The Naked Scientists

The Naked Scientists Forum

Author Topic: How does mass increase at higher speeds?  (Read 45838 times)

Offline Pmb

  • Neilep Level Member
  • ******
  • Posts: 1838
  • Physicist
    • View Profile
    • New England Science Constortium
Re: How does mass increase at higher speeds?
« Reply #125 on: 26/01/2013 15:45:19 »
I pay close attention. You just never make any sense and you ignore all the derivations provided to you. You're the one who insists on refusing to explain how physicists, in physics journals none the less, do what you claim can't be done and yet get the correct results.

Is there a good reason why you keep refusing to provide a definition of the term "localized" as you insist on using it? I case your response is to claim that you already have please post the time and day of your response.
« Last Edit: 26/01/2013 15:48:52 by Pmb »
 

Offline JP

  • Neilep Level Member
  • ******
  • Posts: 3366
  • Thanked: 2 times
    • View Profile
Re: How does mass increase at higher speeds?
« Reply #126 on: 26/01/2013 15:49:41 »
Is there a good reason why you keep refusing to provide a definition of the term "localized" as you insist on using it? BTW photons are always localized when their position is measured

But a photon that's been measured is no longer a photon.  The entirety of this argument comes down to the fact that Lightarrow uses photon to mean a single photon Fock state, which cannot be localized by definition, and you're using photon to mean a classical pulse.  A measured photon is no longer in a Fock state, so it is no longer a photon by that definition.
 

Offline Pmb

  • Neilep Level Member
  • ******
  • Posts: 1838
  • Physicist
    • View Profile
    • New England Science Constortium
Re: How does mass increase at higher speeds?
« Reply #127 on: 26/01/2013 16:51:32 »
Quote from: JP
But a photon that's been measured is no longer a photon.
I’m aware of that, of course. I wasn’t sure he was aware that when a photon’s position is measured that it was localized.

Quote from: JP
The entirety of this argument comes down to the fact that Lightarrow uses photon to mean a single photon Fock state, which cannot be localized by definition, and you're using photon to mean a classical pulse..
Sorry, but I don’t know what a Fock state is.

In any case, that’s not what I meant by a “classical photon.” Recall the definition that I used. A classical photon is a particle whose inertial energy is related to its momentum by E = pc and interacts with charges via the electromagnetic interaction. There is no associated wavelength since that’s a quantum property just as a classical electron has no wavelength. By this definition it moves on a classical trajectory, has a position vector, etc.  This is what they use in the derivations for the mass-energy equivalence relationship where they use the conservation of the center of momentum. It’s also what relativists use when they draw a worldline of a photon.

It doesn’t matter at this point. I don’t want to discuss it anymore. I merely wanted to see what lightarrow thinks “localized” means. I've already had enough of his broken record responses.
 

Offline Pmb

  • Neilep Level Member
  • ******
  • Posts: 1838
  • Physicist
    • View Profile
    • New England Science Constortium
Re: How does mass increase at higher speeds?
« Reply #128 on: 26/01/2013 17:05:54 »
I checked all my texts on quantum mechanics and none of them mentioned Fock space. However a friend of mine just gave me his text Quantum Mechanics II: A Second Course in Quantum Theory by Rubin H. Landau.

I guess this is where this second quantinization stuff I hear about so often is addressed. I've never studied QM at this level before. Thanks for mentioning it. It'll give me a goal to reach after I refreshen my quantum mechanics in the next few months.  :)
 

Offline JP

  • Neilep Level Member
  • ******
  • Posts: 3366
  • Thanked: 2 times
    • View Profile
Re: How does mass increase at higher speeds?
« Reply #129 on: 26/01/2013 19:20:57 »
I guess this is where this second quantinization stuff I hear about so often is addressed. I've never studied QM at this level before. Thanks for mentioning it. It'll give me a goal to reach after I refreshen my quantum mechanics in the next few months.  :)

It's interesting stuff.  I've studied the basics, but haven't really applied it to anything.  A single Fock state can't be localized, but physics can and do write approximate photon wave functions when considering photons emitted by a source and absorbed by a detector.  I briefly read a section on this in Optical Coherence and Quantum Optics in Mandel and Wolf when this question came up previously, but I didn't have the time to really dig into the details.  Again, I'm not going to wade into the argument of whether we should call localized wave functions that aren't single-photon Fock states "photons," but some physicists definitely do so in practice.
 

