Open Questions: Dark Energy
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See also: The cosmological constant --
The vacuum --
Dark matter
Site indexes
Sites with general resources
-
Supernova/Acceleration Probe
- Home page of proposed satellite mission to measure supernova
distances very precisely in order to determine rate of acceleration
of expansion of the universe. This would involve a more precise
determination of the cosmological constant and matter density
of the universe.
-
Resource Book on Dark Energy
- A directory of survey papers on dark energy, focused on
the nature of dark energy and the study of it by means of
supernova observations. Includes
other references.
Maintained by
Eric V. Linder.
-
SuperNova Legacy Survey
- Home page of research group producing better measurements of
the universe's expansion. "The Canada-France-Hawaii Telescope Legacy
Survey Supernova Program aims primarily at measuring the equation
of state of Dark Energy. It is designed to precisely measure
several hundred high-redshift supernovae."
Important results were announced November 22, 2005.
-
HETDEX - The Hobby-Eberly Telescope Dark Energy Experiment
- A research project to investigate dark energy using a
ground-based telescope to map the expansion of the universe.
"HETDEX is a project designed to understand the evolutionary
history of dark energy. ... The goal is to use results from
HETDEX to precisely describe how the Universe expands, thereby
illuminating the nature of dark energy."
-
Evidence for Cosmic Acceleration from Supernovae
- Slide presentation by Robert Kirshner at the
2001: A Spacetime Odyssey conference.
-
The Runaway Universe
- Companion Web site to the November 2000 PBS documentary.
-
High Redshift Supernova Search
- Home page of the Berkeley Supernova Cosmology Project.
-
The High-Z SN Search
- Home page of Harvard-based research group searching for high red-shift
(very distant) supernovae in order to determine rate of expansion of
the universe.
Surveys, overviews, tutorials
-
Accelerating universe
- Article from
Wikipedia.
See also
Dark energy,
Quintessence.
-
Dark Energy
- Excellent single-page overview of dark energy by
Adam Riess, leader of the
High-z team, which discovered evidence that the expansion
of the universe was accelerating.
-
Dark Energy and the Preposterous Universe
- A brief overview of the place in cosmology of dark energy
and the cosmological constant, by
Sean M. Carroll.
A shorter and more elementary page on this topic by Carroll is
here. A more detailed exposition with some mathematics is
here.
A list of many other reviews and talks by Carroll on related topics in
general relativity and cosmology is
here.
-
What Is Dark Energy?
- April 2009 Space.com article giving a brief overview of the
topic.
-
The Cosmological Constant
- 2000 review paper on the physics and cosmology of the
cosmological constant, by
Sean M. Carroll.
-
What Is Dark Energy?
- Very brief page about NASA's plans to investigate dark
energy as part of the
Beyond Einstein program.
-
3D map of Universe bolsters case for dark energy and dark
matter
- A page at
Max Tegmark's site describing observations of galaxy distributions
reported in October 2003 which confirm the existence of dark
energy making up 70% of the universe. It is based on results
obtained from the
Sloan Digital Sky Survey.
-
Dark questions remain over dark energy
- December 2009 article about whether the discovery of different
kinds of type1a supernovae may affect conclusions about the
existence of dark energy.
-
The hunt for dark energy
- Brief April 2009 article on dark energy research.
-
Dark energy may disguise shape of universe
- August 2009 New Scientist article.
"As we learn more about dark energy and its effect on the
expansion of space and time, we find that dark energy and
the shape, or geometry, of the universe are worryingly intertwined."
-
Dark energy: the decade ahead
- December 2007 article from
Physics World, by
Eric Linder and Saul Perlmutter.
"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 the authors describe, advances in observational
techniques promise to shed light on this revolutionary physics
in the decade ahead."
-
A dark future for cosmology
- December 2007 article from
Physics World, by
Lawrence Krauss.
"Even with the many observations planned over the next
decade, there is a real chance that we will never understand
the true nature of dark energy."
-
Dark Energy
- December 2007 article from
Physics World, by
Robert Crease.
"The competition between the two teams of scientists that
discovered that the expansion of the universe is accelerating
reveals how hard it can be to assign scientific credit -
particularly when a Nobel prize may one day be at stake."
