Generating Electricity using Gravity

People are so smart, we're so ingenious; we can put a man on the moon, yet, our home loses power then it takes a phone call to our internet provider's 'tech. support' department, a half-hour conversation, and another hour, crawling around on the floor, under the computer desk, attempting to get back online.. only so we can check email and hope to do some business online??

So I am wondering about our ability to build some sorta large machine that uses gravity and the Earth's rotation to create electricty. I don't see why it is not possible. Am I not making sense?