The nature of force

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Jim</i>
<br />How do you have momentum without mass if it is a product of velocity and mass?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">The QM answer is that the momentum of a "photon" is h*nu/c, where h*nu is the photon energy, and all energy is interchangeable with mass via E = m c^2. Substituting this last into the original formula, it reduces to m*c, which is indeed a momentum.

The MM answer is not so devious. Every wave (e.g., a water wave) has momentum because it is composed of smaller entities that have mass and velocity. It is no different for lightwaves, which are composed of elysons that have mass and velocity. -|Tom|-

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by tvanflandern</i>
<br /><blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Thomas</i>
<br />This question only makes sense in Classical Mechanics to which inelastic collisions do not belong.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">One of the things that I dislike about QM is answering common sense questions with "that question does not make sense in QM".<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">The point is that QM actually assumes energy- and momentum conservation to hold for inelastic collisions although this is an unjustified generalization from Classical Mechanics (i.e. elastic collisions).


<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">I can only see two possibilities here:
1) a resonant quantum mechanical system (e.g. an atom) absorbs all the pre-collisional kinetic energy of the approaching particle in its reference frame (i.e. both would move together with the original velocity of the atom).<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">If two neutrons collide, how would they decide which had the "original velocity"?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Are there any inelastic collisions between two neutrons? I am only aware of resonant reactions between neutrons and nuclei. I can't actually see that inelastic collisions between identical particles could exist at all as you need a resonant system and something else that excites it. If you have two resonance systems then you could only have a part of one system exciting the other system (e.g. an electron of one atom excites another atom). In this case it would be a matter of chance which system excites which (i.e. which has the 'original velocity').


<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">the concept of a momentum can not be applied to light).<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">How can a non-standing wave fail to have momentum? Even water and sound waves have momentum. And how does light manage to push staellites and asteroids around if it has no momentum?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Water and sound waves are mechanical waves i.e. perturbations of a system of particles. Obviously, these have a momentum.
Light waves are immaterial electromagnetic oscillations and merely release electrons on the surface of objects which then can collide elastically with surface atoms to produce the observed 'radiation pressure'. The fact alone that photoelectrons are actually primarily released in the direction of the electric field vector of the e.m. wave rather than in direction of propagation of light proves that 'photons' can not be considered as particles.

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www.physicsmyths.org.uk
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<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Thomas</i>
<br />Light waves are immaterial electromagnetic oscillations and merely release electrons on the surface of objects which then can collide elastically with surface atoms to produce the observed 'radiation pressure'.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">How can something "immaterial" affect something material? Define "immaterial". This appears to me to be a contradiction on its face, so you must be using a specialized definition.

One of my basic points is that it is not sufficient in physics to point to equations that work. In physics, all actions must be conveyed by tangible, material entities, where "tangible, material" means having a physical form capable of interacting with other physical forms. Only properties and concepts can be "immaterial" in this sense, but neither of those is capable of pushing a real body, or even of "releasing electrons" from one.

And how are these "released electrons" supposed to produce a force of repulsion in the direction of the original lightwave/photon? Can you describe the momentum transfer details here? Where does the momentum come from, and how does it move from body to body if electrons are somehow involved as intermediaries? It appears that the electrons must be going the wrong way!

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">The fact alone that photoelectrons are actually primarily released in the direction of the electric field vector of the e.m. wave rather than in direction of propagation of light proves that 'photons' can not be considered as particles.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">I agree that light is a pure wave, and am not arguing for particulate "photons". But you seem to be arguing that a wave can exist without being composed of particulate entities at a smaller scale (i.e., a medium). That is a mathematical notion unsupportable in physics. It means only that we have not yet discovered the medium, but not that no such medium exists. Even relativists have to refer abstractly to "the space-time medium" when pressed for physical details about "what waves".

In case it is not yet obvious, I'm a strong opponent of mystical "fuzzy-think", which seems to permeate the field these days. If we don't insist on adherence to physical principles, we can do magical things -- but we have left the field of physics. -|Tom|-

Tom is a single particle existed in empty space, could it not have a range of potential influence with a much larger radius. This potential does nothing unless it comes in contact with something else at which time it becomes kinetic triggering other "potentials" that travel about until they comes in contact with some other "potential or kinetic"?

As far as smallest and largest scale, we can't know yet. But, empty space is possible until the potentials make contact. So, space appears empty, but there are all these potential flying about.

Sounds like a ghost story....

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by rousejohnny</i>
<br />if a single particle existed in empty space, could it not have a range of potential influence with a much larger radius.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Sure. But a "potential" is a field of smaller particles, much like an extended atmosphere. For gravity and electrodynamics, the potentials are what we now call "elysium", which is composed of "elysons".

What I objected to was attributing magical abilities to potential fields -- such as the ability to act on something else without itself being tangible and material.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">This potential does nothing unless it comes in contact with something else at which time it becomes kinetic triggering other "potentials" that travel about until they comes in contact with some other "potential or kinetic"?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">This is starting to get "magical". Let's stick with the concrete notion that a potential field is an extended atmosphere of a particle, and is made of elysium (the light-carrying medium).

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">As far as smallest and largest scale, we can't know yet. But, empty space is possible until the potentials make contact. So, space appears empty, but there are all these potential flying about.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">In MM, truly "empty" space cannot exist. But lots of space can appear empty because what fills it is smaller than our ability to detect. -|Tom|-

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by rousejohnny</i>
<br />The only problem I have is densities seem to define a finitness that althought infinately divisible, does imply limitations. It seems that since some areas are less dense than others on one scale makes finite possible. A ball moving at 1000 mph back and forth between two points a meter apart, try and stick your hand threw it, it may hurt. The same ball moving at the speed of light would be a solid wall to your hand, and it probable would not hurt at all. There is no necessity for anything to exist between the two points except space.
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We still have the problem what constitutes the collision. My hand must evetually touch the substance of the ball, so what substance is the first to claim to have collided with my hand and vice versa?