Engines of Our Ingenuity

No. 1201:
THE FIXED LINK

by John H. Lienhard

Click here for audio of Episode 1201.

Today, we link land to land. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

Henry Petroski has written much about bridges. Now he looks at a bridge just being completed -- the Confederation Bridge linking Prince Edward Island to mainland New Brunswick. This bridge, including a mile of approach spans, is eight miles long and it's costing just under a billion dollars. As the bridge nears completion, over 40 piers, 800 feet apart, march across the water, rising 130 to 200 feet from the sea bottom. This is one of the last really heroic constructions of the twentieth century.

But Petroski isn't here to tell us about the wonders of his own field of civil engineering. Rather, he's writing about what he calls the fixed link question -- an ongoing engineering dilemma.

Tunnels and bridges form fixed links between two land masses. When I visited Prince Edward Island in the late '70s, a ferry boat took me to a completely quiet and rural farming community. It was Canada's smallest province, about the size of Delaware and home to only 100,000 people. It was peaceful and bucolic.

By contrast, consider Manhattan Island, tied by vast bridges and tunnels to New Jersey, Long Island, and the Bronx. The only place New Yorkers still routinely visit by ferry is Staten Island.

There's nothing bucolic about Manhattan Island. Its fixed links to the surrounding world have converted it to the high-pressure center of America -- off-center though it may be.

England lies on another island only recently connected to mainland Europe by a fixed link, the Channel Tunnel. Technology that could have built a Chunnel has existed for over a century. But this link has stirred fear as long as engineers have dreamt it. The English feared it would let in rabid animals, or the French, or anything else that goes bump in the night. But before you laugh, wait a few years. England will be changed, and we don't yet know just how.

While no one can know just what this bridge across Northumberland Strait from New Brunswick to Prince Edward Island will do, it has awakened plenty of resistance. It will certainly hurt the ferry business. You can bet it will end the pastoral isolation of the Island. Then there's environmental impact: bridge piers tend to anchor ice that would've broken up much sooner. That can delay fishing and hurt the Island's economy. But the bridge will also bring in tourists. And, through better commerce, it'll be a force that cuts the Island's high unemployment rate by putting it in balance with the rest of Canada.

Now those spans march across the water carrying radical change to a quiet land. The genie of technology won't stay in its bottle. That genie always turns the known world upside down, and Petroski's fixed links are among the most powerful agents of technological change we know. The march of the Confederation Bridge is as inexorable as entropy -- and as sure as tomorrow's dawn.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)


Petroski, H., The Fixed Link. American Scientist, Vol. 85, No. 1, January/February 1997, pp. 10-14.


The Engines of Our Ingenuity is Copyright © 1988-1997 by John H. Lienhard.

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