[grigjd3]

It's important to note that gravitational waves themselves contain energy and angular momentum. Relativists often use the terms mass and energy interchangeably. When I worked in numerical relativity, we used units such that the speed of light was 1, so E=mc^2 (really E^2=m^2c^4+p^2) simplifies to E=m.

[nthcolumn]

I have no idea what these people are talking about but I always thought as a small child that c should = 1. That square really bugged me - why squared, why not cubed or halved or more realistically some bally awkward number... Sounds like fun this numerical relativity!

[Chronos]

It's squared because energy is work, work is force times displacement (distance), force is mass times acceleration, acceleration is velocity per time, and velocity is vector distance per time. So you get:

mass × distance × ((distance ÷ time) ÷ time)

mass × distance^2 ÷ time^2

mass × (distance ÷ time)^2