This video segment, adapted from NOVA, traces the evolving history of theories about gravity and a force that may oppose it, along with our understanding of the impact of both of these forces on our expanding universe.

In this video segment adapted from NOVA, a meteorologist explains how an unusual weather pattern led to one of the most devastating floods of this century.

This collection of six images captures the magnificence of human development -- the transformation from baby to woman.

This video segment explores how one marine biologist used the scientific process to discover how whales hear.

In this video adapted from Bullfrog Films, GwichŰ__Ű__ŒŒÇin Chief Evon Peter of Arctic Village, Alaska, describes his people's connection to the caribou and their passion to protect Alaska Native land and traditions.

Although repeatedly exposed to HIV, Steve Crohn's blood cells were never infected. Dr. David Ho investigates in this video segment from NOVA: "Surviving AIDS."

In this ZOOM video segment, join Hana as she learns traditional Japanese drumming with her Taiko group.

In this video adapted from the National Science Center, observe a demonstration to discover how helium gas is inert and hydrogen gas is reactive.

This video segment adapted from Interactive NOVA profiles two scientists who were surprised in 1984 to discover a hole in our atmosphere's ozone layer as big as the United States.

This narrated animation from Interactive NOVA: "The Secret of Life" illustrates DNA replication.

This video segment adapted from NOVA describes the emergence of life on the islands of Hawaii from a barren volcanic platform under the ocean waves to the rich explosion of life that covers the many climate zones of the islands today.

In this video segment adapted from NOVA, dramatic footage of avalanches and animations of ice crystals illustrate how a layer of weakly-bonded snow can contribute to a devastating avalanche.

In this video segment adapted from NOVA, scientists use computer simulations to explore the question of how supercell thunderstorms produce tornadoes.

From this original story, young readers and listeners learn about four tools scientists use to study climate - climate stations, weather balloons, satellites, and buoys. The story is available at two reading levels and in three formats - text-only, illustrated booklet, and electronic book. Glossary included. Each issue of Beyond Weather and the Water Cycle contains an original story that expands on the theme.

This illustrated essay from A Science Odyssey Web site explains the science behind radio waves, including the role of electrons and electromagnetic fields.

In this video segment adapted from Shedding Light on Science, observe demonstrations of the fundamental idea that light travels in straight lines.

In Blazing a Genetic Trail, by the Howard Hughes Medical Institute, follow this three-step approach to treating genetic diseases.

This video segment adapted from the Space Telescope Science Institute shows what the Hubble telescope found when it stared at a single, nearly empty spot in the sky for 10 days in 1995. The unexpected result was a picture of a multitude of galaxies stretching into the distance.

Students learn how the human body self-regulates to maintain a stable internal environment despite changes in the external environment.

Students investigate hominid evolution. They learn the difference between a relative and an ancestor, study the emergence of bipedalism, and chart patterns of hominid migration.