Whats the second focus of an ellipse?
There is nothing at the other focus of a planet’s ellipse. It is theoretically possible for a planet’s orbit to be perfectly circular with the sun at the center, but this is never the case in reality. It helps to think abut the extreme case when considering this question. Think of a comet that starts very far away from the sun and begins falling toward it due to gravity. The comet speeds up due to the acceleration from gravity. As it gets closer, the gravitational pull gets stronger and stronger. When it passes by close to the sun, the gravitational force is extremely strong (because the comet is so close to the sun) and the comet whips around the sun at very high speed in a tight arc, due to the huge force. It sort of gets “slingshot” around the sun and flung way back out into space. But now it is fighting the sun’s gravity so it will go very far out and slow down, eventually stopping. Now since it has come almost to rest, it will fall back towards the sun again. Clearly in this scena
