Dark energy, even more mysterious than dark matter, is pushing the universe to expand more and more quickly. Science magazine's Breakthrough of the Year in 1998 by the Supernova Cosmology Project (SCP) and the High-Z SN Search teams leads to more questions than it answers. In particular, is dark energy a constant vacuum energy or something even more exotic that has changed or will change in the future? Measurements and characterizations of its properties are the focus of work of the SCP / High-Z search, and include research on baryon oscillations, weak lensing, and cluster searches such as South Pole Telescope and APEX.

 

 

Dark Energy Rules the Universe (and why the dinosaurs don't)

The revolutionary discovery that the expansion of the universe is speeding up, not slowing down from gravity, means that 75 percent of our universe consists of mysterious dark energy. Berkeley Lab physicist Eric Linder delves into the mystery of dark energy as part of the Science in the Theatre lecture series.

 

 

For Students: The Universe Adventure/Dark Energy

In the most basic sense, Dark Energy is akin to negative gravity. Where gravity is attractive, Dark Energy is repulsive. Dark Energy causes the Universe to expand at an increasing rate. For example, to a viewer on earth, gravity would attract a distant galaxy towards Earth, but Dark Energy would cause the galaxy to move away from the Earth. Similarly, neither force can be directly seen. We detect gravity by observing the effect between two masses. We detect Dark Energy by measuring the expansion of the universe through the comparison of standard candles.

 

 


Dark Energy's 10th Anniversary Part I, Announcing the Accelerating Universe

10th Anniversary Part II, Success Breeds Competition

Dark Energy's 10th Anniversary Part III, The Aftermath: Confirmation and Exploration
by Paul Preuss

Saul Perlmutter announced the Supernova Cosmology Project's evidence for a cosmological constant at the annual meeting of the American Astronomical Society in Washington, D.C., on January 8, 1998. On February 18 of that year, Gerson Goldhaber and Perlmutter discussed the SCP evidence at the UCLA conference on Dark Matter in Los Angeles, where Alexei Fillipenko announced similar results from the High-Z Supernova Search Team.

What they had observed was the accelerating expansion of the universe, presumably caused by Einstein's cosmological constant (lambda). Initially a purely mathematical term in the equations of General Relativity — which Einstein later dropped — theorists by the end of the 20th century had come to regard the cosmological constant as a manifestation of the vacuum energy described by quantum mechanics.

The proposed SuperNova/Acceleration Probe (SNAP) satellite (pictured) inspired DOE and NASA's Joint Dark Energy Mission. It will find and measure thousands of Type Ia supernovae and will measure the distribution of matter in the universe through weak gravitational lensing. Read more

 


September 15, 2008

BOSS: the Baryon Oscillation Spectroscopic Survey - A Unique Way to Measure Dark Energy With Galaxies and Quasars by Paul Preuss, LBNL

The Sloan Digital Sky Survey (SDSS) uses a 2.5-meter telescope with a wider field of view than any other large telescope, located on a mountaintop in New Mexico called Apache Point and devoted solely to mapping the universe. We now know that some three-quarters of the universe consists of dark energy, whose very existence was unsuspected when telescope construction began in 1994 and still controversial when the first Sloan survey started in 2000. Read more here.

 

 

Dark Forces at Work, April 2008  Ten years ago two teams discovered that the universe will expand forever at an ever faster rate, thanks to an unseen energy. The leader of one of the groups, Saul Perlmutter, expects that new observations will soon illuminate the universe's dark side. Read more by David Appell

 

Scientific American Q & A with Saul Perlmutter

_______________________________________________________________________________________

 


Dark, Perhaps Forever  - The universe is expanding at an ever-increasing rate.
By Dennis Overbye, June 2008

 

 



Dark energy: The Decade Ahead physicsworld.com

"Ten years after astrophysicists discovered that the expansion of the universe is accelerating, further measurements have given us few clues into the nature of the dark energy that drives it. But, as Eric Linder and Saul Perlmutter describe, advances in observational techniques promise to shed light on this revolutionary physics in the decade ahead." Read more from physicsworld.com here.

 

 

Saul Perlmutter's "Supernovae, Dark Energy, and the Accelerating Universe" examines the history of cosmic expansion. Physics Today, April 2003  PDF



On the Trail of Dark Energy One of the most remarkable discoveries of recent years is that the universe appears to be dominated by some form of "dark energy." Eric Linder, Cern Courier  PDF

 

Cosmic Sound Waves Rule In the microwave background and the distribution of galaxies, relic imprints of primordial sound waves have contributed to an extraordinarily detailed history of the cosmos. And they provide yardsticks for solving a great mystery. By Daniel Eisenstein and Charles Bennet PDF


 

 

Strung Out on the Universe: Scientific American interviews Raphael Bousso about dark energy and string theory

 

SDSS-11: The Baryon Oscillation Spectroscopic Survey (BOSS)

BOSS aims to measure baryon oscillations in the clustering of luminous red galaxies at redshifts <0.7, as well as make a first detection in the Lyman-alpha forest at a redshift of 2.5. Using baryon oscillations as a standard ruler, BOSS will measure the distance to z=0.3 and 0.6 to 1%, and to z=2.5 to 1.5%. These precision distance measurements will allow us to improve constraints on the nature of dark energy by a factor of 3. In addition, BOSS will be a scientifically rich data set, improving our knowledge in subjects as diverse as the evolution of massive galaxies, the nature of the intergalactic medium, and properties of quasars at high redshifts. Poster PDF

The SDSS 2.5 meter telescope at Apache Point, New Mexico was used to create the new map of the universe.


 


New Frontiers from Dark Energy

Beyond Einstein: What happens when gravity is no longer an attractive force?


Image: Scientific American

 

Discovery (SCP, High-Z 1998): 70% of the universe acts this way!



This represents fundamentally new physics - Cosmology is the key.

______________________________________________________________________________

 

The Nature of Acceleration

 

 

How much dark energy is there? energy density ΩΛ

How springy is it? equation of state w, w'

Does it clump on subhorizon scales? Couple to matter? Couple to gravity non-minimally?

 

___________________________________________________________________________________

 

BCCP associates researching dark energy: Saul Perlmutter, Martin White, David Schlegel, Nikhil Padmanabhan, George Smoot, Eric Linder, Joanne Cohn, Adrian Lee, and William Holzapfel.

Theoretical understandings of its presence are the target of investigations by Hitoshi Murayama and Raphael Bousso.

 

 

 
 

 

Back to top