Question

If the area ESF in the given figure is equal to area ASB, what will you infer about EF?

Answer 1

Kepler's second law states that the line joining the Sun and a planet sweeps out equal areas in equal intervals of time.

Since the area ESF = area ASB, the planet takes the same time to travel from E to F as it does from A to B.

Because the planet is farther from the Sun when it is near E and F, it moves more slowly there. To sweep out the same area in the same time, it must cover a shorter distance.

Therefore, EF is shorter than AB (the planet covers a smaller arc near aphelion because it moves more slowly).