Photon Question

[Ben]

I must point out that gravity is caused by energy, not by mass per se. A "massive" body only causes gravity because of its energy content.

For we non-physicists, I would think this assertion needs to be argued in some detail. Granted, Riemann geometry is decidedly non-linear, also granted that Einstein speculated that the energy content of a body is proportional to its mass but that's a big leap to your assertion.

 

Show us the reasoning (arithmetic preferred)

 

A vector field is an effect, caused by a dynamical rotating entity in non-uniform space.

NO, it is most certainly not - you are thinking of the curl of a vector field. A vector field is simply the smooth assignment of some vector to each point in our space of choice.

 

If you want to be more technical (which I doubt) it is a section of the vector bundle over this space, which is, of course a manifold.

 

I did read the whole of this thread, and only felt moved to offer a contribution because the answers didn't seem to be getting to the bottom of it.

And you have? Say what, you don't ring my bell with your poorly-understood quotes from Wikipedia, but then again, unlike you, I do not PRETEND to be a physicist, so, unlike you, I am willing to be corrected.

[Qfwfq]

Maybe a separate thread then?

Exactly. Why then did you put it all here? Some of it is fit for Strange Claims Forum anyway.

 

I know the field equations have the energy-momentum tensor in them but that isn't the point at all.

[modest]

I must point out that gravity is caused by energy, not by mass per se. A "massive" body only causes gravity because of its energy content.

For we non-physicists, I would think this assertion needs to be argued in some detail. Granted, Riemann geometry is decidedly non-linear, also granted that Einstein speculated that the energy content of a body is proportional to its mass but that's a big leap to your assertion.

 

Show us the reasoning (arithmetic preferred)

 

In gtr the stress energy tensor tells spacetime how to curve. The components are the density and flow of energy and momentum. [math]T^{00}[/math] is the density of energy (i.e. the flow of momentum in the time direction) which is relativistic mass. Most physicists prefer to call this quantity "energy" avoiding the concept of relativistic mass all together.

 

The term "mass" is usually understood to mean rest mass or invariant mass. In this sense, no, it is not mass which curves spacetime. You could say "energy curves spacetime" or "relativistic mass curves spacetime", but you wouldn't want to say "mass curves spacetime".

 

~modest

[Qfwfq]

Most physicists prefer to call this quantity "energy" avoiding the concept of relativistic mass all together.

 

The term "mass" is usually understood to mean rest mass or invariant mass. In this sense, no, it is not mass which curves spacetime. You could say "energy curves spacetime" or "relativistic mass curves spacetime", but you wouldn't want to say "mass curves spacetime".

 

~modest

Correct, except that I one of those who prefers to define mass as rest energy (for a composite body this includes the appropriate kinetic and potential energies of its parts) and so I consider "rest mass" as redundant terminology.

 

In GR however it is still so typical to say mass that I do myself, even though I know it's only a way of being concise. For most phenomenology it doesn't make an essential difference. Of course, a massless particle is deflected because it follows a null geodesic, but all the same the equivalence principle is illustrated as the equality between gravitational and inertial <whatever-ya-wanna-call-it>.

 

In any case, let's get back to topic.

[Farsight]

Modest: Thank you.

 

Why then did you put it all here?

Because it's the only way to answer the OP. Whilst the answer I gave is unfamiliar to you, it really does have a pedigree going back to Maxwell. See Quaternion - Wikipedia, the free encyclopedia. Also see Science of LIGO and note where it says The space-time ripples cause the distance measured by a light beam to change as the gravitational wave passes by. Electromagnetic waves are similar, but the change is only 3.86 x 10ˉ¹³ m.

[Qfwfq]

Because it's the only way to answer the OP.

It is hardly even one way, let alone the only way. What you say here is totally irrelevant to supporting your contention.

 

I'd say that's enough off with topic and pointless contributions.

