I have found several videos and articles about rest mass but I continue to have a few questions:
Finally, let go of the common picture of a fundamental particle as some kind of very tiny, material pebble. When physicists refer to mass, they mean one of two identical kinds of mass, gravitational mass or inertial mass. The first means how much gravity it exerts, the second how much it resists change in motion. The two calculations always give the same number (thankfully).
This helps me get closer to understanding but I still have questions.
Here are my notes so far:
Inertia - The tendency of an object to resist a change in state of motion.
Or the tendency of an object to resist acceleration.
Inertial Mass: A measure of Inertia
A measure of an objects resistance to acceleration.
Gravitational mass and Inertial mass are experimentally identical.
1. The Photon is measured at rest, how do we actually know what the mass is when a Photon is not at rest?
2. According to the following link:
http://www.desy.de/user/projects/Physic ... _mass.htmlLight is composed of photons, so we could ask if the photon has mass. The answer is then definitely "no": the photon is a mass-less particle. According to theory it has energy and momentum but no mass, and this is confirmed by experiment to within strict limits.
Please tell me what are these experiments are? What is being measured or how? Especially since Photons are measured at rest?