Question About Floating Cities

[SaxonViolence]

I'm asking this here, cause I can't imagine it being a real possibility...

 

But still, I have a question.

 

If you look at some old SF Magazines or browse some of the imaginary landscapes on "Deviant Art" you'll see the meme of Floating Castles or Cities, over and over again.

 

Let us suppose that you come up with an Anti-Gravity device.

 

#1} If your city is weightless, why doesn't it float completely away from Earth?

 

That ones easy. Don't cancel 100% of the gravity—just 98% or whatever, to make your city just lighter than air...

 

#2} If your Anti-Gravity device blocks gravity like a sunscreen—why aren't all your inhabitants blocked from the Earth's Gravity as well?

 

#3} Even if you could make your "City" float—seems like it would have to be very strong to hang together.

 

Ships can't bear their own weight when unsupported by water.

 

_{{We assume that the Anti-Gravity applies to your structure as a whole, but you cant exempt portions of a skyscraper from bearing its own weight for instance...}}

 

But here's my main question:

 

You build your floating city.

 

Tons and tons of Structural Steel, Reinforced Concrete, Glass, Soil, Water, etc.

 

Now here comes a Tornado or Hurricane...

 

Seems like it would tear your floating City to shreds.

 

Well, its all kinda fanciful but it is interesting—to me at least—to imagine.

 

 

Saxon Violence

[CraigD]

Having recently played the latest of the Bioshock video games, which is set in an alternate history’s 1912, in a floating metropolis called Columbia, which was funded by the US, displayed in part at the 1893 Worlds Fair, and lauched as a real city in 1900, the subject of fictional floating cities is fresh in my mind.

 

From that game’s dialog:

Elizabeth Comstock: They - well, she - invented the technology that keeps this city afloat!

Booker DeWitt: Giant balloons?

EC: Quantum particles, suspended in the air.

BD: So... not giant balloons?

 

The game’s writers at least give nod, in exposition like this, that you can’t practically float a city using balloons, propellers, and the like, while offering the fairly standard soft SF cop-out that the technology relies on some magic-like large-scale quantum mechanics.

 

Regardless of whether of how you could get something city-size to float, here’s my 2cents on your questions, SV:

#2} If your Anti-Gravity device blocks gravity like a sunscreen—why aren't all your inhabitants blocked from the Earth's Gravity as well?

I think you answer your own question with this one. A “gravity shield” would make the stuff you still want to experience a downward force – water, pedestrians, etc – to float, like the rest of you city. Ergo, better not use such a technology (which I doubt is possible, anyway) for floating cities.

 

#3} Even if you could make your "City" float—seems like it would have to be very strong to hang together.

This is, I think, within the grasp of 19th+ century technology, as we’ve been building tall building as long bridges that withstand comparable forces for that long.

 

Ships can't bear their own weight when unsupported by water.

But ships don’t need to be supported by a single small point, as presumably neither would be floating cities. Both need only to withstand much smaller horizontal forces due mainly to waves (in the case of ships) and wind.

 

_{{We assume that the Anti-Gravity applies to your structure as a whole, but you cant exempt portions of a skyscraper from bearing its own weight for instance...}}

Presumably (and we can presume a lot when talking about practically fictional technology :)), you could build your city with whatever anti-gravity force producing stuff or machinery – be it giant balloons or quantum magic – distributed as needed under the different structures it supports.

 

I think the potentially catastrophic worries with a floating city would be more of balance than structural strength – how do you keep it from tipping, for example, when lots of people, or worse, big volumes of water, shift around? Even small tilts could overflow artificial lake and river banks, and wreak havoc with piped water pressure, while a complete capsize would obviously be catastrophic!

 

Now here comes a Tornado or Hurricane...

 

Seems like it would tear your floating City to shreds.

I don’t think this would be a problem, because small powerful wind systems like hurricanes exist only at low-altitudes. The record for tornados is, I’ve read, around 3500 m (10,000 feet) ASL. Hurricanes are, I believe, similarly low-altitude phenomena, and in addition, involve strong wind speeds only relative to stationary, objects such as ones affixed to the ground. A floating city would move with strong winds, so like present day high-altitude balloons that enter the jet streams, have only small “surface winds”.

 

Since to be safe, a floating city would need to be 3500+ m ASL, breathing comfortable in the open air would be an issue, especially when working or playing strenuously, so my guess is these fictionally high-tech marvels would need have either air-containing covers, and/or oxygen concentrators like those used inside high-altitude mining dormitories, much scaled-up. Otherwise, a day in the park would feel like a walk around the summit of Mt. Everest!