Ask any question you want about Physics

originally posted by: delbertlarson
In fact, I know this because of a similar error I made in my early days. I wrote to John Bell about a theory I had that there was no length contraction, as I had derived equations showing how everything came about from time dilation alone. John Bell wrote back to tell me he didn't see how a length contraction could come out of time dilation, and I realized I had done the calculations at a single point (just like the author you referred me to). Once I did things at two separated points it got a lot more difficult.

Thanks for taking a look, I'll have to take another look and see if that's what he did but if so I'm not sure how that works because you need at least two points for a length so how could one even try to calculate a length contraction from a single point?

I don't see many others making his claim the models are identical, but he does cite other sources saying the models are experimentally indistinguishable. I understand your position is they be experimentally distinguishable, but we just haven't performed the right experiment yet to demonstrate the difference, so until we have an experiment to demonstrate the difference, the "experimentally indistinguishable" claims he cites haven't been falsified.

originally posted by: mbkennel
a reply to: Arbitrageur

I would worry more about experiments than theory.

Consider the recent diphoton hump. Two lhc experiments showed a potential excess of events. Over a year, theorists wrote 700 papers on this, with perhaps 250 varying theoretical proposals, of which maybe 50 could be quite theoretically plausible. (Just a guess).

So they took more data, and after a year, the bump went away, it was just an unusual coincidence. Theorists were plenty creative.

Theory is not going to provide much of the road to new physics, thats the lesson. Mathematical consistency and beauty is not enough.

I suppose you and I see different lessons in that, because I don't think it shows that "Theory is not going to provide much of the road to new physics" at all and I'm surprised you'd say that. All it shows is that it didn't happen in that one example, it says nothing about what will happen in other cases. I could cite more examples, like the Pioneer anomaly, which also created "new physics" ideas to explain the phenomenon, but again in that case it turned out the anomaly wasn't really an anomaly after a more detailed analysis, so it just shows that people tried creating or applying new theories where no new theories were really needed. This doesn't tell me anything about people creating new theories where they really are needed, and most physicists seem to agree we need better models for black holes and the earliest part of the big bang.

originally posted by: Nochzwei
exactly right

I've never seen any coherent "theory" from you and as I said I could write an entire book about what's wrong with your experiment, but in fact even more carefully performed experiments are still subject to experimental error and other problems so I find enough reason to worry about some theories and some experiments. The amount of worry varies depending on the specifics of the theory or experiment. I haven't seen much reason to doubt Newtonian mechanics at non-relativistic velocities so I don't worry about those experiments for example, but as my signature implies not only do I worry about string theory, I don't think it's really a theory, at least not yet.

originally posted by: DanDanDat
If the big bang occurred at a singular point in … what every existed before the big bang; and all mater emerged from that spot and has expanding outward ever since…

where exactly does our galaxy sit in that expanding sphere of our universe?

For example are we at the exact center (where the big bang occurred)? … I would imagine not. Or are we at the outer most shell of the universe? … again I would imagine not. So where between the center and the outer shell are we?

We don't imagine the geometry of the universe to work this way, and it's better to think of the big bang as occurring "everywhere in the universe at once" instead of at a single point. We've never seen the outer edges of the universe; we can only observe the observable universe which is a smaller sphere then the entire universe, as far as we know.

… that we can see light from galaxies that left their galaxies 13.1 billion years ago (700 million years after the big bang); shouldn’t we be able to look in the exact opposite direction and see the end of the universe?

No.

With the age of the universe being around 13.82 billion years; there can’t be 13.82 billion years of distance in all directions from our current location.

You are correct, there's not. As far as the experts can tell there is at least 46.5 billion light years in all directions, which is the radius of the observable universe, the edge of which is receding at over 3 times the speed of light, and accelerating. We don't know what's beyond the observable universe and whether the universe has any edges or not, it might not. In fact we don't even know if the universe is finite or infinite in size. Flatness measurements show the universe is fairly flat which tends to imply an infinite size but due to measurement limitations this doesn't rule out a very large finite size.

Observable Universe

Today the diameter of the observable universe is estimated to be 28 billion parsecs (about 93 billion light years). This diameter is increasing at the rate of about...6.5 times the speed of light...

