By Anupum Pant
Everyone knows a circle. Consider a circle and think about its center for a minute. Now, imagine that the center of the circle actually has another center below it, overlapping. The interesting thing about a circular pool table would be that if you kept a ball in the center and hit it, it would come back to the center, no matter where you hit on the table’s edge. (Assuming perfect physics is happening on that table)
Now imagine these centers are pulled apart. You have an ellipse. A figure that’s more or less a circle with two centers separated by some distance. If a pool table was shaped that way and you hit a ball kept at one of the centers, the ball would bounce back from the edge, no matter where you hit, and go back to not the initial center, it would go back to the other center. Each of these center is called a focus of an ellipse. Don’t call them centers when your mathematician friend is around, you’ll put yourself in unnecessary danger.
Only if pool tables like these could exist, so thought the mathematician too and actually made it. Here’s the demonstration…