Over the last half a billion years, there have been five major mass extinctions, when the diversity of life on Earth suddenly and dramatically contracted. Scientists are currently monitoring the sixth extinction, predicted to be the most devastating since the asteroid impact that wiped out the dinosaurs. But this time around, writer Elizabeth Kolbert says, humans are causing the extinction.
Yale's William Nordhaus has been running the numbers on Earth's climate troubles. He says charging a fair price for any dumping of carbon dioxide into the air is a cost-effective solution. But at least half the planet must cooperate, his math suggests, or it will be all pain, no gain.
When "Benjamin," the world's last captive Tasmanian Tiger, died in 1936, a 23-million-year run of marsupial (pouch-bearing), doglike animals very likely disappeared from the planet. But before Benjy went, he had his revenge on the humans who hunted his kind to extinction.
As an acoustic engineer, Trevor Cox has spent most of his career getting rid of bizarre, unwanted sounds. But in The Sound Book, Cox turns up the volume on those sonic oddities. The book explores weird echoes and unexpected noises from around the globe — including "whisper galleries" and a chirping pyramid.
Why was Marius, a healthy 18-month-old giraffe, killed on Sunday at the Copenhagen Zoo? Employees say it's because Marius had genes too similar to other giraffes and was killed to avoid inbreeding. But the act has caused an uproar on social media and among animal activists. Robert Siegel talks to Bengt Holst, the scientific director at the Copenhagen Zoo, about the decision to put the giraffe down.
Skipping a meal triggers the munchies in a similar way that marijuana does, a study in mice finds. And it works, at least in rodents, by boosting the sense of smell. Receptors in the brain that get activated when the animals are stoned also light up after they've been fasting.
Today's political polarization makes it seem harder than ever to tackle climate change. Republican Bob Dixson says the goals of going green aren't only for liberals. His town of Greensburg was hit by an unusually strong tornado, and now he's working on a White House task force to prepare communities like his.
A report on health and social media finds that Wikipedia is the "single leading source of medical information" for patients and health care professionals. But not all the articles are accurate. To address that issue, Dr. Amin Azzam requires his fourth-year medical students to revise and publish medical articles on the site.