I haven't tried these online cosmology courses but they might be of interest to you (the source I found them at says they are free):

The Accelerating Universe

Astrophysics: Cosmology

a reply to: Arbitrageur

Thanks for taking a look, I'll have to take another look and see if that's what he did but if so I'm not sure how that works because you need at least two points for a length so how could one even try to calculate a length contraction from a single point?

You are of course correct that we can't calculate a length contraction of a single point. What we can do is derive the Lorentz transformation of a single point in two different coordinate systems, which is what I did before I wrote to Bell. Since the Lorentz transformation is known to include both time dilation and length contraction effects, when I derived the transformation I thought I was done. But there was more to it than that. Once you do the calculations for a space-like separation of two events, then the issues of simultaneity become clear. My published paper (Google "Larson Absolute Theory") does things correctly.

I don't see many others making his claim the models are identical, but he does cite other sources saying the models are experimentally indistinguishable. I understand your position is they be experimentally distinguishable, but we just haven't performed the right experiment yet to demonstrate the difference, so until we have an experiment to demonstrate the difference, the "experimentally indistinguishable" claims he cites haven't been falsified.

I believe we already have experimentally tested Lorentz vs. Einstein. The experiments are an offshoot of a proposal by Einstein himself, along with Podolski and Rosen - the experiments are the Bell's Theorem tests done by Aspect, Dalibard and Roger. The issue is that physicists have (in my opinion) a religious attachment to relativity that they just can't give up. So you get all the modern day hocus pocus just to save a single theory.

a reply to: Arbitrageur

a reply to: delbertlarson

Light is just a transverse wave on the solid aether, a photon just a wave packet in the aether, and the aether is essentially just two infinite seas of charge interacting with each other.

What do you mean by 'infinite' seas? There can be no such thing as quantitatively infinite. But you seem to be suggesting you believe that there is a solid aether, I have also seen you mention you might believe in God, and I think that might be why there is some hesitance to Aether theory, because such could give more credence to God, and well I must ask, is there a way for there to be a purely natural, two component solid aether? (is this why science may be hesitant with your theories?; God said let there be light, so he finagled a two component solid aether the size of the universe).

You say a photon is just a wave packet in/of the aether. Can I ask, what you think the aether itself is, or do you describe it physically, I am sorry but I do not want to look up your videos, I would prefer to ask general and simple questions that can be answered simply here, by the yourself the source.

(Note that Dirac proposed a single sea; it turns out there are two.) Static electric force results from a bit of the sea being separated out, which then displaces the like charges making up the sea, and forces on charged particles result from such displacements. Magnetism is more complicated, and is best explained through the vector potential in the model.

Charge is one thing, aether/EM field is another; there are many charges, are there many parts of the aether/EM field.

Is there such thing as a particle existing with no charge (what is positive charge mean, and does it interact with EM field?) Does every type of matter, even no charge, interact with EM field?

Why do you say there are two seas? And are you mixing things up, by saying there is a sea of charges, but then also referring to the aether as a sea? If you are referring to the fact that many charged particles exist, the only meaning of charge particle, negative or positive, meaning, it interacts with EM field;

So there are two different seas of charges? Or there are two different aethers? Or there is the aether and then there are all charged particles; or there is the light aether, the gravity aether, and then all that exists that is not exactly light or gravity? And all that is not light or gravity interacts with light or gravity?




So the sun is a ball of material, that is moving through the aether, what percentage of radiation from the sun would you say is due from just the fact that the sun is moving through the light aether, or is it difficult to say and think of in terms of what is causing what precisely;

Because what is keeping the sun together really, does space continuously compress the sun into a ball, is that gravity aether,

Well, I guess thats one question, how exactly does gravity remain the sun as a ball, or when it is said that gravity keeps bodies together, is it meant, that gravity originally created the sun, but now it is not the main reason the sun is a ball;

the particles of the sun, are magnetically and nuclearly attracted, thats what keeps it together?

the sun is traveling the revolution around galaxy center; the gravity of the galaxy is causing the sun to travel that way;


I guess one of the things I am trying to ask; forget the percentage, but just, is any radiation, due to the fact, if you believe, an aether exists; which imagine a swimming pool full of marbles, and then imagine shooting a cannonball through it (at a small fraction of the speed of light, the specifics of this thought is not important, just the generalities)

Is this something like what you imagine the relationship of sun and aether; the sun as a body, is constantly traveling through a substance, and that is causing x amount of radiation; but then also, the separate quantized material of the sun moves in relation to one another, and of course, movement in relation to the aether, the marbles, cause the aether, the marbles to move?


