[EvaH (OP)]

Gaither wants to know:

If E = M C squared, and a photon has zero mass, then E = 0....., then how/why is there energy in a photon?

Can you help?

[Kryptid]

Photons don't have a rest mass, but they do have a relativistic mass that is produced by their energy.

[PmbPhy]

Gaither wants to know:

If E = M C squared, and a photon has zero mass, then E = 0....., then how/why is there energy in a photon?

Can you help?

Its better to say that a photon has energy rather than it has energy inside of it because there is no "inside" a photon.

The E = mc^2 that you're referring to is what I call inertial energy and the m is called inertial (aka relativistic) mass. This mass is defined so that mv is a conserved momentum, where mv momentum. If the particle in question travels less than the speed of light then m is a function of speed. If m = 0 but p does not equal zero then E = pc and there for since p = mc when put into E = pc gives E = mc^2.

[Janus]

Gaither wants to know:

If E = M C squared, and a photon has zero mass, then E = 0....., then how/why is there energy in a photon?

Can you help?

E=mc^2 is a special case for the more general equation E^2 = sqrt(p^2c^2+m^2c^4)

It only gives the energy equivalence for the rest mass of something.  As pointed out, light has zero rest mass, so for it, the equation simplifies to E=pc, where p stands for the momentum of the photon. And for a photon, p = h/L, with h being Planck's constant an L being the wavelength.
Note that while in Newtonian physics, p=mv, and relies on m, this is not strictly the case with Relativity.  This type of thing can be a stumbling block for people when they first try to understand Relativity,  They try to carry over concepts directly from Newtonian Physics that don't remain the same under Relativity.

[PmbPhy]

Gaither wants to know:

If E = M C squared, and a photon has zero mass, then E = 0....., then how/why is there energy in a photon?

Can you help?

E=mc^2 is a special case for the more general equation E^2 = sqrt(p^2c^2+m^2c^4)

It only gives the energy equivalence for the rest mass of something.  As pointed out, light has zero rest mass, so for it, the equation simplifies to E=pc, where p stands for the momentum of the photon. And for a photon, p = h/L, with h being Planck's constant an L being the wavelength.
Note that while in Newtonian physics, p=mv, and relies on m, this is not strictly the case with Relativity.  This type of thing can be a stumbling block for people when they first try to understand Relativity,  They try to carry over concepts directly from Newtonian Physics that don't remain the same under Relativity.

I disagree. I myself never mistake. Those who learn SR learn what E = mc^2 means. Also p = mv works when m is relativistic mass. Also F = dP/dt is also holds as does E = K + U. Newton's first and second law remain unchanged. His 3rd law works with all contact forces (note that in Newtonian physics the 3rd law doesn't always hold). The only thing that changes is the transformation from one inertial system to another.

As you know, there are two definitions of m. One is proper mass (aka relativistic mass) and one is inertial mass (aka proper mass). Over half of my SR texts use relativistic mass, most of which are recent publications such as Special Relativity by Farook Rahaman, Springer, page 106. Currently there is an entire lab in Harvard's course called Relativistic Mass where they measure it. The lecture notes by Alan Guth for his early universe course where he explains that light has mass where he's referring to the relativistic mass.

See - http://www.newenglandphysics.org/other/guth.jpg

where he explains that light has mass where he's referring to the relativistic mass.

[alancalverd]

there are two definitions of m. One is proper mass (aka relativistic mass) and one is inertial mass (aka proper mass).

Pete: would you care to review that statement? Or does it hide some deeper truth? It looks as though you have said

A=B, C=A, but C≠B!

[PmbPhy]

there are two definitions of m. One is proper mass (aka relativistic mass) and one is inertial mass (aka proper mass).

Pete: would you care to review that statement? Or does it hide some deeper truth? It looks as though you have said

A=B, C=A, but C≠B!

What I said is correct. Some physicists use relativistic mass and use the letter m whereas others use proper mass and also label it m. As I'm sure you know there has been a heated debate about this.

[chiralSPO]

there are two definitions of m. One is proper mass (aka relativistic mass) and one is inertial mass (aka proper mass).

Pete: would you care to review that statement? Or does it hide some deeper truth? It looks as though you have said

A=B, C=A, but C≠B!

What I said is correct. Some physicists use relativistic mass and use the letter m whereas others use proper mass and also label it m. As I'm sure you know there has been a heated debate about this.

Is proper mass the same as inertial mass or relativistic mass?

[PmbPhy]

Is proper mass the same as inertial mass or relativistic mass?

Relativistic mass.

[jeffreyH]

Proper or invariant mass.
https://en.m.wikipedia.org/wiki/Invariant_mass

[yor_on]

Two choices
Energy is mass

No it isn't

Photons are 'quanta' of energy. Do they then have a mass?

They have a momentum, a 'birth' and a 'assimilation'
And a energy

In a 'field' they are 'excitations' of it.

On their own they don't have a defined propagation. Unless you believe in 'indirect evidence'
But that's a simplification

[alancalverd]

Here's the simple answer to the original question. Is there energy in a photon? Is there chocolate in a chocolate button? It's a quantum. Different makes of chocolate buttons are different sizes, but each is a quantum of chocolate.

Come to think of it, every coin is a quantum of money.

[yor_on]

at they say when I ask for my tax return.

"Can you quantify that Sir?"