We depend on air for our survival. More specifically, we depend on oxygen. Without it, we would die. But with it, we thrive. Enough oxygen must reach the tiny cells throughout our body to feed them, giving them the energy necessary for life. As the NOVA mountaineers climb ever higher up Mt. Everest, their bodies must try to get enough oxygen to their cells, despite the thin air at extreme altitude. But sometimes, no matter how fit the body, it falls victim to the effects of low oxygen—fatigue, hyperventilation, fainting, or worse.

Understanding water and ice helps scientists study glaciers. Some glaciers contain water wells. Tell students that in this activity, they are going to investigate how ice and water can coexist.

To the Sherpa people, Mount Everest is Chomolongma, "Mother Goddess of the Universe." To a team of Sherpa women, climbing the mountain is an opportunity to make history. Set the stage for this activity by showing students where Mt. Everest is on a map and pointing out regional political boundaries and physical geography features.

At first glance, it may seem that the life cycle of a glacier couldn't be more straightforward: snow accumulates at the high end of a glacier, and the ice that the snow turns into flows downhill until it melts, evaporates, or falls into the sea. Well, it turns out that a biography of your average glacier is more eventful than that, as you'll discover when you follow the journey of a single snowflake as it takes a ride through a glacier, a process that can take as much as 30,000 years to complete.

To make a responsible bid for the summit of a mountain as extreme as Denali, climbers need to have years of climbing experience, have mastered a host of skills, and be physically and mentally prepared for the challenge. Denali is so massive that it creates its own weather. Storms blast climbers with hurricane-force winds and temperatures can sink to -40°F. The objective hazards on the mountain include crevasse fields, avalanches, and steep slopes. While the skills necessary to survive such weather and terrain cannot be practiced via the Internet, we have illustrated four that climbers must learn before tackling Denali.

Climbing at high altitude can be nauseating, dizzying, and it can kill you. It's cold up there, and let's face it, humans have evolved to live in relatively warm climates. If had we had evolved to live in constant cold, our bodies might have grown thick hair all over, we might store more fat, and our body shape might be rounder and shorter to prevent heat loss. In addition, Denali is the highest mountain in North America. And the higher you climb, the thinner the air is and the harder it is to breathe.