The entirety of my direct experience with AM radio has occurred at night, in a car, on a highway. During one of these drives I was told, while listening to a man explain how he copes with his ability to read minds, that AM radio signals behave differently during daytime and nighttime.
The science of AM radio functioning struck me as somehow poignant. AM radio crouches low and weak during the glare of day, but at night unfolds humble wings and reaches across great distances. From Wiki:
During the day, AM signals travel by groundwave, diffracting around the curve of the earth over a distance up to a few hundred miles (or kilometers) from the signal transmitter. However, after sunset, changes in the ionosphere cause AM signals to travel by skywave, enabling AM radio stations to be heard much farther from their point of origin than is normal during the day.
I am also moved by this:
AM radio signals can be severely disrupted in large urban centres by metal structures, tall buildings and sources of radio frequency interference (RFI) and electrical noise, such as electrical motors, fluorescent lights, or lightning. Wiki.
AM radio is driving through the middle of nowhere in the dark listening to the fringes of human endeavor being put forth with a no gloss earnestness and meandering passion. We use AM waves to project into the clear, dark everywhere/anywhere our most basic, contentious, awkward human endeavors–extreme partisan politics, religion, the supernatural, ufos, as well as, a few songs that you will never hear again anywhere else.
The oddly hollow tone of AM radio further adds a layer of remoteness that relates to the cold, dark hum of deep space, with its vast distances between stars, planets, galaxies.
Oh, I also discovered that I happen to share a birthday with AM radio:
AM radio began with the first, experimental broadcast on [December 24th] of 1906 by Canadian experimenter Reginald Fessenden, and was used for small-scale voice and music broadcasts up until World War I.