Understanding the Mass of Light: Wave or Quanta?

[FUNKER]

Does Light Have Mass?

does light be it in wave or quanta have mass in any situation?
please any answers would be appreciated

 

[HallsofIvy]

No, light does NOT have mass. Haven't we had this question a number of times?

 

[FUNKER]

thanks bro get tht shiz a crackin

 

[Link]

My physics teacher says gravity anything that has a mass. According to the General Theory of Relativity, gravity bends light... but if light don't have a mass, how can this be possible?

 

[russ_watters]

Originally posted by Link
My physics teacher says gravity anything that has a mass. According to the General Theory of Relativity, gravity bends light... but if light don't have a mass, how can this be possible?

In high school, you generally don't go past the Newtonian theory of gravity. It works in a lot of cases, but isn't quite right for all.

In Einstein's gravity, the gravitational field around an object with mass is a curvature of space, much like the way a bowling ball curves a trampoline. Light travels in a straight path in space but to us, with space itself curved, it looks bent.

 

[Link]

so the universe is a sphere?

 

[brum]

in a bomb in which some atoms are converted to light & energy (a la E=mc^2), how does that satisfy the conservation of mass then?

 

[chroot]

There is no such thing as a conservation of mass. There is a conservation of mass-energy, the sum of the two combined.

- Warren

 

[HallsofIvy]

My physics teacher says gravity (affects? attracts? verb missing!)anything that has a mass.

Okay, and that's true (hey, I wouldn't argue with your physics teacher!) but your physics teacher did not say that that was all that was affected by gravity. In the general theory of relativity, gravity works by changing space-time itself and has nothing to do with "mass". In fact, a major impetus for the creation of general relativity was the fact that mass always cancels out of problems involving gravity.

 

[Tron3k]

Isn't it interesting that a box filled with light is literally heavier than an empty box?

 

[wasteofo2]

That could actually be true, but the difference would be negligable.

I saw a special on the discovery channel about the future of space travel, and one proposition was a very small craft with a giant sort of parachute that would be propelled away from the sun based solely on the energy from the sun bouncing off of it and pushing it forward.

So this same sort of force could push down on a box slightly. Certainly nothing that you'd even care to, or be able to measure without some insance scale.

 

[brum]

Originally posted by wasteofo2
I saw a special on the discovery channel about the future of space travel, and one proposition was a very small craft with a giant sort of parachute that would be propelled away from the sun based solely on the energy from the sun bouncing off of it and pushing it forward.

So this same sort of force could push down on a box slightly. Certainly nothing that you'd even care to, or be able to measure without some insance scale.

likewise, the light would bounce of the top of the box. and the sides. (and thus, no net force)


on the parachute, that's a different story.

ever see one of those spinning things in a glass dome, about the size of your fist, that has 4 spinning squares rotating around an axis? and the 4 squares are silver-ish on one side & black on the other side, which causes the 4 squares to move in the same direction around the axis because of the sun's light being absorbed by the silver side and not by the black side.

or something like that.

 

[neutroncount]

Not quite Brum. That trick is done in a partial vacuum and is because of a temperature differential. A solor sail deals with momentum of photons being imparted onto the sail. The force is very light but given a large and long enough source of light, the final velocity can be very quick.

 

[gmorgan]

The interesting thing about light is it has no mass but has momentum determined by De Broglies(momentum=Planck's constant/wavelength) equation from QM. De Broglie believed that light did have a tiny mass such that it would be slightly slower than what we call the speed of light, however, this mass or speed difference has never been detected.

As for the rotating thing. Generally they are carnival tricks caused by temperature differentials you can however do it with a laser if the turntable is in a vacuum.

 

[rocketcity]

Why is a box of light heavier than a box of dark?

If I'm understanding this correctly, it's *not* because of light pressure (pressure is a scalar and thus non-directional) but because the captive photons, just like photons traveling through free space, are 'pulled towards' massive objects by the curvature of space.

