For those following along at home, I’m very interested in the Cosmic Microwave Background because it is currently the best available evidence we have about large-scale structures in the universe, particularly the intriguing question of whether the universe is larger than we can possibly see.

I’d noticed that a gentleman had uncovered that some of the microwave radiation seemed to be coming from our solar system. He evidently has refined his analysis, and now it appears that almost all the low notes come from our solar system.

What does this have to do with the shape of the universe? You can imagine the big bang as if it were someone striking a big drum, and the CMB is the remnant of the “sound” it made. All instruments produce sound waves that are various fractions of their maximum amplitude; an upright bass produces lower notes than a violin because the vibrating string is longer. Thus, the presence of certain amplitudes allows us to infer that the universe is at least “so” big.

If the low notes are locally generated, that suggests that the universe is just about as big as we can possibly see - that is, it’s about as big as a light cone with an origin at ~13bn years ago. An extraordinarily large volume, but still a finite one.