I'm no

nuclear physicist, but here's what I've gathered from various

confusingly technical websites:

Assume that

all matter is energy.

Everything we deal with

on a daily basis has a

positive energy.

Protons,

elections,

neutrons,

photos,

radio waves,

all of it.

Dirac's

equations (based on

Einstein's, i believe)

predicted that there should also be

negative energy. Today we know this energy as

antimatter. But how can you have

negative energy?

Less than none?

Dirac explained this by saying that all

measurements are taken

relative to

empty space, in which all of the

negative energy levels have been filled.

Imagine a graph with

positive energy levels at the top and

negative energy at the bottom. All

energy levels below zero are filled in. This is the "

Sea of Dirac" or "

Dirac Sea".

According to Dirac's theory (as I understand it), antimatter would not be matter with negative mass, but an absence of "negative mass". Antiparticles are the holes in the negative energy sea.