*Would* this increase the measured weight of the box, to someone looking at a scale outside the box (even assuming an ideal scale)? I'm trying to compare this to *gas molecules* inside a box increasing its weight just by using a kinetic theory argument, i.e., the molecules collide with the bottom of the box more frequently, or at higher speeds, than those that strike the top of the box.

Is a similar phenomenon responsible for the 'weight' of the light?

Related question : if you fire a 5E15 Hz laser beam straight up from a massive object, will the light have a lower frequency at infinity due to loss of energy in climbing out of the gravity well? (S'pose the massive object is stationary in an inertial reference frame, and the observer at infinity is also similarly stationary.) (Can you even make that assumption, since massive objects inherently make reference frames non-inertial?)

P

 

[chroot]

Originally posted by rocketcity
If I'm understanding this correctly, it's *not* because of light pressure (pressure is a scalar and thus non-directional) but because the captive photons, just like photons traveling through free space, are 'pulled towards' massive objects by the curvature of space.

Pressure counts too. It gets wrapped up in the stress-energy tensor, which determines the amount of gravitational curvature.

*Would* this increase the measured weight of the box, to someone looking at a scale outside the box (even assuming an ideal scale)? I'm trying to compare this to *gas molecules* inside a box increasing its weight just by using a kinetic theory argument, i.e., the molecules collide with the bottom of the box more frequently, or at higher speeds, than those that strike the top of the box.

You can use the same argument, I believe. And yes, an observer outside the box will see the increased weight.

Related question : if you fire a 5E15 Hz laser beam straight up from a massive object, will the light have a lower frequency at infinity due to loss of energy in climbing out of the gravity well?

Yes. See the Pound & Rebka experiment for just one example.

- Warren

 

[Tron3k]

If you guys really want to know why a box full of light has more mass than an empty one, read this paper:

Light is Heavy

It's an excellent analysis.

 

[NateTG]

Originally posted by brum

ever see one of those spinning things in a glass dome, about the size of your fist, that has 4 spinning squares rotating around an axis? and the 4 squares are silver-ish on one side & black on the other side, which causes the 4 squares to move in the same direction around the axis because of the sun's light being absorbed by the silver side and not by the black side.

A radiometer?

There's a long story about how they work. It turns out that the effect has to do with interactions that occur at the edges of the blades, and not do to pressure differences caused by heat.

 

[Arcon]

Originally posted by FUNKER
does light be it in wave or quanta have mass in any situation?
please any answers would be appreciated

That depends on how you define the term mass. Light does have a non-zero relativistic mass (aka inertial mass) and has zero proper mass. Relativistic mass is the coefficient of proportionality between relativistic momentum and 3-velocity. I.e. it is the m in p = mv. It also has a non-zero active gravitational mass (it generates a gavitational field) and a non-zero passive gravitational mass (it is deflected by a gravitational field).

link wrote

My physics teacher says gravity anything that has a mass. According to the General Theory of Relativity, gravity bends light... but if light don't have a mass, how can this be possible?

You're mixing up the different meanings of the term "mass." Light does have mass because it has energy. As Feynman said in the Feynman Lectures Vol -I page 7-11, Section entitled Gravitation and Relativity

One feature of this new law is quite easy to understand is this: In Einstein relativity theory, anything which has energy has mass -- mass in the sense that it is attracted gravitationaly. Even light, which has energy, has a "mass". When a light beam, which has energy in it, comes past the sun there is attraction on it by the sun.

russ watters wrote
In Einstein's gravity, the gravitational field around an object with mass is a curvature of space, much like the way a bowling ball curves a trampoline. Light travels in a straight path in space but to us, with space itself curved, it looks bent.

