Key Questions in Physical Science

Much of what you experience from the things you see to the sounds you hear travels to you in waves. But how do sound and light waves work? For thousands of years, scientists have been testing hypotheses about waves and learning from the results of observations and experiments. These tests ultimately lead to more questions: How can we see colors? Why can light travel in a vacuum while sound can't? How does the pitch of a sound change as it gets closer to you? The answers are sometimes quite surprising! Find out how sound and light waves help us interact with the world around us.

You probably know that electricity powers your computer and other electronics. But what is electricity? How does it work and where does it come from? Scientists have been asking questions about electricity for centuries. Does it come from frog muscles? Can magnets create electricity? How could people harness the energy from gas or wind to power devices far away? Scientists have asked all these questions and more, and they've conducted countless experiments to learn the answers. Find out what they discovered and how we use electricity to power homes and businesses.

You've probably noticed that when water gets really cold, it freezes. And you've probably seen steam coming from a pot of boiling water. But do you know why that happens? Do you know how wood burns or what's inside a fire extinguisher? When scientists have questions like these, they conduct experiments to find the answers. Through countless experiments, scientists have learned about different states of matter: solids, liquids, and gases, and what makes matter change from one state to another. Explore the fascinating discoveries scientists have made about the matter we use every day.

Forces and motion are at work all around you when you kick a ball, ride a bike, or drop a book. But what exactly are forces? And how do they make things move? For thousands of years, scientists have been testing hypotheses about forces and motion and learning from the results of their experiments. These lead to more questions: Why do you speed up when you're biking down a hill? Why are heavier objects harder to pull? Why doesn't the moon float off into space? The answers may surprise you! Find out how forces and motion are at play with everything on Earth and beyond.

You've probably heard lots of things about energy. You may know that your body needs energy or that there's energy in sunlight. But what exactly is energy? Where does it come from and where does it go? How do plants, people, and machines use energy? Scientists have wondered about these things too. They conducted experiments to learn the answers to their questions. How do cells get energy from food? What is nuclear energy? How does a roller coaster move? Find out what scientists have discovered about energy and how we use different forms of energy every day.

You've probably played with magnets or seen them on a refrigerator door. But did you know that magnets are used in everything from laptops to electric guitars? Why and how do these magnets work? Throughout the centuries, scientists have wondered about magnetism. Why are some objects always magnetic while others are magnetic for only a short time? How do compasses work? Do migrating animals use magnetism to navigate? When scientists have questions like these, they complete experiments to find the answers. Learn what they have discovered about magnets and magnetism.