All talks at Winchester Discovery Centre, Jewry Street 7.15 for 7.45 unless otherwise advertised.
Licensed bar serving hot drinks, cakes and snacks. No charge to attend. Contributions welcome.
Mon 2nd March “When stars fall into black holes: going beyond the equivalence principle.” – Dr Adam Pound, STAG
One of the cornerstones of Einstein’s theory of general relativity is the equivalence principle, which says that in a sufficiently small patch of spacetime, physics is just the same as in any other sufficiently small patch anywhere else in spacetime. One consequence is that a sufficiently small and light object in free fall in a gravitational field, no matter its internal composition, always moves on a “geodesic” (a path of longest time) in spacetime.
But this is only an approximation. In reality, any patch has finite size, and any object has both finite size and finite weight (or more precisely, creates a finite gravitational field). So how exactly is the equivalence principle corrected when these facts are accounted for?
Remarkably, gravitational-wave astronomy will soon allow us to answer this question with incredible precision. LISA, a gravitational-wave detector that will operate in outer space, will observe the inspiral of black holes and neutron stars, weighing roughly as much as our Sun, into supermassive black holes millions of times larger. Over the space of a year or two, as it slowly falls inward, the smaller object in such a system will execute hundreds of thousands of intricate orbits around the enormous black hole, and its tiny deviations away from geodesic motion will be precisely encoded in the gravitational waves it creates.
This talk will discuss these so-called “extreme-mass-ratio inspirals”, gravitational-wave astronomy, and what they might teach us about both general physics and the nature of the huge black holes that reside at the centres of galaxies.
Adam Pound is a Royal Society University Research Fellow and permanent member of staff in the School of Mathematical Sciences at the University of Southampton. He has published in fields ranging from experimental polymer physics to theoretical astrophysics. His research focuses on classical general relativity and gravitational-wave science, where he has made many contributions to the theoretical understanding of relativistic motion and binary mechanics. He is a member of the LISA Consortium, a network of about 1000 scientists involved in the LISA mission, and he leads the Consortium’s ongoing effort to develop theoretical models of extreme-mass-ratio inspirals.
Mon 6th April 2020 “Languages of the World: Identifying the Language of Text” Alan Ratner.
This talk is in the field of Computational Linguistics which analyzes the bit patterns of human language. It is at the intersection of Computer Science and Linguistics and is closely related to Information Theory.
There are 3 kinds of language: spoken (sequences of phonemes), written (sequences of graphical characters), and text (sequences of characters encoded for computers). This talk will focus on the languages of the world, especially in the form of text. Say you have some text such as a web page or email in a language you do not recognize. Of the many thousands of languages which one is it? Identifying the language may allow you to forward it to someone who knows the language or to the appropriate automatic translator. Difficulties include: a) some text will contain few words or may be contain more than one language, b) the ratio of linguistic information to web formatting may be quite small making everything look like English, and c) speed requirements may limit you to extremely simple algorithms (if you wish to perform this task on billions or trillions of web pages or real-time on rapidly streaming text) . This talk will provide a brief introduction to the world’s scripts (alphabets, etc.) and the languages encoded using those scripts and how languages can be identified.
Alan graduated from the Massachusetts Insititute of Technolgy and Yale University. Specializing in radio propagation in plasmas, Alan responded to a job ad placed by the US National Security Agency looking for someone to study radio propagation in the ionosphere and worked there for 35 years as a communications engineer, with 7 of those years stationed in England. As analogue communications were replaced by digital communications his interest in the physics and engineering of communications was repaced by the linguistics and computation of communications. After Alan retired from the government he became Chief Knowledge Engineer at Northrop Grumman Information Systems using parallel computing to make sense of vast data sets including text, images, audio, video, network traffic, network security and financial transactions. He retired to England in 2017.