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Sunday, September 15, 2019

Shock Waves, Sound Waves

Original publication, Methow Valley News, September 11, 2019

That was a lovely little storm, wasn’t it? I have not enjoyed a raucous storm in years. Five years, to be precise. But this time was different. I thoroughly reveled in the cacophony of light and sound. Perhaps because there was an accompaniment of rain, or maybe because it is September, and the leaves are starting to turn, a delightful presage to snow.

In the morning after the storm, I strolled through the woods. My hands slid over the tops of heavy sodden shrubs, releasing a cascade of raindrops from the golden red leaves to fall once more to the ground. I thought of a certain poem, expressing the angst of a summer storm, versus the sigh of relief exhaled when a storm ushers in autumn. 

Mother, Summer, I - Philip Larkin
My mother, who hates thunder storms,
Holds up each summer day and shakes
It out suspiciously, lest swarms
Of grape-dark clouds are lurking there;
But when the August weather breaks
And rains begin, and brittle frost
Sharpens the bird-abandoned air,
Her worried summer look is lost,
And I her son, though summer-born
And summer-loving, none the less
Am easier when the leaves are gone
Too often summer days appear
Emblems of perfect happiness
I can't confront: I must await
A time less bold, less rich, less clear:
An autumn more appropriate.

Is a thunderstorm a power anthem of Mother Nature? A single bolt of lightning travels 200,000 mph and is hotter than 50,000 degrees Fahrenheit. The sun is practically frigid in comparison at slightly over 10,000 degrees Fahrenheit.

Lightning occurs during a dance of molecules and temperature. As water vapor rises into the heights of the atmosphere, it cools and forms ice. As more molecules join the party, they dance with a greater frenzy. Bumping and grinding, these ice crystals collide and build up an electrical charge. Positively charged ions are lightweights, and rise to the top of the cloud. Negatively charged particles carry more weight, and drop to the bottom of the cloud. When these particles build up to a tipping point, a bolt of lightning streaks between the positive and negative charges, bringing equilibrium to the cloud once more…and the dance continues. If there are positive charges on the ground below, then a lighting bolt of energy will occur between the ground and the cloud. But you already knew all this.

The extreme heat of the lightning bolt, five times greater than the sun, attempts to expand into the cold air of the cloud. But, traveling at 200,000 mph, there is no time or space for the release of energy to expand. The force of energy results in a shock wave that rips open a tunnel through the cold air. As the tunnel collapses, the shock wave is then expressed as a sound wave. Rolling thunder that goes on and on is an audible signature of the length of the tunnel as it closes behind the shock wave created by super-heated lightning bolts. And now you know a thing, that perhaps you already knew.

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