The nervous system consists of the brain and spinal cord (central nervous system) and the peripheral nervous system which is the network of nerve cells (neurons) that collect and distribute signals from the central nervous system throughout the body.

The cerebellum is a large cluster of nerves at the base of the brain that's responsible for balance, movement, and muscle coordination.

The electromagnetic spectrum covers all possible wavelengths and frequencies of radiation. From lowest frequency (longest wavelength) to highest frequency (shortest wavelength) radiation: radio waves → microwaves → infrared waves → visible light → ultraviolet light → X-rays → gamma rays.

Unlike mechanical sound waves that require a physical medium for propagation, light waves are electromagnetic and can travel through empty space. Light waves are also much faster, travelling at 186,000 m/s vs. 343 m/s for sound waves.

The speed of a sound wave will vary with the medium. Sound travels fastest through media that has particles that are very close together, like metal. Thus, it travels faster through water than through air and doesn't travel at all through a vacuum (there are no particles in empty space to vibrate).