So the light field/aether; you just imagine to be like pixels, or balls, sitting at every point in space?

There is a finite quantity of quanta, electrons, quarks;

There must be a finite quantity of 'field/aether' substance

photons



You imagine in a 3d/4d volume (of total universal space);

Photons exist all over;

Electrons and quarks exist here and there;

Electrons and quarks move, and the photons are a more subtle substance, so they move faster;

The thing I have trouble with is understanding how the aether exists, how the photon field exists, right now, how exactly does the universe appear, if you could see everything that is not nothing;

Where are all the photons, where are all the electrons, how much volume is occupied by pure nothing;

Are photons like separate marbles, part of the quantum weirdness seems to be the declaration that the universe is not just like different sized marbles bouncing off each other;

The biggest thing I have trouble with, is wanting to know, if the aether actually does exist, how it does and how it could; when you look into the night sky and see just black; I guess I want to know how dense the aether is, and how it is connected to itself;

I believe the major problem in physics is relativity. It leads to a requirement of point-like particles, which in turn leads to infinities which cannot be handled well.

I know it is not the smallest scale, but like, a pebble, a pebble is an example of a point like particle? Though I know, you mean 1/0d point like particle, which I encountered discussion of a few years ago on here, I never took it seriously, I assumed it was just shorthand, or map/key exaggeration, I never assumed any one could actually believe that it was possible for something to physically really exist at quanta like be 1/0d, so I cant imagine Einstein would believe that something could exist and be 1/0d.

The concept of relative simultaneity also presents problems with regard to understanding Bell's theorem results.

The problem of simultaneity is merely the difficulty in coordinating and proving simultaneity occurred, which seems sensical and intuitive as a difficult problem.

It is merely a problem of the fact that when machines with many or maybe any subtle and sensitive moving parts, are moved potentially at all, potentially fast, potentially in relation to others, potentially over time, there mechanics might change, and jeopardize the trustworthiness of the mechanism? I have seen the gedunkens of Einstein with tunnels and trains and light and stop watches and cameras about simultaneity, but I may need a refresh on why you think it totally collapses relativity theory, and why relativity theory is such a big problem.

a reply to: delbertlarson

Other problems are the abandonment of objective reality and the abandonment of underlying physical modelling by modern physics, which has been replaced by a search for terms in a Lagrangian. (Physics is devolving into pure math, with no physical modeling anymore.) These abandonments have also come about because of relativity, in order to save relativity from Bell's theorem tests.

I think part of the abandonment of objective reality, was maybe on fine small scales, the declaration, not that objective reality does not exist, but that it maybe cannot exactly be mapped, at the smallest scales in real time.

Show me a, not exactly to scale (like the trees on my map of my neighborhood are not the same size of the trees in the neighborhood, they are not too scale in that regard, but accurately scaled down, you know what I mean, if the size of the houses and trees kept dividing by two, and then mapped the smaller version it would be scaled down), but scaled down version, or I guess in this case it would be accurately scaled up, mapping of every electron in your body in real time;

Or every electron between earth and the sun.

Such questions are enough to make some given this job, to say, welp, objective reality does not exist.

As for my own challenges: 1) My theorizing at the moment does not handle gravity at all - I have never studied it;

Well gravity cannot be ignored in a fundamental theory. If the gravity aether exists everywhere, which again, is difficult to understand how the light aether and gravity aether can both exist everywhere, contradiction, so how exactly do they exist and interact. if gravity is the ultimate background substance, the most subtle with light; then every event passes through, every movement, every charge particle moving on earth, every particle, every time you think about how light is generated from moving particle, the gravity field is also right there, and must interact in some way too?

