Road Testing Your Alibi

Hey, Matt:

Which is a tighter seal, "air tight" or "water tight"?

-- Bay Park Jay

Even the elves -- not always tuned to the usual human-being wavelength -- were a little perplexed by this one. All they could figure was that you're building an alibi. So, let's say you make your alibi out of a bag full of the usual hot air sealed to keep water out and air in. The internal pressure of the thing is normal sea level, 14.7 pounds psi. Now take your alibi to Windansea and force it under water 33 feet and you've doubled the outside pressure (to 29.4 pounds psi) and your alibi is looking sucked-up and flimsy as the inside air is compressed. At 66 feet your incredible shrinking alibi is fighting three atmospheres. Too many variables to be able to predict if it will survive under that pressure, but our guess is you'll be whimpering like a baby and begging for forgiveness at that point.

If we hop in the car and take our alibi to Denver, a mile above sea level, the outside air pressure is about 93% of San Diego's and our alibi is looking a little puffier than it did at home. At an altitude of 10 miles, 90% of sea-level pressure, it's pooching out more; but we'd have to go, oh, maybe 18,000 miles up before the alibi's inner air pressure is twice the outer air pressure. At some point, our alibi will go high enough to literally blow up. But from the elves' incredibly precise scientific calculations here, it's obvious you'd better concentrate on water tightness if you expect to get away with anything.

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