“For example, the force of electricity between two charged objects looks just like the law of gravitation: the force of electricity is a constant, with a minus sign, times the product of the charges, and varies inversely as the square of the distance. It is in the opposite direction-likes repel. But is it still not very remarkable that the two laws involve the same function of distance? Perhaps gravitation and electricity are much more closely related than we think. Many attempts have been made to unify them; the so called unified-field theory is only a very elegant attempt to combine electricity and gravitation; but, in comparing gravitation and electricity , the most interesting thing is the relative strengths of the forces. Any theory that contains them both must also deduce how strong the gravity is.”