2) My ABC Preon Model so far has not calculated lepton masses, nor quark masses, nor does it have a sufficiently strong theoretical underpinning (it is just a good high level model at this point);

What does mass mean to you, how could mass be calculated? What do you think of Higgs, does the concept make any sense to you? Why is it said Higgs theory is needed?




a reply to: delbertlarson

As an example of entanglement we can consider a wave-function that contains two photon wave packets within. One photon goes one way, the other the opposite way. But the wave-function encapsulates both, and, for this example, we will say that the total spin is zero. Within the individual packets the spin is unmeasured, and by my philosophy the spin has a spread of values within each packet. Upon measurement of one packet the spread of the spin is reduced by the measurement, and at that instant the spin of the other packet is also collapsed due to the constraint of zero total spin. At that point the two wave packets are now almost completely separate and independent entities, since momentum has also been transferred in the detection process and this collapses the position spread of each photon such that there is essentially zero overlap between the two photons. They are no longer entangled after the measurement.

The above description is viable in a world where we have an underlying objective reality and an absolute simultaneity. However, it is not viable if we accept relativity. The above description is a simple and clear way to model the quantum world, it is consistent with all known experiments, and it can appeal to our common sense. We need only set aside relativity and return to an absolute theory of space and time to make sense of these things.

The collapse itself is something that is different from physics in the classical realm. Essentially, a portion of the wave-function disappears and the remainder is increased in its magnitude. And the process must happen at speeds much faster than the speed of light. It would be fascinating if we could arrange for experiments internal to the wave-function, but at the present time such efforts are beyond what we can do. While it may be fun to speculate about the internal goings-on, it isn't really science unless our speculations lead to tests we can do.

When you use the term 'wave'; this is an important crux of my trouble and wondering;

ie photon wave packet, transverse wave in aether

by 'wave', do you mean; something going up and down?


About absolute theory of space and time; I think relativity was merely saying, it is difficult/impossible to absolutely know the geometry of space, since it is always moving, since the planet is always moving, since the moving bodies move the 'space/gravity aether' and the moving gravity aether moves bodies;

So the earthly ocean is quite vast; it would be difficult to in real time map the geometry of every square inch of the ocean but such a process would be something of an absolute understanding of the space of water?

It is difficult to do that to the gravity field; which I think is why relativity, suggests, that all data must be recorded from a bodies perspective, and then another bodies perspective, and then the difficulty might be in attempting to reach that ultimate, absolute, objective, actual perspective, since the only way of approaching such, would be to carefully piece together the totality of all perspectives,

Well and then another difficulty, is that when measurements are made they are made moving, and light is moving, and different measurements are made relating to different movements;

Would there be a difference in results of measurement, of a person traveling toward a flashlight measuring the intensity of the light, and a person traveling toward the flashlight at a much slower rate, and a person traveling perpendicular to the flashlight? If noone had access to the flashlight, it might be difficult for them to agree on the true intensity of the light? Is that part of the gist? its all about the difficulty of insuring and assuring calibration it seems.

a reply to: delbertlarson

One of the main things I was attempting to express about my wondering of how you view the light field/aether;

I was wondering about density, how much of the total volume of the entire universe, is full (And what does full mean, density)

Like lets say the total volume of the universe is 1,000, how much of that volume is taken up by electrons, how much by quarks, how much by photons, how much by gravity field material?

when the concept of light aether and gravity aether is brought up, it would appear that answer would appear something like electrons: . quarks: . photons: 490 gravity: 490;

But that says nothing of quantity or quanta, that is volume of area; do we assume that whatever type of substance makes up the photon field (light aether) is small and tiny and particularized like electron and proton neutron (and if we assume, it appears the neutron and the proton are separate particularized existent real physical items, we assume the quarks are too, because unreal unseperate unparticulazed 'somethingness' cannot create real separate particularized somethingness? But this view of particulate, quanta, separate, real, physical item, reduces to thinking of marble like, but the phenomenon appear to be impossible if it were just different sized marbles colliding with one another, which I think nudges the quantum thought, of, how can a reality be anything other than separate marbles colliding;

How can a reality be anything other than real facts, interacting; and how can a physical fact be represented by anything other than a bit of information, and how can a bit of information be represented physically real, as anything more fundamental than a sphere,

well, perhaps something could have caused fundamental particles to have irregular shapes;

How subtle, fine grain could the gravity and light field be; how classical like could substance be on the smallest scales?

