I awoke early this morning, confused in my half-asleep stupor as to why the neighbors were rolling the garbage cans up and down the driveway while at the same time the nearby naval air station was staging extremely low-flying drills about 10 feet from the roof.

After I ruled out the garbage can theory (garbage day is Wednesday, so that would just be silly) and I didn't see Maverick and Goose buzzing the house tower, I thought, "Is that thunder?" It couldn't be - I'd never heard thunder like that, and I grew up in the upper midwest where tornadoes are the only relief from mosquitoes.

But it was.

Continuous low rumbling with no distinct break for several minutes. Since I wasn't getting any sleep anyway, I tried to find out if there's a name for that kind of thunder. Turns out, not that I could find. But I did find all sorts of other cool thunder trivia along the way.

Thunder is a really popular word for movie titles, bands, soccer teams, smart phones, trains/planes/automobiles, and a great intro riff for AC/DC. Chances are that you're experiencing a thunderstorm right now - about 2,000 are occurring around the globe at any given time.

Epenthesis (Patrick, this one is for you!) - the word thunder is an example of ἐπένθεσις, or epenthesis, the addition of one or more sounds to a word, especially to the interior of a word. A "d" was added to the Old English thunor.

Cause - Thunder is the audible pressure (compression) wave produced by lightning, according to the National Lightning Safety Institute. Thunder is produced by the explosive expansion of heated air surrounding a lightning channel and can be heard from a maximum distance of about 10 miles (16 km) under good atmospheric conditions.

Nearly all lightning is generated by thunderstorms. However, the NLSI says, "lightning has also been observed during snowstorms, in columns of billowing smoke from forest fires, in erupting volcanic debris clouds, near fireballs created by nuclear explosions, and on some planets and moons in our solar system. Lightning is a giant static electrical spark. Where there's lightning, there's thunder, and vice versa."

A man in Minneapolis was struck by lightening during a blizzard. Go MN! The NLSI site has a few interesting paragraphs on the science of thunder, so check it out.

Early theories - lightning was the weapon of choice for the mythological beings like Thor (Norse), Zeus (Greek), Indra (Hindu) and Jupiter (Roman). Navajos believed in the Thunderbird, which flapped its wings and created the sound of thunder, and was the source of lightening (sunlight reflected in its eyes).

The early Greeks, Romans and Vikings (not the football team, they can't find their way off a boat in Lake Minnetonka) believed thunder to be a number of phenomena, including that it was caused by clouds colliding.

Castle thunder - the original Frankenstein film (1931) featured this iconic sound, which was then featured in a bazillion other movies and cartoons including Scooby Doo, Ghostbusters, Back to the Future, Mary Poppins and the Brave Little Toaster. Imagine a dark sky, scary castle, organ music in minor key, maybe a psychadelic hippie van full of meddling kids.

The return stroke - Britannica says the loudest thunder heard after a flash to the ground is actually produced by the return stroke that follows the path forged by the initial stroke, or stepped leader. "The return stroke is louder because it contains a larger and faster-rising electric current than either the leader or a discharge within a cloud. Because the path of a lightning channel is usually branched, tortuous, and very long, sound waves from more distant portions arrive later than those from nearer portions, accounting for the duration of thunder and for the 

characteristic claps and rumbles."

You know what is tortuous? Trying to convince your frightened kitty that the rumbling noises aren't going to get him while unsure yourself if indeed that thunder might not just come through the window and send you into oblivion, courtesy of Queen Bavmorda.

Timing - the distance to a lightening flash can be estimated by measuring the time delay between the flash of light and the thunder - rule of thumb is 5 seconds per mile (3 seconds per km).

And given that the total energy in a large thunderstorm is more than that in an atomic bomb, don't forget Lightning Safety Awareness Week, which strikes during the last full week in June.