Simple mathematics says the Space Station has a problem. What are the chances that there's a "launch vehicle failure" (the rocket blows up) when one of the pieces is being taken for assembly in orbit, asks New Scientist? Surprisingly high - almost 75 per cent, according to calculations based on the fact that, on average, good rocket launchers deliver their payloads successfully 92 per cent of the time. For US Space Shuttles, the figure is 99 per cent. Sounds good - but with 33 Shuttle missions and 12 Russian launches required just to get the bits up there, statistics suggest that the chances of losing none is only 26.4 per cent.

Things are tense anyway between Nasa and Russian space chiefs. Last week a Russian official described as "regrettable and unpleasant" the testimony of Dan Goldin, head of Nasa, who told the House of Representatives Science Committee that with hindsight he wished the US was building the key service module part of the station. The service module is now set to be launched in the spring of 1999, one year behind schedule.

We're all getting a lot older. In 2025, 15 per cent of the world population will be aged 60 or older - up from nine per cent in 1997, according to a study published in Science by Thomas Johnson, professor of behavioural genetics at the University of Colorado, and colleagues.

Partly it's because the post-war baby-boom generation is getting older, and getting better medical care and nutrition. But there is another factor: once people make it to old age, they hang in there - especially women. Mortality rates for octogenarians and nonagenarians are falling in Japan and the US.

The population of 100-year-olds of various developed countries has doubled every 10 years since 1960.