So, the internet. It’s a pretty big deal.   The human race generates a lot of data -- and these days, we’re all about storing it in the cloud.    And even though we talk about the cloud as though it’s this weird space of non-being, all of that data that we send to it are actually sitting on very real, physical hard drives somewhere. And managing it takes a lot of energy.   That’s where data centers come in.   Data centers are huge, warehouse-like buildings that are filled with servers -- computers that are designed to store data so that they can be retrieved as quickly as possible.    These servers hold the world’s information, from 2005’s stock market trends to those adorable pictures of your kids at the park last week.   Each individual request, like pulling up SciShow’s YouTube channel, might not be demanding. But add all of them together, and the internet uses a significant amount of the world’s electricity.   In 1992, data transfers worldwide added up to a modest one hundred gigabytes per day.   By 2013, that rate had gone up to more than 28,000 gigabytes per second.   Since then, that number has continued to increase.    And any time you try to access any of the data stored in the cloud, it has to be pulled up from a server, which uses energy.   The estimate changes depending on how you calculate it, but according to one study, in 2011, the internet used around 2 percent of the world’s energy. That was 2011, so that percentage has increased since then, as more people connect and are using more devices.   Data centers seem to be the best way to manage the problem. By sharing resources, companies save more energy than they would if they tried to have their own small set of servers -- by as much as 87 percent, according to some estimates.    But as valuable as they are, data centers come with their own set of challenges when it comes to energy efficiency.   The servers in data centers are always running, because even when they aren’t active, they need to be ready to retrieve data at any moment.   And for a data center, up-time is key. That’s why many servers are only running at 10 to 15 percent capacity. Some even end up as zombie servers, transferring no data at all, just waiting to be called into action.   But whether they’re actually being used or not, all those servers generate a lot of heat, and as anyone with an air conditioned home will tell you, keeping things cool is one surefire way to inflate the electric bill.   According to a report by the Natural Resources Defense Council, data centers in the United States alone used up 91 billion kilowatt-hours of electricity in 2013. It would take 34 relatively large coal-fired powered plants to generate that much energy.   By 2020, the report predicts that data centers will consume 140 billion kilowatt-hours a year -- that’s 51 coal plants.    So if we want to make the internet more energy-efficient, data centers are a good place to begin -- starting with finding new ways to keep servers cool while using less energy.    One way to do that is by having hot and cold aisles.   Every server has an air intake, where it sucks it in, and an exhaust, where it blows it out. Along the way, the air is meant to cool the server by absorbing some heat, making the air from the exhaust about five degrees warmer than the intake.   But if you have the servers neatly arranged in a rack so that they’re all facing the same way, you’re going to have problems. Hot exhaust from one server is going to blow toward another’s air intake, and it’s going to take much more A/C to make up for that extra hot air.   If you flip around every other rack of servers so that intakes and rack exhausts face each other, you end up alternating cooler intake aisles and warmer exhaust aisles.    With this arrangement, fans use up to 25 percent less electricity to keep servers cool.   You can also cut the amount of electricity that air conditioning uses by actually raising the temperature.    Servers run just fine using air that’s between 18 and 27 degrees, but many data centers are kept at 13 degrees, or even colder.    Every half a degree increase in temperature can add up to a five percent decrease in energy costs.   So while a 27-degree room might be a little toasty for some people, there’s no reason we can’t just raise the temperature in the room and save a lot of energy.   Another, more dramatic way to make data centers more efficient uses something called server virtualization.   Virtualization lets you take multiple servers and stick them onto one machine. There’s only one physical server involved, but it can store and retrieve data as if it is many.    Before, you might have had 10 servers, each running at 5 percent capacity. But virtualize them so they all run on one machine, and you’ve just saved as much energy as it takes to cool nine servers -- and you’re still only running at 50 percent.   Depending on the setup and demand, virtualization can save 10 to 40 percent of energy costs.   And every year, more data centers are adopting these kinds of strategies.   The internet is not going anywhere -- at least, I hope not! -- but maybe it doesn’t have to consume quite so much of our resources.    Thank you for watching this episode of SciShow, and thank you to Emerson for sponsoring it. If you want to keep getting smarter with us, you can go to youtube.com/scishow and subscribe.