So You Think You Can Solve a Cosmology Puzzle?

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Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
Whitney.clavin@jpl.nasa.gov

Feature: 2010-407 Dec. 6, 2010

So You Think You Can Solve a Cosmology Puzzle?
Scientists challenge other scientists with a series of galaxy puzzles

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2010-407&cid=release_2010-407

Cosmologists have come up with a new way to solve their problems. They are inviting
scientists, including those from totally unrelated fields, to participate in a grand
competition. The idea is to spur outside interest in one of cosmology's trickiest problems -
- measuring the invisible dark matter and dark energy that permeate our universe.

The results will help in the development of new space missions, designed to answer
fundamental questions about the history and fate of our universe.

"We're hoping to get more computer scientists interested in our work," said cosmologist
Jason Rhodes of NASA's Jet Propulsion Laboratory in Pasadena, Calif., who is helping to
organize the challenge, which begins on Dec. 3, 2010. "Some of the mathematical
problems in our field are the same as those in machine-learning applications -- for example
facial-recognition software."

JPL and several European Universities, including The University of Edinburgh and
University College London in the United Kingdom, are helping to support the event,
which is funded by a European Union group called Pattern Analysis, Statistical
Modelling and Computation Learning. The principal investigator is Thomas Kitching of
the University of Edinburgh.

This year, the competition, which has operated since 2008, is called GREAT 2010, after
GRavitational lEnsing Accuracy Testing. The challenge is to solve a series of puzzles
involving distorted images of galaxies. Occasionally in nature, a galaxy is situated behind
a clump of matter that is causing the light from the galaxy to bend. The result is a
magnified and skewed image of the galaxy. In the most extreme cases, the warping
results in multiple images and even a perfect ring, called an Einstein Ring after Albert
Einstein, who predicted the effect. But most of the time, the results are more subtle and a
galaxy image is distorted just a tiny bit -- not even enough to be perceived by eye. This is
called weak gravitational lensing, or just weak lensing for short.

Weak lensing is a powerful tool for unlocking the fabric of our universe. Only four
percent of our universe consists of the stuff that makes up people, stars and anything with
atoms. Twenty-four percent is dark matter -- a mysterious substance that we can't see but
which tugs on the regular matter we can see. Most of our universe, 72 percent, consists of
dark energy, which is even more baffling than dark matter. Dark energy is gravity's
nemesis -- where gravity pulls, dark energy pushes. By studying lensed, or distorted,
galaxies, scientists can create better maps of dark matter -- and by studying how dark
matter changes over time, they can better understand dark energy.

Weak lensing is a promising method for tackling these questions. The 2010 U.S. National
Research Council Decadal Survey on astronomy and astrophysics has ranked mission
proposals using this method as high priorities.

The GREAT 2010 challenge is designed to improve weak-lensing know-how. Participants
will start with fuzzy pictures of galaxies that have been distorted ever so slightly by
invisible dark matter parked in front of them. The effect is so small that you can't see it
with your eyes. The problem is even trickier because the telescopes are also distorting the
galaxy images to an even greater degree than the dark matter. It takes complex techniques
-- mathematical models and image-analysis algorithms -- to tease apart these various
influences and ultimately discover how dark matter is warping a galaxy's shape.

"This is an image-analysis challenge. You don't need to be an astronomer or cosmologist
to help measure the weak-lensing effect," said Kitching. "This challenge is meant to
encourage a multidisciplinary approach to the problem."

Participants will have nine months to solve a series of thousands of puzzles. The winners
will be announced at a closing ceremony and workshop held at JPL. Prize-winners can
expect some kind of cool gadget -- as well as the satisfaction of having brought the world
one step closer to understanding what makes our universe tick.

To participate in the venture, in-depth technical information is available online at:
http://www.greatchallenges.info .

JPL is managed by the California Institute of Technology in Pasadena, for NASA.

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