THE SPIDER WEB AND THE LASER BEAM

THE SPIDER WEB AND THE LASER BEAM
Tuesday, September 29, 2009
By Larry Delano Coleman, Esq.

A laser beam lives at the base of my garage door. So does a spider.
The laser beam is dormant until I activate the electronic garage door
opener. The spider, meanwhile, does what it does, quite indifferent to
me, my electronic garage door opener, or my latent laser beam.

This arachnid blithely spins its web, spreads its net, in search of food
at my garage door’s base--apparently oblivious to all else.

In spreading it net, however, its arachnid membrane occasionally
bisects the path of my laser beam. There’s no intent involved here,
and, as far as I can discern, no obvious harm to the spider’s spindle nor
to the laser’s beam. The spider’s web and the laser’s beam seem to
coexist placidly and peacefully. Harmoniously. All is well.

All is well, that is, until I attempt to lower my garage door after
exiting, on certain random occasions. Sometimes, my garage door
will not shut. That is to say, it won’t go all the way down. It descends
to the level of the laser beam and then goes back up. Whenever I
depress the electronic garage door opener to close the garage door, on
those occasions, it won’t go down. It goes back up, no matter the
number of attempts I make to override the problem.

The first several times this happened, I had to get out of my car and
investigate. “Dear, dear, what could the matter be?” I wondered.
Unable to readily ascertain the source of the problem, and impatient
to depart, I called the garage door repair folks for help. Their answer
surprised me. Among other things, dust could impair the head of the
laser beam‘s light, or even spider web strands, they explained. They
suggested that I clean the laser head with a soft towel. I did, and the
door closed, thankfully. But that was not the end of my dilemma.

How, I marveled, can a spider web impair the path of a laser beam?

Yes, I had read of birds, especially Canadian geese, being the bane of
jet engines. Witness the miracle on the Hudson River with American
Airlines’ Captain Chesley Sullenberger, after birds were sucked into
his passenger plane’s engines.
http://en.wikipedia.org/wiki/Chesley_Sullenberger
Geese, at least, are flesh and bone and blood--in short, mass, and
one messy mass, at that, once emulsified by turbine engines!

But, how a single, diaphanous strand of a spider’s silky web can impair
something as cutting edge as laser light, baffles me?

Lasers “have been widely regarded as one of the most influential
technological achievements of the 20th century… A laser (light
amplification by stimulated emission of radiation) is a device which
uses a quantum mechanical effect, stimulated emission, to generate a
coherent beam of light from a lasing medium of controlled purity,
size, and shape.” http://www.wordiq.com/definition/Laser

Spiders, after all, are lowly creatures, whose antiquity certainly
antedates our own, by four hundred of million years, some say.
http://www.australianmuseum.net.au/Spider-Origins

What possible affinity, then, can lasers have with spiders. And what
affection for them? The internet discloses that spiders have an
irresistible “thing” for lasers. Spiders, in fact, appear to lust after laser
light, following and chasing laser pointers all about, as these you-tube
clips demonstrate. The spiders are most persistent, indeed, downright
incessant. But why?
http://www.youtube.com/watch?v=KrARj57-3yM
http://www.youtube.com/watch?v=4Q3bgMaD8bA&feature=related

Adding to this quixotic serendipity, one application of laser beam is
even nick-named “spider:”

“We report a new version of spectral phase interferometry for direct
electric field reconstruction (SPIDER) requiring only a single phaseshaped
laser beam. A narrowband probe pulse is selected out of a
broadband ultrafast laser pulse by a phase pulse-shaping technique
and mixed with the original broadband pulse to generate a secondharmonic
generation (SHG) signal.”
http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-33-13-1404

There is certainly some kind of “harmonic generation signal” between
lasers and spiders and my garage door. Lest you think I’m just a poor
housekeeper (or garage-keeper) with a profusion of spiders, Proverbs
30:28 provides: “The spider taketh hold with her hands, and is in
kings’ palaces.”

If, upon inspection, you also discover that a spider’s strand has
randomly obstructed your laser beam’s path, marvel at the
harmonious merger of the 400 million year legacy of the humble
arachnid, with the recent invention of the laser beam, and rejoice that
you, too, are blessed to witness and to participate in such a wonderful,
awe-inspiring pageantry, at the humble base of your garage door.

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