Successful public symposium 'History and Future of Dark Matter'
The public symposium on the History and Future of Dark Matter, held on Sunday June 22nd in the beautiful Koepelkerk, was a wonderful prelude to the Astroparticle Physics conference (23-28 June in Amsterdam). The impressive line-up of speakers drew a wide audience, which was not deterred by the early onset of the symposium (9 AM) or by the beautiful weather.
Gianfranco Bertone (Institute of Physics, and PI of the UvA research priority area GRAPPA) opened the symposium with a nice overview of past, current and future dark matter research. Next on stage was Jim Peebles, the current Albert Einstein Professor Emeritus of Science at Princeton University, and one of the founding fathers of modern cosmology. “In 1970 dark matter was ignored. It was known, but not considered a productive line of research. In 1980 dark matter was accepted. By now, dark matter is established.” To which he added, tongue-in-cheekish: “Although I cannot say what it is.”
Michael Turner, director of the Kavli Institute for Cosmological Physics was up next. Right, that’s Michael Turner from the famous ‘Kolb and Turner’ - a book also known as ‘The Early Universe’ - the standard reference on modern topics in cosmology since 1990. He enchanted the audience with his beautiful hand drawings, and he drew a couple of rolling laughs from the audience with his witty remarks. He does not have much affinity with a particle candidate for dark matter, nor with a modification of Newtonian dynamics, such as the one proposed by Mordehai Milgrom (1981) to solve the galaxy rotation curve problems. Turner: “The most conservative hypothesis for dark matter is that it is a new form of matter. Not necessarily the right hypothesis, though.” And: “If MOND is right, I’ll eat my powerpoint presentation. And that includes the laptop”.
Albert Bosma (Laboratoire d'Astrophysique de Marseille) was the next scientist on stage who wrote history himself. In his PhD thesis (1978, Groningen, the Netherlands) he presented rotation curves of spiral galaxies of various morphological types in the 21 cm hydrogen line. Since the HI signal extends out to distances (sometimes far) beyond the outer edge of the optically visible regions, it is a much better probe for dark matter than optical rotation data, such as published at about the same time by Vera Rubin. When trying to answer the question why it took so long before dark matter was considered a serious scientific problem, he suggests: “Observational astronomers are not prepared to accept the existence of things they cannot see.”
The next three speakers highlighted the various experimental methods that could shine light on the nature dark matter in the near future. Bernard Sadoulet (Berkeley) elaborated on direct detection of dark matter, in experiments like XENON1T (run by GRAPPA team member Patrick Decowski). Joe Silk (IAP) summarized the various indirect detection methods, many of which require telescopes in difficult places, such as the South Pole (IceCube), the bottom of the Mediterranean (Antares), or outer space.
Simon White, one of the scientists behind the Millennium Simulations, had by far the most beautiful video to show. As mind-absorbing as staring into a burning fireplace, the Millennium Simulation shows the dark matter distribution in a patch of the universe, and the effect it has on galaxy formation. With a stunning remark to the not so distant past - ‘When we started programming, we used punch cards,’ - White points out that: “The fastest growing aspect in astrophysics is computing power.”
Questions about the true nature of dark matter, or how and when it will be found, still remained unresolved during the symposium. But it certainly added an extra dimension to one’s comprehension to have been able to listen to these distinguished pioneers of dark matter research.
For many participants, the public symposium formed a wonderful teaser to the Astroparticle Physics conference organised in the Tuschinski theater from 23-28 June, as a merger of the TeVPA and IDM conference series.
Videos of all lectures will be available online in a couple of weeks through the GRAPPA website.