The Straight Dope 01/12/2007

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

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THE STRAIGHT DOPE 01/12/2007

Dear Cecil:

News articles say the next magnetic pole shift is imminent. Magnetic
fields in Africa are getting weak and they say in some places you can't
get accurate compass readings. What will happen to us without protection
from the sun's radiation? --Tristan in Vermont

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Cecil replies:

Don't stress, kid. When talking about the magnetic poles flipping, we
can say three things with reasonable confidence: it's going to happen,
we don't know when, and it probably won't be as bad as some people
think.

As far as scientists can tell, the earth has had a magnetic field for
billions of years. The ancient Chinese were likely the first to discover
the field's effect on lodestones, although Europeans may not have
figured it out till the Middle Ages. In 1600 a physician in Queen
Elizabeth's court named William Gilbert proposed that the earth itself
generated the force that moved compass needles. Scientists began
measuring the strength of the earth's magnetic field in the 1830s using
a magnetometer invented by Carl Friedrich Gauss. Since then the magnetic
field has been subject to intensive if somewhat inconclusive study, the
upshot of which is that we're not certain why it's there, but we're
lucky it is -- it does a lot more than make compasses work. In
combination with the atmosphere it shields us from many of the solar and
other charged particles that would otherwise spatter the planet's
surface and its inhabitants; it also protects the atmosphere itself from
erosion by the solar wind.

While the experts are vague on the details . . .

For more, see:
http://www.straightdope.com/columns/070112.html

STAFF REPORT

Dear Straight Dope:

When a bullet is fired from land into water how far can it travel?
Movies portray a long trajectory, but I remember reading an Ian Fleming
book many years ago where he described that a bullet travels a yard at
most before it loses its speed and thereafter just slowly sinks. Given
that some bullets are more aerodynamic (hydrodynamic?) and some can have
greater speeds, how far can a bullet travel when fired into water? --A.A.

SDStaff Bricker responds:  

It's almost a shame that Cecil chose to assign this project to the SDSAB;
it strikes me as a fine candidate for the sort of hands-on experimentation
for which the Straight Dope is famous. However, you can see where letting
Little Ed near live ammunition might not be entirely wise.  

Besides,  somebody beat us to it, namely the daredevils on "Mythbusters,"
who have a bigger budget anyway. In an episode airing July 13, 2005 on the
Discovery Channel, the M-busters team built a water tank with thick
acrylic sides braced with iron T-bars. Ballistics gel -- in place of human
flesh, thank goodness -- was placed in the tank at various depths to
simulate the terrified swimmer escaping a bloodthirsty assassin. The team
collected a doomsday arsenal consisting of a 9mm semi-automatic pistol,
an M1 carbine, a hunting rifle chambered for .223 ammunition, a
shotgun, a .50 caliber "armor piercing" rifle, and, for fun, a replica
Civil War-era black powder rifle.  

In their first experiment . . . 

For more, see: 
http://www.straightdope.com/mailbag/mgununderwater.htm

STRAIGHT DOPE CLASSIC - 07/15/1988

Dear Cecil: 

The questions you deal with in your column are usually pretty cosmic,
but maybe as a change of pace you wouldn't mind taking a whack at the
following shallow topics: (1) What are those red or orange balloon
things you see on high-voltage utility wires when you're driving out in
the country? I've heard several theories, but none seems to hold up
under critical examination. (2) Is there any rhyme or reason to the
assignment of area codes? Why aren't numerically sequential codes given
to geographically adjacent areas? When I call Mom in area code 414
(eastern Wisconsin) but get San Francisco (415), it seems like a plot to
separate me from more of my money. --John R., Madison, Wisconsin

Cecil replies:  

Johnny, Johnny, Johnny. (Kinda Garboesque, ain't it?) The
telephone company is your friend. One of the reasons area codes are
assigned the way they are is precisely to prevent you from dialing the
wrong code by mistake. But let's take your questions in order. 

(1) The "balloon things" are aircraft warning markers intended to prevent
some joker in a Piper Cub from clotheslining himself. You see them near
airports with a lot of general aviation traffic-- i.e., low-flying small
planes--or else in areas where they do crop dusting. Typically the
markers are fiberglass spheres tricked out in some high-visibility
color, but occasionally you see other designs as well. They've
definitely inspired their share of carrot-brained theorizing. I knew a
guy who said the purpose of the balloons was to "scare away the birds."
Tragic evidence of the impact of the thinning ozone layer. 

(2) The assignment of area codes may seem random or even malevolent
to you, John, but this merely reflects your troubled inner being. Actually
it's pretty sensible. The North American Numbering Plan, of which the area
codes are a part, was worked out in the late 1940s to ensure
standardized numbering nationwide, helping to make direct-dial long
distance possible. (Prior to that time you had to go through an
operator.)  

For more, see:
http://www.straightdope.com/classics/a3_283.html

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