[Farsight]

Ben was wrong about energy not causing gravity, you were wrong about the light wave, and you're wrong to think what I say is irrelevant. Think about it. I said the the magnetic field is a "turn" field. Now since Ben mentioned curl, look at this:

 

http://en.wikipedia.org/wiki/Curl_(mathematics)

 

"In vector calculus, the curl (or rotor) is a vector operator that describes the rotation of a vector field. At every point in the field, the curl is represented by a vector. The attributes of this vector (length and direction) characterize the rotation at that point. The direction of the curl is the axis of rotation, as determined by the right-hand rule, and the magnitude of the curl is the magnitude of rotation".

 

Another word for curl is "rot", which is short for rotor. And since you brought up gravity, take a look at this:

 

Gravitomagnetism - Wikipedia, the free encyclopedia

 

"The main consequence of the gravitomagnetic force, or acceleration, is that a free-falling object near a massive rotating object will itself rotate".

 

That's gravitomagnetism, and it's associated with rotation. That's what Gravity Probe B is all about. See Lense-Thirring precession. The magnetic field really is a turn field. And it's relevant because you really do make an electron (and a positron) from a photon, via pair production The electron has angular momentum, it really is a dynamical rotating entity. It affects the surrounding space. Think of it as a little like frame dragging, resulting in curved space as opposed to curved spacetime.

 

Take a single electron. It has an electric field, all around. Now consider a series of electrons arranged on atop the other. The electric field is now more cylindrical. Move down the stack of electrons, and it's like the current in the wire: you experience a magnetic field. So that right hand rule and Minkowski's wrench is telling you the electric field really is a twist field, because in truth there's only one field, the electromagnetic field. How you experience it depends on relative motion. And when you annihilate an electron with a positron you get back to photons, with their transient field variation. So when a photon moves you past it's going twist/turn untwist/unturn. All of this is on topic. You shouldn't think of it as a strange claim just because it's unfamiliar to you. Maxwell's original work used quaternions, originally devised for mechanics in three dimensional space, and behind imaginary numbers there's usually some underlying geometry.

[Qfwfq]

Ben was wrong about energy not causing gravity, you were wrong about the light wave, and you're wrong to think what I say is irrelevant.

This is argumentative fallacy.

 

You are wrong to teach me things that I studied many years ago and haven't been neglecting here and you are wrong to draw non-sequitur conclusions from these facts, this is another fallacy called a red herring.

 

Shoot electrons, protons, neutrons and their respective antiparticles through a same (non zero) EM field and they won't all follow a same path that could be called a geodesic; they simply won't have the same acceleration at a same given point (with the same EM field value). Neutron and anti-neutron might, where there is no strong gradient of B. Since you are so eagerly volunteering to teach me that stuff above, did you get what I said about the fundamental difference between the connections of these two gauge theories? They are usually written like:

 

[math]A_{\mu}[/math] for EM and [math]\Gamma^{\rho}_{\mu\sigma}[/math] for GR.

 

Notice there's a striking difference in the indices! Why?

[Little Bang]

In my opinion understanding the photon in a non-mathematical way is paramount to understanding the Universe. I must admit that explaining the photon in everyday terms may be akin to explaining a magnetic field the same way. We all know the effects of a magnetic field. We make use of them many times every day but using a language to explain one would be an almost impossible task. Below is a list of a few items I think we know about the photon and we can see if they generate any interesting responses.

 

Everyone already knows the items below.

 

WRS = with respect to the source

WRO = with respect to the observer

 

Gravity: A photon propagating out a gravity well is red shifted WRS.

A photon propagating into a gravity well is red shifted WRS and blue shifted WRO in the well.

 

Motion: An object moving toward a light source sees the light blue shifted, Away from the source red shifted.

 

Another type of motion that produces Doppler shift is located here, post #29 http://hypography.com/forums/physics-and-mathematics/20793-relativity-discussion-from-what-time-thread.html#post279488

 

All of the items above have one thing in common, a changing frame of reference.

 

I would like to show somewhat of a relationship between the above and the Big Bang. I don't know of what the BB was composed. Some mixture of virtual quarks and other particles or maybe it was just pure gamma radiation. I'm going to use Occam's razor and pick the radiation. If it was radiation that should suggest if spacetime was expanding then the BB had a frame of reference and that as spacetime expanded it's frame of reference was also changing. This would imply that as the light expanded it's wavelength would get longer, not by very much, say on the order of 10^-36 meters/meter.

