This is your chance to take part in some of the world's largest mass participation experiments.

Megalab '99 is a special, one-hour television programme which will be broadcast on BBC One on Wednesday, 17 March.

Run jointly by the BBC's Tomorrow's World science series and the Daily Telegraph, Megalab will give millions of viewers the opportunity to get involved in scientific experiments live on-air.

These include the production of the world's first Internet single, on which pop stars from around the globe will be contributing their vocal and musical talents via the Net. The single will be a re-working of Bob Marley's "Them Belly Full (But We Hungry)".

Lighthouse move

There will also be a report on the move of the Belle Tout Lighthouse, live from the East Sussex coast. This listed building and tourist attraction at Beachy Head is in danger of falling into the sea due to the erosion of the cliff face.

The remarkable rescue plan involves sliding the 850 tonne stone tower, in one piece, along a specially constructed track to its new position, 17m (56 feet) back from the cliff edge.

This unique operation will take place during the course of one day and reach its conclusion during Megalab '99.

There will be participation experiments to understand the workings of the human brain and a report on Megalab's Turing Test last week in which Net users challenged the intelligence of online computers.

Megalab is transmitted between 19:00 and 20:00 GMT. The programme, which is put on to coincide with the UK's National Science Week, is presented by Tomorrow's World regulars Philippa Forrester and Peter Snow.