# Does light have a mass?

Discussion in 'Physics & Math' started by GRO, Apr 6, 2002.

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1. ### Joeblow93132Guest

Crisp,

I thought that the "curved space" model described the effects of gravity completely. But you are stating that a particle(graviton), is responsible as well.

How exactly does the graviton fit into the "curved space" theory???

Tom

3. ### c'est moiall is energy and entropyRegistered Senior Member

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@James R
"There are lots of neutral particles around, such as photons, gluons, Z bosons, and composite particles like neutrons, neutral pions, Kaons etc."

impossible to be EM in nature? (I mean, a photon is already EM itself!!)
could it be possible that neutral particles (not talking about composite ones - the effect is neutral but the particles they are consisted of are really EM) have such a small charge that our instruments cannot detect it (maybe in the future)? I mean, we do depend on our technical skills for this no?

"I also wonder, since I learnd this photon thing about EM-fields, how do they see a charge?

How do what see a charge?"

yes, what is a charge? (I think strider unknown has said some things about it, have to reread that)

"Atoms in one magnet emit virtual photons which travel to the other magnet, carrying the magnetic force. The important thing to realise is that virtual particle interacts can result in attractive forces as well as repulsive ones."

carry magnetic force ... you mean the momentum is transferred
magnetism = momentum?

@ Thed

"As photons are the particle analog of EM fields a photon can interfere with a EM wave. The interelation of things is quite complex. "

I see, charge is interference of photons
in combination with absorption and emittion of photons??
like,
*repel between neg./pos. and neg./pos. = both emit photons or both absorb photons
*attraction between pos. and neg. = one emits photons, the other one absorbs photons
(just some thoughts)

"The hardest aspect of quantum theory to grasp is that things are both waves and particles, at the same time. EM is not comprosed of photons, it is photons. Which we detect depends on the method of detection. You use the relevant model also."

yes, but that still doesn't answer my question

"This leads to the wild concepts of quantum gauge theories where instead of a field having force and direction at given points the field is a set of quantum properties. No, I don't really understand it either."

I like the idea though

5. ### c'est moiall is energy and entropyRegistered Senior Member

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indeed

what are "photon charges"?

I really like that thought

could you share some more thougths on that holographic stuff of photons and atoms ... wasn't so much clear for me
following Pribram (for the brain in this case) and Bohm in their holographic ideas???

7. ### c'est moiall is energy and entropyRegistered Senior Member

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".......and of what kind of nature is that other matter? "

nobody knows?

8. ### CrispGone 4everRegistered Senior Member

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Hi Tom,

"How exactly does the graviton fit into the "curved space" theory???"

Simple: it doesn't

.

Bye!

Crisp

9. ### c'est moiall is energy and entropyRegistered Senior Member

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of course it doesn't
Autodynamics speculates the pico-graviton
I believe they can perfectly explain mercurius etc., and all the rest they should be able to explain with this particle

10. ### Joeblow93132Guest

Crisp,

You said:

"The mainstream idea however is indeed that gravity is also mediated by particles (gravitons) that form the gravitational field."

"How exactly does the graviton fit into the "curved space" theory???"

"Simple: it doesn't"

Now I'm confused. Are you indicating that "curved space" and the graviton theory are two SEPERATE models of gravity??? If so, are you indicating that the graviton model is the mainstream theory, and that the "curved space" model is no longer the mainstream theory??? How much progress has been made in the graviton model?

Tom

11. ### c'est moiall is energy and entropyRegistered Senior Member

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sometimes the mainstream doesn't know anymore what mainstream is

12. ### Joeblow93132Guest

c'est moi,

Some people an this board know what mainstream is so well, that they can't even consider alternate explanations.

13. ### c'est moiall is energy and entropyRegistered Senior Member

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yes and they don't even address the points one posts. silence = admitting = defeat, it's that simple

14. ### ImaHamster2Registered Senior Member

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Silence may mean that there is nothing constructive to add. Or that responding may take the discussion along a fruitless pathway or diverts attention from more important issues. Or silence may be implicit agreement. Silence has many meanings.

(Didnâ€™t want hamster silence to imply agreement in this case. Hehe.)

Last edited: Apr 20, 2002
15. ### thedIT GopherRegistered Senior Member

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Or silence means that you know that anything you say will be twisted and distorted by the other party so silence is the only answer.

