*‘Far be it from me, a ‘pub’ physicist to question one of the brightest minds of the 20*^{th} century, but is the most famous equation in physics, e=mc², actually completely accurate……’

**What Does it Actually Mean……?**

Einstein was trying to demonstrate the second law of thermodynamics, the conservation of energy, which you’ll remember from school says that energy can not be created or lost, only changed from one *‘type’* to another.

In the famous equation, e=mc², Einstein was telling us that energy and matter are two sides of the same coin and, that theoretically you could convert mass completely into energy, as with an atomic bomb which had not been invented at that time……

**So why is it Wrong……?**

It’s a case of splitting hairs. Read on……

**Energy and Mass**

The equation states that energy *‘e*’ ,converts completely into mass *‘m’*, proportional to the square of the speed of light *’c²’*. That statement is for all intents and purposes true. However, a photon, about the smallest amount of stuff you can get, which can be thought of as a particle of light, does have mass. Mass and energy cannot exist in isolation and can only be thought of as *‘mass energy’* ……

**Momentum……**

Had Einstein chosen to write his equation thus e=m๐c², indicating that the mass was at rest, this would have been correct but because a particle can’t be at rest, even at absolute zero you have to take momentum into account……

**The Solution……**

The solution isn’t that hard to work out but doesn’t look so neat.

The actual equation is:

Despite the nit picking, the relationship between mass and energy is mind blowing. If you could extract it there’s enough energy in a glass of water power the earth for a year. Liberating it is the problem……

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