“You cannot just replace the old stock with new stock, without changing a lot of stuff around it,” said Viren Doshi, a London-based consultant at Booz Allen Hamilton, who has studied the telephone and electricity industries. “So they keep on patching up the old stuff.”

In many ways, big old things are also more dependable. Air Force One is a Boeing 747-200. That model went out of production in 1991, but the Air Force prefers models that have already had the bugs worked out of them.

And technology can keep big old things working. Arguably, the heavy pieces of metal in some old hardware are safer now than when new, because they are inspected with industrial radiography, ultrasonic tests and other modern wizardry.

Of course, there are several prerequisites for big old things to attain eternal life. One is knowing what you’ve got. For nuclear plants, that means counting how many neutrons have hit the reactor vessel metal, each one making the steel a bit more brittle.

Plenty of safety measurements were taken of the I-35W bridge in Minneapolis. Technicians used modern diagnostic tools to look for cracks. But maybe they mismeasured or measured the wrong things. Or maybe the engineers in the mid-1960s, barely out of the slide-rule era, made an error then that doomed the bridge now. Eternal life also requires that big old things survive changes in the surrounding environment. Anything that sits around long enough will experience earthquakes, which weaken foundations. That is an early, and still possible, suspect in the Minnesota bridge collapse.

In the future, big old things may need to survive climate change, which some experts fear will produce more extreme weather, including droughts or deluges (although it may be hard to link climate change to any specific event, like the deluge in New York last week).

Of course, not all big old things will survive. The utility industry has operated coal-powered generators that are more than 50 years old because new power stations are expensive. But now, with demand growing fast, the industry is proposing to build new coal plants with technology that will get more electricity out of a ton of fuel.