Offline Pmb

  • Neilep Level Member
  • ******
  • Posts: 1838
  • Physicist
    • View Profile
    • New England Science Constortium
Re: How does mass increase at higher speeds?
« Reply #130 on: 26/01/2013 21:55:15 »
I guess this is where this second quantinization stuff I hear about so often is addressed. I've never studied QM at this level before. Thanks for mentioning it. It'll give me a goal to reach after I refreshen my quantum mechanics in the next few months.  :)

It's interesting stuff.  I've studied the basics, but haven't really applied it to anything.  A single Fock state can't be localized, but physics can and do write approximate photon wave functions when considering photons emitted by a source and absorbed by a detector.  I briefly read a section on this in Optical Coherence and Quantum Optics in Mandel and Wolf when this question came up previously, but I didn't have the time to really dig into the details.  Again, I'm not going to wade into the argument of whether we should call localized wave functions that aren't single-photon Fock states "photons," but some physicists definitely do so in practice.
What we were talking about was the position vector of a single photon in a system of only a few photons. Can that be done by using some sort of centroid?
 

Offline JP

  • Neilep Level Member
  • ******
  • Posts: 3366
  • Thanked: 2 times
    • View Profile
Re: How does mass increase at higher speeds?
« Reply #131 on: 26/01/2013 23:43:47 »
The short answer is yes.  I found part of the book I was talking about on Google books:

http://books.google.com/books?id=FeBix14iM70C&pg=PA480&lpg=PA480#v=onepage&q&f=false

They come back to the plane wave description I was giving earlier: if you have a single plane wave it is not localized in space and time, but if you have many added together, it can be localized. 

In the same way, if you have a single Fock state, it cannot be localized, but if you add many single-photon Fock states together, it can be.  But since this is quantum, the addition of many Fock states can be a single-photon state, since each Fock state represents a configuration of a photon, and the whole state describes the probability of finding that photon in each configuration.

But as they say, you have to be careful when interpreting "localized" photons, since they are defined from second quantization of the field, and do not have all the properties of a particle such as an electron, which can be described in terms of first quantization of a particle.
 

Offline Pmb

  • Neilep Level Member
  • ******
  • Posts: 1838
  • Physicist
    • View Profile
    • New England Science Constortium
Re: How does mass increase at higher speeds?
« Reply #132 on: 27/01/2013 00:12:23 »
Thanks JP. Speaking about electrons, I just read an iteresting comment in French and Taylor's QM text on page 9
Quote
Millikan demonstrated very directly what he called the "unitary nature of electricity," the fact that electric charge is quantized and transferred in multiple integrals of e.
So lightarrows attempt to use the term "quantized" as part of the definition of photon has the defining "quantum mechanical" property is flawed since we know that referred only to it being a discrete amount of something and not as "quantum mechanical" also finds its use as in the defining property of the electron as well. In fact they use it to first describe the electron and only much later to describe the photon. As I said before, you have to be careful of how you interpret the use of the term "quantized" or "quantum." For the most part it refers to discrete lumps of matter more that it does to the name of a theory. :)
 

Offline Pmb

  • Neilep Level Member
  • ******
  • Posts: 1838
  • Physicist
    • View Profile
    • New England Science Constortium
Re: How does mass increase at higher speeds?
« Reply #133 on: 27/01/2013 02:24:00 »
Quote from: Pmb
Recall the definition that I used. A classical photon is a particle whose inertial energy is related to its momentum by E = pc and interacts with charges via the electromagnetic interaction.
This has been bothering me recently. It appears to me now that such a classical photon cannot interact with other particles in such a way that it would change its energy E. There’s no way for such a particle to change its energy so when a charged particle interacts with it it can’t change its energy. So a classical photon can’t change its kinetic energy, since E = kinetic energy. A quantum photon can change its kinetic energy by changing its wavelength. So a classical photon cannot change its speed.

