1. That's Kepler's law number one.

2. But, Kepler's law would also be true, actually, if things were going away.

3. And, you'll see that if we reformulate Kepler's Law in terms of vectors, and if we work a bit with these vectors, we are going to end up with something that's actually completely obvious to us now.

4. So, let's try to see, what does Kepler's law say in terms of vectors?

5. So, actually, if you look at motion of charged particles in an electric field caused by a point charged particle, it also satisfies Kepler's law, satisfies the same law.

6. We'll talk about this much later when we deal with orbits and with Kepler's Law.

7. Using a geometric method and computer simulation, the second Kepler's Law is studied. The calculated result shows that the areal velocity is approximately constant with an accuracy of 10 -13 .

8. Outside the nucleus the rotational velocity would decrease geometrically with distance from the center, in conformity with Kepler's law.