Like the smooth phenomenon of water or lava, or jello; could the light field and/or gravity field be similar though uniquely smooth and have such qualitative characteristics;

It is wanted to be said, it is more than just the shape of fundamental particles which result in the qualitative events of reality; it is more than just the shape, and it is more than just the speed, and it is more than just a potential real rotation/spin;

if there were small spheres and triangles and cubes made of marble, and they traveled different velocities, still I think it would be difficult to create a mechanism like magnetism... I mean... maybe....


But now we can really see how size does really have an impact, because the size of the photon, the size of the electron, the obviously the size of a volume of water could not be the same, the size of the gravity medium,

the thing is that it is thought, water is not really a fundamental thing, water is really fundamental particles in a particular momentary relationship, due too, not their shape,

well, I started wondering what exactly interacts with the light field, and how, in order to physically cause those molecular bonds and such;

so I was wondering, it must be more than shape and velocity and potentially real spin/rotation, interacting with some more fine grain fundamental substance;

I mean I guess I was thinking, the if the electron is fundamental, quark, photon, etc. well a proton as a real object, an ice cube as a real object, is a conglomerate of tinier fundamental things, but the tiny things creating the bigger classical thing, can have real, novel, qualitative effects on the environment, well I guess I was really wondering, if the light field might have classical effects; or if the obvious answer is that it is just represented in classical things, magnetism, chemistry etc.


So what it comes down to, the term aether implies all encompassing, it implies a tight network, it implies that photon is not tiny separate marbles/snakes/slinkies/strings/wobbling jump rope; but that every pico space, from one end to the universe to the other, is connected , one long perfect grid of 'subtle' marble/jello/water/lava/snake/slinky/string/rope... and that is difficult to fathom, and controversial if experiment supports such


The only reason I had any reason to think there might be a light aether, is because I cannot fathom how magnetism could occur in a real pure vacuum. (which if there is aether, there is no such thing as real pure vacuum, ... because magnetism works; though, perhaps it may be that the aether could be pushed to the side, and a real true vacuum could be made..... but then would we not assume magnetic attraction would not be able to work; because magnetic attraction does not merely require two particles, but a third substance, (light aether), which the two particles interact with, via their shape and movement (and what else, volumetric size... what does it mean that mass is anything other that that, well density, yes), which compels them to remain in close proximity, , and for some reason which can be quite difficult to remove;

What does it mean, or is this even true, that all chemical phenomenon is primarily due to magnetism? Is that true? Gravity too, and I have not seen evidence that the nuclear forces are not extra results of the light and gravity field, I do not know if there is also an all encompassing strong field and weak field.

originally posted by: delbertlarson

The uncertainty principle. My view of the uncertainty principle is that it is a representation of the spread of things, not a representation of an uncertainty. If we have a wave packet of light, within that packet we will have a spread of frequencies. This is well known classically by doing a Fourier analysis of the packet. That spread of frequencies is equivalent to a spread of momenta, and there is also a spread in the spatial size of the wave packet. There is nothing really uncertain about it. The idea of an uncertainty principle, in my opinion, only arose from the philosophy of believing in a point-like electron residing probabilistically within the wave-function. But if we instead view the wave-function as the square root of the density of an electron cloud, then there is no uncertainty at all. It is just a description of the elemental size of things.

It doesn't matter if you use point particles (DeBroglie interpretation) or probability waves with areas of high and low probability density (Copenhagen). Both make predictions that prove correct and uncertainty is equally in both.

You don't get around the U. Principle.
The more potential particles you have the harder it is to predict the future.

originally posted by: delbertlarson
Einstein's more radical approach stipulates that time itself changes as an observer moves, and I've never believed that made much sense. However, as physicists, we must set aside what we think is sensible and reduce any theory to experimental tests. And on that score there are very few tests that can separate the Einstein and Lorentz theories.

