photon

A Photon has no mass. It can’t rest.

A) A Photon has no mass. B) A implies “It can’t rest”. C) Therefore it doesn’t have rest mass. D) Photon rest mass is zero.

Assertion and reasoning; A is correct. B is correct and follows from A. C is correct, it does follow from B. But D is incorrect it does not follow from A, B, or C. Its erroneous, a sloppy language that has been thought to be correct for ages now.

The trick is to realize there is no property called mass of photon — at-least in the same sense as it is for other particles with mass, therefore no rest mass. To say rest mass is zero is a special value of mass or rest mass. It just doesn’t have rest mass, as it neither has mass, nor rest, which are equivalent formulations, one leads to other. But A, B or C do not lead to D. They are not equivalent way of saying each other. They invalidate each other actually.

What happens when squirrels do not move.

Stationary state and squirrels !

Okay so the squirrel isn’t moving around so much, giving a fuzzy image. We can call the instant during which the squirrel wasn’t moving akin to a “gross” stationary state.

But why is the railing of window fuzzy? It isn’t moving !

Diffraction.

Due to diffraction enough light is coming from the other side of the iron bar, to enable us to see whats there. That quadrangle is diffracting the light. But why its fuzzy?

Diffraction is by its own very nature even though purely classical in many sense, fuzzy towards energy if time window is small. [due to energy vs time uncertainty]

That is, full energy cycle isn’t available, because a small time window is chosen. If you time-lapse the photograph, diffraction will become quite insignificant. Although it might still be there depending on details.

Uncertainty Principle and Photography !

why a moving object becomes fuzzy when you take its picture. Speed bears an uncertainty with momentum (hence energy ) just like time with energy and position with momentum. But for photons which are always ultra-relativistic we should not talk about its positions. Due to speed (relative motion of objects such as your and moving while other body parts being still) energy and momentum are uncertain. Hence position becomes uncertain. (Do not confuse between position of photon vs position/location on your image although its connected to wave-function collapse BEFORE or AFTER the observation ? is the question you should be asking, BEFORE the observation no sense of photon’s position, but AFTER collapse we do see only a particular outcome in terms of fuzzy images.)

A particle that defies classical mechanics !

A photon has no mass but energy and it has speed and it has momentum although it does not have mass. Thats impossible in Classical Mechanics. Because Classical Mechanics associates with every mass; momentum and kinetic and potential energy. All those would be zero if mass were to be zero.

Also the speed of the photon is constant while its energy and momentum are changing. This is unimaginable in classical mechanics. In CM first momentum can’t be defined from mass and speed if mass is zero, then while speed is not changing how is momentum changing? So both variables speed and mass fail to define a momentum for the photon, and not just the failure to have a mass. How then momentum is defined for this particle? Its not defined as long as photon is just a particle. Thats impossible.

The photon saga.

5. Photon is a zero mass particle (not a zero rest mass particle) and its deflection in gravitational field, called gravitational lensing is due to two reasons; i. single photon effective mass is due to the definite energy and momentum of the same. ii. multiple photons have non-zero invariant mass, hence they behave like any ordinary particle with mass, bends under gravity therefore, in both cases.

6. talk about inertial or non-inertial frames hardly does complicacy (unless its a particle with mass, hence further degrees of trade-off in phase space) especially if you are dealing in terms of energy and not force etc. Which is why Physics is formulated on higher parameters like energy and action, from where these concepts do not make difference. Energy is already integrated and having an acceleration on every instant has already been taken into consideration.

I THINK THATS ENOUGH FOR YOU TO REMEMBER ABOUT PHOTONS FOR NOW. IF I STUMBLE ACROSS ANY MORE CONFUSION WE WILL DISCUSS MORE.