-
Dark energy
- May 2004 article from
Physics World, by
Robert R. Caldwell. "New evidence has confirmed that the expansion
of the universe is accelerating under the influence of a
gravitationally repulsive form of energy that makes up two-thirds
of the cosmos."
-
Quintessence
- November 2000 article from
Physics World, by
Robert R. Caldwell and Paul J. Steinhardt.
"Cosmologists have proposed that a mysterious substance called
quintessence can explain why our universe is accelerating. But what is
it made of?"
Roughly 70% of the value of Omega requied for a flat universe
may consist of some sort of "dark energy". It may be energy related
to the cosmological constant, or some other form of energy that
has been named "quintessence".
Article has good links to other resources.
-
String theorist explores dark energy and our unique 'pocket'
of the universe
- February 2005 press release describing a talk by
Leonard Susskind on dark energy, string theory, and
"pocket universes".
-
Dark Energy: Astronomers Still 'Clueless' About Mystery Force
Pushing Galaxies Apart
- January 2002
article from Space.com.
Presents general overview of the concept of dark energy and
observations that suggest its existence.
-
Dark Energy Lecture
- A presentation by Michael Turner, in PDF format, from
an October 2001
conference
on cosmology.
-
Dark Energy in the Accelerating Universe
- A "brochure" describing the basic facts and theories about
dark energy and the rate of expansion of the universe. Good
explanations, marred by not so good site design.
-
Dark Energy and Particle Astrophysics
- June 2001 lecture by Eric Linder, in PDF format.
-
Dark Energy
- Basic information on dark energy. Part of NASA's
Imagine the
Universe site.
-
More evidence for the accelerating universe
- September 1999 news article from
PhysicsWeb
about improved evidence for accelerating expansion of the universe.
-
Evidence mounts that the expansion of the Universe is
accelerating
- November 1998 news article from
PhysicsWeb
about supernova evidence that the expansion of the universe
is accelerating.
-
The Next Frontier for Cosmologists: Dark Energy
- May 2001 press release from Dartmouth College, providing a
brief explanation of dark energy, by Robert Caldwell.
-
Starry data support revved-up cosmos
- March 2001 news article in Science News about new
supernova data that further support the hypothesis of dark energy.
-
Dark Matter and Dark Energy in the Universe
- 1998 technical/expository paper by Michael S. Turner.
-
Why Now?
- November 20, 2000 Physical Review Focus article, about
the coincidently similar magnitudes of the densities of
matter, "dark energy", and ordinary energy in the universe.
-
Turning On the Universe
- An article about quintessence from the Physical Review Focus
(February 24, 2000).
-
Dark Forces at Work
- April 2008 Scientific American article by David Appell.
"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."
-
Discovering a Dark Universe: A Q&A with Saul Perlmutter
- April 2008 Scientific American article.
"Dark energy is pushing the universe apart at an ever faster
rate. Astrophysicist Saul Perlmutter recounts the experimental
approaches he took to make that discovery."
-
Boom or Bust
- October 1999 Scientific American Science and the Citizen
article, subtitled "New doubts about whether the universe's
expansion is accelerating." (The doubts have since appeared to be
unfounded.)
-
A Hundred Billion Years of Solitude
- April 1999 Scientific American Science and the Citizen
article, subtitled "Evidence for an accelerating universe continues
to pile up."
-
Dark Energy Fills the Cosmos
- June 1999 article by Paul Preuss in the LBL
Science Beat.
-
Does Dark Energy Really Exist?
Timothy Clifton; Pedro G. Ferreira
Scientific American, April 2009
-
-
The Universe's Invisible Hand
Christopher J. Conselice
Scientific American, February 2007
-
- Too Cold for Comfort
George Musser
Scientific American, May 2005
-
- A Cosmic Conumdrum
Lawrence M. Krauss; Michael S. Turner
Scientific American, September 2004
-
The Expanding Universe: From Slowdown to Speedup
Adam G. Reiss; Michael S. Turner
Scientific American, February 2004
- Distant supernovae are revealing the crucial time when
the expansion of the universe changed from decelerating to
accelerating.
- Will Dark Energy Steal All the Stars?
