A Brief History of Time: the plot so far. In yesterday's instalment of what to do with unread copies of said book, Mollie Caird tried to fling hers away, but it returned, boomerang-like, from its trip in curvilinear space. Sian Cole interleaved hers with rude pictures, and Geoffrey Langley cut his neatly along the diagonal to form a gnomon. Now read on:

"Send them round the world at above the speed of light," says RJ Pickles, "so the copies return before the book was written, then send them down a black hole." Or, he suggests, "just be grateful he didn't write A Lengthy History of Time." Fiona and John Earle have observed how alarm clocks run normally during most of the day, then speed up in the time between going off and your having to get up. The book would be more widely read, they say, if Stephen Hawking had explained that point.

Jack and Renee Dolan suggest using hardback copies for patio paving and ridge tiles, or piling them up to make a causeway across the Thames to the Millennium Dome.

Paul and Steph intelligently ask why it's the unread copies we're trying to dispose of, rather than the ones that have been read. I suppose it's because there are more of them to go round. And you only need 12 of them, as several readers pointed out, to go round Mr Langley's gnomon to complete the sundial. (Steph, incidentally, cleverly started reading hers at the end, knowing that time was circular). Philippa Cragg suggests cutting out pages from inside a hardback to make a home for Tamagochi.

Prizes to Andrew Moyce, Mary Flavin (with apologies for spelling her name wrong yesterday) and Mollie Caird. Next week: holes in the road. Meanwhile, any ideas for things to do with bulldozers will be welcome at: Creativity, 1 Canada Square, Canary Wharf, London E14 5DL.