The curvature in Einstein's GR is an analogy taken from geometry. And it is not spacetime curvature that is responsible for deflection of light in a gravitational field. It is the gravitational force that is responsible. Spacetime curvature is just another name for tidal force. But there is no need to assume that tidal forces are present in order for there to be a gravitational field. E.g. there is no spacetime curvature in a uniform gravitational field and yet light is still deflected. And light is deflected because it has non-zero relativistic mass.

chroot wrote
There is no such thing as a conservation of mass. There is a conservation of mass-energy, the sum of the two combined.

That is incorrect. In fact many derivations on relativity were based on the postulate of conservation of mass. Even if one wishes to define "mass" as "invariant mass" as Taylor and Wheeler do in Spacetime Physics Second Edition there is still mass conservation. I.e.
http://www.geocities.com/physics_world/stp/pg_249.htm

"Thus part of the mass of constituents has been converted into energy; but the mass of the system has not changed/"

By the way, "mass-energy" is a synonym for "relativistic mass"

HallsofIvy

In the general theory of relativity, gravity works by changing space-time itself and has nothing to do with "mass".

That is incorrect. Mass acts as the source of gravity in the same way that charge acts as the source of the EM field. The complete description of mass is the energy-momentum tensor (or mass tensor if you prefer) just as the complete description of charge is the 4-current 4-vector.

Since the time-time component of the stress-energy-momentum (SRM) tensor is proportional to relativistic mass, i.e. T⁰⁰ = c²(mass density), and since the SEM tensor is divergenceless it follows that mass is conserved. But then again that tensor is almost designed that way so one expects that to me the case. So long as mass is defined so that p = mv (p and v are 3-vectors) is conserved then mass is conserved.

For details see Cosmological Principles, Peacock, Cambridge Univ. Press, (1999). See pages 17-18
http://assets.cambridge.org/0521422701/sample/0521422701WS.pdf

rocketcity

Why is a box of light heavier than a box of dark?

Because the light transmits forces to the walls of the box and it is that transfer of momentum that causes the box to weigh more. This should be measureable in principle. There was a paper published on this subject in the American Journal of Physics. It's called

The mass of a gas of massless photons, H. Kolbenstvedt, Am. J. Phys., 63(1), Jan 1995

chroot wrote

Pressure counts too. It gets wrapped up in the stress-energy tensor, which determines the amount of gravitational curvature.

Pressure is just one component of the SEM tensor. And you need to SEM tensor to describe the inertial mass of a box. Not just to describe the gravitational mass of a body. If the SEM tensor is divergenceless then the mass of the entire system will always transform as M = gamma*M₀.

*Would* this increase the measured weight of the box, to someone looking at a scale outside the box (even assuming an ideal scale)? I'm trying to compare this to *gas molecules* inside a box increasing its weight just by using a kinetic theory argument, i.e., the molecules collide with the bottom of the box more frequently, or at higher speeds, than those that strike the top of the box.

Yes. That is correct.

 

[Monique]

Originally posted by HallsofIvy
No, light does NOT have mass. Haven't we had this question a number of times?

doesn't energy automatically have a mass associated with it? e=mc2? Arcon made a good reply..

 

[Monique]

Ah wait, invariant mass and relativistic mass are very different things :) where invariant mass would be the inertia of the body at rest? Apparently Einstein explicitly adviced against using relativistic mass..

 

[Arcon]

Originally posted by Monique
Ah wait, invariant mass and relativistic mass are very different things :) where invariant mass would be the inertia of the body at rest? Apparently Einstein explicitly adviced against using relativistic mass..

Yes. Invariant mass, m₀ (aka "rest mass," "proper mass") is different than relativistic mass, m(v). In special relativity they are related by

m(v) = \frac { m_{0}}{\sqrt{1-v^{2}/c^{2}}}

Einstein didn't exactly advise against relativistic mass. He advised against a mass M = m_o/sqrt[1-(v/c)^2]. So in special relativity he did advise agains this usage. But relativistic mass has the value

m = m_{0}\frac{dt}{d\tau}

In the case of a slowly moving particle in a gravitational field the mass is a function of the gravitational potential and is therefore different from rest mass. Einstein discussed this in his book on relativity The Meaning of Relativity in connection with Mach's Principle.

