usenet weirdness

As if you would have any clue what you are talking about.

So, finally you saw the light? ;-)

It _does_ have mass. That has to do with the fact that the mass of a

See also:

PBS SpaceTime: The Real Meaning of E=m c^2

"Realistic"? Otherwise this is correct.

Misleading. The energy density of electromagnetic radiation was larger than the energy density of matter then. See also:

In a sense. A photon is NOT a little ball of energy.

Correct, in a sense.

The latter is word salad.

They are not "affected by gravity". This has nothing to do with gravitation:

Gravitation is a consequence of the curvature of spacetime (according to GR).

The deflection ("bending") of light near other objects is another consequence of the latter.

"Gravitational" redshift and "gravitational time dilation" are yet other consequences of the latter. Notice that I put those terms in "scare quotes" here because they are *convenient misnomers*; they do not mean exactly what they say, but we are somehow stuck with them, either for lack of a better term or intellectual laziness.

There is not, at least not an *inertial* reference frame; the existence of such a rest frame would contradict the theory that it is based on.

He did not because the concept of a photon did not exist yet. What he wondered about, reportedly, was how it would be to ride alongside a light

They are lacking a proper (i.e. own rest) frame that is an *inertial* one because of that.

So... a photon moving at speed of light has some energy-mass-whatever-equivalent, which is sufficient to warp spacetime. That change may cause other photons' paths to "bend" as if gravity were a force, regardless of time effects, because it's not a force, it's a shape.

I think I got that part [*].

I wonder, though, if there were some non-spacetime actual "force" between photons (I realize there isn't, but imagine one for a moment). If said force obeyed the usual F=ma, *now* would time dilation come into play wrt photons? Two photons travelling next to each other, from their point of view (or any other), how would that force evolve itself over "time" ?

(yeah, stupid question maybe, but I still find the answers aka discussions interesting ;)

No.

And if you continue this mindless crosspost I will ignore you completely.

Am Donnerstag000012, 12.02.2026 um 10:39 schrieb Martin Brown: ...

Most of these objections came actually from physicists.

E.g. there was a physics professor with some reputation named Herbert Dingle, who wrote 'Science at the crossroads'.

I personally have analyzed Einstein's 'On the electrodynamics of moving bodies' of 1905 and found, that it contains roughly four-hundred errors.

That particular article violated all known rules for scientific papers and contains about 100 serious(!) errors in all possible circumstances.

IOW: this particular article is total crap.

This is interesting, because that particular article is still regarded as a masterpiece and the pinnacle of human endeavor.

This means, that the 'community' is unable or unwilling to correct the errors within that paper, even if the errors are obvious and easy to find, because thousands of critics have already named them (many of them physicists!).

That in turn would suggest, that physicists are collectively cheating and tell the public, what simply ain't true.

TH ...

You make it very obvious that you have no idea at all of what the life of real working scientists is like,

Jan

'as if' is the word here.

As already noted else-thread photons do interact electromagnetically. (a purely QED effect)

What is 'stupid' is your need to conceptualise this as a force acting on a point particle. The classical equivalent of it are extra, non-linear terms in Maxwell's equations. This might become observable in extremely strong fields in laser focus experiments.

Not,

Jan

DJ Delorie snipped-for-privacy@delorie.com wrote or quoted:

Everything has a "stress-energy tensor", including photons. (There is a Wikipedia page "Stress-energy tensor")

That tensor changes the curvature of space-time, which influences the paths of everything moving in space-time, including photons.

Whether gravity is a force depends on the model. In general relativity, it's not a force, but in other fields it's sometimes a force. In high-school physics, it certainly is a force.

Yes, there is photon-photon scattering in QED (virtual charged particle loops), but it is a very weak effect that rarely matters in practice.

Both effects (a photon's stress-energy tensor and photon-photon scattering) are very weak and therefore not observable in practice.

Time dilation does not matter here because everything can be described from one single frame of reference (the lab frame) while it cannot be described from the "point of view of a photon".