[Farsight]

This is argumentative fallacy. You are wrong to teach me things that I studied many years ago and haven't been neglecting here and you are wrong to draw non-sequitur conclusions from these facts, this is another fallacy called a red herring.

It's no fallacy. And I'm not wrong. The material you studied was inadequate, and the fundamentals of electromagnetism is no red herring.

 

Shoot electrons, protons, neutrons and their respective antiparticles through a same (non zero) EM field and they won't all follow a same path that could be called a geodesic; they simply won't have the same acceleration at a same given point (with the same EM field value). Neutron and anti-neutron might, where there is no strong gradient of B. Since you are so eagerly volunteering to teach me that stuff above, did you get what I said about the fundamental difference between the connections of these two gauge theories? They are usually written like:

 

[math]A_{\mu}[/math] for EM and [math]\Gamma^{\rho}_{\mu\sigma}[/math] for GR.

 

Notice there's a striking difference in the indices! Why?

Because those are covariant and contravariant lower and upper indices. But let's not throw up mathematical formalism again because we can't deal with the OP. See Jefimenko's equations - Wikipedia, the free encyclopedia and note where it says:

 

There is a widespread interpretation of Maxwell's equations to the effect that time variable electric and magnetic fields can cause each other. This is often used as part of an explanation of the formation of electromagnetic waves. However, Jefimenko's equations show otherwise. [3] Jefimenko says, "...neither Maxwell's equations nor their solutions indicate an existence of causal links between electric and magnetic fields. Therefore, we must conclude that an electromagnetic field is a dual entity always having an electric and a magnetic component simultaneously created by their common sources: time-variable electric charges and currents."

 

This dualism is the crux of what I've been saying. There is only one field, the electromagnetic field, but your measurement and observation of that field depends on your motion relative to it. Remember that stack of electrons with a cylindrical electric field? There is no magnetic field. But move down the stack, and as per the right-hand-rule, you perceive a magnetic field. A magnetic field is most definitely associated with "turn" as per gravitomagnetism and the fourth image here: Single Particle Motion in Electric and Magnetic Fields. The turn is there because that stack of electrons displays a cylindrical field with a twist to it, just like the reamer.

 

Re your various particles, let's take an electron and place it in an electric field between two large plates. It moves down to the lower plate. Why? Because of vector potential? Because the electric field is a vector field? No, that is not an adequate reason. A vector field is merely the effect, not the cause. It isn't getting down and dirty as to why the electron moves. Minkowski's wrench does. The electron can be created from pair production, and has the property of spin. In simple terms an electron can be viewed as a photon travelling in a twisting turning circle. Drop the electron into a cube of space. If we take a side view of the component photon at one instant in time, we can envisage a vertical slice like this ׀ moving left to right. When we twist the cube from top to bottom, the vertical slice is tilted like this: / . So the component photon is now spiralling downwards while it’s also travelling in a twisting turning loop. Hence the electron moves down through the electric field like a drill bit. That’s attraction. Repulsion is the same sort of thing, but of course a positron goes the other way, like a drill in reverse, because it has an opposite chirality. Hence they don't follow the same "geodesic" path that you're thinking of. The same principle applies to the proton. A proton is more complex than the positron, and moves in different fashion again. The neutron is akin to a proton closely coupled with an electron, and is again affected in a different fashion. See Neutron magnetic moment - Wikipedia, the free encyclopedia and Beta decay - Wikipedia, the free encyclopedia.

[Ben]

The material you studied was inadequate

This is a very bold, not to say rude, statement, unsupported by any of your posts

 

Because those are covariant and contravariant lower and upper indices.

FAIL. You haven't grasped the fundamental similarity, yet subtle difference, between the gauge connection [math]A_{\mu}[/math] and the Levi-Civita connection on a pseudo-Riemann manifold. So explain what each does, in its own domain of applicability

But let's not throw up mathematical formalism again because we can't deal with the OP.

Why not be formal? It is to my understanding that math IS the language of physics, not your silly hand waving

There is only one field, the electromagnetic field

Hello Maxwell. You will, of course, be very familiar with his equations? Care to write them down, either in vector or co-vector form?

