Death Valley Sky: Dan Duriscoe for the U.S. National Park Service

Also in today's links, using geo-tags to reverse map the world, uncovering a lake hidden under a city and more.

• Two-thirds of U.S. residents and one-fifth of the world population cannot see the Milky Way because of light pollution. As the International Year of Astronomy gets underway, advocates hope that economic pressure and concern for night light's effect on migrating birds will also help curb this issue. Here are pictures of what most people are missing.
• In another instance of technology turning the usual process of development on its head, a team at Flickr is trying to reverse-map the world, based on the tags provided by shots taken at a location. San Francisco was easy; other places, not so much.
• Surprise! A huge underground lake was found underneath the city of Budapest. It is currently being explored by, among others, scientists apparently swimming around in black water with only a headlamp to light their way. That's got to be a little alarming.
• First came solar panels on cemeteries, now harnessing the power of a crematorium in Sweden to heat buildings in town. Don't the dead ever get to rest?
• A new study finds that women who smoke during pregnancy are more likely to give birth to aggressive children who are described as quick to bite, fight, kick or bully. The article doesn't say, though, whether aggressive women are more likely to smoke while pregnant.