I had intended to start the week with a look at Charlie Stross' ideas on the 'starship' metaphor, but I'll hold the Stross essay until tomorrow because I want to finish up Marcus Chown's piece in New Scientist. On Friday we talked about the idea of using Hawking radiation from a man-made black hole to propel a starship. That's outrageous idea number one, but Chown actually began the article with a look at Jia Liu's ideas on using dark matter to propel a ship, something along the lines of a Bussard ramjet without the hydrogen. The Uses of Speculation I enjoy looking at speculative concepts, even when they're so far out on the edge that they've attained a kind of intellectual redshift, but New Scientist's squib for the story surprised me: "We could reach the stars if we built a black hole starship or a dark matter rocket - we've got the physics to do it." Er, no, we don't have the physics to build a dark matter rocket. We don't know what dark matter is. The case for its existence seems...

When you consider that conventional chemical rockets extract a mere 10-8 of the energy locked up in their fuel, the attraction of antimatter becomes undeniable. Could we build an engine that extracts 100 percent of the energy created by matter-antimatter annihilation? Louis Crane (Kansas State University) is dubious, pointing to problems of storage and the difficulty of making enough antimatter to get the job done. Black Holes as a Propulsion Option Working with colleague Shawn Westmoreland, Crane has been exploring a different and far more speculative option for upping the energy extraction levels. What about using black holes for propulsion? Specifically, Crane and Westmoreland ask whether Hawking radiation from black holes can power a starship, calculating that a black hole of about a million tons would be just the right size, small enough to generate the needed Hawking radiation, while large enough to survive for the duration of a century-long star crossing. Adam Crowl has...

If you're going to snare dark matter, you'd better have incredibly accurate detectors. So the thinking goes at Case Western Reserve, where researchers are planning the most sensitive experiment yet to go after WIMPs (weakly interacting massive particles). WIMPs are almost impossible to detect because they don't give off radiation and pass through normal matter unimpeded. The CWRU group has received a three year $3.2 million National Science Foundation grant to design a new WIMP detector. The existence of dark matter is a theory that received support in 2006 when the collision of two distant galaxies was analyzed in ways that seemed to show the effects of dark matter on a cloud of galactic gas. Dark matter could provide the needed mass that keeps galaxies like the Milky Way from flying apart, but we still need a direct detection. The new experiment is a 20-ton liquid xenon detector called LZD. The Case Western group proposes LZD as an experiment for the Deep Underground Science and...

By Larry Klaes We have much to do as we scramble to explain the universe's continuing acceleration. Dark energy seems to be demanded by the data, but there are holdouts who argue for a reinterpretation of General Relativity. Tau Zero journalist Larry Klaes looks at one proponent of a revised GR who sees exceptions to the rule in a far earlier era. Albert Einstein's work created one of the biggest revolutions in the history of science and radically changed our perceptions of the Cosmos. One of his later breakthrough ideas is the Theory of General Relativity, or GR for short. Really massive objects such as the Sun literally warp space and time around them as they move through the heavens. Since Einstein first published his ideas on GR in 1915, scientists have been able to use the theory to understand the behaviors of even more massive celestial bodies and the very beginning of the Universe itself. Image: This key Einstein paper included the effect of gravitation on the shape of space...