The problem is this.
According to Einstein, mass is equivalent to energy. That is
That is, mass is proportional to energy.
Therefore we cannot but imagine that a mathematical product of energy can generates gravitational force.
Since m1 is energy and m2 is also energy, then the product of m1 and m2 means energy squared, and this energy squared quantity becomes gravitational force.
In much the similar way, electric charges q1 and q2 can generate Coulombic force. By reverse inference, the electric charge q1 and q2 must be proportional to energy.
The conclusion is this. The electric charge might be equivalent to energy.
How do you think, Sirs?
A Pithecantropus Japonicus who is, in a cave, reading a book sent from 21th century by time machine
March 24, 2013