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**New Theories / Re: Does a photon have inertia?**

« **on:**04/03/2017 18:01:06 »

I note pmb's answers above.

Yes.

Yes, but we normally say p=hf/c.

No. It doesn't gain energy or inertial mass. Conservation of energy applies. If you send a 511 keV photon into a black hole the black hole mass increases by 511 keV/c˛.

No. It isn't deflected by the curvature of spacetime. Spacetime curvature relates to the tidal force, not the "force" of gravity.

No. The speed of light is spatially variable, and because of this the photon changes direction. See EInstein saying it here:

Yes.

Yes.

Yes.

From the above discussion, I take it that:

*A photon has an "inertial mass", which equals its "gravitational mass", and is equal to E/c*^{2}= hf/c^{2}Yes.

*A photon has momentum = mc = E/c*Yes, but we normally say p=hf/c.

*A photon falling into a gravitational well gains energy and inertial mass (and the opposite when it leaves)*No. It doesn't gain energy or inertial mass. Conservation of energy applies. If you send a 511 keV photon into a black hole the black hole mass increases by 511 keV/c˛.

*A photon passing by a gravitational well is deflected due to the curvature of spacetime.*No. It isn't deflected by the curvature of spacetime. Spacetime curvature relates to the tidal force, not the "force" of gravity.

*This affects the photon's velocity (a vector which includes direction), but not its speed (a scalar which is constant c in a vacuum).*No. The speed of light is spatially variable, and because of this the photon changes direction. See EInstein saying it here:

*Inertial mass is also a scalar, and ignores direction.*Yes.

*When a photon "leaves" a gravitational well, it has the same inertial mass as when it "entered" (...to the same distance, in the frame of reference of the massive object)*Yes.

*Some of the photon's momentum can be transferred to other objects (eg electrons, in Compton scattering). This reduces the photon's momentum and inertial mass by reducing its frequency, but not changing its speed.*Yes.