If you take a look at Thorne and Blanchard's new book which is located online. For example see
http://www.pma.caltech.edu/Courses/ph136/yr2002/chap01/0201.2.pdf

You'll see that the authors use the term "rest mass" when they mean rest mass. They do not mean invariant mass at any place when the simply write "mass." But I do see them use the term "mass" to it mean "relativistic mass", i.e.

..in the first expressioin dE is the total energy (or equivalently mass) in the volume dx dy dz. ...

In other chapters they use the term "mass-energy" i.e. in
http://www.pma.caltech.edu/Courses/ph136/yr2002/chap23/0223.1.pdf
they write

Moreover, the total density of mass-energy rho as measured in the fluid's local rest frame can be expressed as the density of rest mass-energy rho₀ plus the density of internal energy rho₀u

\rho = \rho _{0}(1+u)

That implies relativistic mass.

 

[Nim]

--------------------------------------------------------------------------------

chroot wrote
There is no such thing as a conservation of mass. There is a conservation of mass-energy, the sum of the two combined.


--------------------------------------------------------------------------------


That is incorrect. In fact many derivations on relativity were based on the postulate of conservation of mass. Even if one wishes to define "mass" as "invariant mass" as Taylor and Wheeler do in Spacetime Physics Second Edition there is still mass conservation. I.e.
http://www.geocities.com/physics_world/stp/pg_249.htm

"Thus part of the mass of constituents has been converted into energy; but the mass of the system has not changed/"

By the way, "mass-energy" is a synonym for "relativistic mass"

I always figured that they said mass is conserved because even though you can decrease the amount of mass in the universe, that decrease corrisponds to an increase in energy which can be converted back to mass. Is mass conserved because "anything which has energy has mass" and so the increase in energy gives rise to an increase in mass that equals the amount of mass that was converted into energy?

 

[Arcon]

Originally posted by Nim
I always figured that they said mass is conserved because even though you can decrease the amount of mass in the universe, that decrease corrisponds to an increase in energy which can be converted back to mass. Is mass conserved because "anything which has energy has mass" and so the increase in energy gives rise to an increase in mass that equals the amount of mass that was converted into energy?

That's difficult to answer until you define what you mean by "mass."

If you simply calculate the total value of the relativistic mass then that sum is a constant. To see how this works in application to, say, nuclear energy see

http://www.geocities.com/physics_world/sr/nuclear_energy.htm

Trying to define "mass" as the total energy in rest frame divided by zero and then at the same time trying to do away with relativistic mass is quite illogical. For there to be a mass-density there must be relativistic mass since such a density implies relativistic mass since it associates a location with the mass and this implies relativistic mass.

 

[Monique]

Relativistic mass is dependent on kinetic energy, which is dependent upon your frame of reference. Why can't a photon have an invariant mass m₀?

I think the answer lies somewhere in this sentence "For there to be a mass-density there must be relativistic mass since such a density implies relativistic mass since it associates a location with the mass and this implies relativistic mass." by Arcon.. ;)

 

[Monique]

Originally posted by Monique
Relativistic mass is dependent on kinetic energy, which is dependent upon your frame of reference. Why can't a photon have an invariant mass m₀?

Oh wait, never mind: speed of light is constant I'm a little confused at the moment :)

 

[Arcon]

Originally posted by Monique
Relativistic mass is dependent on kinetic energy, which is dependent upon your frame of reference. Why can't a photon have an invariant mass m₀?

I think the answer lies somewhere in this sentence "For there to be a mass-density there must be relativistic mass since such a density implies relativistic mass since it associates a location with the mass and this implies relativistic mass." by Arcon.. ;)

The term "invariant mass" refers to the m₀ in

E^{2} - (pc)^{2} = m_{0}^{2}c^{4}

This relation can be derived from

E = \frac{m_{0}}{\sqrt{1-v^{2}/c^{2}}}

The relationship between energy and momentum for radiation is E = pc. This was demonstrated by Poincare in 1900. Substitute this into the first equation and you'll get

E^{2} - (pc)^{2} = 0

It's not a really valid thing to do since the first relation above is derived with the assumption that m₀ is not zero. But that is the terminology that we're stuck with!

