to gravity than that.

Gravity is a long range attractive force between all objects with mass:

it's what keeps us from falling off the earth, it's what keeps the earth in orbit around

the sun, and it's what caused the sun itself to form four and a half billion years ago!

It's amazing to think that every massive object attracts every other in the universe –

that means that your dog, the earth, and a black hole in the Andromeda galaxy 2.5

million light years away are all gravitationally attracted to you,

and you to them.

In the 17th century, Isaac Newton discovered that the strength of the gravitational force

decreases by the square of the distance between two objects – so if you're twice as far

away, gravity is only one fourth as strong! He also discovered that the strength of gravity

is proportional to the mass of the objects in question: the more massive an object, the

stronger the gravitational force. That's why we can all feel the Earth pulling on us, but

don't really notice the pull of the moon – it's smaller, and farther away! (the moon's gravity

is strong enough to cause the tides, though!)

And when I said earlier that gravity is an attraction between objects with mass, I lied.

I meant objects with Energy. Because in addition to massive objects, gravity also attracts

light and other massless (but energetic) particles, so that a photon of light can be bent slightly

passing the sun, or trapped completely by a black hole.

Now do you understand the Gravity of the situation?