In 1687, Sir Isaac Newton suggested the idea that gravity was the force that caused apples to fall (Although a falling apple inspired his thinking, the apple didn't hit him on the head!) and, which pulled an object, such as a ball, thrown upwards back to the Earth. He also figured out that the Moon would travel in a straight line without the attraction from the Earth pulling it into a curved path.

Gravity is a universal force and, as such, is not limited only to the Earth. According to Newton's Law of Universal Gravitation, any two objects in the Universe attract each other. The more mass the objects have the stronger the attraction. Also, the closer the two objects are, the more strongly they will attract each other.

Example - Two people, one metre apart, would attract each other with greater force than two mice one metre apart. Additionally, the closer the people (or mice) are to one another, the greater the attractive force. Theoretically, you actually weigh less flying in an airplane at 10,000 meters above Sea Level than you do on the ground. The reason is because the distance between you and the Earth is greater in the airplane. Of course, the difference in weight is so small that you would never notice it.

The greater the gravitational force, the more an object will weigh when close to that force.

Example - The gravitational force on the moon is 1/6th of the Earth's gravitational pull. So, if you weigh 60 kilograms here on earth, you would weigh only 10 kilograms on the moon. The reason? Well, the Moon has much less mass than the Earth and the smaller a mass is then the smaller its force of gravity.

So, to sum up, gravity is a function of mass and the distance between two objects. Despite this universal force, humans have become quite accustomed to coping with these forces. We easily stand, walk, lift objects and even send machines into the sky - seemingly in defiance of gravity.

So why do we need to study it?