Merry Christmas
If photons are particles, it seems only natural that they have mass, and since they move with great velocity through space, it is only natural that they have momentum because momentum = mass x velocity. This equation can be used to calculate the momentum of a moving train or a photon whizzing along at the speed of light.
In the 1870s, James Clerk Maxwell, a Scottish physicist, carried out some famous experiments that resulted in his ability to calculate the velocity of light, and it enabled him to derive some fundamental equations that characterize the energy and momentum of light. He gave us this equation: momentum = E/c
Where E is the energy of light and c is its velocity. Obviously Maxwell thought that photons were discrete particles with mass.
Notice, that Maxwell’s equation for momentum can be rearranged to give us the more famous equation: E = mass c2. Just substitute momentum with mass x velocity.
In other words, Einstein did not derive this equation. However, he was forced to reinvent its meaning in 1905 because it did not fit his special theory of relativity. According to his theory, nothing with mass can travel at the speed of light. For this reason, he proposed that a photon in flight has no mass. In addition he theorized that mass can be converted to energy. This is a subject we will spend a great deal of time on in future blogs so don’t worry too much about it now.
The exact relationship between oscillation frequency and the energy of a photon was determined by Max Planck, which is the subject of the next blog. Kelland—www.vestheory.com
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