"scalar gravity" -Feynman lectures on gravitation Hi all, I'm trying to understand the following claim from Feynman's lectures on gravitation, section 3.1 (p.30 in my edition). He's considering how heating or cooling two clouds of gas would change their mutual gravitational attraction. I don't understand this statement. The electric scalar potential is the time component of a four vector which gets dotted into another four vector, so that the resulting physics is invariant. I don't see anything in the expression for a Yukawa potential that I can identify with the velocity dependence he's talking about. Can someone please explain? Thanks in advance.