Closing a few open tabs.

* The New York Times has an article on Fermi problems and the importance of intuition in mathematics. (There's a game.) (Via Boing Boing.) Kottke links to some such calculations at 3quarksdaily, saying they used to be part of the interview process of Microsoft and Google.

* Roger Ebert explains why some people say he gives movies too many stars.

* The new season of the Ricky Gervais podcast is out.

* More radio: an episode of This American Life from May that explains the origins of the mortgage crisis.

* And Bill Gates is investing heavily in algae fuel. We're saved!

While I've been finishing up my absurdly busy weekend, Wall Street has apparently collapsed around our ears.

A brief history of the liquidity crisis, in cartoon form.

At Windy Ridge, a recently built starter-home development seven miles northwest of Charlotte, North Carolina, 81 of the community’s 132 small, vinyl-sided houses were in foreclosure as of late last year. Vandals have kicked in doors and stripped the copper wire from vacant houses; drug users and homeless people have furtively moved in. In December, after a stray bullet blasted through her son’s bedroom and into her own, Laurie Talbot, who’d moved to Windy Ridge from New York in 2005, told The Charlotte Observer, “I thought I’d bought a home in Pleasantville. I never imagined in my wildest dreams that stuff like this would happen.”

In the Franklin Reserve neighborhood of Elk Grove, California, south of Sacramento, the houses are nicer than those at Windy Ridge—many once sold for well over $500,000—but the phenomenon is the same. At the height of the boom, 10,000 new homes were built there in just four years. Now many are empty; renters of dubious character occupy others. Graffiti, broken windows, and other markers of decay have multiplied. Susan McDonald, president of the local residents’ association and an executive at a local bank, told the Associated Press, “There’s been gang activity. Things have really been changing, the last few years.”

In the first half of last year, residential burglaries rose by 35 percent and robberies by 58 percent in suburban Lee County, Florida, where one in four houses stands empty...

Suburbs: the new slums. See also.