A brief history of the gravitational constant G is made and the current value is given. G for the Earth is calculated at perihelion and aphelion, resulting in different values. G is variable on a revolution in all cosmic bodies. Variable G is calculated for the solar system. The physical consequences with variable G are explained, which are valid for all cosmic bodies. Measurements of G are suggested to be made on Earth at perihelion and aphelion, on the International Space Station, and on the Moon.

I shall define the magnetic field and the equivalence between a body's mass and its electric charge. On this basis, the mass of the Earth's core shall be theoretically calculated, and shall result in a value that corresponds to established findings. The Earth is like a magneto, of which its rotor behaves like an alternator. The inner and outer cores rotate in opposite directions to each other, with the inner core behaving like an inductor and the outer core being induced. Then I shall obtain the electric charge, the force of electric fields and the electric potential at the Earth's surface. Throughout, I shall be applying some theoretical propositions to the concept of Earth's electrical energy. I shall calculate the frequency of alternating electric currents generated by the Earth.