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.