Undersea cables have made big news in the last few days, ever since several cables were cut last week near Dubai and Alexandria, disrupting Internet service all over the Middle East. (The latest news: It looks like a ships anchor sliced one of the cables. Oops!) The accident draws attention to how much our modern lives depend on unseen cables—just three inches thick and buried under sand—that most of us have never even thought about. There are hundreds of thousands of miles of these things snaking under our seas, with even more on the way.