# pmb

Senior Members

379

• #### Last visited

• Birthday 10/25/1960

## Profile Information

• Location
Haverhill, MA
• Interests
Physics/Relativity, watching TV/movies, hanging around Boston, Book stores and computer stores. Lived through Acute Leukemia and am proude of it. I enjoy helping people understand physics
• College Major/Degree
BA Physics/Math
• Favorite Area of Science
Relativity
• Biography
Raised on Boston's North Shore, stuxied math and physics as an undergrad and in grad school
• Occupation
Disabled Physicist

12

1. ## is mass equal to energy?

You have to be cautious in forums suchs this. Different people mean different things when they use the term mass. For example, in A first course in general relativity by Bernrd F. Schutz the author writes on page 94 ..energy and 'inertial mass' are frame dependant ... and on page 104 he writes ...energy and mass are the same.... Other people refer to mass as being synonymous with proper mass. Severian is talking about proper mass (aka rest mass). I think that with this in mind you'll better understand the subject matter. The way Taylor and Wheeler describe mass then in such explosions the mass remains unchanged. In their text the term "mass" refers to what is known as invariant mass. This means that we sum up all the energies of all the particles and cal it E and sum up all the momenta of the particles and call it p. The mass according to them is the m in $E^2 - (pc)^2 - m^2c^4$ and this remains constant during a nuclear explosion. This is because energy is conserved and in the zero momentum frame E = mc2 In a sense, sure. The energy is bound up in what is called binding energy which is essentially potential energy, which is negative. While its true that both energy or mass are conserved, its also true that matter changes form. When an electon and a positron annihilate what is left is photons. So the form of the matter changed. Ya got me.
2. ## CAn we get an ignore list?

This thread degenerated into a stream of insults so I deleted all my posts.
3. ## Proper Mass redux

It's hardly silly. Many relativity textbooks us it. Percentage wise about 67% of textbooks published between 1970 and now use it. I see no valid reason to think it silly when that many physicists use it That's incorrect. I was speaking to a well-known cosmologist/particle physicist yesterday and he told me that in cosmology physicists use the term "mass" to refer to E/c2. H'e's very very well-known in his field so I trust him. Plus I have several relativity texts which prove otherwise. The list inlcludes such texts by such authors as Misner Thorne and Wheeler (page 141), Mould, Rindler, D'Inverno, Schutz. Stephani. You can see a short list here with the relevant quotes http://home.comcast.net/~peter.m.brown/ref/relativistic_mass/relativistic_mass.htm That relation doesn't always hold. On example is when the body is under stress. $p=\gamma m v$ is inlid under such a case but p = mv is still valid. Another example is an extended body which is emitting radiation. In such a case the mass per unit length of the rod can be uniformly decreasing. In an inertial frame moving parallel to the rod the mass per unit length is not uniform. The proper time in this case has no meaning so that $p = m\frac{dt}{d/tau}$ has no meaning. However p = mv still has meaning. For details please see http://home.comcast.net/~peter.m.brown/sr/invariant_mass.htm See last section entitled An Incorrect Application of Invariant Mass

5. ## Light has mass?

I don't know what this is supposed to say. It appears to say Total Mass of Sun = Mass of Sun + Photon Mass of the Sun The mass of the sun is a complicated function of the mass-energy of the particles in the plasma that mack up all the matter of the sun, radiation included. This includes the rest mass of all the nuclei in the sun plus the kinetic energy of all those nuclei. This includes the contribution to the mass of the sun by the radiation in the sun, i.e. photons. To be precise, pressure is also a source of gravity. It has more relevance for objects such as neutron stars. The active gravitational mass of a perfect fluid is $\rho_g = \rho + 3p$ where $\rho_g$ is active gravitional mass, $\rho$ = proper energy density and p = pressure. For disordered radiation both $\rho$ and p are non-zero. Nice! The point you made is the same point made in the physics literature. I prefer the term proper mass ove rest mass anyday. Even though the proper mass of photons is zero we still have 1) Inertial mass (aka relativistic mass) of photon is non-zero 2) Passive gravitational mass of light is non-zero 2) Active gravitational mass of light is non-zero Ummmm ........ he's here to learn physics. Hence his questions.
6. ## Particle wave duality

