Recycling expert Jeremy O'Brien responds to a student's question about why some materials can be recycled and others can not.

A 2008 study shows that climate change has caused available water to shrink in the western U.S. during the last half century. And even bigger changes may lie ahead ..

"Now when we look to the future, Greenland and Antarctica are the big gorillas. If Greenland were to melt, it's about 23 feet vertically for sea level." Read more on climate change.

Crewless robotic aircraft will fly into the lowest and most turbulent layers of hurricanes, spiral up the eye, or loiter above the top of the storm to gather data beyond reach using traditional methods.

By early October, we humans had already consumed all the resources Earth will produce for 2007. That's the basis of Ecological Debt Day, announced by Mathis Wackernagel of the Global Footprint Network.

Will Earth survive an expanding sun? Let's take a look at the star V 391 Pegasi, 45,000 light-years away. It might reveal a possible future for our planet Earth.

Fluorescent proteins move from the ocean to the lab. Read more in "Glow in the Light".

Scientists believe that Earth's water was brought here early in Earth's history. They think icy comets and asteroids bombarded the young Earth for hundreds of millions of years. According to astronomer Bob Kandel the impacts heated the ices, causing them to evaporate. Eventually there was so much water vapor in the atmosphere it would have rained out onto Earth's surface.

How does the media portray the deep sea, and how does this coincide with what scientists discover about it? Read more about perceptions of the deep sea.

The "faint sun paradox" has to do with the relationship between the sun's size and Earth's climate.