... Armagh Observatory, College Hill, Armagh BT61 9DG, +44 (0)28 3752 2928 . Two public lectures are provided, one on the risk to Earth posed by comet and asteroid impacts with our planet, the other a review of efforts during the eighteenth century to measure the size of our solar system and the role played by very rare planetary transits across the face of our Sun. ... Prof. Mark Bailey, Director, Armagh Observatory . ... Measuring the Solar System: The Eighteenth Century Transits of Venus" . ...