Time to overhaul Newton's Theory of Gravitation? (Forwarded)

ROYAL ASTRONOMICAL SOCIETY PRESS INFORMATION NOTE

Issued by RAS Press Officer:
Robert Massey
Tel: +44 (0)20 7734 4582
Mobile: +44 (0)794 124 8035
E-mail:
RAS Web site: http://www.ras.org.uk

CONTACT(s):

Joel Brownstein
Perimeter Institute for Theoretical Physics
31 Caroline Street North
Waterloo
Ontario N2L 2Y5
Canada
Tel: +1 (519) 569-7600 ext. 8084
Fax: +1 (519) 569-7611

Professor John Moffat
Department of Physics and Astronomy
University of Waterloo
Waterloo
Ontario N2L 3G1
Canada
Tel: +1 (519) 569-7600 ext. 6611
Fax: +1 (519) 569-7611

Date: 26 October 2007

Ref.: PN 07/44

Time to overhaul Newton's Theory of Gravitation?

For almost 75 years, astronomers have believed that the Universe has a large
amount of unseen or 'dark' matter, thought to make up about five-sixths of
the matter in the cosmos. With the conventional theory of gravitation, based
on Newton's ideas and refined by Einstein 92 years ago, dark matter helps to
explain the motion of galaxies, and clusters of galaxies, on the largest
scales.

Now two Canadian researchers at the Perimeter Institute for Theoretical
Physics suggest that the motion of galaxies in a distant cluster is more
easily explained by a Modified Gravity (MOG) theory than by the presence of
dark matter. Graduate student Joel Brownstein and his supervisor Professor
John Moffat of the University of Waterloo present their results in a paper
in the 21 November edition of Monthly Notices of the Royal Astronomical
Society.

The two scientists analysed images of the 'Bullet Cluster' of galaxies made
using the Hubble Space Telescope, Chandra X-ray and Spitzer infrared
observatories and the Magellan telescope in Chile. The Bullet Cluster
consists of two merging clusters of galaxies and lies at a distance of over
3 billion light years in the direction of the southern constellation of
Carina.

This arsenal of instrumentation gave them maps of the 150 million degree hot
gas between the galaxies and show the effect of gravitational lensing, where
the gravity of an intervening object -- here the Bullet Cluster -- deflects
the path of light emitted by a more distant galaxy.

Previous studies suggested that the Bullet Cluster clearly demonstrates the
presence of dark matter. But when Brownstein and Moffat compared the
observed gravitational lensing and distribution of gas with that predicted
using MOG theory, they found no evidence for this. In other words, it is
more natural to explain the appearance of this cluster using a revised
theory of gravitation than by including dark matter.

MOG theory emerges from a generalization of relativity that eluded even
Einstein. The theory has been developed by Moffat for nearly thirty years
and is now yielding astronomical and cosmological results. It has been used
to successfully explain the movement of stars in over 100 galaxies and the
motion of galaxies in more than 100 clusters. MOG theory may also explain
the apparent anomalous deceleration of the Pioneer 10 and 11 space probes,
launched in the early 1970s and now more than 12000 million km from the Sun.

The two physicists are enthusiastic about their findings. Brownstein
comments, "Using Modified Gravity (MOG) theory, the 'normal' matter in the
Bullet Cluster is enough to account for the observed gravitational lensing
effect. In time, better observations will lead to higher resolution pictures
of the systems we are studying. Continuing the search for and then analysing
other merging clusters of galaxies will help us decide whether dark matter
or MOG theory offers the best explanation for the large scale structure of
the Universe."

Professor Moffat adds, "If the multi-billion dollar laboratory experiments
now underway succeed in directly detecting dark matter, then I will be happy
to see Einsteinian and Newtonian gravity retained. However, if dark matter
is not detected and we have to conclude that it does not exist, then
Einstein and Newtonian gravity must be modified to fit the extensive amount
of astronomical and cosmological data, such as the bullet cluster, that
cannot otherwise be explained."

NOTES FOR EDITORS

Brownstein and Moffat's full paper will be 'online early' prior to
publication in Monthly Notices and can be viewed at
http://www.blackwell-synergy.com/loi/MNR from Friday 26 October.

The Royal Astronomical Society (RAS), founded in 1820, encourages and
promotes the study of astronomy, solar-system science, geophysics and
closely related branches of science. The RAS organizes scientific meetings
in Burlington House, its London HQ, and throughout the country, publishes
international research and review journals, recognizes outstanding
achievements by the award of medals and prizes, maintains an extensive
library, supports education through grants and outreach activities and
represents UK astronomy nationally and internationally. Its more than 3000
members (Fellows) include scientific researchers in universities,
observatories and laboratories as well as historians of astronomy and
others.

IMAGES:

Images can be found at:

http://www.perimeterinstitute.ca/per...ion/index.html