# pmb

Senior Members

379

1. ## Back from rest

See? That sabatical ended up being less than a week long. It's my belief that since I now said my piece to whom I was frustrated with then I don't need to bother with it again. Hopefully the forums nature to ingnore errors will be the way to go. That's the rule of thumb I got from all the people here that I've spoken with, who shall remain nameless. Personally I think its a bad mistake. It'd confuse newbies. But I'm not going to take responsibility for others actions so I'll state my piece and leave it alone. I don't have the physical strength to keep making arguments everytime I see them. There are way too many. Plus its easier this way. Best wishes to all, Pete
2. ## E=Mc2

I never showe you where that expression came from. I posted a derivation which was similar to Einstein's in essense. It's at http://home.comcast.net/~peter.m.brown/sr/mass_energy_equiv.htm It goes like this. In frame S a body emits a two photon of equal enegy in opposite directions. In a frame moving relative to that frame we see the same thing. This time the photons don't have the same energy. They therefore don't have the same momentum. The sum of the momenta of the two photons yields a total momentum which is non-zero. This means that the momentum of the box decreases. This means that the body's mass decreased. Since the speed can be arbitrarily small the mass of the body decreases. Relativity is used to find a relationship between the energy lost E and the mass lost m. That relationship is E = mc2. I think that there is another derivation which proves the generality of that expression.
3. ## Photons???

John Wheeler was seconded only by Albert Einstein in 20th century physics. If physicists and chemists didn't appreciate his work then they just didn't read it. It's just that simple. Your impressions about this "course grained" nonsense is just empty gibber-jabberging that shouldn't even be acknowledged.
4. ## Light has mass?

Well this post is a good excuse as any to come back from my sabatical. What you claimed about Einstein (but again never proved) is wrong. In one of his early articles published between 1906 and 1908 Einstein said that radiation density (aka light) has mass density. This is the same thing that Alan Guth still uses in his cosmology course. The term you're looking for is ignorant which means having a lack of knowledge. When people go to college they gather information/knowledge. They don't get smarter for the most part. There is a small increase in IQ in that the educated man has a better ability to present a more logical an argument than the uneducated person. I disagree. It sure does get affected by gravity. In a uniform gravitational field a beam of light is still deflected and in such a field the spactime curvature is zero. That is very very true. And anyone who reads Einstein's relativity book will learn that Einstein never said that gravity is a curvature in spacetime. Einstein disagreed with that interpretation.

6. ## Suicide

That's kind of you to say. Funny part of all of this is that I injured my back just as I was going back to work. I was actually alrady disabled due to the attack of Leukemia. Sheesh! I should never have tried to go back to work. LOL!!
7. ## Suicide

I'm now on Suboxone. That means that I'm in mild to moderate pain but only if I don't leave the house, wherein it gets much worse. And people don't understand why I get irritated easily!! lol!! Now I'm told I am at high risk for diabetes and it I don't eat better and get more exericise I'll most likely to contract it. There's a catch 22 for ya! Then again I'd wager that with diabetes it'd be easier to commit suicide.
8. ## Suicide

I doubt it. Yes. In fact I tried it back in February. I have a damaged spinal cord (four herniated disks) and the pain was too much to live with. I begged doctors for help but they ignored my pleas. So I took a razor and sliced my throat open. In a moment of weakness I called my oncologist to take one last shot at getting help. That plea went unheard yet again. Byt he police came, busted down the floor and then I ended up in a VA nut house for a month. Yes. But only in cases like mine, i.e. when you're suffering far too much with no end in site. I still wish my first attempt back in 2000 failed. I could have missed all that suffering in the mean time. Man-O-Man, you can't believe the amount of pain you can get when you have a herniated disk. Its freaky bad! I heard that too. Perhaps smart people are tired of being around so many people who aren't as smart as they are.
9. ## Taking a sabatical

Are you intentionally breaking forum rules or are you just ignorant of them? I'd say a combination of both. See http://www.scienceforums.net/index.php?app=forums&module=extras&section=boardrules and http://www.scienceforums.net/topic/7813-science-forums-etiquette/ Many of the people in this thread have broken one or more of the forum rules. It's the lack of enforcement that drove me away. It'd be silly for me to want to be around so many of the flammers I now see in this thread. There are so many greener pastures on the internet. Too many flamers in this one with no policing to take action against flamers and trollers. Please grow up and learn to be an adult by learning how to accept criticism without attacking the messanger. And never ask why people leave here. You've just shown them why they should.

