The Future Is Here

# Gizmodo Monday Puzzle: Can You Answer Elon Musk’s SpaceX Interview Question?

## Figure out where you are in the world using just a few clues.

There is a long tradition of posing puzzles at interviews for technical positions. Despite my respect for puzzles, I don’t believe one’s ability to solve one quickly in a high-pressure situation provides an accurate forecast for their future job performance. Google, once known for its notoriously difficult interview puzzles, retired the practice in 2013, with the senior VP of people operations at the time stating that they were “a complete waste of time. They don’t predict anything. They serve primarily to make the interviewer feel smart.” This week, your interviewer is Elon Musk. Try to solve his preferred puzzle to give to engineers vying for a job at SpaceX. While the puzzle is not rocket science, it will require some ingenuity.

Did you miss last week’s puzzle? Check it out here, and find its solution at the bottom of today’s article. Be careful not to read too far ahead if you haven’t solved last week’s yet!

## Puzzle #14: Elon Musk’s Interview Question

You are standing somewhere on the surface of the Earth. You walk 1 mile south, then 1 mile west, and then 1 mile north, and you end up back at the same point where you started. Where are you? Assume the Earth is a perfect smooth sphere.

The most natural answer to this question is the North Pole. And it’s correct! Walking a mile south from the North Pole, then a mile west, and a mile north again will land you right back at the top of the planet. According to Musk’s biographer, Ashlee Vance, when engineers would get this correct, Musk would respond, “Where else could you be?” That problem is significantly tougher, and solving it is your task for the week.

The South Pole doesn’t work. Traveling south from the South Pole isn’t even a meaningful concept, since moving south is by definition moving toward the South Pole. It helps to remember that we’re on a big sphere. Think of lines of latitude not actually as horizontal lines but as circles traced around the globe that get progressively wider toward the equator and narrower toward the poles.

Good luck solving the puzzle this week, and rest easy that your career doesn’t depend on it.

I’ll be back next Monday with the solution and a new puzzle. Do you know a cool puzzle that I should cover here? Send it to me at gizmodopuzzle@gmail.com

## Solution to Puzzle #13: Mouse Trap

Were you able to snare the mouse from last week’s puzzle? You can guarantee that you catch the mouse in six days. There are several solutions. Numbering the cabinets in order from 1 to 5, one solution is to check them in this order: 2, 3, 4, 2, 3, 4. A clever observation is that the mouse must alternate between odd- and even-numbered cabinets each day.