Replaced with fiber optic cables, the copper was sold as scrap metal for recycling into new products.

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Silicon Valley took root south of San Francisco, in simpler places, where the streets were not interwoven with ships that docked and never left. Over the past two generations, the innovation machine has crept up the 101 and into the city.

This has happened at a moment when the screen and the city are the two hottest ways for young people to spend their time. It would seem these activities were in competition, but it appears that engaging with one drives desire for the other.

On the screen, all the richness of human codes is available: knowledge, communication, all the furious chaos of one's social life can be compressed and sent to hand.

But a flatness prevails. There is no sense of decay, of time passing, of Treat Ave following a curve that turns out to be the spine of old Mission Creek. At any point in the physical world, there is infinity in all directions, a grid that is not just spatial but temporal.

No matter how one tries to quantify any piece of land, any building, any space, it will always escape the spreadsheet. There will always be more that could be known.

So many people want to talk about what tech companies and people are doing to San Francisco. But this is just one city, and the people building the companies that are the Internet control communications for vast swaths of the world.

What can San Francisco, the place, teach tech companies about the full measure of the world? Perhaps historical depth will seep into the applications made inside the walls of a place like 140 New Montgomery. Who knows how precisely the streets we walk shape the way we walk them, but they do. We know this.

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While it was the tallest building in the city, the roof of 140 New Montgomery served as the official city storm warning station. During the day, it flew symbolic flags, and at night, powerful electric lights could be used to deliver messages seen for miles around. Two red flags or one white and one red light meant a gale with winds up to 54 miles per hour; a red flag with a black center, or two red lights, signaled an even worse storm.

Futurist Bruce Sterling recently gave his annual keynote at SXSW Interactive in Austin, Texas. The conference (and the keynote) are a yearly ritual for many of the technology workers in the Bay. Sterling told them, "The future is about old people, in big cities, afraid of the sky."

For now, those old people are the young people jauntily striding into the lobby, taking out their earbuds, checking Facebook, and preparing to work. Before them stretches a day, and also a life. "The best cities I've been in have a continuum of time," said the architect Simon.