Physics: Gravity and Forces

Aerodynamics: What Causes Lift?
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.

Anatomy of a Firework
There's more to a fireworks display than meets the eye. This interactive activity from the NOVA Web site looks at the technology behind each burst of light.

Antarctic Ice Movement: Part I
This video segment adapted from NOVA explains why ice sheets move. To find out how fast they move, scientists carve a tunnel through a glacier.

Astronauts Speak: Gene Cernan
In this audio resource from NOVA, astronaut Gene Cernan recounts his harrowing experience during America's first attempt to do work in outer space.

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.

Booming Sands
This video segment, adapted from NOVA scienceNOW, presents basic concepts of physics behind "booming" sand dunes. See how surface tension affects potential and kinetic energy and how it all works together to create sound.

Buoyancy Basics
This illustrated demonstration from the NOVA Web site explains the concepts of buoyancy and density by showing what happens when different kinds of wood blocks are dropped in water.

Buoyancy Brainteasers: Boat-in-Pool Puzzler
This interactive brainteaser from the NOVA Web site challenges you to figure out what happens to the water level when a rock is resting in a boat and when it is submerged in water.

Centripetal Force: Pulling Cs and Gs
In this interactive activity from NOVA, discover how centripetal force can affect you when riding in a car or flying at high speeds in a fighter jet.

Deep-Sea Vents and Life's Origins
Deep-sea vents are home to life forms that do not rely on the Sun's energy. They depend instead on energy from volcanoes on the ocean floor. This video segment adapted from NOVA hypothesizes that life on Earth may have begun in this extreme environment.

Earthquakes: Los Angeles
In this video segment adapted from NOVA, animations are used to show how the hills around Los Angeles were formed by earthquakes at small thrust faults that extend outward from the larger San Andreas fault.

Einstein: A Timeline of His Life
This illustrated timeline from the NOVA Web site follows Albert Einstein's life, including 1905, his "Miracle Year," during which he developed his Special Theory of Relativity and the equation, E=mc².

Einstein's Thoughts on the Ether
Do light waves travel through the ether like waves on a lake travel through water? In this video segment adapted from NOVA, a young Albert Einstein grapples with this question while examining the speed of light.

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.

Free-Falling and "Weightlessness"
Discover the difference between free-falling and weightlessness in this interactive activity from the NOVA Web site.

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'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.

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.

Getting Airborne and Wing Design
What makes an airplane fly? Discover the connection between Newton's third law of motion and flight in this interactive activity from the NOVA Web site.

The Grand Canyon: How It Formed
This video segment adapted from NOVA uses animation to present the theory of how the Grand Canyon was formed and features rare footage of a phenomenon known as debris flow.

Gravity at Earth's Center
In this video segment from NOVA scienceNOW, learn about the effects of gravity as astrophysicist Neil deGrasse Tyson falls through a virtual hole through Earth's center.

How Big Is the Universe?
In this media-rich essay from the NOVA Web site, astronomer Brent Tully of the University of Hawaiʻi walks you through the latest scientific theories about the size of the universe.

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

Island of Stability
In this video segment adapted from NOVA scienceNOW, follow scientists in their quest to understand how stable elements are made and how to create the elusive element 114.

The Leaning Tower: Where It Stands Today
Will the Leaning Tower of Pisa give way to gravity? In this interview from the NOVA Web site, engineer John Burland relates the difficult job of saving the tower.

Levers: Raising the Moai on Easter Island
In this video segment adapted from NOVA, a team of archaeologists and engineers explores different uses of the lever by recreating the engineering feats of the ancient Easter Island peoples.

A Nanotube Space Elevator
In this video adapted from NOVA scienceNOW, find out about the discovery of a new building material, the carbon nanotube, whose physical properties could theoretically enable the creation of a 22,000-mile elevator to space.

Newton's Third Law of Motion: Astronauts in Outer Space
In this video segment adapted from NOVA, NASA learns hard lessons from the first American attempt to do work while "walking" in space. The video also explores Newton's third law of motion.

The Origin of the Moon
This video segment adapted from NOVA follows the Apollo 15 astronauts as they collect samples of ancient rock from the Moon's crust, whose discovery helps lead to a radical new theory about the Moon's origin.

Relativity and the Cosmos
This illustrated essay from the NOVA Web site introduces the basic concepts of Einstein's General Theory of Relativity and what we know about cosmology as a result.

Smart Bridges
In this video segment adapted from NOVA scienceNOW, learn about engineering innovations that could help detect a bridge's structural weaknesses before they become dangerous.

Sound Waves Underwater: True or False
This interactive quiz from the NOVA Web site features an array of interesting facts about the nature of sound underwater.

String Theory: A Sense of Scale
This interactive activity from the NOVA Web site puts the infinitesimally small world of string theory into perspective.

String Theory: A Theory of Everything?
This video segment from NOVA introduces the basic ideas behind string theory and looks at the quest for unification.

String Theory: Elementary Particles
This interactive activity from the NOVA Web site looks at the fundamental forces and particles that make up all matter.

String Theory: Newton's Embarrassing Secret
This video segment from NOVA chronicles Newton's theory of gravity and Einstein's discovery that contradicted it.

String Theory: Strings to the Rescue
This video segment from NOVA discusses the challenge of unifying the force of gravity and the forces described by quantum mechanics into a single theory of unification.

The Structure of Metal
In this interactive activity from the NOVA Web site, animations explain different aspects of the properties of metal.

To Survive at High Velocity
This video segment adapted from NOVA looks at speed, velocity, and centripetal force on the racetrack.

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.