Learn how to make waves of all different shapes by adding up sines or cosines. Make waves in space and time and measure their wavelengths and periods. See how changing the amplitudes of different harmonics changes the waves. Compare different mathematical expressions for your waves.

Match shapes and numbers to earn stars in this fractions game. Challenge yourself on any level you like. Try to collect lots of stars! The main topics of this interactive simulation include fractions, equivalent fractions, and mixed numbers.

Explore fractions while you help yourself to 1/3 of a chocolate cake and wash it down with 1/2 a glass of orange juice! Create your own fractions using fun interactive objects. Match shapes and numbers to earn stars in the fractions games. Challenge yourself on any level you like. Try to collect lots of stars!

In this video segment adapted from NOVA scienceNOW, hydrogen fuel cell cars promise pollution-free driving, but will we see them anytime soon?

In this video segment adapted from FETCH!, contestants are challenged to use materials from a garbage dump to build a boat that floats, can be steered, and is propelled by something other than oars.

Just after World War II, nuclear scientists turned their attention from fission to fusion. This video segment adapted from AMERICAN EXPERIENCE looks at the beginnings of thermonuclear power generation.

During a scavenger hunt and an art project, students learn how to use a handheld GPS receiver for personal navigation. Teachers can request assistance from the Institute of Navigation to find nearby members with experience in using GPS and in locating receivers to use.

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.

Build a gene network! The lac operon is a set of genes which are responsible for the metabolism of lactose in some bacterial cells. Explore the effects of mutations within the lac operon by adding or removing genes from the DNA.

Kibera, a poor community, in Nairobi, was a blank spot on the map until recently. This video from Penn State Public Broadcasting’s Geospatial Revolution shows how geospatial technology enabled residents to map resources to help their community.

Learn how scientists regulate a nuclear reactor in this animation-enhanced essay from the FRONTLINE Web site.

This video segment adapted from NOVA/FRONTLINE looks at the future of global warming as developing nations, including India and China, increase their need for energy.

Is the hydrogen car the answer to global warming? This video segment adapted from NOVA/FRONTLINE looks at the pros and cons of this developing technology.

This lesson introduces students to the concepts of air pollution and technologies that have been developed by engineers to reduce air pollution. Students develop an understanding of visible air pollutants with an incomplete combustion demonstration, a "smog in a jar" demonstration, construction of simple particulate matter collectors and by exploring engineering roles related to air pollution. Next, students develop awareness and understanding of the daily air quality and trends in air quality using the Air Quality Index (AQI) listed in the newspaper. Finally, students build and observe a variety of simple models in order to develop an understanding of how engineers use these technologies to clean up and prevent air pollution.

This lesson introduces the MRI Safety Grand Challenge question. Students are asked to write journal responses to the question and brainstorm what information they will need to answer the question. The ideas are shared with the class and recorded. Students then watch a video interview with a real life researcher to gain a professional perspective on MRI safety and brainstorm any additional ideas. The associated activity provides students the opportunity to visualize magnetic fields.

Students are introduced to the Robotics Peripheral Vision Grand Challenge question. They are asked to write journal responses to the question and brainstorm what information they require to answer the question. Their ideas are shared with the class and recorded. Then, students share their ideas with each other and brainstorm any additional ideas. Next, students draw a basis for the average peripheral vision of humans and then compare that range to the range of two different focal lengths in a camera. Through the associated activity provides, students see the differences between human and computer vision.

Explore the world of lines. Investigate the relationships between linear equations, slope, and graphs of lines. Challenge yourself in the line game!

In this video segment adapted from NOVA, watch residents of the Peruvian Andes build a suspension bridge made entirely of grass. The ancient Inca were a textile society and thus skilled in working with natural fibers including alpaca and cotton. Still, it might surprise people today that their solution to crossing the canyons and gorges of their mountainous empire featured another fibrous material: grass. When you consider how they built a simple suspension bridge, you'll realize that not only was this a practical solution, it was also a safe one. In this video segment adapted from NOVA, watch residents of the Peruvian Andes as they build a traditional and functioning grass bridge the likes of which enabled the ancient Inca people to flourish for several hundred years. Grades 3-12.

Visualize the gravitational force that two objects exert on each other. Change properties of the objects in order to see how it changes the gravity force.

How do greenhouse gases affect the climate? Explore the atmosphere during the ice age and today. What happens when you add clouds? Change the greenhouse gas concentration and see how the temperature changes. Then compare to the effect of glass panes. Zoom in and see how light interacts with molecules. Do all atmospheric gases contribute to the greenhouse effect?