Question: What does e = mc2 mean

Nicholas Pearce answered on 8 Nov 2015:

Hey Memphis,

E=mc2 is perhaps the most famous equation in the world and was formulated by a guy called Albert Einstein (yeah, you’ve probably heard of him, he’s kind of a big deal).

The equation in words (not symbols) is energy is equal to mass multiplied by the speed of light squared:
E = energy
m = mass (the amount of stuff you have)
c = the speed of light

So what that means is that energy is mass and mass is energy – they are the same! The equation is usually called mass-energy equivalence to signify this. The speed if light comes in just as a constant – a number that you multiply the mass by to convert it to energy (like to convert meters into centimeters you times by 100). The speed of light is a big number though, and gets even bigger when you square it, so this means that even if you have a small amount of mass, you still have a lot – A LOT of energy.

If you were able to convert a normal object, like an apple entirely into energy you would get enough to light a bulb for 3 million years! Nuclear bombs work because of this equation and that explains why they are so powerful!

Bonus:
If you’re wondering why the speed of light is given the symbol c: I used think it stood for constant (Einstein realised that the speed of light was constant, it didn’t change), but found out a few months ago it stands for celeritas, the latin word for quickness.