From: "Erica VD Ginter" <eginter at klgai.com>
To: "'WSFA members'" <WSFAlist at keithlynch.net>
Subject: [WSFA] Re: the earth tips over
Date: Sun, 24 Mar 2002 20:15:01 -0500
Reply-To: WSFA members <WSFAlist at keithlynch.net>

I may have had it the wrong way around--either way it's an interesting
comparison.

Erica
whose irregularities can be detected by fingertips

-----Original Message-----
From: ronkean at juno.com [mailto:ronkean at juno.com]
Sent: Sunday, March 24, 2002 2:38 AM
To: WSFAlist at keithlynch.net
Subject: [WSFA] Re: the earth tips over

On Sat, 23 Mar 2002 19:46:54 -0500 "Erica VD Ginter" <eginter at klgai.com>
writes:

> I saw a science program (PBS, maybe Nova) a few years back that
> showed, by way of photomicrography for size comparison of surface
features,
> that Earth is smoother than a billiard ball. Just an interesting
factoid and/or > point to ponder.

The earth is about 8,000 miles in diameter, and there are many mountain
peaks scattered around which are about 4 or 5 miles above sea level.  The
highest (Everest) is about 5.5 miles.  Over broad areas, the oceans are 2
to 4 miles deep, and there are mountains under the sea as well as on
land.

Billiard balls are 2 1/4 inches in diameter (except for the cue ball), so
the equivalent feature height on the surface of such a ball would be
about 1.5 thousandths of an inch, if we ignore undersea topography, and
perhaps 2.5 thousandths if we measure from the ocean floors to the
highest mountains on land, rather than from sea level.  One or two
thousandths of an inch is about the height of features on the face of a
coin.  Usually, a roughness of only one ten-thousandth of an inch can be
felt with the fingertips.  So it seems that the roughness of the earth's
surface, reproduced on a billiard ball, could probably be seen and felt
as well as the features on the surface of a coin.

The earth is about one third of one percent fatter at the equator than it
is pole to pole, so the 2 1/4 inch billiard ball would have to be about 8
thousandths of an inch fatter at its 'equator' to reflect that.