What is the experimentally measurable difference between rest mass and the 'relativistic mass' of the photon ??!!
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From: PD on 21 Apr 2010 14:22 On Apr 21, 12:39 pm, "Y.Porat" <y.y.po...(a)gmail.com> wrote: > > > > Porat, I think you are suffering from an idea that is hobbling you. > > ------------------ > nothing is hobbling me > ------------------ > just a moment i am going to see inthe dictionary what is hobbling > -(:-) > --no i ddint find > anyway lets talk physics argument > specific arguments and not abstract hand wavings > -------------> You apparently think that when you see an equation like E=mc^2, that > > each of those variables can be attributed to a word like "energy" or > > "mass", > > -------------- > not energy or mass?? > !! > so what else for instance (:-) As I told you, Porat, the E in E=mc^2 is *rest energy*. The E in E^2 = (mc^2)^2 + (pc)^2 is total energy. Same symbol, two completely different meanings. This is why context is important. It is also how you confuse yourself by looking at these two expressions and thinking they are referring to the same thing. > -------------- > > and furthermore each of those words can mean one and only one> thing. So you see "m" and think "mass" and you furthermore believe > > that "mass" can have one and only one meaning, > > -------- > that exactly waht i want to prove that > tereis jsut one kind of mass There is no argument that can *prove* that. It is not a matter of argument. It is a matter of defining the symbol in the context where it is used. If you want to know what a symbol means, you ASK what it means in that context. No amount of arguing will change the meaning of that symbol in that context. > BECAUSE > unlike literature > if you are going to invent another kind of mass > the burden of prof is **on you** > and that is exactly our discussion about !! It is not a matter of invention. It is a matter of *defining* the term where it is used. > -------------- > > and that it is the> meaning you have in mind. Likewise, you see "E" and think "energy" and > > that "energy" can mean one and only one thing and it is what you have > > ---------------- > why obfuscate > we are dealing now about energy of EM radiation > do you have something else in your mind ?? There is still more than one kind of energy there. There is rest energy, which for EM radiation is zero. There is total energy, which for EM radiation is not zero. You see? > ------- > > > > > This is simply not true. You cannot oversimplify physical laws to make > > them conform to your understanding. > > -------------- > one of he greatest tasks of mine is to simplify > physics Nature is as simple as possible, but no simpler. You are trying to make it simpler than it is. > > it seemst aht one of your intentions is to complicate it > btw > i hope that you got already that > one of the secretes of good analysis > is to ry and dis-mental a complicated probel to its > sub smaller problems !!! > > ------------- > > > When you see an equation like E=mc^2, each of those terms means > > something that may be dependent on the context, > > ----------- > wrong !! > that formula s power is in its being universal !! That is flat wrong, Porat. The meaning of a formula depends on the context and the definition of the terms used in it. This is PRECISELY the point I've made over and over and over to you. For example, you see the formula p=mv and you have the belief that it is universal. It is not. It is not even true for massive objects that are traveling at high speeds, and it is in no case true for light (using c for v). That formula is NOT universal. Another example is Fdt = del(p). That formula is NOT universal. Another example is KE = (1/2)mv^2. That formula is certainly not universal. If you were led to the impression that these expressions are universal, you were mistaught. They are not universal. > ---------------- > and the E in one> equation might mean something completely different than the same E in > > a different equation. It is therefore extremely important to not look > > at equations in stand-alone fashion, but to use them only in context, > > so pleae tell us what is specifically > our context about mass of the EM rqdiation !! > ---------------- > > > where the meaning of those variables is carefully explained along with > > the presentation of the equation. This means work, but if you don't do > > it, you end up being mistaken about what you're looking at. Insisting > > --------------- > why do you speak riddles > why not talk specifically > after all we are not just philosophers but try > to be practical physicists !! > that bring some concrete use to our places > ------------ > ------ > > > that the variables can mean one and only one thing only makes the > > mistake a deeper one. > > ok take the lead tomake it > pinted to specific direstions > like > does energy of EM has mass or not > does the phootnhas mass or not > but still > dont dsiperse it to a hundred directions > because i tild you oneof the secretes of good analysis ie to > concentrate -to be targeted to some specific > problem forinsatnce as i did it in my op post > how about it ??? (:-) > if you like to take some break for breading > lets take some break !! > and may be others (not including Artful (:-) > can get in meanwhile > and say what they think and examine all about it > ATB > Y.Porat > --------------
From: Tony M on 21 Apr 2010 14:42 YP, PD, Artful, Heres my opinion. You are all right and wrong about certain aspects. (Not to say that I'm right about any.) Photons DO have mass (equivalent to their energy). Photons DO NOT have rest mass as they cannot be at rest. E=Mc^2 and E=hf are equivalent and they BOTH APPLY to photons. Again, M here is NOT rest mass and its NOT zero. I dont know what the correct term for this mass is, so call it whatever you like. As such, P = h/lambda = hf/c = E/c = Mc are all correct for a photon (but not applicable for anything at v<c). Formulas containing v, gamma or rest or invariant mass apply ONLY to objects or systems where v<c; they do not apply to photons. That doesnt mean that a formula containing mass is wrong for photons, but in this case mass is NOT rest mass.
