Image of the Day: Northern Lights in a Dazzling Display
This extraordinary image from the International Space Station shows Ireland in the foreground, still in darkness with city lights easily visible; the shimmering glow of the aurora borealis, or northern lights, on the left-hand side of the curving horizon, and the brilliant glow of the oncoming sunrise refracting through the Earth's atmosphere. It's hard to believe, but true nonetheless, that such a thin layer of gases — only 100 miles or so thick, compared with the planet's 8,000-mile diameter — can trap enough heat to make life possible on a world that would otherwise be perpetually frozen. Thanks to human-generated greenhouse gases, that thin slice of atmosphere is trapping more heat than at any time in many tens of thousands of years.