Comments such as this on the graduate level text I quoted you, and which you failed to shoot down, doesn't speak well for the quality of your opinion. There simply doesn't exist a text or a peer reviewed physics journal article which says the the wave-particle duality is a myth. Many of us, such as myself, know quantum mechanics very well (graduate level) and know what you've been claiming is total nonsense. Don't you understand that? My appologies. I was simply commenting on the tact that I'm taking here.
7. ## Particle wave duality

I haven't insulted juan and I never said anything rude. I also haven't stated something that wasn't true, e.g. that I never said a particle is a wave. The worst thing I did was to point out that juan was using a personal attack on immortal and is inccesant false accusations claiming I said something which I'd never say to anybody. It really bothers me to see people insult/attack others. But in order to take on a new state of politeness and civilness I have deleted those remarks. What are we supposed to do when people make false accusations? You give off the impression that it I say that someone is usig a falsehood that I'd get into trouble for pointing it out, regardless of how I go about it. What are we supposed to do we do in those cases?
8. ## Particle wave duality

You're wrong. I already told you that and you simply ignored it. That is not how a cogent argument progresses. Prove me wrong. Reference a post where I said a particle is a wave. Until then stop putting words into my mouth.
9. ## Particle wave duality

I myself go by books for the basics of physics and this is a well-known fact in quantum mechanics and is quite often addressed in text books. That's why I rely on them so much. Papers don't address basic physics for the most part so its much harder to find such an article. Here is a section from Shankar's QM text (graduate level). From Principles of Quantum mechanics - 2nd Ed. by R. Shankar (graduate level quantum mechanics text), page 113 That and $\lambda = h/p$ expresses the wave-particle duality. He's very selective about what he posts. I guess that's just human behaviour. He never mentioned the wave-particle duality as mentioned by Feynman in QED but posted other comments, which when taken out of context, appears to support his position. CERN has better things to do with its website then post basic QM. Or maybe I can find something that juan overlooked (intentionaly?). I'll search the website and see what I find.
10. ## My recent banning

While I don't condone that behaviour I believe that I can, to a certain extent, empathize with your feeling. It appears that way to me too. I hope you change your mind. I find this place more tolerable with you here. From our discussions in private I've gotten to know you personally and that side of you doesn't come out here. If it did then I'm sure you wouldn't run into such problems.
11. ## Particle wave duality

Today I followed an ad hoc derivation of Schrodinger's equation. I confirmed what I long knew, i.e. that a wave function of the form $\psi(x, t) = Ae^{i(kx - \omega t)}$ is a solution to both Schrodinger's equation and the wave equations. Are you familiar with such a derivation?
12. ## Particle wave duality

Please don't put words into my mouth. I never said any such thing. In my opinion your arguement is flawed in that nobody has suggested that a single particle is a wave, nobody whatsoever, and your arguements are based soley on that false assuption that someone said that particle is a wave. Nobody said that in this thread. Lok for yourself. If what you say is true then you'd be able to give us a post number where it occured. I myself have never said, thought, or implied any such thing. Herein lies the flaw in your argument. In fact in my very first post in this thread, i.e. post #16, I said that I love the way Feynman explains it in his Lectures. In V-II page 1-1 Feynman writes Bolding is mine. That means that a particle is not a wave. If you look in Feynman's book QED and check the index then you'll see that Feynman explains the wave-particle duality on pages 23 and 37. What I found relavent is one the wavelike character of electrons on page 84. On page 84 he hits the nail on the head when he writes The bolding is mine. This is pecisely what we've all been saying all this time and which you claim is wrong. Feynman clearly said wavelength of an electron. This is what it means for a beam of electrons or an ensemble of them. to have wavelike properties. IT must be the fact that each electron has a wavelike property in order for the Davisson-Germer experiment to demonstrate wavelike characteristics. The term "wave like characteristics" does not mean that a particle is a wave.
13. ## dr. undefined    pmb

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14. ## Particle wave duality

Nobody in this thread has suggested that a particle is a wave. That's why I quoted Feynman. He said just the opposite, i.e. from post #16 See what I mean? We know that they don't behave like waves.
15. ## Particle wave duality

All that means is that the people that you're quoting don't understand the wave-particle duality. What part of $\lambda = \frac{h}{p}$ probability density = $|\psi(x)|^2$ don't you understand? Those two relations epitomizes the wave-particle duality. Which of those two expression are you claiming is wrong and why?
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