Daylight - When you are outdoors and need to know how much daylight you have left to make camp or to return to your car from a hike, stand facing the sun, extend your arm forward while holding your hand horizontally at a 90 degree angle facing you. Hold your hand so that the top of your thumb touches the bottom of the sun. The distance from the top to the bottom of your hand represents an hour. You can use your other hand below to measure another hour and so on. Once the sun sets, there is roughly a half hour of usable light remaining.
Distance - When you see lightning, thunder soon follows, because light travels faster than sound. By counting the seconds between the light and the sound, you can estimate the distance between you and the lightning. Sound travels roughly 1000 feet per second, so 5 seconds equal a mile. When the lightning storm approaches you, the delay grows shorter. When the lightning storm departs, the delay grows longer. Remember, if you can hear thunder, you are close enough to the storm to be struck by lightning, so seek shelter immediately.
Depth - Ever wonder how deep that pit or shaft is? Providing no one is below, you can drop a pebble and count the seconds before you hear it hit the bottom. The actual time is not linear as the object gains speed during it’s decent, however, the following linear time table is a rough guide to depth:
Elapsed Time / Velocity
1 second / -32 feet per second
2 seconds / -64 feet per second
3 seconds / -96 feet per second
4 seconds / -128 feet per second
5 seconds / -160 feet per second
6 seconds / -192 feet per second