The Straight Dope 03/03/2006

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

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THE STRAIGHT DOPE 03/03/2006

Dear Cecil:

Cecil, always enjoy your column, however you've got this [airplane and
conveyor belt business] absolutely wrong. . . --strafe, via the Straight
Dope Message Board

It's all about the interpretation of the question. Unfortunately, Cecil
commingled two different interpretations in his column. --zut, via the
SDMB

My confidence in Cecil has taken a gigantic hit. . . Cecil has fallen
into the common trap of believing that the velocity of the treadmill in
this case is what is important. It's not. What is important is the
acceleration of the treadmill. I swear, on pain of retaking physics
before I graduate as an ME, that if I accelerate the treadmill at a rate
of 2 x (force from engines)/(mass of tires) that the plane goes
absolutely nowhere. treis, via the SDMB

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Cecil replies:

I knew this was going to happen. Everyone else, forgive me. This week's
column is for the geeks.

Here's the original question: "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?" (The Straight Dope: 060203.)

The implicit assumption is that if the conveyor belt's speed backward
exactly counteracts the airplane's "speed" (whatever that means)
forward, the plane remains stationary relative to the earth and, more
importantly, to the air. (We assume the winds are calm.) With no wind
moving past its wings, the plane generates no lift and can't take off.

But the assumption is false. 

For more, see:
http://www.straightdope.com/columns/060303.html

STAFF REPORT

Dear Straight Dope:

I have a friend in San Francisco who recently received a live chick as a
pet. He keeps it in a rabbit cage, and believes that it is worth keeping
for the eggs it will eventually lay. Having raised chickens while
growing up in Oregon, and having shoveled more than my share of chicken
droppings, I know them to be primarily poo-machines, laying eggs only as
an afterthought. Apart from the city code issues involved, I don't think
keeping a single chicken in the city is worth the feed, mess, or (most
importantly) sheer volume of crap he'll be dealing with in exchange for
the two or three eggs he'll get per week. I promised my friend that I'd
help him build a coop if I'm wrong, but I'm betting that a chicken
produces more poop in a year, by volume, than eggs. Am I right about
this, or should I start buying chicken wire? --Steve, San Francisco

SDSTAFF Una replies:

Don't think I'm obsessed with poop. However, for reasons having purely
to do with scientific interest, this is a subject I happen to know a lot
about.

The first comment my ladyfriend made upon reading your question was, "He
should make sure of the gender of the chick, because if it's a male
chick, I can tell you right now that the ratio of eggs to waste is going
to be fairly poor." But assuming that you're dealing with a future hen
here, you're really asking two questions--first, how much waste relative
to eggs is produced, and second, whether it's economical to raise your
own chickens for eggs. Both are difficult questions to answer,
especially the second one, because there's such a wide variety of
chickens and eggs. So I'll try to stick to some generalities in my
assumptions, especially in terms of the overall economics.

First, let's define chicken waste. 

For more, see: 
http://www.straightdope.com/mailbag/mchickenegg.html

STRAIGHT DOPE CLASSIC - 09/23/1988

Dear Cecil: 

I was just reading about those boat people in Southeast Asia who had to
resort to cannibalism to survive and it reminded me of something I heard
once. Is it true that cannibalism was outlawed because people developed
laughing sickness afterward and died by literally busting a gut?
--Listener, Dick Whittington show, KIEV radio, Los Angeles  

Cecil replies:  

Let's take this step-by-step. Number one, forget about
laughing sickness. It's possible to die laughing, a topic I have
addressed in the past, but that's not the disease you allegedly get from
people eating. Most likely you're thinking of kuru, a fatal neurological
ailment characterized by trembling. From 1957 to 1977 kuru was epidemic
among certain New Guinea tribes and was suspected of being contracted by
eating human flesh. But cannibalism had been outlawed long before.  

The question you should have asked, if you don't mind my saying so, is
whether cannibalism (or anthropophagy, as we intellectual snobs like to
call it) occurs on a systematic basis at all. In a 1979 book called The
Man-Eating Myth, anthropologist William Arens argues that cannibalism is
the equivalent of an urban legend: lots of researchers say they've heard
about it, but hardly anybody has actually seen it happen. 

For more, see:
http://www.straightdope.com/classics/a3_054.html

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