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119
Reaching for the Stars
free Einstein equations as a viable alternative to general
relativity, selected by the journal
Classical and Quantum
Gravity
as oneof the ‘Highlights of the 2011–2012 collection’.
In addition, Professor Ellis contributed another highlight to
this collection with his 2012 work ‘Inhomogeneity effects in
cosmology’. The group is renowned not just for challenging
the standard paradigms of modern cosmology but also for
offering viable alternatives. In particular, the Chameleon
particle, a compelling and testable DE candidate that can
be observed not only through its effects on the largest
scales but also in purpose-built laboratory experiments,
was pioneered by UCT’s Dr Weltman. Research in this area
has driven a new industry in DE testing with significant
investment internationally. A flurry of experiments has
ensued in the USA and Europe to test this theory, with Dr
Weltman playing a key role in the GammeV and GammeV
CHASE experiments at Fermilab, a US Department of
Energy national laboratory specialising in high-energy
particle physics.
Within the ACGC, the Cosmology and Gravity Group,
hosted in the Department of Mathematics and Applied
Mathematics, focuses on both observational aspects of
cosmology and theoretical cosmology. The Cosmology
and Gravity Group is renowned for challenging the
standard paradigm and proposing tests to the standard
concordance model of cosmology. This is particularly
pronounced in studies of the Dark Universe.
Everything we see and experience on all scales of
human experience makes up less than 5% of the total
matter in the universe. All of the substance making up
planets, stars and oceans is fractional compared to the
vast amount of the universe that is dark, quite literally
– not observed through the electromagnetic field. The
remaining 95% is split between Dark Matter (DM – 23%)
and Dark Energy (DE – 72%).
DM clusters and DE clusters can be inferred from
their effects on galaxy rotation curves as well as on
gravitational lensing. DE drives the universe to expand
ever faster with time – the observation of which earned
scientists in the field the Nobel Prize for Physics in
2011. Remarkably, there is no convincing explanation
of either the driving force behind DE or indeed
the coincidental timing. DE seems to dominate our
universe coincidentally around the era of humanity's
existence, when we are here to observe it as such.
Explaining these observations and indeed challenging
the status quo is all in a day’s work for UCT’s cosmologists.
Alternative explanations to this concordance model are
studied using a multipronged approach to test if our
application of Einstein's General Relativity Theory is
applicable on the scales considered by testing key
assumptions underlying all of present day cosmology.
UCT’s Dr Chris Clarkson, Emeritus Professor George
Ellis, Professor Charles Hellaby, Professor Peter Dunsby
and Dr Amanda Weltman all study different approaches
to this challenge.
Collaborations between members of the Cosmology and
Gravity Group (Professor Ellis) and the recently established
Laboratory for Quantum Gravity and Strings (QGaSLab) (Dr
Jeff Murugan) have resulted in a publication on the trace-
All of the substance making
up planets, stars and oceans is
fractional compared to the vast
amount of the universe that is
dark, quite literally – not observed
through the electromagnetic field.
Dr Amanda Weltman and Dr Albert van Jaarsveld,
CEO of the National Research Foundation