Remember that stack of electrons with a cylindrical electric field?

What is a "stack of electrons". What is meant by "a cylindrical electric field"?

A vector field is merely the effect, not the cause.

This is nonsense. A field is NOT an effect, and neither is it a cause. It is a very real thing - the assignment to each and every point in spacetime of some quantity, scalar, vector, tensor or what-all-have-you. In this case a vector. You should be aware that that there is no, repeat NO, canonical way of assigning such a field - each choice is equally valid (hint: this statement is somewhat related to Q's challenge)

 

I'm afraid I could not read any more of this rubbish.

 

PS. No doubt I shall incur another infraction for insulting a "valued" member, but this sort of nonsense makes even a non-physicist's blood boil

 

PPS It might surprise you to learn that all on this site have internet access. If we want to consult Wikipedia, or whatever, we are quite able to do that without your links.

[Little Bang]

Ok, here is a picture of a photon. Maybe not the true picture but it at least explains the magnetic and electric components in the original post. Imagine a donut. The donut is a wave in the shape of a donut Now imagine a football with it's thickest part exactly equal to the diameter of the donut. Place the tip of the football just touching the center point of the donut. The donut is the electric component ( charge stationary with respect to the observer ). The football is the magnetic component ( charge moving with respect to the observer ). If two photons with the same wavelength met donut to donut or football to football they cancil. Football to donut they add.

[Qfwfq]

Hmmm, I can't figure out your analogy Little Bang. Constructive and destructive interference are usually much more simply described and I don't see your description matching up with it. Consider a quite ordinary case such as the Young slits, how do you match up with that? :confused:

 

...and the Levi-Civita connection

Gosh I thought it was called the Christoffel symbol and Levi-Civita wuz that [imath]\epsilon_{\mu\nu\rho\sigma}[/imath] thingy! I guess he's right about the material I studied being inadequate! :doh:

 

Anyway thanks Ben for sparing me some of the effort, however, don't get toooooo upset and angry, :) debunking can be fun too ya know...;)

 

...and the fundamentals of electromagnetism is no red herring.

Pointless to say whether it is or isn't, statements aren't red herrings per se, they are such when you say them just to fill your speech with true statements but they don't prove your contention, nor disprove the opponent. It is also blatant fallacy to "prove" me wrong about this because Ben and I had each blundered about something else; what a conclusive argument, eh?

 

A vector field is merely the effect, not the cause.

The vector field is a description of the physical reality. The Lorentz formula gives the force on a moving charge and Newton's third axiom gives the acceleration. In relativistic notation it reads:

 

[math]qF_{\mu\nu}u^{\nu}=f_{\mu}=m\frac{du^{\mu}}{d\tau}[/math]

 

Nobody obliges you to call it the cause if you don't want to, but neither does this make it "the effect" of that charged particle's motion. This of course uses the [imath]F_{\mu\nu}[/imath] tensor, which knocks out the arbitrarity Ben mentions as a hint about my point.

 

In simple terms an electron can be viewed as a photon travelling in a twisting turning circle.

Well I guess the material I studied was terribly inadequate, it said nothing of that sort but instead chuntered about Fock space and Dyson T products and the likes, propagators for the lines in Feynman diagrams, interaction terms in the Lagrangian for the vertices in them......:shrug:

 

Repulsion is the same sort of thing, but of course a positron goes the other way, like a drill in reverse, because it has an opposite chirality.

Unlike the neutrino, the electron and postron can have the chirality they like and choose and it doesn't even coincide with helicity.

 

Hence they don't follow the same "geodesic" path that you're thinking of.

Fine, so they don't. Doesn't that mean the EM field is deviating them from the geodesic, so it can't be described in terms of space-time geometry? This deviation depends heavily on charge mass ratio.

[HydrogenBond]

One observation about a photon, that nobody addresses, is how can something moving at C show more than one output in terms of distance and time. A red photon and an X-ray both move at C. There should be total distance contraction and time dilation, due to C, yet both show different distance and time effects (wavelength and frequency).

