 When I try to picture really big or really small numbers, I like to break it down into something else that I can understand a little better, just so that I have some idea of what's going on. In this lesson, we read a paper by this group of scientists, and they estimated that between the 1950s and the 1990s, Alaskan glaciers lost an average volume of around 50 cubic kilometers of water every year. And then between the 1990s and the early 2000s, those same glaciers lost closer to 100 cubic kilometers per year of water. Do you have any idea how much water is in a cubic kilometer, much less several cubic kilometers? Let's do a little calculation to try to put that into perspective. What if I took one cubic kilometer of water, and I wanted to apportion that water out for the entire world so that every single person in the world would get some of that cubic kilometer? How much water would everybody get? Well, we can do that calculation. If I have one cubic kilometer, that is a box that's 1,000 meters on a side, right? So that equals 1,000 times 1,000 times 1,000 meters. That is a billion meters, cubic meters. And we also know that in one cubic meter, there are 1,000 liters. So if we have a billion cubic meters and there's 1,000 liters in each cubic meter, that means we have 10 to the 12th liters of water in a cubic kilometer. Now is a good time for me to give a shout out to my 12th grade government teacher from Blacksburg High School, Karen Kostin, who explained to our class that she thought that one of the reasons Jimmy Carter did not get elected as a second term is because he tried to convert this country to the metric system. And we all know how well that worked, not very well. So I don't think most people can actually even picture what a liter probably is. But all of us non-scientists, milk-drinking Americans, probably know what a gallon looks like. It looks like this. And there's about four liters in every gallon. Okay. So if I have 10 to the 12th liters and I divide that by four to get gallons, then that's about 0.25 times 10 to the 12th gallons. And as of late 2012, there were about 7 billion people in the world, so we just have to divide this number by 7 billion and we'll figure out how many gallons of water everybody's going to get. And that number is... We can write this in a much more normal way by just moving this decimal three places over to take care of this exponent. And what we find out is each person in the world gets about 36 gallons of water if we had one cubic kilometer of water and we apportion that up over everybody. But remember, in this paper, we're not talking about one cubic kilometer of water. We're talking about between 50 and 100 cubic kilometers of water every year. That is a lot of water, my friends.