the blast is spent, the vacuum sucks all that air back in again, causing a kind of reverse-shock wave. It’s this effect that actually causes the distinctive mushroom cloud - the shockwave compresses the cloud on the way back in. Thus buildings, people, what have you, have to survive not only the temperature and the radiation, but also two massive shockwaves and brief exposure to near vacuum. Not a lot of buildings can do that, and far fewer people.
However, in space there’s no air to commute the force of the blast, so you get no atmospheric effects whatsoever. A nuke could go off right next to Babylon 5, and it wouldn’t affect the station at all. Well, not through a shockwave. The radiation would definitely be a problem, but the blast itself was no big deal, assuming it’s not physically touching the station. Conversely, if the same bomb was INSIDE the station, B5 would be toast. There’s a lot of debate as to what would happen if the bomb was outside the station, but touching it. There’s no atmospheric damage, of course, but the hull itself would clearly be partially vaporized, the hull would convey much of the shock, and the interior atmospheric compression caused by this combination would do a world of hurt. How much is dependent upon the size and placement of the bomb, of course, and some stuff that we have no practical experience with. (To my knowledge, no one’s blown up a space station yet, much less a LaGrange colony). At the very least, however, everyone inside the thing is gonna’ be bleeding from the ears. At the worst, they won’t notice they’re bleeding from the ears. My hunch, though, is that it probably wouldn’t blow up the station, but it would almost certainly give it a permanent, possibly mortal wound.
So when the Galactica got hit? Could it survive? Sure, why not? The Galactica is a mile long, and has armor yards thick. Assuming it was a fairly small bomb in the 5 to 10 Kiloton range, it’s possible. If a cutting edge piece of 1927 technology can survive TWO nuclear blasts, I’m thinking’ a behemoth like the Galactica could. It does seem excessive to me that the Pegasus shook off six hits in one episode, but what do I know?
Details about the effectiveness of nukes in space are available here http://www.hq.nasa.gov/office/pao/History/conghand/nuclear.htm
What about cities? Well, hell yeah! Nukes’ll take out cities with aplomb. It’s what they were designed for, after all. There’s absolutely no getting around that. Here’s a blast impact calculator to graphically show you the various radii of total and partial destruction, http://www.carloslabs.com/node/16 For instance, if you set off the Hiroshima bomb right in the middle of the Washington Mall, everything across the river in Virginia is fine, and the destruction to the north stops just a little bit outside of DuPont Circle. If you use a 50 Megaton bomb in the same location - and 50 MT is the biggest one ever set off - then pretty much everying from Elicott City in Maryland down to La Plata, Virginia is totally destroyed. Here’s another calculator you can use, just for comparison’s purposes http://www.fas.org/programs/ssp/nukes/nuclear_weapon_effects/nuclearwpne...
I’m also intrigued by the fact that virtually everyone who fears Nuclear Weapons is totally ignorant of how many of the damn things have been set off. Ask most people, and they’ll say “Two, and they killed millions” (Sigh). Slightly more informed people assume a dozen or so - test bombs before and after the war. Factoring in the French and the Soviets, you know, fifty to a hundred tops, right? Certainly that’s what I assumed when I was younger.
Nope. Wrong. Dead wrong.
There have been approximately TWO THOUSAND nuclear detonations! The US alone has conducted more than a thousand, including 331 ‘above ground’ tests. The Soviets did more than 700 tests between 1950 and 1990. The uncharacteristically trigger-happy French have detonated more than 200 bombs, 50 “Above Ground,” all in Polynesia. England blew up 45 bombs, half in the Australian outback. China has done at least that many, half above-ground.
If Aliens discover the world, they’re going to see all those craters, all that radiation, all the destruction from those 2000 blasts, and they’re just going to assume we *had* a global thermonuclear war already. They’re probably going to be very confused about what Polynesia, Nevada, Siberia, and Australia did to piss us off so badly. The aliens would be wrong, but only technically: we’ve already detonated far more bombs than any respectable World War III would require, the only qualifying difference being that *We Weren’t Actually Fighting* at the time.
Amazing, no? And no one seems to know this.
The bottom line here is that Nuclear Weapons are pretty devastating and awful, however they are a known quantity, and an unbelievably big hell of a lot of them have been blown up without most of the world noticing. As a weapon of fear, paradoxically, they managed to prevent war, but, in fact, they’re not amazingly effective outside of a fairly narrow range of parameters and….well….I’m tired of typing now. You get the point, right? We’re grown up now, and Fear no longer becomes us. As Science Fiction fans, it behooves us to ask questions and not just follow the herd like the opposition does. Sometimes the answers will be disturbing, sometimes they’ll be reassuring, and sometimes - as in this case - they’ll simply be wildly different than you probably expected. But in the end it’s worth it because the devil you know is far less frightening than the devil you don’t know.
And it’s far more fun as a plot device, too!
EDIT: This story initially went up on June 27th, 2009, and was written about six weeks before that (We like to schedule ahead if at all possible). Now, on July 10th, it appears that IO9 agrees with us http://io9.com/5310474/why-an-urban-nuclear-explosion-is-not-hopeless (On this one subject, if nothing else) I would like to point out that we're not accusing them of plagiarism. I'm sure they've never even heard of us.