All Planet Sizes

This illustration from the Lunar and Planetary Laboratory shows the approximate sizes of the planets relative to each other. Note that the planets are not shown at appropriate distances from the Sun.

Explore the Moon

See what it is like to walk on the Moon by viewing this collection of QuickTime images from NOVA Online. Stunning 360-degree panoramas from each of the six successful Apollo Moon landings are featured.

Extreme Temperatures on the Moon

In this video segment adapted from Interactive NOVA, astronaut John Young experiences extreme temperatures on the Moon that are a result of the Moon's low gravity and lack of atmosphere.

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Galileo: Discovering Jupiter's Moons

This video segment adapted from NOVA shows how Galileo, using his newly developed refracting telescope, observed four of Jupiter's moons, the first astronomical bodies to be discovered since ancient times.

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Galileo: Sun-Centered System

In the early 1600s, most people believed that the Sun revolved around a stationary Earth. This video segment adapted from NOVA tells how Galileo proved that the Sun, not Earth, is at the center of our universe.

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Galileo: Sunspots

This video segment adapted from NOVA shows how Galileo used his telescope to carefully observe and study sunspots.

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Gallery of Auroras

View this stunning collection of auroral displays from NOVA Online to find out why auroras appear in different colors and shapes and whether they occur on other planets.

How Big Is Our Universe?

This interactive resource from Harvard Smithsonian Center for Astrophysics uses images and activities to understand the scope and scale of our universe. Featured are technologies used by generations of explorers.

Ingredients for Life: Carbon

This video segment adapted from NOVA illustrates why carbon is at the center of life on Earth. It also asks whether carbon-based life might exist on other planets.

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Jupiter: Earth's Shield

Jupiter's immense gravity protects Earth from asteroids. In this video segment adapted from NOVA, scientists searching for signs of life in the universe identify solar systems with Jupiter-like planets that may be shielding smaller nearby Earth-like planets from comets and asteroids.

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Mars Dead or Alive: Mars Up Close

NASA scientist Steve Squyres narrates this visual tour from NOVA Online of the most revealing discoveries made by the Spirit and Opportunity rovers on Mars.

Origins of the Solar System

This video segment adapted from NOVA scienceNOW examines the scientific debate over the events that triggered the birth of our solar system.

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Robotic Exploration of Space Timeline

This interactive timeline from NASA journeys through the last century, detailing key discoveries, experiments, missions, and other events that brought robotic space exploration from science fiction to reality.

Solar Magnetism

This video segment adapted from NOVA describes how the Sun's magnetism can have an effect here on Earth, from dramatic auroras to a mini-Ice Age in the 1600s.

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A Strange New Planet

This video segment adapted from NOVA features the first planet to be discovered outside our solar system. Its surprisingly large size and short orbit sent scientists back to their data and led them to discover similar planets.

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Tidal Curiosities

This illustrated essay from the NOVA Web site answers questions about irregularities in the tides.

The Wall of Time

This illustrated timeline from the Lunar and Planetary Institute provides a journey through four-and-a-half billion years of time from the birth of our solar system to its current existence today.

What Is a Planet?

This video segment, adapted from NOVA scienceNOW, presents the ongoing debate over the definition of a planet, including the status of Pluto.

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Your Weight on Other Worlds

This interactive resource from the Exploratorium calculates your weight on other bodies in our solar system and offers an explanation of mass and weight and the relationship between gravity, mass, and distance.