The Straight Dope 02/03/2006

The Straight Dope -- By Cecil Adams
http://www.straightdope.com

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THE STRAIGHT DOPE 02/03/2006

Dear Cecil:

Please, please, please settle this question. The discussion has been
going on for ages, and any time someone mentions the words "airplane" or
"conveyor belt" everyone starts right back up. Here's the original
problem essentially as it was posed to us: "A plane is standing on a
runway that can move (some sort of band conveyer). The plane moves in
one direction, while the conveyer moves in the opposite direction. This
conveyer has a control system that tracks the plane speed and tunes the
speed of the conveyer to be exactly the same (but in the opposite
direction). Can the plane take off?"

There are some difficulties with the wording of the problem,
specifically regarding how we define speed, but the spirit of the
situation is clear. The solution is also clear to me (and many others),
but a staunch group of unbelievers won't accept it. My conclusion is
that the plane does take off. Planes, whether jet or propeller, work by
pulling themselves through the air. The rotation of their tires results
from this forward movement, and has no bearing on the behavior of a
plane during takeoff. I claim the only difference between a regular
plane and one on a conveyor belt is that the conveyor belt plane's
wheels will spin twice as fast during takeoff. Please, Cecil, show us
that it's not only theoretically possible (with frictionless wheels) but
it's actually possible too. --Berj A. Doudian, via e-mail

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Cecil replies:

Excuse me--did I hear somebody say Monty Hall?

On first encounter this question, which has been showing up all over the
Net, seems inane because the answer seems so obvious. However, as with
the infamous Monty-Hall-three-doors-and-one-prize-problem (see The
Straight Dope: "On Let's Make a Deal" you pick Door #1, 02-Nov-1990),
the obvious answer is wrong, and you, Berj, are right--the plane takes
off normally, with no need to specify frictionless wheels or any other
such foolishness. You're also right that the question is often worded
badly, leading to confusion, arguments, etc. In short, we've got a topic
screaming for the Straight Dope.

First the obvious-but-wrong answer. 

For more, see:
http://www.straightdope.com/columns/060203.html

STRAIGHT DOPE CLASSIC #1 - 09/28/1990

Dear Straight Dope:

Please end the anxiety I've suffered over this question. What are those
white spots that appear on my fingernails and where do they come from?
--Katina Uribe, Flower Mound, Texas  

Dear Katina:  

Sorry to lay this on you, kid, but I figure if you're going to be 
anxious, you might as well be anxious big time. What you've
got is what's known as punctate leukonychia (medicalese for
"white spots.") Extreme cases of leukonychia, in which the
nails turn entirely white (leukonychia totalis) or develop white
bands (striate leukonychia), can indicate anything from arsenic
poisoning to leprosy. Leukonychia has also been linked to typhoid 
fever, frostbite, trichinosis, gout, diphtheria, cholera, acute
rheumatism, myocardial infarction, colitis, and any number of
other ghastly ailments.  

But don't sweat, you probably don't have any of them. Mere spots
are extremely common and undoubtedly harmless. 

For more, see:
http://www.straightdope.com/classics/a3_035.html

STRAIGHT DOPE CLASSIC #2 - 08/03/1990

Dear Cecil: 

How do astronauts perform their bodily functions in space? I've seen
mentions of "collection systems," but that's about it. By the way, do
you pay a reward for good questions? It would help to stimulate my
thinking. --Anxiously Awaiting Book 3, Calgary, Alberta, Canada  

Dear Anxious: 

 A reward? You mosquito, the search for knowledge is its own
reward. Besides, we're out of T- shirts this week.  

Up until Skylab, "waste management systems" aboard spacecraft
were primitive. The "device that collected the feces was a plastic
bag that was stuck to the posterior [with adhesive] during defecation,"
NASA bluntly reports. "The system used for urination was a version
of the time- honored `motorman's friend,' so called because the 
hose-and-bag unit was worn by the streetcar motorman, whose job
gave him little opportunity for a rest stop."   Cecil frankly is appalled--
not that the astronauts were subjected to this indignity (there wasn't
much choice), but that the motormen were. Gives new poignance to
the term "labor unrest." 

For more, see:
http://www.straightdope.com/classics/a3_032b.html

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