Einstein deriving special relativity, for an audience, in 1934. Public domain.

The Three Meanings Of E=mc², Einstein’s Most Famous Equation

It’s so much more than mass-energy equivalence; it’s the key to unlocking the quantum Universe.

For hundreds of years, there was an immutable law of physics that was never challenged: that in any reaction occurring in the Universe, mass was conserved. That no matter what you put in, what reacted…