What if we covered a city in a giant glass dome?

There's a very funny conversation that happens between Calvin and Hobbes in one of their comic strips. It goes like this:

Hobbes: A new decade is coming up.

Calvin: Yea, big deal! Humph. Where are the flying cars? Where are the moon colonies? Where are the personal robots and the zero gravity boots, huh? You call this a new decade?! You call this the future?? Ha! Where are the rocket packs? Where are the disintegration rays? Where are the floating cities?

Hobbes: Frankly, I'm not sure people have the brains to manage the technology they've got.

Calvin: I mean, look at this! We still have the weather?! Give me a break!

CALVIN AND HOBBES © Watterson. Reprinted with permission of UNIVERSAL PRESS SYNDICATE. All rights reserved.

People think about domed cities because, as Calvin points out, we haven't figured out a way to control the weather. If everywhere in the world could have weather like San Diego, it probably wouldn't be an issue. Unfortunately, in big cities like Buffalo, Minneapolis, New York and Chicago, the weather is decidedly NOT San Diego -- especially in the winter!

Digital Vision/Getty Images
A In a covered city, there would no longer be snow days, snow men or snowflakes.

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 feet of living space (pretty typical in suburban America), another 500 square feet of open space for things like hallways, walkways, parks, common areas, elevators, and so on, then this city could house almost 200,000 people. However, it's likely that real estate under the dome will be extremely valuable and that people will fit into much smaller spaces than they typically do today. In other words, the space occupied per person might total only 500 square feet. That would allow the city to hold more than half a million people.

2007 Photodisc
In a covered city, your legs might be the only form of transportation.

How much would it cost to build?
In today's dollars, space in a skyscraper costs something like $400 per square foot to build. The Eden greenhouses cost around of $400 per square foot too, so we'll use that number. The total cost for this project would be something on the order of $140 billion, or $250,000 per resident. That's not so unreasonable, when you think about it.

What will it cost to heat and cool this huge structure?
That's impossible to say because it depends on the type of construction, the location, and so on. However, it's interesting to note that the Mall of America doesn't have to spend money on heating, even though it's located in Minnesota. The lights and people provide plenty of heat. The problem will be cooling this massive structure, especially when the sun is shining. One way to solve this dilemma would be to locate the domed city in a very cold climate.

How will people get around?
The maximum distance between any two points in the city will be about one mile, meaning that a person can walk anywhere in a half-hour or less. Walking will be the primary, and possibly the only, means of transportation for the residents of the city. There will need to be some way to accommodate the movement of food and retail products into the city. Underground train systems or roads for trucks might be the best solution.

The thing that you come to understand after thinking about a domed city is that it's not such a far-fetched idea. There's a good chance that we will see such a city developed over the next decade or two. Finally, people will be able to plan their weekends without having to worry about the weather!