Have you ever been to the crest of a rollercoaster and have seen the whole amusment park and beyond. Well some guy with WAY too much time, created a formula to determine how far out you can see in miles!
The formula is pretty easy:
(A=altitude in FEET)
Distance in Miles= 1.22 X (square root of A)
For example if a rollercoaster's crest is 400 feet above sea level than you would see for 24.4 miles out (1.22 X square root of 400)