Energy to Rest-mass Conversion

All stars convert mass to energy. Is there a mechanism that converts energy into mass?
- Richard Rap (age 79)
El Paso, TX. USA

In one way, they're just the same thing, so no conversion is needed or possible. The inertial mass and energy are just different words for one quantity, often expressed in different units. That energy can be in the form of particles with more or less rest mass. I think the pocees you're asking about is the conversion between high rest-mass particles and ones with no rest mass, like photons. Sometimes the zero rest-mass ones are called "pure energy" although they really aren't so pure. The have angular momentum, for example.  

Anyway, yes, two photons can collide and make two particles with rest mass, for example an elecron and a positron.

Mike W.

(published on 09/13/2020)