MARCH 2, 2001


Contact: Cheryl Gundy, Space Telescope Science Institute (STScI)
(Phone: 410-338-4707, e-mail:

Dark Universe Symposium and Science Writer's Briefing at STScI

In recent years astronomers have been forced to confront a cosmic mystery nearly as clueless as the pitch-black monolith in the film "2001: A Space Odyssey."

Collectively it can be called the "dark universe" - one nearly as foreboding as the "dark force" invoked by Darth Vader in "Star Wars." The dark universe contains an invisible form of matter that accounts for most of the physical content of space. But that's not all -- there is also a pervasive repulsive force that emerged from the shadows a few billion years ago to nearly burst the expanding universe apart at the seams. Einstein called such a force his "greatest blunder," now it seems to be a mind-numbing reality.

Dark matter and dark energy have the potential to undo the very bedrock of our understanding of basic physics, the fabric of space and time, the notion of gravity, the history of the universe. Solving its mystery may ultimately lead to realization of parallel universes and the solution to our universe's ultimate destiny.

The field's top astronomers and physicists will meet at the Space Telescope Science Institute (STScI) in Baltimore, MD in a quest to better understand this "unseen" force and determine its abundance and distribution within our universe during the The Dark Universe: Matter, Energy, and Gravity symposium on April 2-5, 2001.

Additional information and the agenda for the Dark Universe symposium are available at

Concurrent with the Dark Universe symposium, STScI's Office of Public Outreach will host a briefing for science writers on Tuesday, April 3 from 12:30 p.m. to 2:00 p.m. in the Lyman Spitzer Boardroom (STScI 4th floor, room 401A).

Lunch will be available in the STScI Cafeteria prior to 12:30 p.m. at cost.

All media representatives interested in attending the Symposium and/or the Science Writer's Briefing should contact
Cheryl Gundy by e-mail at "", by telephone at
410-338-4707, or by fax at 410-338-4579.

Media registration is free. The deadline for registration is
Thursday, March 29, 2001.

The invited speakers and topics for the science writers briefing are:

Dr. Megan Donahue (Space Telescope Science Institute)
"Hot Gas in Clusters" -- Hot gas has been detected in many clusters of galaxies. From the temperature of this gas, the mass in the cluster can be determined, and from that, the density of matter in the universe can be estimated. Somewhat paradoxically, if clusters in the past were very massive, this indicates a low cosmic density of matter. Donahue will explain why, and the implications for cosmological parameters.

Dr. J. Anthony Tyson (Bell Labs, Lucent Technology)
"Gravitational Lensing" -- The image distortion and time delay of light from distant objects, caused by foreground gravitational lensing, offers a purely physics-based technique for studying the distant universe. Measurements of redshifts, angles, and arrival times of intensity fluctuations can probe the rate of expansion of the universe, the acceleration of the expansion, and the total amount of matter in the universe.

Dr. Adam Riess (Space Telescope Science Institute)
"Cosmological Parameters from SNe 1a" -- Recent observations of distant Type Ia supernova explosions appear to show that the expansion of the universe is accelerating. However, In the more distant past, before the Cosmological Constant ('Dark Energy') started to dominate, it is expected that the cosmic expansion was decelerating due to gravity. Observations of the most distant supernova observed yet will be used to test this hypothesis.

Dr. Paul Steinhardt (Princeton University)
"Quintessence" -- An invisible energy field is causing the cosmic expansion to accelerate. This dark energy appears to constitute some 70% of the energy density of the universe, and it could consist either of something like Einstein's Cosmological Constant, or of a quantum field known as quintessence. Quintessence forces the expansion to accelerate somewhat less rapidly than the cosmological constant, and it may explain why the dark energy started to dominate in the recent history.

Dr. Gia Dvali (New York University)
"Theories of Gravity" -- The apparent existence of various forms of 'dark matter' and 'dark energy' may simply mean that we misunderstand gravity. Our universe could lie on a membrane floating within a higher-dimensional space. These extra dimensions could help unify the basic forces of nature and could contain other universes.

Dr. Mario Livio (Space Telescope Science Institute)
Conference Summary: An Astrophysicist's Perspective" -- So, how can all of this be put together? Is it true that 30% of the matter in our universe is in the form of exotic particles which dominate galaxies? Is it true that almost 70% of the energy density in the cosmos is in some form of 'dark energy' which causes the expansion to accelerate? or are we being fooled? Can one rank all the existing theories in terms of their probability of being correct, and in terms of their internal 'beauty"?