Quiz time: Can you name Newton's first law of motion?
No? (Don't feel bad, I had to look it up, too.)
Newton declared, "Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it."
In other words, if you are flying in the International Space Station and toss an apple out the window (come on, use your imagination), it will keep going in that same direction forever, unless something stops it (like a planet, gravity or alien life form).
Although Newton was talking about physics, little did he know he was also describing life.