1. The problem statement, all variables and given/known data the sun sets, fully disappearing over the horizon as you lie on the beach, your eyes 10 cm above the sand. you immediately jump up, your eyes now 130 cm above the sand, and you can again see the top of the sun. If you count the number of seconds (=t) until the sun fully disappears again, you can estimate the radius of the Earth. Use radius of earth, 6.38*10^3 km, to calculate the time (t). 2. Relevant equations I have no idea really, but maybe: arc length=theta x radius... 3. The attempt at a solution i tried some geometry and made arc length= t/86400sec x 360 x pi/180 x 6.3x10^3...but i'm really clueless and think im approaching this too much as if it were geometry. help plz.