Sound in the early universe is pretty much the same as sound you used to hear me. Sound is transmitted through variation in the density of air and you can hear a variety of frequencies in the early universe, the regions of higher and lower density due to the sound waves result in hotter and colder spots in the cosmic microwave background and we know the wavelength of the loudest sound.
So seriously now. How big is the universe?
Asking how big the universe is seems like a silly question. How big you might ask?