C'est Moi, this has nothing to do with "The Mainstream" being blinkered. It has a lot to do with the non-mainstream either being unaware of the full facts or deliberate mis-representation. Like yourself.

You obviously know a lot more than you admit and enjoy twisting what people are saying to elicit a response and steer the argument your own way. I for one am not playing that game any more.

16. ### CrispGone 4everRegistered Senior Member

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Uit de context gerukt

Hi all,

Tom,

"Now I'm confused. Are you indicating that "curved space" and the graviton theory are two SEPERATE models of gravity??? If so, are you indicating that the graviton model is the mainstream theory, and that the "curved space" model is no longer the mainstream theory??? How much progress has been made in the graviton model?"

With "mainstream" I was referring to the idea that is generally assumed amongst physicists who investigate the quantum nature of gravity. When talking about gravity, scientists still use General Relativity because it is correct, and because there is no working or consistent quantum alternative yet.

But I have to be carefull saying that, and this refers to the first part of your question (on two seperate models of gravity). Yes, there are several models of gravity: there's a Newtonian model, that is easy to work with and works perfectly on earth, with satellites, ... There's also General Relativity that describes the extreme situations (eg. objects of solar masses and beyond). Physicists use different models depending on the magnitude scale of the problem. There's no point in applying quantummechanics to the earth-moon system, the results are FAR more difficult to obtain, and the precision you gain is absolutely neglegible (I never worked out the maths ofcourse, but Newtonian mechanics describes the earth-moon system to a HIGH degree of accuracy). Don't be suprised that there are different ways of describing things, it just depends on the situation and the amount of accuracy required.

In some situations, there's no choice: to describe electron-proton interactions, you simply have to use quantummechanics to get results that are consistent with the experiment (Newtonian predictions are plainly wrong in most situations). If you want to describe light passing objects of several solar masses, you simply have to use General Relativity because other theories will produce results that are not compatible with measurements.

What scientists are trying to do is to unify all theories: as you correctly remarked, there are several ways of describing situations. The idea behind unification is to have one theory that fits all situations. To describe nature, you need to describe how particles interact, so (roughly said) you need to describe the forces that exist between particles (and we have a very good hunch that there are four fundamental forces in nature). The main idea behind unification is hence to create a theory that describes all four forces. Electromagnetic, weak and strong interactions have been unified, the problem now is to create a theory that also incorporates gravity. (And as a sidenote: string theory seems to be an ideal candidate since it simply requires gravity to be present together with the three other interactions).

Hope this clarifies some of my more vague previous posts

c'est moi,

"sometimes the mainstream doesn't know anymore what mainstream is."

One of the basic properties of a scientist is to be sceptical. Sceptical towards existing theories and new theories. I agree that this scepticism is mostly used to debunk non-mainstream theories, and I am pretty confident when I say that most new theories simply don't pass the test. However, that does not mean that all scientists desperately hang onto existing theories. Why do we use General Relativity ? Well, simple, because it works. From the moment it no longer works and a good alternative is available, scientists will surely use that theory.

"silence = admitting = defeat, it's that simple."

Ah, interesting point. You should know that today it is impossible to know everything there is to say in physics; everybody specializes. We have specialists in Special and General Relativity on this board, specialists in Field theory, Newtonian mechanics, Statistical mechanics, Solid state physics, .... It is well possible that the questions you ask remain unanswered because nobody here knows the answer. This does not necessarily mean that physics is wrong

. You should also consider that sometimes there simply is no time to answer a question, or that it requires a 50 page introduction (and then there's a lack of time to write that again) .... But I wonder what exact question never got answered ?

Crisp

Last edited: Apr 21, 2002
17. ### James RJust this guy, you know?Staff Member

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34,224
c'est moi:

<i>could it be possible that neutral particles (not talking about composite ones - the effect is neutral but the particles they are consisted of are really EM) have such a small charge that our instruments cannot detect it (maybe in the future)?</i>

Yes, it is possible. However, I am sure that there are some experimentally determined limits on how big any such charge could be, and that the charge, if any, would have to be incredibly small. Also, there's a problem: every particle we know of has charge in units of the electron charge e. In other words, charge is <i>quantised</i>. A particle can have a charge of zero, 1e, 2e, 3e etc. but nothing else. There is one exception to this. Quarks have fractional charges of plus or minus (1/3)e and (2/3)e, but the particles they make up always have integral charge (e.g. the proton has charge +1e, the neutron has charge 0).

