Travel Reference
In-Depth Information
Virtual
Ammonites
surface waves had tugged at the buoy, dragging its tethered cage below to a
greater depth on the steeply tilted sea bottom.
First visible only as a faint patch of light in the deeper blue of the sea,
the trap eventually metamorphosed into a large chicken wire and rebar cube.
But instead of the eight living nautiluses that I had placed there for safe-
keeping, I could now see only shell fragments. When we finally muscled the
trap over the boat's side, the disaster was confirmed. Eight fleshy carcasses
rolled lifelessly about on the bottom of the trap, already much scavenged by
the countless smaller denizens of the sea. Yet it was the shells that were of
most interest; it was they that told the tale. They were smashed into numer-
ous small pieces, as though some malicious giant had whacked each with a
large hammer. The pieces were priceless: They made possible a detailed
analysis of how pressure caused mechanical failure in a shelled cephalopod,
for the nautilus and the
Thresher
had fallen victim to the same sad fate. Both
had exceeded the greatest pressure that their shell was designed to withstand.
Implosion, a terrible end for a submarine, is the handmaiden of hydro-
static pressure. This inexorable force pushes against every square inch of any
submerged vessel containing gas-filled spaces, and it increases with depth. It
is the force that causes ear pain in a swimming pool. It is the force that killed
the
Thresher.
Such a Damoclean sword is certainly noticed by the engineers
who design submarines, and it has certainly been noticed by nature's engi-
neer, the principle of natural selection. It comes as no surprise that most in-
terpretations of ancient submarine design—the form of the nautiluses and
their close relatives, the extinct ammonites—have been viewed with this
paramount fact in mind: Shell strength must be the primary concern of every
one of these ancient or modern diving devices. So I was taught by the great-
est student of these creatures, Professor Gerd E. G. Westermann of McMas-
ter University in Ontario, and until tecently I had no doubt about the ve-
racity of this interpretation. Now my mind has been changed—a reversal
brought about not by the study of any new fossil, living animal, or military
submarine, but by experiments conducted by another investigator and his
trusty Silicon Graphics workstation. The life of ancient ammonites has been
resurrected by the development of a virtual ammonite.
