Streaming music and movies over the internet may seem more eco-friendly than stocking up on CDs and DVDs. After all, you’re saving the plastic needed to make the physical media, the trees needed to print the liner notes, and the gasoline needed to ship all those discs across the country. But there’s a hidden cost to online streaming: the coal needed to power the computer data centers that deliver all that content.

Get in-depth coverage of current and future trends in technology, and how they are shaping business, entertainment, communications, science, politics, and society.