From: PD on 21 Apr 2010 15:11 On Apr 21, 1:42 pm, Tony M <marc...(a)gmail.com> wrote: > YP, PD, Artful, > > Heres my opinion. You are all right and wrong about certain aspects. > (Not to say that I'm right about any.) > > Photons DO have mass (equivalent to their energy). Photons DO NOT have > rest mass as they cannot be at rest. This would be an unusual definition of mass. Indeed, this was the basis for the invented concept of "relativistic mass", which basically made an *analogy* to the initial statement E=mc^2 which referred only to rest mass and rest energy, by extending the concept in this way: What would be the *analogous* concept to mass, if we took energy to be the total energy rather than just the rest energy? Thus arises something that is not rest mass but is something else dubbed "relativistic mass". Then people played around with the idea to see if, for example, you could put relativistic mass in F=ma to get something that was still true relativistically. This met with mixed results at best, and this is why the notion has been mostly dropped from usage. Mass today is taken to be the invariant quantity, for the most part. This is the thing that for a system is m^2 = E^2 - p^2 (using natural units where c=1). The invariant mass of a photon is experimentally indistinguishable from zero, to very high precision. > > E=Mc^2 and E=hf are equivalent and they BOTH APPLY to photons. Again, > M here is NOT rest mass and its NOT zero. I dont know what the > correct term for this mass is, so call it whatever you like. As such, > P = h/lambda = hf/c = E/c = Mc are all correct for a photon (but not > applicable for anything at v<c). > > Formulas containing v, gamma or rest or invariant mass apply ONLY > to objects or systems where v<c; they do not apply to photons. That > doesnt mean that a formula containing mass is wrong for photons, but > in this case mass is NOT rest mass.
From: Tony M on 21 Apr 2010 15:24 YP, Do not mix discussions about photons and other particles. While photons are particles, not all particles can be treated equally. Particles are divided into massive and massless. That grouping has nothing to do with how light or heavy particles are, and it doesnt mean that some particles have no mass. All particles have both mass and energy. Massive particles can only travel at v<c and have non- zero rest mass. Massless particles exist only at c and have no rest mass. Therefore, one must be careful about the form of the equations one uses to describe the two types of particles, especially when using m, gamma or v.
From: artful on 21 Apr 2010 20:15
On Apr 22, 5:24 am, Tony M <marc...(a)gmail.com> wrote: > YP, > > Do not mix discussions about photons and other particles. While > photons are particles, not all particles can be treated equally. > Particles are divided into massive and massless. That grouping has > nothing to do with how light or heavy particles are, and it doesnt > mean that some particles have no mass. Actually .. it does. But that does not mean that the energy of such a particle cannot have an mass-equivalence (ie an amount of mass that that energy could possibly be converted to) > All particles have both mass > and energy. They all have a combination of mass and energy. Photons, for example, are little packets of energy and are all energy (no mass). > Massive particles can only travel at v<c and have non- > zero rest mass. Massless particles exist only at c and have no rest > mass. When we say 'mass' we generally mean the invariant / proper / rest mass, unless the context implies we are talking about something else. > Therefore, one must be careful about the form of the equations > one uses to describe the two types of particles, especially when using > m, gamma or v. Yeup |