The earliest scientists first observed the waves that earthquakes produce before they could accurately describe the nature of earthquakes or their fundamental causes, as discussed in Lessons 1–5.

Waves transfer energy from one place to another. Light from the Sun travels through space and through the atmosphere, transferring energy to the Earth and other planets. Sound travels from a ...

Introduction You may have heard that light consists of particles called photons. How could something as simple as light be made of particles? Physicists describe light as both a particle and a wave.