How is the speed of gravity derived from general relativity?
We know that Force of attraction between two objects is given by F = (G*m1*m2)/d^2 Where G = Gravitational Constant 6.67 x 10^-11 N m^2/kg^2 m1 = Mass of object one m2 = mass of object two d = the distance between those masses Let mass of earth be M and mass of an object be m. Let us assume that object in on the surface of the earth so the distance between the earth and the object will be the radius of the earth. So the force of attraction in that case will be, F = G*M*m/r^2 For earth we know the values of M and r M = 5.9736×10^24 kg r = 6,371,000 m (average) Substituting the values F = ((6.67 X 10^-11 N m^2/kg^2) x (5.9736 x 10^24 kg) x m ) / (6,371,000 m)^2 Carrying out the calculation, we get, F = m x 9.9634 m/s Comparing it to F = ma a = 9.9634 m/s. this acceleration is known as acceleration due to gravity(g). That is the acceleration produced in any object due to the force of attraction of the earth. However commonly used value is 9.8 m/s That is how you derive it. EDIT: To prove
