more completely, it's E^2 = (m c^2)^2 + (p c)^2 where m is the rest mass of the particle and p is the current momentum. It's a nice triangle relationship. As f

more completely, it's E^2 = (m c^2)^2 + (p c)^2 where m is the rest mass of the particle and p is the current momentum. It's a nice triangle relationship. As for the interpretation thereof, you're going to need someone else.