In this 7-minute video astronomer Dr Meghan Gray explains the relationship of the Earth's rotation and its revolution around the Sun, resulting in the need to add an extra day to our calendar every four years. She describes additional adjustments required to keep our calendar aligned with the Earth's movements. Dr Gray explains the Julian date and its usefulness.

In this physics activity, learners build their own rockets out of film canisters and construction paper. Learners discover how a chemical reaction (from a mix of water and Alka-Seltzer) creates gas pressure to propel the craft. The activity explores the three states of matter and Newtonäóťs Laws of Motion.

This page's description of the various kinds of radioactivity includes some discussion of the history of its discovery, illustrations, and hot links to related sites.

This animated essay from the American Experience Web site explains the difference between alternating and direct electric current and offers in-depth explanations about the role played by a battery, light bulb, wire, and generator. Grades 6-12.

In this activity, learners investigate how different materials repel or absorb water. Learners use spray bottles to explore how everyday items like sponges, cardboard, feathers, etc. respond to water differently. This activity also introduces learners to the scientific method as learners make predictions about which materials will absorb or repel water.

This page is from a comprehensive and comprehensible tutorial in physics. Schematic drawings, questions for understanding with the answerers, and links to animations are included.

Using students' step length to understand the relationship between distance, speed and acceleration. Includes graphing of data and interpretation of graphs.

Acid-Base titration applet that plots pH changes as student adds acid or base. Gives choice of indicators (only two right now). Compares plots for titration of traditional solution and a buffered solution (several choices for comparison). Can alter starting concentrations.

In this video segment, the ZOOM cast demonstrates how to use cabbage juice to find out if a solution is an acid or a base.

In this video segment adapted from ZOOM, two cast members demonstrate what happens when vinegar is added to baking soda inside a container. The resulting chemical reaction produces enough carbon dioxide to launch their paper rocket skyward.
Recommended for: Grades K-5

A car propelled by the reaction between lemon juice and baking soda has more in common with rockets and jet aircraft than one might think. In this video segment adapted from ZOOM, two cast members demonstrate the power of rocket-propelled vehicles and how to exploit the force produced by the carbon dioxide gas. Grades 3-8.

It would seem that bottles of lemon juice and rockets have only their basic shape in common. However, as two cast members from ZOOM demonstrate in this adapted video segment, when baking soda is added to the mix, a plastic bottle can act very much like a real rocket. Grades 3-8.

How does an airplane stay aloft when upside down? This media-rich essay from the NOVA Web site offers an explanation based on Newton's third law of motion. Grades 6-12. ***Access to Teacher's Domain content now requires free login to PBS Learning Media.

In this activity (page 1 of PDF), learners will construct an air cannon by cutting a hole in the bottom of a bucket and stretching a garbage bag over the other end. Then, they aim the cannon at a paper target and try to knock it over by giving the plastic bag a good whack. Learners also experiment with hole size to make the cannon more effective. Relates to the linked video, DragonflyTV: Forecasting.

Students investigate air and how it is something that occupies space, has mass, and exerts pressure.

In this physics activity, challenge learners to lift a book with just air using a plastic bag and a straw. This activity demonstrates compressed air and forces.

Without highly controlled jet propulsion, rockets and other aircraft would zip through the air as unpredictably as so many untied party balloons. In this video segment adapted from ZOOM, two cast members find out how slowing the amount of air expelled from a balloon and changing the direction of that air can affect the balloon's behavior. Grades 3-8 ***Access to Teacher's Domain content now requires free login to PBS Learning Media.

In this video segment adapted from ZOOM, cast members make their own hovercraft and demonstrate how the air leaking out of a balloon can make a plastic plate hover above a table.

In this activity, learners simulate Otto von Guericke's famous Magdeburg Hemispheres experiment. In this modern, low cost version, a pair of learners try to pull apart two suction cups (dent pullers). Learners then calculate the amount of force holding the dent pullers together.

In this activity related to Newton's Laws of Motion, learners build a boat powered by a propeller in the air. The airboats can be designed in many ways and can include various recyclables like plastic bottles, craft sticks, Styrofoam, and cardboard. This activity guide includes step-by-step instructions with images, an explanation of Newton's Laws, and focus questions.