Gravity Probe B Confirms the Existence of Gravitomagnetism . ... Credit Copyright: Gravity Probe B Team, Stanford , NASA Explanation: Does gravity have a magnetic counterpart? Spin any electric charge and you get a magnetic field. Spin any mass and, according to Einstein , you should get a very slight effect that acts something like magnetism . ... These four sphere s, each roughly the size of a ping-pong ball, are the key to the ultra-precise gyroscopes at the core of Gravity Probe B . ...