Journey to Planet X
April 1990

“Journey to Planet X,” Friend, Apr. 1990, 26

Journey to Planet X

Pretend that you have been chosen for the first manned flight to Planet X in Solar System Z and that your spaceship is programmed so that each day your rate of speed doubles (i.e., you travel twice as far the second day as you did the first day, and so on). Now pretend that you leave Earth on February 15, 1992, and that you land on Planet X on July 19, 2003. How many leap-year days do you need to include when you figure out the date on which you were halfway there?


  • None—if you doubled the previous day’s distance each day, you were halfway to Planet X on July 18, 2003, no matter how many leap-year days were included. Incidentally, you would have been traveling on three February 29ths (1992, 1996, and 2000).