Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: Density of water.



I don't think (in this unconscionably long thread) anyone has mentioned the
importance of the insulating quality of ice in protecting aquatic life. This I
think is the difference between freezing from the bottom up or the reverse.
However, what ever the conditions (already stated on this thread?) no ocean is
going to freeze, unless we have an ice age much more intense than the earth's
ever experienced (barring the creation of the earth before the sun)..

bc

Rick Tarara wrote:

But once the whole body of water has cooled and mixed to a nice uniform 0.1
degree C and then cools a little more----one big ice cube! Somewhat
devastating to temperate (and artic) zone aquatic life and therefore to the
diversity of aquatic life, but unless one can cite evidence of sustained sub
zero global temperatures during the past 2 billion years, then life itself
is not necessarily threatened.

Rick

**********************************************
Richard W. Tarara
Professor of Physics
Saint Mary's College
Notre Dame, IN 46556
rtarara@saintmarys.edu

FREE PHYSICS INSTRUCTIONAL SOFTWARE
www.saintmarys.edu/~rtarara/
PC and MAC software
NEW! SIMLAB2001--DYNAMIC CARTS now available.
CD-ROMs now available
******************************************************

----- Original Message -----
From: "Brian Whatcott" <inet@INTELLISYS.NET>
To: <PHYS-L@lists.nau.edu>
Sent: Sunday, December 02, 2001 9:18 PM
Subject: Re: Density of water.

At 12:25 PM 12/2/01, Jim Green wrote:
At 23:51 01 12 2001 , Bernard C wrote:
Right, Hewitt plots (ordinate) the volume of one gram of water instead
of the
inverse. No matter, he's plotting water not ice. Ice (normal near
zero C
[ice I]) 917 kg / m^3 or sg ~ .92 Water @ 100 C is 1.04 mL / g or sg
0.96 So
ice floats as per your experience (and mine).

Bernard, you seem to be missing the essential point -- the fact
that makes life possible! Water at freezing is less dense than water at
4C therefore water freezes on the _surface_ of the body of water.

Jim Green
mailto:JMGreen@sisna.com
http://users.sisna.com/jmgreen


This gee whiz item is a favorite of the divine design folks.

If water density uniformly decreased above freezing point,
it would cool at the surface of cooler air as usual - and becoming denser
when cooler then sink, until it reached it reached its density level.
Relatively warmer water at the bottom would rise, and so I suppose,
there might be a vigorous circulation while a temperature gradient exists.
And quite possibly on significant bodies of water, there would always be a
gradient, and a circulation, so that icing would be postponed perhaps
banished from significant bodies of water....

This does not seem specially lethal to life, when I consider the life that
thrives
in sulphide springs at great depths.


Brian Whatcott
Altus OK Eureka!