In this animated video essay, "Sunday Morning" contributor Robert Krulwich and animator Nate Milton go inside one of Nature's mysteries, to examine why an adult male elk, weighing around half a ton, makes such an uncharacteristically high-pitched sound.

A Rubens' tube is an antique physics instrument for demonstrating acoustic standing waves in a tube. Invented by German physicist Heinrich Rubens in 1905, it shows the relationship between sound waves and sound pressure, as a primitive oscilloscope.

Sound is invisible, yet it's all around us! What's going on here? What exactly is a sound, anyway?

This is the first time, scientists have directly detected gravitational waves - ripples in space and time - in addition to light from the spectacular collision of two neutron stars. To get these sounds, astronomers used the U.S.-based Laser Interferometer...