Since the uses I've seen for such a particle never invoke a change of energy this isn't a serious limitation.
 

Offline AndroidNeox

  • Sr. Member
  • ****
  • Posts: 251
  • Thanked: 2 times
    • View Profile
Re: How does mass increase at higher speeds?
« Reply #134 on: 27/01/2013 17:04:34 »

Quote
Put a kilogram of matter and one of antimatter into an impregnable box, like a Schrödinger cat box, and the mass of the box (any category of mass you care to choose) will not change when the contents annihilate each other. Even if the box only contains light, the mass(es) will not change.
Correct, but it doesn't confirm your statement.
By the way, there is no need of matter and antimatter and not even of light in a box,  two photons are enough, because such a system have a non-zero mass (I mean invariant mass, not relativistic mass), I have already showed it in a recent thread and in several others, during the years.

It's both correct and does prove my statement.
 

Offline Pmb

  • Neilep Level Member
  • ******
  • Posts: 1838
  • Physicist
    • View Profile
    • New England Science Constortium
Re: How does mass increase at higher speeds?
« Reply #135 on: 27/01/2013 17:50:48 »

Quote
Put a kilogram of matter and one of antimatter into an impregnable box, like a Schrödinger cat box, and the mass of the box (any category of mass you care to choose) will not change when the contents annihilate each other. Even if the box only contains light, the mass(es) will not change.
Correct, but it doesn't confirm your statement.
By the way, there is no need of matter and antimatter and not even of light in a box,  two photons are enough, because such a system have a non-zero mass (I mean invariant mass, not relativistic mass), I have already showed it in a recent thread and in several others, during the years.

It's both correct and does prove my statement.
Forget what he's been saying. He has a way of confusing the poperties of mass with those of proper mass. There are three aspects of mass given three names and each are merely just called "mass" because they all have the same value

(1) inertial mass - m = p/v. The higher the inerial mass the harder it is to change its momentum.

(2) passive gravitational mass - The property of matter to respond to a gravitational force.

(3) active graivtational mass - The property of matter to generate a gravitational field.

proper mass (i.e. what lightarrow is always referring to when he sees the word "mass") has little or nothing to do with the defining characteristics of mass. A photon has zero proper mass but has inertial mass, passive gravitational mass and active gravitational mass.
 

Offline JP

  • Neilep Level Member
  • ******
  • Posts: 3366
  • Thanked: 2 times
    • View Profile
Re: How does mass increase at higher speeds?
« Reply #136 on: 27/01/2013 20:10:03 »
proper mass (i.e. what lightarrow is always referring to when he sees the word "mass") has little or nothing to do with the defining characteristics of mass.

That's because you're defining mass to preclude the use of invariant mass.  Plenty of physicists (mostly in high energy physics) use "mass" to mean invariant mass, which also has desirable properties. 
(1) Invariant mass properly satisfies m=p/v when you use 4-momentum and 4-velocity, while inertial mass doesn't
(2) Invariant mass is invariant when you change inertial reference frames, which is a very elegant property.

I can't comment on your points (3) and (4), since I'm not up to speed on my general relativity.  They probably don't matter much to most particle physicists, since they don't deal with gravity.

It's also important to note that we all agree on the properties of mass in the non-relativistic limit, but all these definitions of mass agree in that limit, so we can't use that as a basis for picking the "best" one. 

