There are those who say we don't need to worry about running out of oil, because there's still lots of oil left in the ground. Experts believe that over the past 150 years we have used up about half the total oil on Earth. In other words, our oil supply "bottle" is still half full. But, if we keep doubling our consumption, all the remaining petroleum will only last for one more doubling! So what time does that make it in our "bottle"? 11:59!