13. ## Taking a sabatical

That's the supposed usage of it. That doesn't mean they use it like that. Consider this thread. You can't seperate what I said from me the person so the number reflects what people judge about me. What is at my heart is that there is a troller who post erroneous claims against my last post I make. I had an open mind form much much longer than I should have. After I realized he made an error in nearly every post he makes I decided not to respond. That didn't mean he stopped making bogus assertions. Now they are just going uncorrected. So be it. I'm leaving for a short time for a good reason. I hope people don't think that I tell them everything that goes into my decision making process.
14. ## Taking a sabatical

Decided to delete content I gotta tell ya. These reputation notes are quite irritating. I can't stand being in a place where they rate me as a person. Perhaps I won't be back. I've always wanted to create my own and I can afford it now. We'll see.
15. ## What is 'mass'?

I am rewriting an earlier part of this thread because michel really wanted me to. Since he was very polite when he asked in a PM to me I thought I’d do it just for michel’s sake! qft1234. This was what I was trying to get through to you earlier. Let g = 1/sqrt(1 - v2/c2), b = v/c, m = inertial mass for v << c. m is also called the proper mass or rest mass) of the particle. I prefer the term proper mass since the term "rest mass" cannot literally be applied to particles at rest and a photon can never be at rest. Let M = gm be the inertial mass of a particle for any speed. It can be shown that the momentum of a classical point particle is (see http://home.comcast.net/~peter.m.brown/sr/inertial_mass.htm) 1) p = Mv = gmv The energy is 2a) E = Mc2 = gmc2 or 2b) E = Mc2 = gE0 where E0 is called the proper energy of the particle Eq. (2a) can be rewritten to as 3) g = E/mc2 Substitue Eq.(3) into Eq. (1) to obtain 4) p = mvg = mv(E/mc2) = mv(E/mc2) = vE/c2 Multiply Eq(4) through by c to obtain 5) pc = Ev/c This can be rewritten as 6) pc/E = v/c A luxon is a particle that always travels at the speed of light. For such a particle v = c. Substitute into Eq. (6) to get (this is really a limiting process) 7) pc/E = 1 ===> E = pc Solve Eq. (2) for M to get M = E/c2 and then plug this result into Eq. (1) to get 8) p = (E/c2)v Multiply through by c to obtain 9) pc = Ev/c = Eb Square both sides to get 10) E2b2 = (pc)2 Now subtract E2 from both sides and rearrange to get 11) E2 - E2b2 = E2 - (pc)2 Factor E2 out of the left side to get 12) E2(1 - b2)2 = E2 - (pc)2 Note that g2 = 1/(1-b2) ==> (1 - b2) = 1/g2 13) E2/g2)2 = E2 - (pc)2 Note that E2/g2 = m2c4. We finally have 14a) E2 - (pc)2 = m2c4 = (mc2)2 or 14b) E2 - (pc)2 = (E02[/sup])2 Recall that for a luxon v = c. If we take the limit in Eq. (14) for v --> c we find 16) m = 0 This is what it means for a luxon to have zero proper mass. Of course this results holds for photons. People often get rid of the adjective "proper" and say "photons have zero mass". Recall the expression for momentum in Eq. (1), p = Mv. Let v = c to get p = Mc. Therefore M = p/c. Substitute p = E/c to get M = E/c2. For a photon E = hf where h = Planck's constant and f is the frequency of the photon. We now have M = hf/c2 which means that a photon has inertial mass. So the two expressions for the mass of a luxon is Proper Mass: m = 0 Inertial Mass: M = p/c = M = E/c2 = hf/c2 Connection between E, p and m: E2 - (pc)2 = (mc2)2 Sorry juan, but a I already explained, I can't keep up with all the mistakes you keep making. See you after my sabatical. I'll see you but that'll be about it. Glad to see you got that book from te library and chose to learn from it. Can this really be true or were you just seeing how wrong you were! Hmmmmm.
16. ## Taking a sabatical

Hi folks, I've decided to take a sabatical from this forum. Just too many rude people around (I just got a rude PM from a moderator whom I never really liked anyway) and don't wish to be around that kind of people so I won't be around for a perhaps long while. There are other forums where the Admit actually admire me. So there are plenty of forums to be of help in. I just don't won't subject myself to the nasty people I've run into here. I made a lot of friends so please feel free to email me. I won't be checking my PMs. Later gators.
17. ## What is 'mass'?

