Albert Einstein is many people’s archetype of the genius scientist, and his most famous equation is E = mc². Or is it? When you look at Einstein’s published scientific papers over decades of work, he didn’t (usually) write the equation in that form. In fact, he pointed out that was an inaccurate form, since it’s a limiting case of a far more general principle. In my latest piece for Double X Science, I argued that the form of the equation is far less important than its meaning, and it doesn’t really matter if Einstein wrote E = mc² or not.

When you study relativity, you find those equations are specific forms of more general expressions and concepts. To wit: The energy of a particle is only proportional to its mass if you take the measurement while moving at the same speed as the particle. Physical quantities in relativity are measured relative to their state of motion – hence the name. [Read more…]