Kepler's laws also provide a means for quantifying gravitational mass.
The observation confirmed that the energy carried by light indeed is equivalent to a gravitational mass.
The key is that both observers are differently situated in their distance from a significant gravitational mass.
Tubes of force are absorbed by bodies imparting momentum and gravitational mass.
This is sometimes referred to as gravitational mass.
To date, no other accurate method for measuring gravitational mass has been discovered.
Newton's concept of universal gravitational mass is illustrated in the image to the left.
A balance measures gravitational mass; only the spring scale measures weight.
Einstein showed inertial and gravitational mass are the same.
No physical difference has been found between gravitational and inertial mass.