The photon is a quantum of an electromagnetic field; that field has a stress-energy tensor; that stress-energy tensor modifies the curvature of space-time. But we do not yet have a "theory of everything" that describes quanta (such as photons) /and/ gravitation. Quantum electrodynamics describes quantum effects in electrodynamics and general relativity describes gravitation.

Indeed, and all of them your personal errors,

Jan

snipped-for-privacy@zedat.fu-berlin.de (Stefan Ram) wrote or quoted:

Or, one could say: "Radiation is converted into matter.".

Ah, ok.

I'm trying to move past my own ignorance ;-)

I remember just barely passing that course in college, so many decades ago... TIL there's a version of Maxwell's equations that aren't dependent on constant time. Thank you!

Ah, ok. That makes *this* question the interesting one, because we don't know yet ;-)

Thank you!

Training teaches repetition. Dogs are trained.

Inventing things is a separate skill. It involves being crazy, exploring the extremes of the solutuin space, staying confused.

There's no legal restrictions on inventing things here in the USA. Lots of people do it, amateurs included.

The vacuum diode (Edison effect), the triode, the airplane, the klystron, electronic TV, the personal computer, lots of stuff was invented by unauthorized people.

But I think there is a negative correlation of inventing vs advanced degrees.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

Bill Sloman snipped-for-privacy@ieee.org wrote or quoted:

Counterexample: The photon. It has energy, but no mass.

Nonsense.

No, _gravitation_ is always just a phenomenon. People who say "gravity is a force" are oversimplifying twice.

No, it _can be_ described as the consequence of a force. It can be better described as a consequence of the curvature of spacetime. There is probably (because we alredady know that there are circumstances where GR stops working) an even better description, perhaps as an interaction with a graviton field.

A photon does not have a stress-energy tensor (what would be the stress?), and a stress-energy tensor (field) is not an effect, but a quantity in theoretical physics.

Nonsense, photon--photon scattering has been observed:

It is *the* quantum of *the* (quantum-)electromagnetic field. That is, it is an elementary excitation state of that field.

Yes, but a photon has not.

No, it _corresponds to_ the curvature of _spacetime_.

Correct.

In a sense. More precisely, is a quantum field theory of electrodynamics.

Not only.

Why are you continuing this mindless amok-crosspost?

The above is not quite correct: Photons *enable* the electromagnetic interaction. There is no such interaction without photons being involved in the first place.

"TIL"?

Maxwell's equations do not depend on "constant time", whatever that is supposed to mean.

The only physics course I took didn't involve a lot of repetition. What's taught is how to recognise a situation, and how to look at it in way that lets you do something constructive with it. Even training sheep dogs involves more that instilling repetitve patterns of behavior.

Not for me, or the inventive people I've known. Alan Dower Blumlein

Electronic TV, as opposed to mechanically scanned systems, was invented by people who had academic training - Blumlein at EMI certainly had, and the crew at RCA who invented much the same system weren't amateurs.

You would. Advanced degrees are about learning stuff. The more you know, the more likely you are to see an unexpected connection which can be exploited in a patentable way. My father had a B.Sc. and got about 25 patents, my boss at EMI had a Ph.D. and got 25 patents, and my friend from my undergraduate days took quite a while to get his B.Sc. and an M.Sc. and has clocked up just as many.

Nothing about academic training strikes me as likely to make you less likely to invent something.

I can't say I've ever noticed that. Pointing out that somebody hasn't taken an effect into account that they should have known about isn't actually calling them foolish, though it can come close.

You don't brainstorm at scientific meetings. You do it in a more cooperative environment where you try to find a new angle of attack on problem that doesn't seem to have an obvious solution.

John Larkin has been the most prolific poster on sci.electronics.design since I started posting here around 1996. He's not innocent - his main aim is to get flattered, and he's not good enough at electronics to earn the kind of praise that he seeks. He's not bad at it, just not as good as he likes to think.