| What (Maybe) Didn't Kill the Dinosaurs: Comets The chunks of ice and dust that make their home in the Oort cloud, far beyond the orbit of Pluto, sometimes become dislodged and head into the solar system as streaky comets. Some disruptions, caused by passing stars and other interactions with the Milky Way galaxy, are severe enough to send Oort comets into orbits that buzz or even collide with Earth. New simulations have revealed a novel mechanism for their entry into our part of the solar system, a method that also suggests that comet showers may not have been strongly involved in major extinctions on Earth.Comet dynamics depend heavily on Jupiter and Saturn: their huge gravitational fields tend to keep objects away from Earth. Comets that manage to skirt Jupiter and Saturn, the conventional thinking goes, had to have originated in the outer reaches of the Oort cloud, where perturbations from outside the solar system can be felt most strongly and are writ large across vast cometary orbits that take hundreds of years to complete. Only during comet showers caused by close stellar passages, the theory holds, have extreme gravitational disruptions brought inner Oort cloud comets into the mix. [More] rss.sciam.com |
Copenhagen: No 'Pass' for Developing Countries COPENHAGEN -- The top U.S. climate negotiator stressed today that the next international global warming agreement must include major commitments from a suite of fast-growing countries; otherwise, greenhouse gas emissions will go up too fast to solve the problem."If you care about the science -- and we do -- there's no way to solve this problem by giving the major developing countries a pass," State Department envoy Todd Stern told reporters during the third day of U.N. climate talks here. "We're not talking about the same kind of need for actions from the vast majority of developing countries. But the major ones, it's going to be absolutely essential." [More] rss.sciam.com |
Worm Charmers (preview) If you happen to be hiking in the right part of Florida at dawn, you might catch the sound of a predator hidden in the vegetation. Surely an alligator must be the source of these calls, you say to yourself. But the sound does not come from an alligator, or a mother bear, or some newly introduced predator from the Amazon. It comes from a human predator--a “worm grunter.”Worm grunters have mastered the art of charming worms out of their burrows so they can be collected and sold as bait. First, the hunters pound a stob, or wooden stake, into the soil, and then they rub the stake with a flat piece of metal called a rooping iron. The vibrations resonate through the ground. In response, hundreds of large earthworms emerge, some as far as 12 meters from the baiter. [More] rss.sciam.com |
Foraging Early Humans Did Not Pass Up Grains Humans were eating sorghum grasses at least 105,000 years ago, an archaeologist reports. nytimes.com |
WHY WE TRAVEL American tourist Therese Madden comments on guided tour of Viogelmir, lava tube cave in Hallmundharaun, Iceland; photo query.nytimes.com |