Science education in American schools is in a disgraceful state.
A customer (and by "customer", I of course mean the product my company packages up for sale to our real customers, the advertisers) decided to call me the other day, wondering why he could hear Rush on his local AM station, and not Jason Lewis, his preferred source of conservative obfuscation. He seemed confused as to why the signal would disappear late in the day.
Here's how it works:
There is a layer of charged particles in the upper atmosphere known as the 'ionosphere'. The ionosphere reflects radio waves in the AM frequency band. AM radio takes advantage of this phenomenon by deliberately reflecting its signal off the ionosphere and back to Earth, thus allowing AM extend its range without a larger draw of power. This is why AM radio stations tend to be cheaper to buy and run, and thus less-popular formats like talk radio manage to be commercially viable.
The FCC is the quasi-governmental organization within the U.S. charged with managing the radio-frequency spectrum. One of the goals of the FCC is to prevent interference and cross-talk: two stations on the same frequency are not supposed to broadcast to the same geographical point, lest their signals overlap and become mutually unintelligible. Although digital radio, particularly encrypted digital packet radio, offers solutions. But that requires an infrastructure not yet in place.
When night comes, the ionosphere rises to a higher altitude. This has the effect of increasing the range of a given AM radio station, allowing it to cover more area. This leads to a tendency for more stations to overlap and come into conflict. The FCC counters that effect by requiring roughly half of the AM stations to power down or off during nightime hours.
Thus, one stands roughly a 50% chance of losing the signal to a given AM station as night comes on. The time in which that happens will tend to get earlier and earlier as the days get shorter. Short of drastically changing the composition of the atmosphere, altering the axial tilt or rate of rotation of the planet, or traveling off-world there is nothing at all that can be done about this. This is not Obama's fault, voting for Santorum or Bachman will not change this (although if either one takes power, I'll lay money that an an increasing number of Americans won't understand why they can't).
Whether one believes is an naturalistic process of planetary formation or prefers to believe in divine intervention, this is the inherent nature of the planet we live in. Denying scientific inquiry will not change this. No longer teaching science in schools will not change this. Stuffing one's head in a bag, ignoring the complexities of the world, and relying only on "common sense" will not change this. The funny thing about the natural world is that it doesn't care whether or not you believe in it. The solar system will keep doing its thing despite all of your denials, pleadings, or conspiracy theories.
Googlebombing for a cause: www.minnesotangos.org