resistance, so the only force acting on both hammer and feather (in the classical use of the term force) is gravity. Their falling at the same rate demonstrates that their weight (the force of gravity on them) is proportional to their inertial mass, something Galileo and Newton assumed as a limiting case but could not test in a vacuum.

Finally, Don's writing presumes that the only particles that count are nucleons, whereas there are a whole host of particles that, as far as we know, have mass and are influenced by gravity regardless of whether or not they are in nuclei or atoms.

He also leaves out the primary forces acting on nucleons, which are the strong nuclear force and the electro-weak force (a unified version of electromagnetic force and the weak nuclear force). These are orders of magnitude greater than gravitational forces on the nucleons.

SO MUCH NONSENSE IN ONE POST, INCLUDING AN UNINTELLIGIBLE CLOSING SENTENCE IN ALL CAPS.

And now, since I have promised myself not to engage further with Hamiltonian nonsense, I will leave it to others in case I have missed a few points. One response is enough for me!

For more about the physics of relativity, see my book Physics: Decade by Decade.

Fred Bortz -- Science and technology books for young readers (www.fredbortz.com) and Science book reviews (www.scienceshelf.com)