There is legitimate controversy in the teaching of physics over which definition to use.  It's my impression that invariant mass is generally winning insofar as it's being adopted in introductory textbooks.  http://en.wikipedia.org/wiki/Mass_in_special_relativity#Controversy
 

Offline Pmb

  • Neilep Level Member
  • ******
  • Posts: 1838
  • Physicist
    • View Profile
    • New England Science Constortium
Re: How does mass increase at higher speeds?
« Reply #137 on: 27/01/2013 23:20:36 »
Quote from: JP
Quote from: Pmb
proper mass (…) has little or nothing to do with the defining characteristics of mass.
That's because you're defining mass to preclude the use of invariant mass.
Not at all. I’ve chosen to state the definitions (not to define them since they were defined waaaay before I was even a gleam i m'daddy's eye! lol!) of mass that describe dynamics. I’m not choosing one particular definition of mass over another to state because I wish to preclude the use of invariant mass. Invariant mass is quite useful. I’d hate to try to work out your typical particle physics problems without it. Proper mass is also a defining property of a particle in that it is the unique limit of inertial mass for low v, i.e. m = M(v) as v->0.

Quote from: JP
Plenty of physicists (mostly in high energy physics) use "mass" to mean invariant mass, which also has desirable properties. 
(1) Invariant mass properly satisfies m=p/v when you use 4-momentum and 4-velocity, while inertial mass doesn't
(2) Invariant mass is invariant when you change inertial reference frames, which is a very elegant property.
Absolutely (Noting that #1 fails for all luxons). Please don’t misinterpret my comments to mean that proper mass is not useful. That would be an outrageously inaccurate assumption.

Quote from: JP
I can't comment on your points (3) and (4), since I'm not up to speed on my general relativity.  They probably don't matter much to most particle physicists, since they don't deal with gravity.
Its my opinion that there are many more particle physicists than other kinds of users of relativity so that the majority of use is mass = proper mass. However that is merely a game of numbers and what’s currently a popular area of research.

Quote from: JP
It's also important to note that we all agree on the properties of mass in the non-relativistic limit, but all these definitions of mass agree in that limit, so we can't use that as a basis for picking the "best" one. 
Except when it comes to photons where there is no such limit, of course.

Quote from: JP
There is legitimate controversy in the teaching of physics over which definition to use. 

Oh yes. That horse has been thoroughly beat upon in virtully every physics forum on the internet ever time the subject of mass comes up. Its become a virus which derails most threads merely because when people say “mass depends on speed” the non rel-mass people have to change it to debate against rel-mass rather than jus think to themselves  “Okay. By ‘mass’ that person means rel-mass.” and then moves on with the discussion. Never happens in practice thought. The problem is that it causes tons of confusion because you then have to explain why light can generate a gravitational field. When it comes to defining mass density for a uniform magnetic field it becomes very dicey.

By the way, I’ve changed my mind on the only properties of a classical photon being its energy and momentum. It’s mass is the real physical property. While in QM the wavelength changes giving a corresponding change in energy in classical mechanics it’s the mass that changes giving a corresponding change in energy, same as in QM but phrased in terms of classical properties.
« Last Edit: 28/01/2013 04:12:41 by Pmb »
 

Offline JP

  • Neilep Level Member
  • ******
  • Posts: 3366
  • Thanked: 2 times
    • View Profile
Re: How does mass increase at higher speeds?
« Reply #138 on: 28/01/2013 05:02:24 »
Quote from: JP
Quote from: Pmb
proper mass (…) has little or nothing to do with the defining characteristics of mass.
That's because you're defining mass to preclude the use of invariant mass.
Not at all. I’ve chosen to state the definitions (not to define them since they were defined waaaay before I was even a gleam i m'daddy's eye! lol!) of mass that describe dynamics. I’m not choosing one particular definition of mass over another to state because I wish to preclude the use of invariant mass.

I'm just taking issue your one line above that I quoted.  Invariant mass has plenty to do with the definition of mass, since it agrees completely with non-relativistic mass in the non-relativistic limit, just as inertial mass does.  It's all a matter of the way you choose to extend that definition into a relativistic framework, and both invariant and inertial mass are useful extensions.
 

