Save the Earth: Turn Off the Lights

I just received an e-mail informing me that tomorrow, March 28, 2009, Saturday is EARTH DAY.
It told us to turn off our lights from 8:30 to 9:30 pm (a.k.a. Earth hour) in order to help save the Earth.
This is actually done by the rest of the world as an annual observance of Earth Day.
I honestly don't know the exact correlation of turning off our electric lights and saving the planet, haha.
But, it would be amazing to watch (from outer space) the whole country shutdown their lights for an hour.