Time doesn't actually change, space and time are proportional so it's simply that the more space you experience (by traveling fast) you experience less time. In a very precise way that has been predicted by Special Relativity and confirmed by experiments.

a reply to: delbertlarson

Another main thing I was trying to express. Everywhere in the universe (the universe is either expanding or not, if it is, when I say everywhere in the universe, I am referring to the real time expansion of the universe, (if its volume is getting larger, the meaning of expansion, when I say everywhere in the universe, that everywhere is constantly equalling a larger volume, so I am acknowledging that; or the universe is not expanding) there is either, quark, electron, gravity material, (maybe, strong weak material, gluon material, neutrio, tau, maybe anti matter); everywhere that there is not those, everywhere there is not all types of possible material (that is not light/photon/em material) there is light material or real absolute pure nothing;

There are the totality of the types of material, light material is one of those, and then there is pure real nothingness; which must in some sense exist besides matter/what is something; and possibly a certain percentage of the potentially increasing meaning of the concept everywhere in the universe;

we can forget the universe expanding or not for a moment, unless it is simple to tag on, how the different types of possible expansion would effect the different percentages of types of material occupying space;

a percentage of everywhere, is occupied by electrons, quarks, etc. etc. light material;

what percentage of everywhere in the universe, is occupied by light material (photon, what besides the photon makes up the 'em field', is the totality of EM phenomenon strictly photon, photon, electron, quark, etc. magnetic attraction is due to photon, repulsion is due to photon, electricity is due to photon, yes? the concept 'EM field' or field lines, is anything other than photon/s?

What percentage of the volume of the universe do you think is pure absolute nothing?

When an electrons momentum is altered the minimum amount possible, how many photons are created?

What real spatial percentage of the universe is occupied by photon?

Why can a photon not not move?

Is the concept of aether something like the concept of if the photon field was tiny 'beads' (like newtons cradle, or a ball pit, or marbles), 3d, and an electron moves and hits the nearest photon, which newton cradles down the line, which is kind of what sound, and wind, and water wave is like, how can the concept of aether or field be anything other than something like that? If it is not that, then photons are like what, separate b b balls, that are few and far between, that were collected sometime ago by elements and molecules like hungry hungry hippos, and some coalesced into stars, and there was volatility, and this caused explosions, which let loose a bunch of photon balls, and shook up the electrons and quarks, and caused them to fuse together in a variety of ways creating planets, but I guess it, where did all the photons come from, how did the material of the sun collect so many photons;

I have a question for the physics experts, We have matter and anti matter, we have mass but is there negative mass (anti-mass) ? Would that be the remaining invisible mass in the universe, just matter but with negative mass?

Another question, do photons have mass? since mass and energy are related they must have mass, and if they have mass how come they can travel at the speed of light since according to Einstein equation their mass should grow exponentially, can an object with "negative mass" or anti-mass be bound by that same restriction or do negative mass objects are exempt of Einstein's equation and therefore can travel at much faster speeds than light?

If you had a trillion electrons in a volume (like from star wars when they are in that trash compactor that encloses, keep getting smaller, and the container is made of the strongest material, most tightly latticed...?) Would anything interesting happen, depending on the material of the container (interesting things would happen to the container depending on material of container, and potential interesting things happen to the 'ball of electrons' depending on the material of the container?)(and also, the same type of question but instead of electrons, other fundamental particles, quarks, photons, etc.) ?

originally posted by: ATSAlex
I have a question for the physics experts, We have matter and anti matter, we have mass but is there negative mass (anti-mass) ? Would that be the remaining invisible mass in the universe, just matter but with negative mass?

There has been an experiment to see if antimatter would fall toward Earth like regular matter or be repelled from Earth, and it behaved like matter gravitationally, so I think that question about anti-matter is answered.

