What is it?
Interactive: You may adjust the volume on this recording of the universe’s background noise: either the cosmic microwave background or quantum noise.
With gratitude to Mark Hanhardt; some CMB audio is a simulation of the Big Bang as derived from the cosmic microwave background, (c) John G. Cramer - 2003.
It makes a slowly declining noise, which can be a little uncanny to the ear; this reflects the lowering temperatures of matter after the Big Bang.
