Since 2002 Perimeter Institute has been recording seminars, conference talks, and public outreach events using video cameras installed in our lecture theatres. Perimeter now has 7 formal presentation spaces for its many scientific conferences, seminars, workshops and educational outreach activities, all with advanced audio-visual technical capabilities. Recordings of events in these areas are all available On-Demand from this Video Library and on Perimeter Institute Recorded Seminar Archive (PIRSA). PIRSA is a permanent, free, searchable, and citable archive of recorded seminars from relevant bodies in physics. This resource has been partially modelled after Cornell University's arXiv.org.
Preon models enjoyed considerable popularity during the early 1980s, but have seen little progress since then. I will describe a correspondence between one of the more successful preon models and a simple game involving the twisting and braiding of ribbons, subject to straightforward topological conditions. This reproduces the fermions and gauge bosons of the standard model, as well as the electromagnetic, weak and colour interactions. The prospect that such structures may occur naturally within Loop Quantum Gravity will be discussed
In honour of the hundredth anniversary of Einstein\'s \'miraculous year\', I will describe the modern view of space and time. I will start with special relativity, then describe how space and time are modified in Einstein\'s general theory of relativity, and end with recent ideas coming out of string theory. In all cases, the view of space and time arising from modern physics is radically different from our everyday experience, yet many of their strange properties have already been confirmed by experiment.
I shall discuss entanglement - assisted invariance (symmetry exhibited by correlated quantum states) and describe how it can be used to understand the nature of ignorance, and, hence, the origin of probabilities in quantum physics. WHZ, Phys. Rev. Lett. 90, 120404 (2003); Rev. Mod. Phys. 75, 715 (2003); Phys. Rev. 71, 052105 (2005) (quant-ph/0405161).
Simon Singh grew up in Somerset, and completed his undergraduate work at Imperial College London, and his Ph.D. at Cambridge University and CERN. He has worked with the BBCs Science Department since 1990. In 1996, Singh directed the award-winning documentary Fermats Last Theorem. The documentary was also nominated for an Emmy under the American title The Proof. He is the author of three books, most recently, the Big Bang, a history of cosmology.
Highest energy cosmic rays reach {\it macroscopic} energies $> 10^{20}$ eV ($\sim 10$ joules; corresponding linear momentum in one proton is similar to a slapshot hockey puck's). Such protons can either be accelerated by nearby astrophysical sources or be by-products of decay of unknown superheavy fundamental particles. After reviewing phenomenology of cosmic rays, I will discuss a novel {\it non-stochastic} acceleration mechanism in jets of powerful active galactic nuclei.
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