Offline Pmb

  • Neilep Level Member
  • ******
  • Posts: 1838
  • Physicist
    • View Profile
    • New England Science Constortium
Re: How does mass increase at higher speeds?
« Reply #139 on: 28/01/2013 06:13:29 »
Quote from: JP
I'm just taking issue your one line above that I quoted.
I smell a debate about proper mass vs rest mass in the air. That's when I must leave the room. Methinks it be bad juju!
« Last Edit: 28/01/2013 06:15:46 by Pmb »
 

Offline JP

  • Neilep Level Member
  • ******
  • Posts: 3366
  • Thanked: 2 times
    • View Profile
Re: How does mass increase at higher speeds?
« Reply #140 on: 28/01/2013 14:31:45 »
Quote from: JP
I'm just taking issue your one line above that I quoted.
I smell a debate about proper mass vs rest mass in the air. That's when I must leave the room. Methinks it be bad juju!

I wasn't the one telling posters that proper mass has little or nothing to do with the definition of mass!  I'm content to call them "invariant/proper mass" and "inertial/relativistic mass" and skip the arguing phase over which meets the definition of mass.
 

Offline Pmb

  • Neilep Level Member
  • ******
  • Posts: 1838
  • Physicist
    • View Profile
    • New England Science Constortium
Re: How does mass increase at higher speeds?
« Reply #141 on: 28/01/2013 16:48:34 »
Quote from: JP
I'm just taking issue your one line above that I quoted.
I smell a debate about proper mass vs rest mass in the air. That's when I must leave the room. Methinks it be bad juju!

I wasn't the one telling posters that proper mass has little or nothing to do with the definition of mass!  I'm content to call them "invariant/proper mass" and "inertial/relativistic mass" and skip the arguing phase over which meets the definition of mass.
Don't get me wrong.I wasn't blaming anyone for anything about that. More later. Gotta go to pain clinic.
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Re: How does mass increase at higher speeds?
« Reply #142 on: 28/01/2013 21:57:50 »
Perhaps the solution should be to elect me the President of Physics
:)
Quote
and I'll rewrite all the textbooks to clear this up?   :P
I like your kind of humour.
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Re: How does mass increase at higher speeds?
« Reply #143 on: 28/01/2013 22:22:34 »
Quote from: lightarrow
I've already explained in simple terms why you can't localize a photon, but you don't accept it because, you say, it works only for photons described in quantistic sense; I tried to show you that this is the only description for the term "photon" and so we are in a loop...
I sincerely don't know what else I could say.
If that is your response then you weren't paying attention to what I was saying. You consistently keep forgetting the approximation and what it would mean to put the photon's position vector inside the area of uncertainty according to how the wave function would average the position. I gave you an example of a pixel of 0.001 mm in width a length and when it detects the photon then its localized in that area and the location of the photon is the location of the pizel) e.g. geometric center.
Ah, yes, localized after detection, of course. The problem is, and this is not the first time I write it, I was talking of localizing it in flight, between source and detector.
Quote
You youy insist on ignoring every single thing I've said regarding approximation then there is no use to continue this conversation. Why should I post something I know you're going to igore?
While you're at it it wouln't hut you to finally state what it is you mean by saying something can or can't be localized. E.g. find a QM texbook and quote the definition of "localized" or "localize" so you won't be vauge anymore.
Have a look also here:

http://stochastix.files.wordpress.com/2008/05/what-is-a-photon.pdf

<<What is a photon?
Rodney Loudon
University of Essex, Colchester, UK>>
...
<<A one-photon excitation in such a mode again carries an energy
quantum ¯hω distributed over the entire interferometer,
including both internal paths. Despite the absence of any localization
of the photon
, the theory provides expressions for
the distributions of light in the two output arms, equivalent to
a determination of the interference fringes.>>
« Last Edit: 28/01/2013 23:27:30 by lightarrow »
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Re: How does mass increase at higher speeds?
« Reply #144 on: 28/01/2013 22:45:31 »
Sorry, but I don’t know what a Fock state is.

