Our understanding of the speed of light and many other things is predicated on the fact that light has no mass. As we can’t weight it directly like on a scale I am wondering (outside of mathematics) how we can test and prove this theory? Is it possible that light does have mass, it is just very very very small?
Further, if light has no mass, does it also have no energy? e=mc2 means energy for something massless would be 0. We know light has energy, so how does this equation work?
In: 42
E=mc^2 is only valid for objects in rest. The complete formula is E= sqrt(m²c⁴+p²c²), where p is the momentum. And as light has an momentum it has an energy.
But it has no rest mass (the mass an object has at rest), as according to special relativity it then would not be able to move at speed of light. If it were, it would need infinite energy which is not possible.
Latest Answers