 

[decibel]

SO at the end of all this...light does NOT have mass ( real kind of mass)...?

 

[Arcon]

Originally posted by decibel
SO at the end of all this...light does NOT have mass ( real kind of mass)...?

I don't know why you'd conclude that. What is it you mean by "real kind of mass"? If you mean "proper mass" when that was already stated a while back - light has zero proper mass.

 

[Integral]

Note to Arcon & DW.

DO NOT START YOUR DEBATE HERE!

Integral

 

[Monique]

Originally posted by decibel
SO at the end of all this...light does NOT have mass ( real kind of mass)...?

To end all of this? Isn't a person allowed to understand? Isn't this a discussion forum? Oh well..

 

[chroot]

Originally posted by Monique
To end all of this? Isn't a person allowed to understand? Isn't this a discussion forum? Oh well..

Monique -- what do you not understand? We'll certainly try to help.

- Warren

 

[Monique]

thanks Warren, I think I have to read up and refresh my mind before I can make a sensible discussion :)

 

[Arcon]

Originally posted by Monique
To end all of this? Isn't a person allowed to understand? Isn't this a discussion forum? Oh well..

I've never understood the desire to end a polite conversation when people still wanted to discuss it. But such is life!

This is one of those topics which has been debated in the physics literature for many decades and has been rather heated even in that literature.

However there is always PM. But I'll do whatever I can to clarify anything.

 

[Michael F. Dmitriyev]

Originally posted by HallsofIvy
No, light does NOT have mass. Haven't we had this question a number of times?

We’ll check up it now.
E=mc^2 (1)
Is it right?
E=h \nu\ (2)
Is it right?
When
mc^2=h \nu\
or
m=k\nu\ (3)

here k= h/c^2
m – the rest mass.
So?

 

[chroot]

No, Michael, that's not right. The equation you want is

E = \sqrt{m^2c^4 + p^2c^2}

In the case of light, m is zero, so this reduces to

E = pc

- Warren

 

[Michael F. Dmitriyev]

Originally posted by chroot
No, Michael, that's not right. The equation you want is

E = \sqrt{m^2c^4 + p^2c^2}

In the case of light, m is zero, so this reduces to

E = pc

- Warren

Whence you have taken m=0? Prove your statement please.

 

[chroot]

Read more.

http://math.ucr.edu/home/baez/physics/Relativity/SR/light_mass.html

- Warren

 

[Arcon]

Originally posted by Michael F. Dmitriyev
We’ll check up it now.
E=mc^2 (1)
Is it right?
E=h \nu\ (2)
Is it right?
When
mc^2=h \nu\
or
m=k\nu\ (3)

here k= h/c^2
m – the rest mass.
So?

Things sure would be easier if terms were explicitly defined when they're used in a thread whose subject is about the meaning of a term. Since the topic of this thread is the mass of light and since there are different answers depending on what mass you're referring to it would be nice if we these terms were defined.

If the equation

E = mc^{2}

is supposed to hold for all values of energy/velocity then m is relativistic mass. If, on the other hand, you wrote instead

E_{0} = mc^{2}

then m would be proper mass (aka "rest mass"). Since you wrote it as it applies to a photon then the "m" is relativisitc mass and not rest mass. This is implied in your equation (2)

E=h \nu\

For this reason you can write

mc^2=h \nu\

But m is not rest mass.

Warren - You used the same symbol, m, to mean rest mass when the context Michael was using it implied it implied it was relativisitc mass.

Note: These arguements/expressions only apply to inertial frames of referance. I.e. the expression

E = \sqrt{m^2c^4 + p^2c^2}

(where "m" is proper mass) is invalid when the frame of reference is not an inertial one.

