The amount the U.S. military spends annually on air conditioning in Iraq and Afghanistan: $20.2 billion.

That's more than NASA's budget. It's more than BP has paid so far for damage during the Gulf oil spill. It's what the G-8 has pledged to help foster new democracies in Egypt and Tunisia.

Civilization is on a collision course. That's the message Paul Gilding, the former head of Greenpeace International, is sounding in his new book, The Great Disruption.

The facts, as Gilding spells them out, are frightening. The United Nations predicts the world's population will reach 9.3 billion by 2050 and humans are already using 140 percent of the Earth's resources.

Archeologists say our garbage provides a glimpse into our actions and values. Now, some scientists say our sewer systems do also. It only takes a teaspoon of waste water to reveal an entire city's eating or drinking habits. Environmental scientist Kevin Thomas talks about what the method can tell us.

It's been called the worst job in the country. And once you get it, unpopularity is practically certain. But it seems there's never a shortage of presidential candidates. Presidential historian Alvin Felzenberg talks about what it takes to make it into that small group.

James Fallows, national correspondent with The Atlantic, talks about the week's news: New York becomes the sixth state to legalize gay marriage; House Majority Leader Eric Cantor walks out of debt ceiling negotiations; and Congress votes on Libya.

State lawmakers made New York the sixth and largest state to legalize gay marriage on Friday night. NPR's Rachel Martin speaks with two Republican state senators: Jim Alesi, who voted for the measure, and Dean Skelos, who voted against it.

The House rebuke of the U.S. role in Libya may signal a new note being heard among Republicans. A growing number of prominent Republicans, including several candidates for president, are calling for speedier withdrawal of troops from Afghanistan, and question U.S. involvement in Libya. Host Scott Simon talks to Rep. Jeff Flake (R-Ariz.), about shifting positions in the Republican Party on military involvements overseas.

Nuts and yogurt came out as big winners in new research we discuss in this week's podcast, while potatoes were losers. The contest? Which foods can help you keep weight off as you age.

Ai Weiwei, the Chinese artist and human rights activist, was released from prison late Wednesday night, and told western reporters, "In legal terms, I'm — how do you say? — on bail. So I cannot give any interviews. But I'm fine."

The state news agency says Mr. Ai was released after 80 days "because of his good attitude in confessing his crimes," which the state says is tax evasion, though he was held by the internal security bureau.

Boston mob boss James "Whitey" Bulger was captured this week after 16 years as a fugitive. His years in hiding were aided by corrupt FBI agents who protected him in exchange for information. Host Scott Simon talks to former Boston Globe reporter Dick Lehr, author of Black Mass: The True Story of an Unholy Alliance Between the FBI and the Irish Mob, about the relationship between Bulger and his contacts.