According to one estimate, around 100 UFOs are sighted worldwide every 24 hours – that's one every 15 minutes. What's causing all these reports? Are they, as believers claim, evidence that we are being visited by aliens from other planets? Or is there  a more prosaic explanation? This hard-hitting talk by Ian Ridpath, astronomy writer and UFO sceptic, traces the growth of the flying saucer myth since the first sighting in 1947, and demonstrates some of the most common causes of UFO reports. The talk will discuss the implication of formerly top-secret government documents recently released under the Freedom of Information Act, and will end with Ian's first-hand account of his own researches into the Rendlesham Forest incident, a major event outside a US Air Force base at Woodbridge in Suffolk, still widely regarded as among the best UFO cases ever.Ian is a science writer and found fame for his investigation into the 'Rendlesham Forest Incident', often called 'Britain's Roswell'. For further reading on the subject Ian's website provides a good starting point to find more out about him and his talks.

Andy Parker is a Professor of High Energy Physics at Cambridge University, with over 160 publications on aspects of particle physics. His current research interests involve experiments to reveal new physics in the Tera-electron-volt energy regime. He is a founder of the ATLAS experiment for the Large Hadron Collider, and for 6 years he was the project leader for the ATLAS Inner Detector, the most complex detector system so far created at CERN. He is also involved in large-scale distributed computing grids, used for various scientific projects. He was awarded the Pilkington Prize for excellence in teaching in 1997.

Rebecca Watson is editor of the Skepchick blog which she describes as: "a group of women (and one deserving guy) who write about science, skepticism, and pseudoscience. With intelligence, curiosity, and occasional snark, the group tackles diverse topics from astronomy to astrology, psychics to psychology." Skepchick is an important part of the wave of science and skeptics sites that have spread across the internet in the last few years. Suddenly it's hip to be a nerd. This is good news, but is it also a defensive response to an increasing trend against science and medicine in society? Originally from Massachussetts, Rebecca is living in the UK at the moment and she has very kindly agreed to come and speak to us about her adventures over the last three years of blogging, organising and campaigning.

David Spiegelhalter is Winton Professor of the Public Understanding of Risk at the University of Cambridge and Senior Scientist in the MRC Biostatistics Unit. His background is in medical statistics, particularly the use of Bayesian methods in clinical trials, health technology assessment and drug safety. He led the statistical team in the Bristol Royal Infirmary Inquiry and also gave evidence to the Shipman Inquiry.

Nick Pope used to work at the Ministry of Defence, where from 1991 to 1994 he was posted to a division where his duties included investigating UFOs. Initially sceptical, his official research and investigation convinced him that the UFO phenomenon raised important defence, national security and flight safety issues. He was particularly interested in cases where the witnesses were pilots or where UFOs were tracked on radar. Nick is now recognised as a leading authority on UFOs and the unexplained.

Professor Chris French is the Head of the Anomalistic Psychology Research Unit in the Psychology Department at Goldsmiths, University of London. He is a Fellow of the British Psychological Society and the Committee for Skeptical Inquiry. He has published over 100 articles and chapters covering a wide range of topics within psychology. His main current area of research is the psychology of paranormal beliefs and anomalous experiences. He frequently appears on radio and television casting a sceptical eye over paranormal claims. He is the editor of The Skeptic and writes a regular column for the Guardian's online science pages.