Riddler Express

By Zach Wissner-Gross

For this week’s Express, I present an apparent coincidence that has bothered me since 2015:

After being ambushed by the forces of the First Order on the planet Jakku, the droid BB-8 narrowly escaped and requires immediate help. Fortunately, there is one person (named Rey) on the planet who can help BB-8, but they’ve never met and BB-8 has no idea where Rey is located.

Even if BB-8 did know where Rey was, what’s the probability that BB-8 could reach her within 24 hours? Assume Jakku has a radius of 4,000 miles (similar to Earth) and that BB-8 rolls along at a speed of 3 miles per hour.

(Note: FiveThirtyEight is owned by Disney, which also owns BB-8, Jakku and whatever ramshackle hut Rey is hiding out in.)


My Solution

At 3 miles per hour, in 24 hours BB-8 can reach anywhere in a circle with a radius of \(3mph \cdot 24hrs = 72mi\), covering an area of \(A = \pi 72^2 = 16286.02mi^2\). Jakku, in Zach’s secnario, has a radius of 4,000 miles and has a surface area of \(A = 4 \pi 4000^2 = 201061930mi^2\). The area that BB-8 can cover makes up 8.10e-05 of the surface area of the planet.