In any case, that’s not what I meant by a “classical photon.” Recall the definition that I used.
Do you mean it's a definition invented by you? It's just a question.
Quote
A classical photon is a particle whose inertial energy
"inertial energy"? Sorry but I've never read this term; it's not another of "your definitions", isnt'it?
Quote
is related to its momentum by E = pc and interacts with charges via the electromagnetic interaction. There is no associated wavelength since that’s a quantum property just as a classical electron has no wavelength. By this definition it moves on a classical trajectory, has a position vector, etc.
Ok. What you have described here is simply a classical pulse of light: an electromagnetic wavepacket. Why do you call it "classical photon"? Well, if I will find it in books of physics, I will conform to it, no problem; don't see any problem in using that term, as soon as it will be defined.
Quote
This is what they use in the derivations for the mass-energy equivalence relationship where they use the conservation of the center of momentum. It’s also what relativists use when they draw a worldline of a photon.
If they use the term "photon" it's a misuse and they could simply talk of an electromagnetic wavepacket. I suspect some relativists don't actually now what "a photon" exactly is; I don't mean I know it well, but it's a lot of time I discuss this specific subject with physicists, at university, first and in the forums.
« Last Edit: 28/01/2013 23:27:00 by lightarrow »
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Re: How does mass increase at higher speeds?
« Reply #145 on: 28/01/2013 23:06:11 »

Quote
Put a kilogram of matter and one of antimatter into an impregnable box, like a Schrödinger cat box, and the mass of the box (any category of mass you care to choose) will not change when the contents annihilate each other. Even if the box only contains light, the mass(es) will not change.
Correct, but it doesn't confirm your statement.
By the way, there is no need of matter and antimatter and not even of light in a box,  two photons are enough, because such a system have a non-zero mass (I mean invariant mass, not relativistic mass), I have already showed it in a recent thread and in several others, during the years.

It's both correct and does prove my statement.
If you say so...
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Re: How does mass increase at higher speeds?
« Reply #146 on: 28/01/2013 23:13:21 »
Forget what he's been saying. He has a way of confusing the poperties of mass with those of proper mass.
;D  Sorry, I wasn't.
Quote
There are three aspects of mass given three names and each are merely just called "mass" because they all have the same value
(1) inertial mass - m = p/v. The higher the inerial mass the harder it is to change its momentum.
(2) passive gravitational mass - The property of matter to respond to a gravitational force.
(3) active graivtational mass - The property of matter to generate a gravitational field.
proper mass (i.e. what lightarrow is always referring to when he sees the word "mass") has little or nothing to do with the defining characteristics of mass. A photon has zero proper mass but has inertial mass, passive gravitational mass and active gravitational mass.
Just "Four" kinds? My God, where has gone your creativity? From you I expected at least a hundreds kinds  :)
You still have a lot of work to do, if you want to write since-fiction books  :)
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11989
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Re: How does mass increase at higher speeds?
« Reply #147 on: 29/01/2013 04:06:03 »
This one does a nice job of explaining the history of mass, and how the idea of passive and active mass came to be. The Equivalence Principle: A Question of Mass 
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Re: How does mass increase at higher speeds?
« Reply #148 on: 29/01/2013 08:40:06 »
This one does a nice job of explaining the history of mass, and how the idea of passive and active mass came to be. The Equivalence Principle: A Question of Mass 
History is interesting, but once physics has established the equivalence of those masses, there is no need to talk about them any longer, there is just one.
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11989
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Re: How does mass increase at higher speeds?
« Reply #149 on: 29/01/2013 17:34:02 »
I think the point of it has to do with light quanta. "A photon has zero proper mass but has inertial mass, passive gravitational mass and active gravitational mass." The 'passive' being what is acting on it, the 'active' being the way it will act on other, the inertial mass being its resistance to change, all as I think of it. But if it is a field then? How many degrees of freedom would be needed to create a static field in where you have the illusion of a arrow, waves/particles, gravity and motion, and all of it being observer dependent?
 

The Naked Scientists Forum

Re: How does mass increase at higher speeds?
« Reply #149 on: 29/01/2013 17:34:02 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums
 
Login
Login with username, password and session length