<i>carry magnetic force ... you mean the momentum is transferred magnetism = momentum?</i>

Yes, momentum can be transferred in magnetic interactions. But magnetism is carried by photons, as I said before. Photons have momentum (but no mass).

<i>Now I'm confused. Are you indicating that "curved space" and the graviton theory are two SEPERATE models of gravity???</i>

Yes. The graviton is a creature of quantum theory. General relativity is not a quantum theory, but a classical one. Some theories (e.g. superstring theories) combine the quantum picture with the classical picture, although there are difficulties with testing those theories at present (or, in some cases, even working out what the theories predict).

<i>= admitting = defeat, it's that simple</i>

Silence can mean many things. Silence can mean "busy doing other things", for example. Silence can mean thinking that one has established one's point with sufficient clarity that repeating it again would be a waste of time. Silence can mean many things.

18. ### c'est moiall is energy and entropyRegistered Senior Member

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Okay, this is one of the things that haven't been answered: Completely fails to explain the observed Binary Star precession

I didn't know the charge was quantised. Strange that nature is so ordened. But *if* they would have a charge, then we could regard the photon as the fundamental quantum of all particles, no?
I wondered, emitting photons is a way of getting rid of an excess of energy (neutrons do this as well), but how do gluons or Z bosons do it then? -> with phoNons?

19. ### ProsoothusRegistered Senior Member

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Note to everyone:

I changed my username from Joeblow93132 to Prosoothus. Recently a new member signed up to sciforums using the name Joeblow, and to prevent confusion I changed my username.

Tom

20. ### ProsoothusRegistered Senior Member

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Crisp,

We have been having a discussion on this board about whether mass truly increases with velocity as stated by Relativity.

C'est Moi indicated that the mass of particles in particle accelerators don't increase as they are accelerated. It just appears that their mass increases, because their acceleration decreases as they approach light speed. The reason for this decreasing acceleration is because the force(electric and magnetic fields) that is pushing(or pulling) them, is traveling at light speed, thereby transferring less of it's momentum or energy to the particles the faster the particles are traveling. In other words, the transferred force(acceleration) is greatest when the particles are at rest, and is 0 if the particles are traveling at c.

I see no flaws in this simple explanation.

Tom

21. ### CrispGone 4everRegistered Senior Member

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Hi Tom,

"The reason for this decreasing acceleration is because the force(electric and magnetic fields) that is pushing(or pulling) them, is traveling at light speed, thereby transferring less of it's momentum or energy to the particles the faster the particles are traveling. In other words, the transferred force(acceleration) is greatest when the particles are at rest, and is 0 if the particles are traveling at c."

I think you better redirect this question to James R, as he seems to be more into field theory and elementary particles. However, I'll give it my best shot.

I don't agree with that explanation, because I think it is confusing two things. It is true that an electric field propagates at the speed of light, c. However, once the field is created at a certain location, it doesn't disappear (assuming the source keeps doing whatever it is doing to create the field). QED learns us that this electric field is quantized, which means that particles interact with the field through the exchange of a minimum packet of energy, the photon. However, I don't think there is no need for the photon to catch up with the passing particle (to name one situation that pops into my mind, the passing particle can "run into" the leading photon and absorb it).

Bye!

Crisp

22. ### James RJust this guy, you know?Staff Member

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I've already given my opinion on this, earlier in the thread. For relativistic reasons, c'est moi's explanation doesn't work.

23. ### ProsoothusRegistered Senior Member

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1,973
Crisp,

I am really surprised by your response. Acceleration decreasing with the increase of speed is not something that is limited to quantum mechanics, we see it in everyday objects. It is observed in cars, planes, rockets, and electric motors. I don't think that there is a case in our everyday world, where acceleration is constant regardless of the speed of the object.

But you believe that particles in particle accelerators act DIFFERENTLY than all the other objects in our everyday world. You believe that the decreased acceleration HAS to be the result of increasing mass.

Forgive me, but it sounds like your reaching.

Note: You assumed that there was an absorbtion or emmission effect of charged particles in an electric field. Let me remind you, this does not have to be the case. The propulsion force of like charges could be the result of the matter refusing to absorb the electric field particles. Let me also remind you that an electric field is not composed of electromagnetic photons in the traditional sense. It may be composed of other particles that bounce of the charged particles in a particle accelerator, forcing the charged particles to move as a result of transferred momentum.

Tom