Negative mass is a different issue. "Exotic Matter" is a term which has been used to refer to negative mass (and some other types of non-baryonic matter) and it's what Sonny White at NASA's advanced propulsion lab needs to make his Warp drive concept work. Dr. White explains that it may not be impossible to have negative mass because dark energy tends to behave the same way as negative mass exotic matter would, and since we know dark energy exists, that suggests his warp drive may not be impossible. The problem he's got is there's no way we know of to bottle up dark energy and put it inside a spaceship to give it warp drive. We don't even understand dark energy well, but from what little we do understand there is very little of it per unit volume, and the only reason it seems to make up most of the mass-energy content of the universe is because space is so vast and all space seems to have it.

originally posted by: ATSAlex
Another question, do photons have mass? since mass and energy are related they must have mass, and if they have mass how come they can travel at the speed of light since according to Einstein equation their mass should grow exponentially, can an object with "negative mass" or anti-mass be bound by that same restriction or do negative mass objects are exempt of Einstein's equation and therefore can travel at much faster speeds than light?

You're going to get the college freshman answer, not the graduate student answer. Photons don't have mass.

Mass and energy are only related by E=mc² in the very narrow case where the object's momentum is exactly zero. If the object has momentum, it's the momentum that increases as velocity increases, and therefore the energy, but NOT the mass. Relativistic mass increase is a common misunderstanding which has even found its way into textbooks, but it's based on an abuse of the E=mc² formula to apply to objects with momentum and that's the wrong formula for objects with momentum as explained here:

Science Quiz #2: Is E=mc² right or wrong?
This is the right formula for objects with momentum, which shows that mass doesn't increase with velocity, only momentum and energy increase with velocity:

For a photon, m=0 so the mass term disappears, and the remaining formula can be simplified as E=pc where p is the magnitude of the momentum vector p. So a photon does have energy and momentum, but no mass.

I was reading the thread on quantum entanglement and pulled up a link in one of the posts.

In the description of the research project, the following comment was made:

NanoRacks-GOMX-2: Small Photon Entangling Quantum System (NanoRacks-GOMX-2) - 07.14.16
www.nasa.gov...

Photon pairs generated via SPDC are useful for studying the fundamental physics governing correlated particles. A thorough understanding of the underlying physics enables the use of correlated particles in numerous applications, ranging from metrology to encryption. In particular, it is interesting to study how these correlated photons can be generated in a microgravity environment and to demonstrate that their correlations are preserved even after the photons have travelled through a changing gravitational field. This enables correlated photon technology to be deployed even in a space-based environment. This mission on the NanoRacks-GOMX-2 satellite is designed to be a technology demonstration to show that it is possible to generate quantum correlated photon pairs in space using the CubeSat platform. If successful, it will pave the way for more ambitious experiments where correlated photons are beamed between platforms (space to ground) or (space to space) so that the correlations can be investigated over large distances.

If photons have no mass, why are they effected by a gravitational field?

I found this explanation of "massless photons" which says that photons develop "nonzero effective rest mass" in a superconductor but the article doesn't talk about photons in a gravitational field.

So how does a photon transition from having no mass to having some mass?

Experimental checks on photon mass[edit] Current commonly accepted physical theories imply or assume the photon to be strictly massless. If the photon is not a strictly massless particle, it would not move at the exact speed of light, c in vacuum. Its speed would be lower and depend on its frequency. Relativity would be unaffected by this; the so-called speed of light, c, would then not be the actual speed at which light moves, but a constant of nature which is the maximum speed that any object could theoretically attain in space-time.[23] Thus, it would still be the speed of space-time ripples (gravitational waves and gravitons), but it would not be the speed of photons. If a photon did have non-zero mass, there would be other effects as well. Coulomb's law would be modified and the electromagnetic field would have an extra physical degree of freedom. These effects yield more sensitive experimental probes of the photon mass than the frequency dependence of the speed of light. If Coulomb's law is not exactly valid, then that would allow the presence of an electric field to exist within a hollow conductor when it is subjected to an external electric field. This thus allows one to test Coulomb's law to very high precision.[24] A null result of such an experiment has set a limit of m ≲ 10−14 eV/c2.[25] Sharper upper limits on the speed of light have been obtained in experiments designed to detect effects caused by the galactic vector potential. Although the galactic vector potential is very large because the galactic magnetic field exists on very great length scales, only the magnetic field would be observable if the photon is massless. In the case that the photon has mass, the mass term [displaystyle scriptstyle [frac [1][2]]m^[2]A_[mu ]A^[mu ]] scriptstylefrac[1][2] m^2 A_[mu]A^[mu] would affect the galactic plasma. The fact that no such effects are seen implies an upper bound on the photon mass of m < 3×10−27 eV/c2.[26] The galactic vector potential can also be probed directly by measuring the torque exerted on a magnetized ring.[27] Such methods were used to obtain the sharper upper limit of 10−18eV/c2 (the equivalent of 1.07×10−27 atomic mass units) given by the Particle Data Group.[28] These sharp limits from the non-observation of the effects caused by the galactic vector potential have been shown to be model dependent.[29] If the photon mass is generated via the Higgs mechanism then the upper limit of m≲10−14 eV/c2 from the test of Coulomb's law is valid. Photons inside superconductors do develop a nonzero effective rest mass; as a result, electromagnetic forces become short-range inside superconductors.[30]

