David W. Hughes was formerly Professor of Astronomy at the University of Sheffield and Vice President of the Royal Astronomical Society. Hughes was a co-investigator on the European Space Agency's Giotto mission to Halley's comet. He has written widely on the history of astronomy and has served on many space advisory committees. Carole Stott was formerly a professional astronomer--she was Curator of Astronomy at the Royal Observatory, Greenwich, UK--and is now a full time writer on space. Stott has written more than 20 books and contributed to many encyclopedias and journals.