“Physics 2005 – A Century after Einstein”
10th – 14th April, 2005, University of Warwick, UK.
Institute of Physics.
In commemoration of the centenary of Einstein’s annus mirabilis of 1905, the Institute of Physics organized a conference at the University of Warwick on the 10th to 14th April entitled: “Physics 2005, a century after Einstein”. The conference was divided into four parallel programmes: Light and Matter; Quantum Physics; Relativity and Cosmology and Physics in Biology. This meant that the spectrum of attendees was much wider than for a usual “single subject” conference.
One of the main aims of a conference is to encourage cross-fertilisation of ideas and to inform scientists about the state of play in fields other than their own narrow backwater. In this respect the conference was successful and I particularly admired the organiser’s decision to include an exhibition of modern art on themes from the natural and life sciences. An article by the artist, Orit Orion, explaining her work was in the July issue of The Pantaneto Forum.
Unfortunately, I was not able to cover every lecture, so I will give an impression of some of the proceedings in the area of Relativity and Cosmology. Cosmology is at present going through one of its periodic crises. I do not refer to the usual sort of Kuhnian paradigm shifts that other areas of science undergo now and then, but the “Universe cannot exist”; “What does it all mean?”; “Everything we thought we knew is wrong” type of super angst that seems to recur with unnerving regularity every generation – this, of course, is what makes the subject so much fun.
To be fair, many of the speakers (and audience) are quite used to this state of affairs, so the lectures were all received with a weighty dose of skepticism and good humour in about equal measure.
Two interesting and entertaining talks were from Joao Magueijo (Imperial College, London) and Mike Murphy (IOA, Cambridge) on the possibility of changing constants of nature. Magueijo’s talk was a review, which included the very profound observation and excellent quotation that “varying constants are quite varied”. Mike Murphy’s talk was on a possible variation in the fine-structure constant. The title of the talk in the press handout was “Sacred constant might be changing”, though in a rare example of a magnificent and uncannily perceptive howler the talk was listed in the contents as “Scared constant might be changing” (my italics) – such is the angst generated by this topic!
The nub of the lecture was work on the very high-resolution spectroscopy of quasar absorption lines. The fine structure constant (alpha) is a number made up of the electrical charge of the electron, the Planck constant, and the speed of light, and its value is 1 divided by 137.0359… The possibility of a varying alpha was mooted in the 1950’s and 60’s and other fundamental constant “variation”, notably the gravitational constant, was suggested in the 30’s.
Quasar absorption lines are due to clouds of gas in the line of sight to distant quasars and very accurate measurements of the wavelengths of these lines can now be made in order to look for changes in alpha. The problem is that looking for extremely small shifts in the wavelength of spectral lines is fraught with a multitude of systematic effects, (some from the instrumentation), any or all of which may (read this as usually does) affect the data. Murphy and his colleagues have an enormously steep hill to climb to convince other scientists that there is evidence that alpha is really changing.
What really happens inside astronomically realistic black holes? The give-away to this highly entertaining talk is the word “really” in the above question posed by Andrew Hamilton of JILA, Colorado. Not content with explanations of the dynamics inside and outside a black hole, Hamilton attempts to take the audience with him inside a black hole using big screen computer graphics. Hamilton ingeniously takes computer graphics one step further by using them, not only for their entertainment value, but also as an educational tool.
Supermassive black holes are thought to lie at the heart of every galaxy. Andrew King (Leicester) leads a group, which have been investigating black hole accretion. King’s talk on supermassive black holes explained the work of his group on the process of accretion of matter onto black hole disks and the resulting energy production, often producing powerful jets.
Even the most distant quasars are thought to have supermassive black holes present within them. An implied link between the formation of black holes and their host galaxies has spurred Martin Rees and his group at IOA, Cambridge to investigate the possibility that supermassive black holes evolve as mergers of small black holes. Martin Haehnelt, on behalf of the group, gave an overview of the various ways in which supermassive black holes might form. In particular, from evidence of reheating from the cosmic microwave background radiation, Haehnelt postulated that this might correspond to an era when small black holes were common, and that resulting mergers between small black holes could result in supermassive black hole formation.
The next group of talks covered the likely make up and nature of dark matter and dark energy, which are thought now to make up respectively 25% and 70% of the energy/mass in the Universe (the other 5% being normal baryonic matter). In a survey talk, Bernard Carr (Queen Mary, London) gave a forensic overview of all the different possibilities, probabilities (and plenty of improbabilities) for the make up of dark matter. So far there are no definite conclusions, other than the fact that no single explanation is sufficient, implying that there has to be at least two different candidates involved and possibly more.
On the dark energy front, George Efstathiou (Cambridge) gave an overview of the current situation. Even though Dark Energy is the main constituent of the Universe (at around 70%), there is still a lot of uncertainty surrounding its nature. The most popular explanation for it is the “cosmological constant” term in Einstein’s equations, but there are other possibilities. Many of these are quite fun, and even though they involve a lot of “hand-waving”, there is a lot of serious physics going on.
A subject close to this reviewer’s heart is gravitational lensing and the talk given by Peter Schneider (Bonn University, Germany) reviewed the work in this field. The beauty of gravitational lensing is that distorted images of background sources give information on the lensing objects, even though the latter may themselves be invisible.
The final talk in this group was from Paul Steinhardt (Princeton) who proposed a cyclic model of the Universe. There is a long history of cyclic models, and in Steinhardt’s model the big bang is seen as a transition point from an earlier phase of evolution and does not represent the “beginning of time”. In this model our present Universe is seen as one part of a continuous cycle. The structure and evolution of the Universe is thus grounded in events and evolution before the big bang, i.e. in another part of the cycle.
Apart from acquainting scientists from different areas of Physics with current thinking in Astrophysics and other areas of Physics, the range and diversity of talks at the Einstein Conference is testament to both how much and how little we know about the physical world.