Gravity Pulls and Pushes on everything in the Universe.
Sit Isaac Newton showed us that two things effect the amount of gravitational force an objects has. Mass Distance
Around the 1650's Newton explained that the same force that caused an apple to fall to the Earth's surface is the same force that keeps the moon orbiting the Earth.
But Newton did not know how gravity worked.
In the early 1900's Albert Einstein started to think about gravity. He wanted to connect Newton's theory of gravity with his theory of space and time. He theorized that gravity travels at the same speed as light and gravity can bend and flex space and time.
The Elegant Universe: Gravity video
