It's probably not what you think. Most people think gravity is a pull caused by a big thing---like a planet. The earth is big and if something out there comes by too closely, the earth will pull it in, right?
Not really.
Gravity does not pull.
A massive object, that means big and dense and not just big, creates a dent in space/time. Imagine a trampoline. Now, put a bowling ball on ... >>full
Billions and billions. Carl Sagan used to say that a lot. He used that expression to make a point and it worked. But was his point valid?
The billions and billions Carl referred to were stars. Yes, there are indeed billions and billions of them. His argument went on to say that because there are so many stars, billions and billions, there must be planets, and therefore, life out there in great numbers.