 

[chroot]

Arcon,

I don't ever use relativistic mass. I should perhaps have stated that I meant that m is rest mass, but I thought it was obvious.

- Warren

 

[Arcon]

Originally posted by chroot
Arcon,

I don't ever use relativistic mass. I should perhaps have stated that I meant that m is rest mass, but I thought it was obvious.

- Warren

It's obvious to me but it was not obvious to Michael.

 

[Michael F. Dmitriyev]

Originally posted by chroot
Read more.

http://math.ucr.edu/home/baez/physics/Relativity/SR/light_mass.html

- Warren

I am informed on that explanation where you gave the reference...

Moderator edit: crackpotism deleted. Michael, please post your personal theories only in the Theory Development forum.

 

[Arcon]

Originally posted by Michael F. Dmitriyev
I am informed on that explanation where you gave the reference...

Moderator edit: crackpotism deleted. Michael, please post your personal theories only in the Theory Development forum.

Moderator - Please don't snip like that. I was comming back to this post to try to understand what Michael was talking about. Now I can't see how or where he was getting confused (which I think is the case).




By the way Michael - I can't recall if I mentioned this already - Since 1906 Einstein always assigned mass to light. The was a conclusion that he reached in his paper The Principle of Conservation of the Center of Gravity and the Inertia of Energy, Albert Einstein, Annalen der Physik, 20 (1906): 626-633.

The first part of the paper he gave this arguement
http://www.geocities.com/physics_world/sr/einsteins_box.htm

In the second part of that paper he used that argument to assign mass to radiation (i.e. light). He then derived an expression for the center of gravity. However this was a theme he maintained throughout the rest of his life.

In the 1906 paper Einstein wrote

If we assign the electromagnetic field too a mass density (rho_e)..

In his 1916 review paper on GR Einstein wrote

The special theory of relativity has led to the conclusion that inert mass is nothing more or less than energy, which finds its complete mathematical expression in a symmetrical tensor of second rank, the energy-tensor.
...
We make the distinction hereafter between “gravitational field” and “matter” in this way, that we denote everything but the gravitational field as “matter.” Our use of the word therefore includes not only matter in the ordinary sense, but the electromagnetic field as well.

That of course means Einstein was saying that light has mass (and therefore he was referring to what we call today 'relativistic mass")
In an section of one of his books Einstein was explaining the bending of light in a gravitational field. He wrote, referring to a man in an elevator

(1938) But there is, fortunately, a grave fault in the reasoning of the inside observer, which saves our previous conclusion. He said: "A beam of light is weightless and, therefore, it will not be affected byu the gravitational field." This cannot be right! A beam of light has energy and energy has mass. But every inertial mass is attracted by the gravitational field as inertial and gravitational mass are equivalent.

For more examples of relativistic mass see
http://www.geocities.com/physics_world/relativistic_mass.htm

There was a paper published a few months ago on this subject, i.e.

Apparatus to measure relativistic mass increase, John W. Luetzelschwab, Am. J. Phys. 71(9), 878, Sept. (2003).

 

[chroot]

Originally posted by Arcon
Moderator - Please don't snip like that.

This is my forum. I am upholding its rules. We have an entire forum for Michael to post his personal theories. This is not it.

- Warren

 

[Arcon]

Originally posted by chroot
This is my forum. I am upholding its rules. We have an entire forum for Michael to post his personal theories. This is not it.

- Warren

How do you know it was his personal theory and not his misunderstanding which needed to be corrected?

 

[chroot]

Originally posted by Arcon
How do you know it was his personal theory and not his misunderstanding which needed to be corrected?

I know the difference. If you'd like to discuss this more, please use the PM feature.

- Warren

 

[GRQC]

Originally posted by Arcon

By the way Michael - I can't recall if I mentioned this already - Since 1906 Einstein always assigned mass to light.