en.wikipedia.org...

originally posted by: Phantom423

If photons have no mass, why are they effected by a gravitational field?

I found this explanation of "massless photons" which says that photons develop "nonzero effective rest mass" in a superconductor but the article doesn't talk about photons in a gravitational field.

Alex, the question is "What is the stress-energy tensor?"

I'd like Post Graduate Modern Physics for $200, please.

originally posted by: Bedlam

originally posted by: Phantom423

If photons have no mass, why are they effected by a gravitational field?

I found this explanation of "massless photons" which says that photons develop "nonzero effective rest mass" in a superconductor but the article doesn't talk about photons in a gravitational field.

Alex, the question is "What is the stress-energy tensor?"

I'd like Post Graduate Modern Physics for $200, please.

??

originally posted by: Phantom423

??

It's the answer to your question. Why are photons, having no rest mass, affected by gravitic fields?

That is in the stress-energy tensor. It's the sort of stuff you get into in your master's level for physics. They generally don't toss tensors at you as an undergrad, although Georgia Tech's EE program does in your last senior semester for EE. You have to have them to solve non-planar networks.

It's not the sort of thing you can explain in English with descriptions. It makes sense if you can do pretty advanced calculus.

The stress-energy tensor will also explain behavior like why two photons coming at each other head on will mutually deflect each other as if they both had actual mass and were deflecting each other due to gravity, and why they don't if they're traveling at right angles to each other, and a lot of other similar questions.

It's one of those things you just HAVE to understand to get past that master's in physics. You can sort of fake understanding some of the crap that requires spinors or ambitwistors or the like, that you get hit in the face with when you do your doctorate. Trust me, you think simple tensors and Lagrangians suck ass, but it gets worse. Much worse.

originally posted by: Phantom423
So how does a photon transition from having no mass to having some mass?

It doesn't. Bedlam is right as usual of course but here's the dumbed down explanation, where he claims we are all "lied to" in school which is probably true depending on your point of view, but it's not a very big lie because in normal circumstances the gravitational effect of a photon is negligible meaning not exactly zero but it's so close you can't typically measure it as being different from zero:

Common Physics Misconceptions


Even though we can't confirm in experiment the mass of a photon is EXACTLY zero, it probably is, so it probably travels at the speed of light in a vacuum.

Why aren't you asking about neutrinos instead, which probably do have a tiny mass, yet we seem to be able to measure them traveling at the speed of light, which is supposed to be impossible for a particle with mass because it would need infinite energy to do that, right? At least now we know the experiment at CERN was wrong which measured them going slightly faster than light.

originally posted by: Arbitrageur
where he claims we are all "lied to" in school which is probably true depending on your point of view...

DId I? It wouldn't be the first time but I don't recall it here. It's been a massive thread though. I do hold that engineering school teaches you very functional, simplified versions of the truth: what you get in Engineering fields, thermo and the like are a bit different than you get if you end up overflowed into the physics versions.

Why aren't you asking about neutrinos instead, which probably do have a tiny mass...

Bite yer toong, lad.

a reply to: Bedlam

Thanks for the reply.