Galileo first introduced the concept of free fall. His classic experiments led to the finding that all objects free fall at the same rate, regardless of their mass. According to legend, Galileo dropped balls of different mass from the Leaning Tower of Pisa to help support his ideas.

A freely falling body is an object that is moving under the influence of gravity only. These objects have a downward acceleration toward the center of the earth.

Newton later took Galileo's ideas about mechanics and formalized them into his laws of motion. NASA scientists have proven theoretically many times that Galileo was right

http://www.grc.nasa.gov/WWW/K-12/airplane/mofall.html
http://www.lerc.nasa.gov/WWW/K-12/airplane/ffall.html
http://science.msfc.nasa.gov/msl1/ground_lab/exp2.htm
http://science.msfc.nasa.gov/msl1/ground_lab/msl1wheenpi.htm
http://www-spof.gsfc.nasa.gov/stargaze/Sfall.htm
http://microgravity.grc.nasa.gov/drop2/how.htm

NASA astronauts of Apollo tried a new version of Galileo's gravity experiment, dropping a feather and a hammer at the same time from the same height. With no air to slow the feather down, the two fell at the same speed. "What do you know?" astronaut Dave Scott said. "Galileo was correct!"

Learn more about Free Fall at http://www.mathandscience4u.com