Physics
Wave Propagation
Quick fact
The speed of wave propagation varies dramatically: sound travels at about 343 m/s in air, while light moves at nearly 300,000,000 m/s—and both are waves, but of very different types.
Why this is interesting
When you drop a stone into a still pond, the ripples that spread outward seem to move across the water—but the water itself barely moves. What exactly is traveling?