The Straight Dope 04/27/2007

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

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THE STRAIGHT DOPE 04/27/2007

Dear Cecil:

Having seen more than my share of photographs of snowflakes, I recently
noticed that most seem to be perfect mirror images. How can the spines on
ONE side of the flake possibly know what random shapes those on the OTHER
are assuming in an essentially random freezing environment? Why would not
all snowflakes be non-symmetrical masses of frozen material with
absolutely NO symmetry whatsoever?--Pete Formaini, Ithaca, New York

What makes those pretty, feathery patterns in the frost on windows during
winter?--Amanda Zsuzsics, Eielson AFB, Alaska

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Cecil replies:

Amanda, meet Pete. My guess is, soul mates you're not.

Scientists have been studying snowflakes since the early 1600s, and while
we don't know everything about how they form, we know a lot, a fair amount
of which I've conveyed in this column over the years. However, since many
of the Teeming Millions weren't yet alive in 1973, you'll excuse a brief
review.

As water vapor rises into the colder upper atmosphere it cools, and when
chilled enough condenses into infinitesimal water droplets, which commonly
form around particles of dust, sea salt, etc, known as nucleation sites.
If the temperature keeps dropping, eventually the droplets freeze into ice
crystals. These crystals start out as tiny hexagonal prisms — the hex
shape resulting from the angle formed between oxygen atoms as the frozen
water molecules line up. Under the right conditions, additional moisture
condenses directly onto the crystal and freezes too. Since the corners
where the crystal faces meet project further into the surrounding vapor
than the flat sides, they accumulate ice faster, typically producing the
familiar six-branched snowflake.

Why are the branches identical? 

For more, see:
http://www.straightdope.com/columns/070427.html

STAFF REPORT

Dear Straight Dope:

What is "martial law"? When can it be declared? By whom? Under what
circumstances? And how does it differ from regular law under the
Constitution?—Lisa Sanford

SDSTAFF Bricker replies:

To adopt the approach of a former U.S. president, Lisa, it all depends on
what the meaning of "martial law" is.

Martial law is a catchall phrase applied to many different situations in
different countries and in most cases has no rigorous legal meaning. In
the United States it refers either to situations in which the
administration of criminal justice is taken over by military authorities
or to the suspension of certain civil rights – chief among them the writ
of habeas corpus, which is used to challenge the legality of detentions.
The imposition of emergency measures such as curfews during disasters by
civil authorities may sometimes be confused with martial law, particularly
if the restrictions seem severe, but we’re purists here at The Straight
Dope and ignore such distractions.

In many countries . . .

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

STRAIGHT DOPE CLASSIC - 03/16/1990

Dear Cecil: 
Is the earth getting heavier or lighter? After all, we've littered the
cosmos with a lot of NASA stuff, which should shave off a few pounds,
along with vapor escaping from the atmosphere. On the other hand, there's
a lot more people and meteorites around than there was in 8011 BC. What do
you think? --Edward M. Smith Jr., Los Angeles

Dear Edward:

Puny humanoid, you think the pitiful efforts of mankind have appreciably
altered the mass of the earth, reliably estimated at 6 sextillion, 588
quintillion tons? (And man, if you don't think it was a bitch getting that
puppy on the scale...) If so, shed your illusions. It's believed the earth
gains anywhere from several dozen to several hundred tons per day due to
meteorites and meteoritic dust--10,000 to 100,000 tons a year. (Sorry, but
estimates vary widely.)

For more, see:
http://www.straightdope.com/classics/a3_355b.html

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