Domed Cities

The goal of a domed city is to take a large urban area and cover it so that:

• The temperature is the same year round.

• There's never any rain or snow to spoil picnics and weddings.

• The cancerous effects of the sun are eliminated during outdoor activities.

Small-scale Domed Cities

There have been lots of attempts to create domed cities on a very small scale. Consider these examples:

• The Mall of America near Minneapolis is a tiny city under glass. It contains about 80 acres of floor space (on 27 acres of ground) holding more than 500 stores, 80 restaurants and an indoor amusement park.

• Biosphere 2 is a giant, completely sealed lab covering 3.15 acres.

• The two Eden greenhouses in England are geodesic domes that together cover about 5 acres.

• Any dome stadium covers eight to 10 acres.

What if we were to expand on these projects in a massive way, moving up to city-size and covering somewhere on the order of 650 acres -- approximately a square mile? We're talking about taking a square parcel of land measuring approximately one mile on each side, or a circular piece of land measuring 1.13 miles in diameter, and completely covering it.

The Mall of America is like a mini city covered in glass.

The first question is what technology would we use to cover such a huge space. Here are three possibilities:

• The Mall of America uses typical mall construction technologies -- concrete and block walls, trusses, skylights, and so on. It's not very glamorous or inspiring architecture (there would be lots of supporting posts and walls in the city, rather than the dazzle of a mile-wide dome), but it is easy to imagine a construction process using these same techniques to cover a square mile.

• The Eden project uses a geodesic dome and hexagonal panels covered with multiple, inflatable layers of a very light plastic foil. The weight of the geodesic frame plus the hexagonal panels is about equal to the weight of the air contained inside the dome.

• The British Columbia Place Stadium is covered with a Teflon-coated fiberglass fabric held up by air pressure. The air pressure inside is only 0.03 psi higher than normal atmospheric pressure. Sixteen 100-horsepower fans provide the extra pressure.

In a project like covering a city with a dome, it may be that buildings form part of the structure for the dome. For example, six tall buildings at the center of the city could act as six pillars supporting the dome's center, with other buildings throughout the city acting as shorter pillars.

What would life be like?

Certainly, using the mall technology, and probably using either of the other two technologies, it's easy to create a protective shell covering a square mile. Here are some of the more interesting questions that would be raised if someone actually tried to do this:

How many people could live there?

We'll assume that the interior of the dome is developed at an average height of 10 stories. Some buildings will be higher, while some places in the city will be parks or otherwise undeveloped, working out to an average of 10 stories. That gives the city about 280,000,000 square feet of floor space. If you assume that the average person needs about 500 square