NOTE: Above figures include non-CSI data. last updated: Sept. 23, 2015 data sources. California Solar Statistics (CSS) is the official public reporting site of the California Solar Initiative (CSI), presented jointly by the CSI Program Administrators and the California Public Utilities Commission.
Sound can travel through air, water, or solids, but it can't travel through a vacuum. It needs the medium to help it travel. Other examples include water waves, seismic waves, and waves traveling through a spring. Electromagnetic waves are waves that can travel through a vacuum (empty space). They don't need a medium or matter. They travel through electrical and magnetic fields that are generated by charged particles. Examples of electromagnetic waves include light, microwaves, radio waves, and X-rays.
The latest rumors are coming from LIGO, which looks for gravitational waves by tracking how they affect spacetime: As a wave passes by, it stretches space in one direction and shrinks it in a perpendicular direction.