Happy Earth Day! Videos, a Gallery, and Our Biggest Giveaway Yet

The BBC's Planet Earth and PopSci team up for an Earth Day extravaganza

Earth Day is a big deal here at PopSci. It's a time for admiring our incredible planet, and for giving back-- to the Earth, and to our readers (that means you). We've teamed up with the BBC to bring you a gallery of stunning images from the popular Planet Earth series, video clips (so you can appreciate the full affect), and our most extravagant giveaway yet.

For a chance at winning one of two DVD box sets of the complete Planet Earth series, or one of six DVDs of volume three (Great Plains, Jungles, Shallow Seas) or volume four (Seasonal Forests, Ocean Deep) from the series, leave a comment below. Eight lucky winners will be randomly chosen and announced on April 30, 2009. Good luck!

Mount Everest

This photograph is not only a beautiful shot, but it is also a monumental achievement for Planet Earth: it represents the highest aerial footage of Mount Everest to date. Part of the Himalayan Mountain range, Everest rests among the greatest concentration of peaks over 5 miles found anywhere on Earth. And while the Himalayas might be the most majestic of all mountain ranges, they are certainly also the deadliest; together, Everest and her sister peak K2 have claimed more lives than any other mountains.Martyn Colbeck

Oryx Herd

This Oryx herd is fleeing a pursuant pride of lions in the Namibian desert. Since lions won't cross the giant dunes, the Oryx can retreat to the safety of the sandbank, but still risk being ambushed when they eventually emerge for water.Richard du Toit

Male Chimpanzee

This male chimpanzee belongs to a community of chimps with over 150 members—the largest found in Africa. Safely inside Kibale National Park in Uganda, the chimps don't have to worry about poachers, but they do keep an eye out for other primate populations. A troupe this size requires lots of land and fig trees to keep everyone happy, but aggressive young males are willing to fight off intruders.Kristen Mosher

Lechuguilla Cave

Lechuguilla Cave in New Mexico holds a lot of titles: fifth longest cave in the world, deepest in the continental United States and one with the toughest door policy. Lechuguilla houses stunning, but fragile, gypsum deposits (shown here), so access to the cavern is extremely exclusive. The camera crew for Planet Earth was one of the first film crews allowed inside the cave, and staff at the Carlsbad Caverns National Park claim it will also be one of the last.Gavin Newman

Baobab Trees

These baobab trees, native to Africa and Australia, are an important part of the Madagascar deciduous forest. Some baobabs are believed to be thousands of years old, but since the wood does not create annual growth rings, it is difficult to track their growth. The trees are a hardy breed though, with some Madagascar species growing directly out of limestone rock.Warwick Sloss

Snow Leopard

The rarest of Himalayan animals, this female snow leopard is returning home to feed her one-year-old cub. On the treacherous mountain slopes, snow leopards rely on pure agility to capture prey, like wild mountain goats and sheep. This photograph marks the first intimate images of a snow leopard ever filmed in the wild.Francois Savigny, via naturepl.com

Iguazu Falls

"Poor Niagara," escaped Eleanor Roosevelt's mouth when she first saw Iguazu falls. Guarani for "great water," Iguazu is located on the border of Brazil and Argentina. At nearly 1.5 miles across, it is one of the world's widest waterfalls. During the rainy months Iguazu sees 13 million liters of water spill over its rocky ledge every second.Mark Brownlow

Superb Bird of Paradise

Nearly 40 varieties of Birds of Paradise live in the jungles of Papua New Guinea, and they have all developed elaborate mating rituals to attract females. Rigorous sexual selection has transformed the male mating ritual into some pretty bizarre displays, demonstrated here by the Superb Bird of Paradise. His blue plumage and intricate dance is intended to impress females by proving himself a formidable suitor—which doesn't sound too different from any neighborhood bar.BBC

Namaqualand Flowers

On temperate plains like this, summer is a time for growth and reproduction. Plants flower and bring vibrant colors to the normally monochrome grasslands, but nowhere is the flowering of the Namaqualand more impressive than on the velds of South Africa.Ben Dilley

Polar Bear Cubs and Mother

Two Polar bear cubs follow their mother across the ice of Hudson Bay, Canada. The sea ice provides a natural platform for Polar bears to hunt seals, but each year, as the climate warms, the arctic holds less ice and makes providing food for dependent cubs difficult.Terry Andrewartha, via naturepl.com