Traditionally, cloud seeding has involved dropping a vapor into the clouds (usually silver iodide) that's designed to bond with the water, making it heavier and creating rain or snow. But this ground-based generator is designed to spray upwards into the clouds. According to the Associated Press, many people believe the U.S. is falling behind in the cloud-seeding arms race:

Government agencies and utilities from California to North Dakota spend an estimated $15 million a year on cloud seeding, and the number of projects has jumped by nearly a third in the last decade.

But spending in the United States is far lower than in many other countries. China spends an estimated $100 million a year on cloud-seeding efforts that include using anti-aircraft guns and rocket launchers to blast the sky with silver iodide.

"What's going on in the U.S. is tiny," said Arlen Huggins, an associate research scientist at the Desert Research Institute in Reno, Nev. "There's more being done outside the U.S. than here."

Other countries conducting cloud-seeding research include Australia, France, Greece, Saudi Arabia, Turkey and Venezuela.

But the National Research Council reported in 2003 that there's no evidence this technique actually works. At the same time, scientists involved in the report say more study and research are needed, and utilities like Pacific Gas & Electric have been doing cloud-seeding for years, saying they've seen an increase in precipitation as a result. (PG&E uses snowmelt in turbine-power plants.)

Another question: whether silver iodide, the chemical used to make water heavier, is safe. Residents of one area where PG&E wants to install seven 20-feet-tall generators are raising questions — but the charmingly named Weather Modification Association insists it's perfectly safe. I love the fact that there's an interest group called the Weather Modification Association.

So with clean water growing scarcer and more precious, are we going to lose the weather-control race before we even know it's happening? And is water laced with silver iodide still considered "clean water"?

Image by AP. [Associated Press]

As we mentioned before, there have been a ton of young-adult postapocalyptic novels, many of them quite disturbing and hardcore. (And our list didn't even mention Uglies or Tripods.) And, Glenn adds:

I can think of a dozen post-apocalyptic movies that I saw as a teen, in the '80s, at the Harvard Square and Orson Welles theaters — including "Planet of the Apes" (1968) and sequels, "The Omega Man" (1971), "Sleeper" (1973), "Death Race 2000" (1975), "A Boy and His Dog" (1975), and of course "Road Warrior" (1981). As hard as it is to believe that adults would go to see "Death Race 2000," though, these movies weren't intended for teen audiences. So they don't count.

There have also been a couple of post-apocalyptic TV shows that seemed aimed at teens: the original "Battlestar Galactica," for example, not to mention "Planet of the Apes." I've never seen "Jericho," so I can't say whether it's aimed at teens. Oh yeah, in England, in the 1980s, there was a short-lived TV adaptation of John Christopher's excellent "Tripod" trilogy.

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Will City of Ember be the first Post Apocalyptic Children's film? [Quiet Earth]
Post-Apocalyptic Kiddie Movies [Boston Globe]

The city is donut-shaped, with a ring of floating platforms and towers and massive hand-cranked gates. There's a pervasive myth that this set was destroyed by a tropical storm, but really just a smaller and relatively minor set sank, says Rodger Pardee, who worked on the production. Think of it as a proof of concept: If the world really does turn into an aquatic dystopia, we really might need to build fortified cities on the water.

The set was 365 feet in diameter and weighed about 1000 tons, writes Pardee, who teaches at Loyola Marymount University. It had to be able to rotate so you could shoot from different angles and have the ocean in the background while it was moored in harbor. And then the filmmakers towed it out to sea so they could get wide shots of it under attack. It's an engineering marvel, as long as Kevin Costner doesn't open his mouth.

Waterworld - On Location [Rodger Pardee's Webpage]

Famous names: Kevin Costner

Crunchy goodness: 1

Bang for your buck: One of the most expensive SF flops of all time, Waterworld racked up the expenses when the floating city was destroyed by a tropical storm and had to be entirely rebuilt.

Most painfully dated moment: The idea that Kevin Costner could be an action hero is what truly marks this as a movie that could only have been made in the 1990s.

The shit: The film is laughably bad, which means it's one of those rarities where bad = good. Plus, the eco-disaster theme is remarkably prescient, and the boat city is actually kind of cool.

Waterworld - Questions, Answers, Fun Facts & Trivia