Science: Update

ULTRASOUND SCANS at frequencies similar to those used on pregnant women appear to interfere with the growth of mice foetuses, say Irish researchers. Several hours after 12 mice were given 15-minute scans at 8MHz, there was a significant drop in the rate of cell division in the small intestine, while cell death had increased. However Dr Patrick Brennan, who led the research at University College Dublin, told New Scientist magazine: "This is a preliminary piece of work... It has been assumed for a long time that ultrasound has no effect on cells. We now have grounds to question that assumption. There are changes happening but we couldn't say whether they are harmful or harmless." Further research is planned.

EUROPEAN astronomers have won "significant concessions" in their ongoing struggle with Iridium, the mobile phone company with 66 orbiting satellites (so you can tell people in any country that you're on the train). An agreement signed last week means that Iridium will provide seven hours of "quiet time" every night and two weekend days a month for British, French, German and Dutch facilities. But Nature magazine reports that astronomers are unhappy; the satellites' design disregarded the interference caused to radio astronomers using terrestrial equipment. Many operating frequencies are close to the 1,612MHz band reserved for radio astronomy; Iridium has agreed to put "non-polluting" satellites in place by 2006.

THE IDEA of "faster than light" spacecraft has had another theoretical boost, with a proposal from Belgium that such vehicles could use a strange form of warped space, involving a "bubble" with a large internal volume but tiny surface area - an idea reminiscent of Dr Who's Tardis. New Scientist reports that Chris Van Den Broeck, of the Catholic University of Leuven, proposes a topology in which a three-dimensional space with a huge volume is "attached" to normal space. A bubble big enough to contain a starship could be formed using just a gram of suitable space-warping material - though that material would have to contain "negative energy" - an even more theoretical concept that leaves warp drives still in the realm of the imaginary.