Photon absorption - Newton vs. Einstein

[zincshow]

A note from Newton's Principles definition #4 in 1687:

Impressed Force - This force conflicts in the action only; and remains no longer in the body when the action is over.

In Einstein's second paper on relativity in 1905, he explicitly concludes:

"Radiation carries inertia between emitting and absorbing bodies". It is important that not only does something receive a "kick" from the momentum of the energy, but the internal inertia (i.e., the inertial mass) of the body is actually increased. (from mathpages.com)

 

[eljose79]

Hello,

Thank you for bringing up this interesting topic. It is true that Newton's definition of impressed force only applies to the action of the force and does not remain in the body after the action is over. However, as Einstein discovered, there is another aspect to consider when it comes to forces and their effects on bodies.

Einstein's theory of relativity introduced the concept of radiation carrying inertia between emitting and absorbing bodies. This means that not only does the momentum of energy transfer a "kick" to the receiving body, but the internal inertia or inertial mass of the body is also affected. This is due to the fact that energy and mass are equivalent and can be converted into one another, as described by Einstein's famous equation E=mc².

This concept is important in understanding the effects of radiation and other forms of energy on physical bodies. It also helps to explain the phenomenon of mass-energy equivalence, which has been experimentally verified numerous times.

In conclusion, while Newton's definition of impressed force is still applicable in many cases, it is important to also consider the effects of energy and radiation on the inertial mass of bodies, as described by Einstein's theory of relativity. Thank you for bringing attention to this important aspect of force and motion.