| How Quantum Effects Could Create Black Stars, Not Holes (preview) Black holes have been a part of popular culture for decades now, most recently playing a central role in the plot of this year’s Star Trek movie. No wonder. These dark remnants of collapsed stars seem almost designed to play on some of our primal fears: a black hole harbors unfathomable mystery behind the curtain that is its “event horizon,” admits of no escape for anyone or anything that falls within, and irretrievably destroys all it ingests.To theoretical physicists, black holes are a class of solutions of the Einstein field equations, which are at the heart of his theory of general relativity. The theory describes how all matter and energy distort spacetime as if it were made of elastic and how the resulting curvature of spacetime controls the motion of the matter and energy, producing the force we know as gravity. These equations unambiguously predict that there can be regions of spacetime from which no signal can reach distant observers. These regions--black holes--consist of a location where matter densities approach infinity (a “singularity”) surrounded by an empty zone of extreme gravitation from which nothing, not even light, can escape. A conceptual boundary, the event horizon, separates the zone of intense gravitation from the rest of spacetime. In the simplest case, the event horizon is a sphere--just six kilometers in diameter for a black hole of the sun’s mass. [More] rss.sciam.com |
Arctic Climate Threat--Methane from Thawing Permafrost (preview) Touchdown on the gravel runway at Cherskii in remote northeastern Siberia sent the steel toe of a rubber boot into my buttocks. The shoe had sprung free from gear stuffed between me and my three colleagues packed into a tiny prop plane. This was the last leg of my research team’s five-day journey from the University of Alaska Fairbanks across Russia to the Northeast Science Station in the land of a million lakes, which we were revisiting as part of our ongoing efforts to monitor a stirring giant that could greatly speed up global warming.These expeditions help us to understand how much of the perennially frozen ground, known as permafrost, in Siberia and across the Arctic is thawing, or close to thawing, and how much methane the process could generate. The question grips us--and many scientists and policy makers--because methane is a potent greenhouse gas, packing 25 times more heating power, molecule for molecule, than carbon dioxide. If the permafrost thaws rapidly because of global warming worldwide, the planet could get hotter more quickly than most models now predict. Our data, combined with complementary analyses by others, are revealing troubling trends. [More] rss.sciam.com |
State Proposes Closing 55 Parks and Historic Sites The parks department is refunding camping reservation fees for 12 recreation areas on the list. nytimes.com |
Spare Times A selected guide to festivals, talks, walks and other events in the New York area. nytimes.com |
What will space tourism mean for climate change? If space tourism ever becomes big business, as plenty of well-heeled backers hope, the danger of the enterprise might not be confined to those who book a ride to the edge of space. A robust suborbital spaceflight industry could deposit enough soot in the stratosphere to cause significant global climate change, according to a new study. [More] rss.sciam.com |