Light does not have mass, nor is mass a quantity which is relativistic. It is on par with proper time, which is a relativistic invariant. Simply put:

Proper time $\tau = \sqrt{t^2-x^2}$

Mass: $m = \sqrt{E^2 - p^2}$

Both are the magnitude of a four vector in spacetime, which is invariant under Lorentz rotations. For photons, both quantities are null vectors, and thus are 0.

The was a conclusion that he reached in his paper The Principle of Conservation of the Center of Gravity and the Inertia of Energy, Albert Einstein, Annalen der Physik, 20 (1906): 626-633.

I'm not convinced he said this, but even if he did: have you never said something, and later realized you mis-spoke your reasoning?

That of course means Einstein was saying that light has mass (and therefore he was referring to what we call today 'relativistic mass")

He wasn't saying that -- you are putting words in his mouth.

There was a paper published a few months ago on this subject, i.e.

Apparatus to measure relativistic mass increase, John W. Luetzelschwab, Am. J. Phys. 71(9), 878, Sept. (2003). [/B]

Am. J. Phys. is not where you go for cutting edge research in GR. It's a teaching journal. Go to arxiv.org instead and find some papers.

 

[eagleone]

Let’s simplify it. And take it my way :).
Does the light have it’s own gravitational field, or is it a source of gravity ?
No - as much as I know, but you’re here to correct me.
And that’s the “type” of mass people (nonphysics) are thinking about when they say “common” mass in this thread Acron - they think on non relativistic one (I believe that there’s better term in English than this one).

I’m more interested in this, on page one russ was talking about curved space (by gravity), and that being the reason why light seems to bee attracted by gravity (by just fallowing the curved space), then Acron sad “no”- light will bee attracted any way, and “attraction” isn’t direct consequence of curved space . So what is it, could we discus this more detail.

Could someone briefly (Warren seems to be good at it) line most important conclusions and consequences deriving from GR, I think that it would help answering some questions from this thread.

Greetings

p.s. what particle has characteristic like photon (non rest mass, but attracted by gravity/bydefault :)/)

 

[pmb_phy]

Originally posted by eagleone
Let’s simplify it. And take it my way :).
Does the light have it’s own gravitational field, or is it a source of gravity ?

Yes. Since light has energy and energy has mass then light will generate a gravitational field. An example was given in

On The Gravitational Field Produced by Light, Tolman, Ehrenfest and Podolsky, Physical Review, Vol(37), March 1, 1931, pg 602-615

See --
http://www.geocities.com/physics_world/grav_light.htm

 

[GRQC]

Originally posted by eagleone

And that’s the “type” of mass people (nonphysics) are thinking about when they say “common” mass in this thread Acron - they think on non relativistic one (I believe that there’s better term in English than this one).

But you can't just go around re-defining accepted terminology to support a "new" claim.

I’m more interested in this, on page one russ was talking about curved space (by gravity), and that being the reason why light seems to bee attracted by gravity (by just fallowing the curved space), then Acron sad “no”- light will bee attracted any way, and “attraction” isn’t direct consequence of curved space . So what is it, could we discus this more detail.

Acron is incorrect if he said that. Light follows geodesics in spacetime (straight lines!). When spacetime is curved, light still follows straight paths on the curved manifold, which end up deflecting the path of the rays.

I don't understand how light can be "attracted" without curvature. To suggest that this is happening is tossing GR out the window. If he really did say that, then his argument is very inconsistent (and hence shows a clear lack of understanding of the subject).

p.s. what particle has characteristic like photon (non rest mass, but attracted by gravity/bydefault :)/) [/B]

Do you mean gravitons? If so, there is no well-established quantum field theory which involves gravitons, so we really can't say for sure if gravity attracts itself (graviton-graviton vertices in the Feynman diagrams). Supersymmetric and supergravity theories involve them, but any quantum gravitational theory is not well founded (and certainly not as well-understood as quantum electrodynamics).