Conference
Report
“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.
Nigel Sanitt