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Holiday calendar: Celebrate the longest night

For those of us who feel as if there's never enough daylight to get all the stuff done that we need to get done leading up to the holidays, here's a ray of hope: Winter officially begins today in the Northern Hemisphere. That means each day from tomorrow on will get a little bit longer.

The longest night of the year is a good time to marvel at how we light up the night. This iconic image, called "Earth at Night," was stitched together from data gathered by a swarm of Defense Department satellites. The "cloudless" view maps the locations of permanent lights on the Earth's surface. It serves as a handy guide for where we live and the state of development around the world.

The lights, overlaid on a map for reference, make clear our preference to settle along coastlines and transportation networks. The interstate system in the U.S., for example, appears as a lattice connecting brighter dots. In northern Africa, the Nile River looks like a bright thread through a sea of darkness.

The brightest areas correspond with the most urbanized areas, but not necessarily the most populated. Note the difference, for instance, between Western Europe and China. More than 100 years since the invention of electric light, some regions of the planet remain thinly populated and unlit. Antarctica looks completely dark, as do vast swaths of jungle in Africa and South America.

For more views of Earth from space, check out these past offerings from the Cosmic Log Space Advent Calendar. We've also included links to other online Advent calendars that have been serving up space images daily since the beginning of the month:

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