On average the ocean is 2.3 miles (3.7 km) deep, but many parts are much shallower or deeper. In the deepest zones, life forms have adapted to live in the dark, under crushing water pressure.

The stars are accessible to everyone, but where can you get the most from the night sky? Here are 10 great dark-sky places - mostly in the U.S. but also in Australia, New Zealand and Chile - for skywatching and stargazing.

Maps of the long filaments of gas that hold the universe together might one day help trace and unveil dark matter.

Air temperatures in the Arctic are increasing at least twice as fast as the global average due to climate change. What worries climate scientists about this?

This hot neighbor, with its surface veiled by thick clouds, hasn't benefited from the attention showered on Mars and the moon. But Venus might offer insights into Earth's future.

Carbon dioxide, CO2, makes up less than one-twentieth of 1% of Earth's atmosphere. How does this relatively scarce gas control Earth's thermostat?

Dorian, the 2nd most powerful Atlantic hurricane on record, has devastated the Bahamas, with the death toll expected to rapidly rise as rescue work gets under way.

If you go by cartoons and T-shirts, you might think evolution proceeds as an orderly march toward a preordained finish line. But evolution has no endpoint in mind.

The ArchaeoGlobe Project assessed knowledge on human land use over the past 10,000 years, through the contributions of more than 200 archaeologists. It concluded that, by 3,000 years ago, most of Earth was already transformed by hunter-gatherers, farmers and pastoralists.

Nearly 40,000 fires are burning in Brazil’s Amazon rainforest, the latest outbreak in an overactive fire season. Don’t blame dry weather, say environmentalists. These Amazonian wildfires are a human-made disaster.