Re: pinhole significant figures

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From: John or Jan Lahr (johnjan@lahr.org)
Date: Thu Jun 26 2003 - 20:38:23 PDT 

Message-Id: <5.1.0.14.2.20030626212314.01e522a8@mail.attbi.com>
Date: Thu, 26 Jun 2003 21:38:23 -0600
From: John or Jan Lahr <johnjan@lahr.org>
Subject: Re: pinhole significant figures

Hi Paul,

One example in reverse is the earthquake magnitude scale. The
magnitude is related to the energy of the earthquake logarithmically.

log E = 1.5 M + 11.8 (Gutenberg-Richter magnitude-energy relation)
E is energy in ergs. M is the magnitude.

A magnitude 1 radiates 2000000 Joules
A magnitude 9 radiates 2000000000000000000 Joules

We can usually only determine the energy to two significant figures, so
it's a lot more convenient to use numbers that range from
one to nine rather than huge numbers that will always
have lots of zeros.

(Note: there is no upper or lower limit to the magnitude
scale. Very very small earthquakes have negative
magnitudes and the largest event so far recorded was
the Chile earthquake of 1960 which registered 9.5.)

Reference:
http://jclahr.com/alaska/aeic/magnitude/

Cheers,
John

At 07:24 AM 6/26/2003, you wrote:
>Hi Pinholers
>
>One of the summer teachers asked if there are any real world examples
>that can be used to motivate students about the use of significant figures?
>
>Got any ideas?
>
>Paul
>D
>
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