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.

Anatomy of a Rover

In this interactive activity from NOVA, learn about the sophisticated scientific instruments on two identical robotic rovers that have explored Mars — Spirit and Opportunity.

Astronomical Images in Different Wavelengths

Visible light is just one portion of the electromagnetic spectrum that a telescope may detect. This collection of images produced for Teachers' Domain features radio wave, infrared, visible light, and X-ray images of distant stars and galaxies as well as images of the telescopes designed to detect the various wavelengths of radiation.

The Beginnings of the Telescope

This animated essay from the NOVA Web site examines the design of Galileo's refracting telescope and Sir Isaac Newton's reflecting telescope.

Birth of a Supernova, Type Ia

In this interactive activity from NOVA Online, learn about a type of exploding star — a Type Ia supernova — that is so bright that astronomers can measure the distance to the galaxy in which it resides, and even learn which elements make up the star.

Birth of a Supernova, Type II

In this interactive activity from NOVA Online, learn about a type of exploding star — a Type II supernova — that is so large it has a mass 10 times greater than the mass of our Sun.

The Elements: Forged in Stars

The story of how elements from lithium to uranium are created by stars is illustrated through animation and a hands-on periodic table in this video segment adapted from NOVA.

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Evidence for the Big Bang Theory

This video segment adapted from NOVA tells the story of two scientists who inadvertently discovered microwave radiation that is now believed to be heat left over from the Big Bang.

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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: His Place in Science

Einstein called Galileo the "father of modern physics." This media-rich essay from the NOVA Web site looks at Galileo's quest to understand the mathematics of motion.

Galileo on the Moon

Watch Apollo 15 astronaut David Scott perform Galileo's falling objects experiment on the Moon in this video segment from NASA.

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Galileo's Big Mistake

Scientists don't always get it right. This video segment adapted from NOVA looks at Galileo's failed theory for the motion of the tides.

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Galileo's Thought Experiment

How can Earth move through space without our feeling its motion? This video segment adapted from NOVA answers this question by dramatizing one of Galileo's thought experiments.

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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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Galileo: Timeline of His Life

This illustrated timeline from the NOVA Web site turns back the clock to the late 1500's to relive the dramatic life of one of the world's most renowned scientists.

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.

Gravity and the Expanding Universe

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.

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