Steve Nadis
Astronomy, March 2003, pp. 42-47
- Dark energy now appears to be a result of
a positive cosmological constant producing "vacuum energy" making
up about 70% of the mass-energy in the universe. This produces
an expansion of the universe at an accelerating rate. If this
hypothesis is correct, about
100 billion years from now no part of the universe other than
stars in our local group of galaxies will be visible.
- Moving Right Along
Mario Livio
Astronomy, July 2002, pp. 34-39
- Measurements of both the brightness of distant type Ia supernovae
and temperature fluctuations in the cosmic microwave background
point to a universe that is composed of about 65% "dark energy".
There is, however, no theory that explains this value.
-
A Dark Force in the Universe
Ron Cowen
Science News, April 7, 2001, pp. 218-220
- The accelerating expansion of the universe detected in 1998
has stimulated several theories of "dark energy" or "quintessence".
Usually associated with the cosmological constant and the energy
of the vacuum, the density of this energy may have changed over
the life of the universe.
- Very Dark Energy
Karen Wright
Discover, March 2001, pp. 70-76
- Various recent observations indicate that the universe is both
flat and also expanding at an accelerating rate. Some sort of
"dark energy" distributed in empty space seems required to account
for this.
- The Quintessential Universe
Jeremiah P. Ostriker; Paul J. Steinhardt
Scientific American, January 2001, pp. 46-53
- It now appears that dark matter of any kind can account for
only about 30% of the "stuff" in the universe which determines its
course of expansion. The remaining 70% is "dark energy", which
could represent either a non-zero cosmological constant
(vacuum energy) or some other type of energy now referred
to as "quintessence".
- More Than Meets the Eye
Michael S. Turner
The Sciences, November/December 2000, pp. 32-37
- Attempts to determine the amount of matter in the universe,
both visible and invisible, indicate that the total mass of such
matter is at most 35% of the amount required for a "flat"
universe. A non-zero cosmological constant, representing the
presence of quantum-vacuum energy, could make up the difference.
- Hubble Warrior
Sally Stephens
Astronomy, March 2000, pp. 52-59
- The story of measuring the Hubble constant and its relation to
the age of the universe is told through a sketch of the career of
astronomer Wendy Freedman.
-
Revved-Up Universe
Ron Cowen
Science News, February 12, 2000, pp. 106-108
- Evidence continues to accumulate that cosmic expansion is
accelerating, which would imply higher estimates for the age
of the universe. One line of evidence is observations of distant
supernovas, which seem to be dimmer (hence more distant) than
expected. Other evidence involves interpretation of density
fluctuations in the cosmic microwave background. This suggests
the geometry of the universe is flat, which implies additional
mass in the form that would explain accelerating expansion.
- White Dwarfs Confront the Universe
Ken Croswell
Astronomy, May 1996, pp. 42-47
- New, more powerful telescopes are making it possible to
identify white dwarf stars at increasingly large distances.
In particular, we can now detect white dwarfs in the galactic
halo, making it easier to determine the age of our galaxy
and establish lower limits on the age of the universe itself.
-
Is There Really a Cosmological Crisis?
Rick Shaffer
Skeptic, Vol. 3, No. 4, 1995, pp. 42-45
- If stars are older than the universe, there is a problem.
- David B. Cline, ed. -- Sources and Detection of Dark Matter and
Dark Energy in the Universe
Springer-Verlag, 2001
- Proceedings of a symposium held in Marina del Rey in 2000.
Although intended for specialists, most of it is understandable by
anyone who has mastered a college astronomy course.
This is a long volume with many papers, which reflects the
breadth of the subject area -- the greatest part of the
universe which is not directly observable (both dark matter and
dark energy). Additionally, both theoretical and observational
issues are covered. It's a good place to look and browse in order to
get one's arms around many of the principle open questions in
this mysterious topic.
- Peter Coles; Feorge F. R. Ellis - Is the Universe Open of Closed?
The Density of Matter in the Universe
Cambridge University Press, 1997
- This is a technical work with some mathematics that deals with
evaluating the different kinds of evidence which bear on the
question in the title. For readers patient enough to follow the
mathematics, it shows how most observations tend to the
conclusion that the density of matter is about 20% of the
critical density.
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Copyright © 2002 by Charles Daney, All Rights Reserved