Science: Theoretically...

Ever get the feeling you're being watched? The one-metre-resolution space imagery already used by high-specification military satellites is now available to us all. Space Imaging, of Colorado, is launching a commercial high-resolution satellite on the Athena II rocket. Once the IKONOS I satellite is in place, customers will be able to order high-resolution pictures of anywhere in the world. Meanwhile, you can order similar images from a company closer to home. GeoInformation International has digital aerial maps of more than 75 cities around the world, available to customers on CD-Rom. The whole of central London is stored in 7GB of data, at a cost of pounds 5,000.

Several frog species have become extinct recently and others are showing alarming rates of deformity. No single cause has been identified, but the first field experiments under natural conditions have confirmed that ambient levels of ultraviolet-B (UV-B) radiation from the sun can cause high rates of amphibian mortality and deformity. According to the proceedings of the National Academy of Sciences, Joseph M Kiesecker compared the embryos of long-toed salamanders, which were shielded from UV-B radiation by mylar filters, with unshielded embryos. He found that 95 per cent of the shielded embryos hatched, compared with only 14.5 per cent of the unshielded embryos. Of the surviving salamanders, 0.5 per cent of those shielded were deformed, compared with 91.9 per cent of those unshielded. Higher levels of an enzyme called photolyase may protect some species.

Earthquakes along the San Andreas fault, north-east of Los Angeles, have occurred more regularly than previously thought and the next big one could come sooner than supposed, says geologist Mark T Brandon. Using his knowledge of lichens to pinpoint the dates of previously unknown ancient earthquakes, a new method called "lichenometry", he found signs of earthquakes larger than magnitude 7, which generated numerous rock avalanches as far as 400km from the epicentre. Soon after the quakes, spongy lichens began to colonise the fresh rock surfaces. Because of their predictable growth rate, lichens make it possible to estimate within 10 and 20 years when an earthquake occurred in the past thousand years. The method was used to identify a major unknown quake near Los Angeles in 1690 and several earthquakes in New Zealand over the past 700 years.

The number of people infected with internal parasites such as tapeworms is soaring - and tourism is being blamed. With more people travelling to Eastern Europe, an area of high infection, the frequency with which people are affected is rising fast. Eating undercooked beef, pork or fish is the main way you can acquire the beastie, which can grow up to 30ft long. Eggs develop into larvae and live in the small intestine. Although an infected person can suffer weight loss and stomach pains, there may be no symptoms. The only sign of infection may be individual white segments of tapeworm emerging from your rectum -- dead or alive. If it is not treated, the patient may develop cystercerosis - a disease in which the tapeworm larvae invade the brain, causing serious mental disturbance.

Scientists from Leicester University are using techniques for studying stars and distant galaxies in the battle against cancer. Detectors normally used to record X-ray emission from space are now being developed for the analysis of human tissue. Scientists in the department of physics and astronomy believe the new detector could make an impact in the investigation of cancer-treating drugs, such as tamoxifen, commonly given as a treatment to women with breast cancer.