 

The speed of light is the same in all references, but the distance/time expressions are dependent on reference. We can get red shift or blue shift between references, but the speed of light stays the same.

 

One way to look at this is that all photons are anchored at C. Using a rubber band, as an analogy, they all stay anchored at C but stretch to form the various output expressions characteristic of finite reference. Is the stretch connected to what we call energy potential? One way to break the anchor at C appears be to incorporate into matter. Now the potential is fully reference dependent.

[Ben]

Gosh I thought it was called the Christoffel symbol and Levi-Civita wuz that [imath]\epsilon_{\mu\nu\rho\sigma}[/imath] thingy! I guess he's right about the material I studied being inadequate! :doh:

Well, what you wrote was indeed the Christoffel symbol, which, in a pseudo-Riemann context, is very strongly related to the L-C connection - can't remember the details off the top of my head. But there are 2 such symbols, and I think (not sure, mind) yours is called "of the first kind"

 

The "thingy" you refer to is called the L-C symbol, and denotes a permutation on indices.

 

don't get toooooo upset and angry, :) debunking can be fun too ya know...;)

Believe it or not, I was pissed for your sake, and all the people like you, who have devoted years of difficult study in physics here being lectured to by one who seems to understand even less physics than I do.

 

And believe me, that is some achievement.

[Little Bang]

Please note that I said it probably is not a true description but if we don't discuss possible geometric descriptions of the photon then we well never get one. The Double Slit is a good point I will include it in my thinking, thanks. Hydro also adds a good point, all photons must be locked to C. Where can I find info on this Levi-Civita connection?

[HydrogenBond]

Years back I did a thought analysis calling C the base reference, since one could argue energy came before matter. This made the inertial universe a function of departure from C. I realize this is backwards, but it tried to address the wavelength-frequency aspects of energy that is characteristic of inertial reference, with energy not losing an anchor at C which is not dependent on inertial reference.

 

Here is how my thinking went. If we were on a spaceship traveling at C and slowed down to finite velocity, energy will be released. So if we anchor at C, and only a part of the phenomena gains characteristics of the (slower) finite reference (wavelength-freqency) the energy difference, is the potential energy within the photon. It is still anchored at C but have potential in inertial.

 

To get wavelength-frequency to add up properly, one needs to start at C and hypothetically slow down reference from C to gain the potential within the inertial aspect. At C, we can see infinite distance contracted into a point. This is infinite distance or infinite wavelength energy which has about zero potential energy. As we slow from C very slightly, we can't see all the way to infinity. This potential loss represents the next wavelength, slightly smaller than infinity where energy potential appears in a photon. If we slow all the way down, but retain the anchor at C, the potential energy is within highest energy photons with the smallest wavelength. I am not saying we slow from C, since there is an anchor. But the size of the wavelength is not connected to C reference, so I use a hypothetical slow down for potential.

 

What we see in inertial reference, will be the opposite of what we would see in the C reference, based on using C as the anchor. state. The more potential remaining in the C aspect of the anchor, the less potential we see in inertial reference. The more we see in the inertial aspects of the photon the less in the anchor at C. The cooling of the universe, as we head toward lower energy is implicit of a return to the C as potential returns to the anchor. With black holes and the generation of infinite wavelength energy, both reference and energy is moving potential to the C anchor.

 

Matter does not have an anchor at C. According to SR, matter can never reach C without infinite energy, which is not available in a finite universe. There is a discontinuity to the C anchor, with respect to matter going directly to C. The only way matter can return to C is through the conversion of matter to energy. This is mediated through the forces of nature, which just so happen to propagate at C. The universe expanding and its energy red shifting, results in energy moving toward lower potential, within inertial, heading back to the C reference of the anchor.

 

Lastly, consider just the C anchor without any potential in inertial. It would not show up as anything in the way of wavelength or frequency. It would appear to be empty of potential energy in inertial, just like empty space. If we tug on the C anchor to pull an aspect into inertial space-time, due to potential with inertial, but in a reversible way, we get dark energy appearing out of nothing. This tug occurs via gravity, at the speed of light, tugging onto the pure C anchor to make potential appear.