What I Already Know
To start gravity is a force that goes in the opposite direction of dark energy. It is theorized that dark energy expands the universe. Gravity is the force that keeps us on the planet and the planet around the sun. Without gravity all the air would float off the planet. Basically, this means gravity keeps us alive. Isaac Newton thought of the idea from an apple falling off a tree.
Galileo and His Ideas for Gravity
Aristotle thought heavy objects fell faster than light objects. Galileo thought Aristotle's ideas were ridiculous. At this time Galileo was a teacher. Most of the other teachers thought Aristotle's ideas were right and turned against Galileo. In his earlier years he discovered a pendulum. A pendulum is a object on a rope that swings back and forth. He discovered that the only thing changing how fast the object gets from one side to the other is the length of the rope. This got him thinking about about what caused this : gravity.
Isaac Newton and the Discovery of Gravity
"Although Isaac Newton did not invent gravity, he discovered and explained how it worked."(1) Isaac Newton, when he was young, kept mostly to himself. His mother wanted him to later continue the family farm. A teacher encouraged his mother to let him attend Cambridge University. After gaining his bachelor's degree his learning was interrupted by the Black Plague. Then, while he was on break he came up with his laws of motion. Shortly after he watched an apple fall from a tree. This gave him the idea of gravity.
Extreme Gravity
When a star explodes ever wonder what happens? Sometimes it just dies out but sometimes it forms a black hole. Black holes have unbelievable gravity. The gravity in a black hole is so powerful that it slows down time. Nobody knows what happens when you reach the center of a black hole. Some people say you would be crushed by the gravity. Others say you would appear in some other space and time. They call that a wormhole.
The Experiment
This experiment is to measure the acceleration due to gravity. I measured it two different ways. I knew the answer so I tested to see which was the most accurate. To make sure I didn't mess up I tested multiple times. The actual "g" is 9.8 meters per second squared. In the first experiment I took a toy tank and and dropped it from my bedroom ceilings and timed how long it took to get to the floor. In order to calculate the acceleration due to gravity, I used the formula g=(2 x height) / (time x time). In the second experiment I tested how long it took for the center point of the toy tank to get from the starting point back and forth ten times. To calculate the acceleration due to gravity from the pendulum experiment, I used the formula g=(4 * π * π * length) / (period x period).
Dropping the BallTrials

The PendulumT = the time for one full swing back and forth
10 T = 13.89 sec T = period = 1.389 sec length = 18 in = 0.457 m g = 9.36 meters per second squared 
Conclusion
The value of the acceleration due to gravity for the pendulum experiment was more accurate than the dropping the ball experiment because 9.36 is closer to 9.8 than 11.74.
Sources
 The Mystery of Gravity by Barry Parker
 College Physics by Paul Peter Urone (for formulas)