Interesting post in The Daily Galaxy
Sent: 9/3/2013 6:29:20 P.M. Eastern Daylight Time
Subj: The Daily Galaxy: News from Planet Earth & Beyond
_The Daily Galaxy: News from Planet Earth & Beyond_
_Extraterrestrial Link to Global Climate Shift 12,900 Years Ago
--Conclusive Evidence Discovered_
Posted: 03 Sep 2013 08:25 AM PDT
For the first time, researchers have discovered conclusive evidence
linking an extraterrestrial impact with a dramatic global climate shift. The
impact occurred about 12,900 years ago, at the beginning of the _Younger Dryas_
period, and marks an abrupt
global change to a colder, dryer climate with far-reaching effects on both
animals and humans. In North America, the big animals vanished, including
mastodons, camels, giant ground sloths and saber-toothed cats. Their human
hunters, known to archaeologists as the _Clovis people_
, set aside their heavy-duty spears and turned to a
hunter-gatherer subsistence diet of roots, berries and smaller game."The
Younger Dryas cooling impacted human history in a profound manner," says
Dartmouth Professor Mukul Sharma, a co-author of the study. "Environmental
stresses may also have caused Natufians in the Near East to settle down for
the first time and pursue agriculture."
It is not disputed that these powerful environmental changes occurred, but
there has long been controversy over their cause. The classic view of the
Younger Dryas cooling interlude has been that an ice dam in the North
American ice sheet ruptured, releasing a massive quantity of freshwater into the
Atlantic Ocean. The sudden influx is thought to have shut down the ocean
currents that move tropical water northward, resulting in the cold, dry
climate of the Younger Dryas.
The report focuses on spherules, or droplets of solidified molten rock
expelled by the impact of a comet or meteor. The spherules in question were
recovered from Younger Dryas boundary layers at sites in Pennsylvania and New
Jersey, the layers having been deposited at the beginning of the period.
The geochemistry and mineralogy profiles of the spherules are identical to
rock found in southern Quebec, where Sharma and his colleagues argue the
impact took place.
"We have for the first time narrowed down the region where a Younger Dryas
impact did take place," says Sharma, "even though we have not yet found
its crater." There is a known impact crater in Quebec — the 4-kilometer wide
Corossal crater -- but based on the team's mineralogical and geochemical
studies, it is not the impact source for the material found in Pennsylvania
and New Jersey.
People have written about many impacts in different parts of the world
based on the presence of spherules. "It may well have taken multiple
concurrent impacts to bring about the extensive environmental changes of the Younger
Dryas," says Sharma. "However, to date no _impact craters_
have been found and our research will help
track one of them down."
The findings appear next week in the online Early Edition of the
_Proceedings of the National Academy of Sciences_ (http://www.pnas.org/)
The Daily Galaxy via http://www.dartmouth.edu/~opa/radio-tv-studios/
Image credit: With thanks to
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_New 'Dark Energy' Mission --The World's Most Powerful Camera to Explore
Unsolved Mysteries of the Universe_
Posted: 03 Sep 2013 07:49 AM PDT
Tonight, and for hundreds of nights over the next five years, a team of
physicists and astronomers from around the globe will use the world's most
powerful digital camera to try to find out why the expansion of the universe
is speeding up, instead of slowing down due to gravity, and to probe the
mystery of dark energy, the force believed to be causing that acceleration.
The survey will obtain color images of 300 million galaxies and 100,000
galaxy clusters and will discover 4,000 new supernovae, many of which were
formed when the universe was half its current size. “We’re looking at this big
galaxy map of the universe as a way of finding evidence for dark energy
and characterizing its nature with cosmic epoch,” said _Ofer Lahav_
of _University College London_
-0.133577777778 (University%20College%20London)&t=h) and head of the DES
Science Committee. “An even more challenging goal for DES is to tell if
what causes the acceleration of the universe is indeed dark energy, or
something entirely different."
On Aug. 31, the Dark Energy Survey (DES) officially began. Scientists on
the survey team will systematically map one-eighth of the sky (5000 square
degrees) in unprecedented detail. The start of the survey is the culmination
of 10 years of planning, building and testing by scientists from 25
institutions in six countries.
“The Dark Energy Survey will explore some of the most important questions
about our existence,” said James Siegrist, associate director for High
Energy Physics at the U.S. Department of Energy’s Office of Science. “In five
years’ time, we will be far closer to the answers, and far richer in our
knowledge of the universe.”
“With the start of the survey, the work of more than 200 collaborators is
coming to fruition,” said DES Director Josh Frieman of the U.S. Department
of Energy’s Fermi National Accelerator Laboratory. “It’s an exciting time
in cosmology, when we can use observations of the distant universe to tell
us about the fundamental nature of matter, energy, space and time."
The main tool of the survey is the _Dark Energy Camera_
, a 570-megapixel digital camera built at Fermilab in
Batavia, Ill., and mounted on the 4-meter Victor M. Blanco telescope at the
National Science Foundation’s Cerro Tololo Inter-American Observatory in the
Andes Mountains in Chile. The camera includes five precisely shaped lenses,
the largest nearly a yard across, that together provide sharp images over
its entire field of view.
The Dark Energy Camera is the most powerful survey instrument of its kind,
able to see light from more than 100,000 galaxies up to 8 billion
light-years away in each snapshot.
“The start of the Dark Energy Survey is an important milestone,” said
CTIO Director Nicole van der Bliek. “The Dark Energy Camera, in conjunction
with the Blanco telescope here at CTIO, will greatly increase our
understanding of the forces that control the expansion of our universe.”
The data collected will be processed at the National Center for
Supercomputing Applications (NCSA) at the University of Illinois in Urbana, and then
delivered to collaboration scientists and the public.
“NCSA is pleased to be producing and distributing the refined data
products that will enable this science,” said Don Petravick, principal
investigator of the DES Data Management Operation.
The survey’s observations will not be able to see dark energy directly.
However, by studying the expansion of the universe and the growth of
large-scale structure over time, the survey will give scientists the most precise
measurements to date of the properties of dark energy.
Counting galaxy clusters. While gravity pulls mass together to form
galaxies, dark energy pulls it apart. The Dark Energy Camera will see light from
100,000 galaxy clusters billions of light-years away. Counting the number
of galaxy clusters at different points in time sheds light on this cosmic
competition between gravity and dark energy.
Measuring supernovae. A supernova is a star that explodes and becomes as
bright as an entire galaxy of billions of stars. By measuring how bright
they appear on Earth, we can tell how far away they are. Scientists can use
this information to determine how fast the universe has been expanding since
the star’s explosion. The survey will discover 4000 of these supernovae,
which exploded billions of years ago in galaxies billions of light-years
Studying the bending of light. When light from distant galaxies encounters
dark matter in space, it bends around the matter, causing those galaxies
to appear distorted in telescope images. The survey will measure the shapes
of 200 million galaxies, revealing the cosmic tug of war between gravity
and dark energy in shaping the lumps of dark matter throughout space.
Using sound waves to create a large-scale map of expansion over time. When
the universe was less than 400,000 years old, the interplay between matter
and light set off a series of sound waves traveling at nearly two-thirds
the speed of light. Those waves left an imprint on how galaxies are
distributed throughout the universe. The survey will measure the positions in space
of 300 million galaxies to find this imprint and use it to infer the
history of cosmic expansion.
The Dark Energy Survey is supported by funding from the U.S. Department of
Energy Office of Science; the National Science Foundation; funding
agencies in the United Kingdom, Spain, Brazil, Germany and Switzerland; and the
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