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RE: Population Growth & Sustainability



	Thank you! Thank you! Thank you for posting that piece.  I've been
looking for it again for 20 years.  Dr. Bartlett also had an accompanying
film with that article, in plain English that a third grader could
understand.  I was working at the time with the DOE on the 'energy crisis'
and what EVERYONE seems to forget is the exponential factor --- which isn't
rocket science.

	I see statistics about how great only 3% growth per annum is...but
what people don't stop to think about is that 3%/year equates to a 23.3 year
doubling rate!  Lousy if you're talking about interest on your investment,
but outrageous when you speak of population growth (or energy usage).

	Thank you again for keeping everything on your desk!

Walker Bennett
wbennett@caldwellspartin.com <mailto:wbennett@caldwellspartin.com> 
wabennett@gw.total-web.net <mailto:wabennett@gw.total-web.net> 
w_bennett@msn.com <mailto:w_bennett@msn.com> 

___________________________________________________________

The best way to accelerate a Macintosh is at 9.8m/sec/sec.

___________________________________________________________



-----Original Message-----
From: mmiller@pcsia.com [mailto:mmiller@pcsia.com]
Sent: Wednesday, October 20, 1999 1:10 PM
To: sanet-mg@ces.ncsu.edu
Subject: Population Growth & Sustainability


A while back, there was a thread about the earth's population reaching
6,000,000,000 souls.  One respondent said something that reminded me of a
paper published back in the energy crisis days that seems to be relevant.
It has to do with when we realize we that we have exceeded the carrying
capacity of the system.

This paper just surfaced on my desk again, mainly because I have no filing
system for papers, ... mumble, mumble...
So here is little excerpt from Am J. Phys, 46(9), Sept. 1978 pgs. 876-888

Forgotten fundamentals of the energy crisis 
Albert A. Bartlett, Dept of Physics, Uof Colorado, Boulder

IV.  Exponential Growth in a Finite Environment

Bacteria grow by division so that 1 bacterium becomes 2, the 2 divide to
give 4, the 4 divide to give 8,etc..  Consider a hypothetical strain of
bacteria for which this division time is one minute.  The number of
bacteria grows exponentially with a doubling time of one minute.  One
bacterium is put in a bottle at 11 a.m. and it is observed that the bottle
is full of bacteria by 12:00 noon.  Here is a simple example of exponential
growth in a finite environment.  This is mathematically identical to the
case of the exponentially growing consumption of our finite resources of
fossil fuels.  Keep this in mind as you ponder three questions about the
bacteria:

1.  When was the bottle half-full?     Answer: 11:59 a.m.!

2.  If you were an average bacterium in the bottle, at what time would you
first realize that you were running out of spaced? 

 Answer: There is no unique answer to this question, so let's ask, "At
11:55 a.m., when the bottle is only three percent filled(1/32) and is 97%
open space (just yearning for development) would you preceive that there
was a problem?"

(snip time dated illustration)  See below.

11:54 am		1/64 full
11:55 am		1/32 full
11:56 am 		1/16 full
11:57 am		1/8 full
11:58 am		1/4 full
11:59 am		1/2 full
12:00 noon		full

Suppose that at 11:58 a.m. some far sighted bacteria realize that they are
running out of space and consequently, with a great expenditure effort and
funds, they launch a search for new bottles.  (Snip time dated material)
and at 11:59 a.m. they discover three new empty bottles.  Great sighs of
relief come from all the worried bacteria, because this magnificent
discovery is three times the number of bottles that had hitherto been
known. This discovery quadruples the total space resource known to the
bacteria.  Surely this will solve the problem so that the bacteria can be
self-sufficient in space.

3.  How long can the bacterial growth continue if the total space resources
are quadrupled?  Answer:  Two more doubling times (minutes).  See below.

11:58 am		Bottle 1 is 1/4 full
11:59 am		Bottle 1 is 1/2 full
12:00 noon		Bottle 1 is full
12:01 pm		Bottle 1 and 2 are both full
12:02 pm		Bottles 1,2,3,4 are all full

Well there it is.  Sorry it is so long but it illustrates an imporatant
point about our ability to preceive a problem with something in exponential
growth and still have time to do something about it.  After pondering this
one maybe Prozac is more in order than coffee :>)  Mike Miller



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