In every popsci discussion of gravitational waves, the waves are said to be like "sound", and that gravitational waves allow us to "hear" the universe. Despite this, I have no idea how gravitational waves are any more like sound than like light. Some possible explanations are:
- Gravitational waves are produced by the vibrations of objects, just like sound waves. But light waves are also produced by vibrating (charged) objects.
- Gravitational waves propagate in a medium (spacetime), just like sound propagates in some material medium. But so does light; it propagates in the quantum electromagnetic field. This is as much a "medium" as spacetime is.
- Gravitational waves are described by rank 2 tensors, like sound waves in a solid. But no popular explanation ever brings this up; tensors are not popsci level.
- Gravitational waves are classical, like sound waves. But there's quantum sound (phonons) and a perfectly good classical description of light.
I must be missing something basic here. What makes gravitational waves more analogous to sound waves?