When I wote "there are no errors" I assumed Ityped everything in write. You never had to make such a big deal out of it. I already said you were right michel. I admitted that I made a mistake the first time you pointed it out. You're now getting carried away. To much at this point with no gain. Moving on: I wanted to get back to the concept of bare mass that I touched on earlier. Again I want to warn everyone that this is about classical EM and the classical electron/charge. Somewhere in this thread or the original one I explained that the contribution of the Coulomb field to the mass of a charged particle is expressed as follows. From Rohrlich's text top of page 137, and using Rohrlich's notation m = mbare + mCoul The first term is defined as the bare mass of the electron, i.e. the mass the particle would have if there it was uncxharged. I originally expressed as dm since that's how its often expressed. Rohrlich uses different notation. m is what is known as the proper mass of the electron.
18. ## Light has mass?

I did a bit of foot work for you. See http://www.scienceforums.net/topic/66737-what-is-mass/ http://www.scienceforums.net/topic/66669-photons/ To be more precise, the source of gravity is mass, of which there are three kinds. These are useful to know if you're studying cosmology. E.g. see the definitions in Peebles text on cosmology on pages 269 Eq. (10.70) and page 453 Eq. (18.02). Peebles uses a perfect fluid as an example. Peebles gives expressions which he identifies as the active gravitational mass density, passive gravitational mass density and inertial mass density. The later two have the same value. The following defines those terms 1) Inertial mass - T he mass of a body as determined by its momentum For those of you who have trouble with this as the definition of inertial mass then please note that its not something I conjured up. Although I've been saying that this is the definition all along that its what I learned from relativity texts and mechanics texts and ajournal articles. Please see http://www.thefreedictionary.com/inertial+mass 2) Active gravitational mass - The source of gravity 3) Passive gravitational mass - That on which gravity acts on. If I can find out how to post Latex then I'll quote the equations. Can someone tell me where there is a Latex tutorial? I think there's one on this site but I don't know how to find it.
19. ## Universed Mathematics

Most of us here are quite familiar with expression such as 1/0. But you didn't prove, o even explain, your assertion that it means what you claim it means is. In a forum like this it is desirable to have people back up their assertions. So while I respond to this post perhaps you can prove what you said about its consequence. 1/0: It mathematics we say that its an undefined quantity. So claiming that it is not infinity is unfounded. Consider the following expressions: 1) f(x) = 1 + x 2) g(x) = x 3) h(x) = f(x)/g(x) Are you familiar with what a limit is? If so then take the limit x--> 0 h(x). This does not yeild a meaningful quantity since the limit does approach infinity. It's meaningless to say it is either infinite or not infinite or anything else. That's the only kind meaning that you can give 1/0.
20. ## New SR/GR text

My friend told me that this text is available online. He said he just googled the name and author and found it. I'm not having as much luck. I'd like to find this so I can refer it to someone who could use an online journal. Pete
21. ## Light has mass?

I believe that there are a few other threads on this subject. Have you seem them? They might contain something you're interested in.
22. ## Light has mass?

All components of the stress-energy-momentum tensor contribute to the source of gravity. Stress is a source of inertia so it follows that its also a source of gravity. In the special case it is well noted that pressure is a source of gravity.
23. ## What is 'mass'?

swansont = Please delete my post. Note: See proper mass at http://en.wikipedia.org/wiki/Invariant_mass
24. ## Light has mass?

That depends on what you mean by the term mass. Does light have inertial mass? Yes. Does light have proper mass? No. However there are circumstances in which it can be said that the rest mass of light is zero. Consider a gas of massless photons. The gas will have a frame in which the total momentum of the photons is zero. The mass of the system of photons will then equal the total energy of the photons divided by c2. So in this case the light has non-zero rest mass. I have a set of lecture notes from a course that Alan Guth teaches. In it he says that light has mass since it has energy. Guth is a smart man. The course is the about the early universe. In a course like that its useful to think of light having mass. See also http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/photon_mass.html Gravity doesn't always bend spacetime. That only happens when there are tidal gradients present. In a uniform gravitational fiel the spacetime is zero and yet light is deflected by the gravitational field. The equivalence principle states that inertial mass is proportional to gravitational mass. For this reason all particles fall at the same rate. It is this reason why geodesics can be created in which light is deflected, and again, that's because it has mass. Consider Feynman's view on this. From the Feynman Lectures, Vol-I, page 7-11