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Jeffrey Sachs said the quality of our lives - and our children's lives - depends on making the human population on the planet more sustainable.
The Copenhagen climate summit is meant to produce a legally binding, agreement for reducing greenhouse gas emissions. Jeffrey Sachs hopes progress will be made.
Jeff Mount said today, river restoration is about creating healthy ecosystems that can sustain human demands and provide benefits to neighboring ecosystems
An earthly lion guards the gates, while, in the sky, a celestial Lion - Leo - ascends. Astrophotographer Jeff Dai of China tells the story.
Jeff Dai created this moontrail photo by keeping his camera still, rather than tracking along with the stars. He said it was about a 3-hour exposure.
There's a nova in the sky now. It's faint and requires a dark sky to be seen, but photos pick it up more easily. Astrophotographer Jeff Dai captured it from Thailand.
Photographer Jeff Dai captured this self-portrait atop a glacier - 17,000 feet (5,300 m) above sea level - in the Himalayas of Tibet.
High above sea level - and far from light pollution - Tibet offers one of the most breathtaking night skies in the world. A collection of photos by Jeff Dai.
Project Nightflight's Erwin Matys and Karoline Mrazek explain what the gegenschein is and how you can see this elusive stargazing target.
The zodiacal light is an eerie light extending up from the horizon before dawn around the Northern Hemisphere autumn. Southern Hemisphere? Look after sunset!
If you're in the Northern Hemisphere, you can see the zodiacal light, or false dawn, at this time of year. If you're in the Southern Hemisphere, look for it after sunset.
And, more to the point, are any asteroids that might be hidden in the Taurid meteor stream potentially hazardous to Earth?
North and South Taurid meteor showers happen simultaneously in late October and November. They're relatively minor showers, but produce a high percentage of fireballs, or bright meteors.
The link between the constellation we know as Orion the Hunter and the Chinese New Year, celebrated throughout Southeast Asia and the world, and coming in 2017 on January 28.
Gravity waves traveling upwards from the lower atmosphere caused this unusual banded structure in airglow above China in late November.
When we look up or down - away from the flat disk of the galaxy or toward it - we're seeing Milky Way stars. But we also see a few more distant objects, visible to the eye alone.
Venus and Saturn were extra close on the sky's dome this past weekend. Now the waxing moon has come back after sunset and is sweeping near them each evening.
The gegenschein, or counterglow, is a faint brightening of the night sky in the region opposite the sun. It's sunlight scattered by interplanetary dust.
Milky Way vs. zodiacal light! Captured over beautiful Yamdrok Lake in Tibet.
"Should there be the same scenery as seen from another place of the Milky Way?"