Multiple comet impacts around 1500 years ago triggered a "dry fog" that plunged half the world into famine.
Historical records tell us that from the beginning of March 536 AD, a fog of dust blanketed the atmosphere for 18 months. During this time, "the sun gave no more light than the moon", global temperatures plummeted and crops failed, says Dallas Abbott of Columbia University's Lamont-Doherty Earth Observatory in New York. The cause has long been unknown, but theories have included a vast volcanic eruption or an impact from space.
Science & Technology
© Michael Jaeger
Comet Lulin was still only about 11th or 12th magnitude when Michael Jaeger took this image on Sept. 2, 2008. He used an 8-inch f/2.8 ASA Astrograph with a SXV H9 CCD camera for this stacked pair of 4-minute exposures. Click image for wider view.
Comet Lulin was still only about 11th or 12th magnitude when Michael Jaeger took this image on Sept. 2, 2008. He used an 8-inch f/2.8 ASA Astrograph with a SXV H9 CCD camera for this stacked pair of 4-minute exposures. Click image for wider view.
© Victoria Feistner
A progression of squeezed triphoton states spiraling outwards. The quantum uncertainty in the triphotons can be represented as a blob on a sphere that becomes progressively "squeezed".
A progression of squeezed triphoton states spiraling outwards. The quantum uncertainty in the triphotons can be represented as a blob on a sphere that becomes progressively "squeezed".
A team of University of Toronto physicists have demonstrated a new technique to squeeze light to the fundamental quantum limit, a finding that has potential applications for high-precision measurement, next-generation atomic clocks, novel quantum computing and our most fundamental understanding of the universe.
Krister Shalm, Rob Adamson and Aephraim Steinberg of U of T´s Department of Physics and Centre for Quantum Information and Quantum Control, publish their findings in the January 1 issue of the international journal Nature.
"Precise measurement lies at the heart of all experimental science: the more accurately we can measure something the more information we can obtain. In the quantum world, where things get ever-smaller, accuracy of measurement becomes more and more elusive," explains PhD graduate student Krister Shalm.
Light is one of the most precise measuring tools in physics and has been used to probe fundamental questions in science ranging from special relativity to questions concerning quantum gravity. But light has its limits in the world of modern quantum technology.
© NRAO/AUI/NSF, SDSS
Gas in Distant Galaxy. VLA image (right) of gas in young galaxy seen as it was when the Universe was only 870 million years old.
Gas in Distant Galaxy. VLA image (right) of gas in young galaxy seen as it was when the Universe was only 870 million years old.
Astronomers may have solved a cosmic chicken-and-egg problem -- the question of which formed first in the early Universe -- galaxies or the supermassive black holes seen at their cores.
"It looks like the black holes came first. The evidence is piling up," said Chris Carilli, of the National Radio Astronomy Observatory (NRAO). Carilli outlined the conclusions from recent research done by an international team studying conditions in the first billion years of the Universe's history in a lecture presented to the American Astronomical Society's meeting in Long Beach, California.
Earlier studies of galaxies and their central black holes in the nearby Universe revealed an intriguing linkage between the masses of the black holes and of the central "bulges" of stars and gas in the galaxies. The ratio of the black hole and the bulge mass is nearly the same for a wide range of galactic sizes and ages. For central black holes from a few million to many billions of times the mass of our Sun, the black hole's mass is about one one-thousandth of the mass of the surrounding galactic bulge.
There's an article on NewScientist.com that might seem astounding. It basically states that laser-based, desktop-sized "atom smashers" could be as effective or more at probing the secrets of the universe as the $9 billion Large Hadron Collider (LHC) in Switzerland, but for a tiny fraction of the cost.
The LHC is a 27 kilometer underground tunnel comprised of over $2 billion worth of equipment (some of which took 20 years of development to produce) to accelerate particles from 450 GeV to 7000 GeV. It is currently broken and will not be up and running until this coming Spring at the earliest. Moving from 450 GeV to 7000 GeV equates to a journey 17 million times around the circle (450 million kilometers) before finally reaching impact speeds.
This large size was due to the limits of the accelerating vehicle, in this case enormously powerful magnets. The idea has come to scientists, however, that it doesn't have to be big to be powerful or fast.
The LHC is a 27 kilometer underground tunnel comprised of over $2 billion worth of equipment (some of which took 20 years of development to produce) to accelerate particles from 450 GeV to 7000 GeV. It is currently broken and will not be up and running until this coming Spring at the earliest. Moving from 450 GeV to 7000 GeV equates to a journey 17 million times around the circle (450 million kilometers) before finally reaching impact speeds.
This large size was due to the limits of the accelerating vehicle, in this case enormously powerful magnets. The idea has come to scientists, however, that it doesn't have to be big to be powerful or fast.
While conducting a routine search for distant supernovae, astronomers observed a bright burst of light that they can't account for. On Feb. 21, 2006, the Hubble Space Telescope first imaged the source of light, which continued to brighten over the next 100 days, peaked, and then finally faded to oblivion over another 100 days.
The time scale of brightening, as well as the particular characteristics of the colors of light seen, do not match any known astronomical phenomena.
"So far it's unlike anything previously observed," said Lawrence Berkeley National Laboratory astronomer Kyle Barbary during a press briefing Tuesday at the American Astronomical Society meeting in Long Beach, California.
Scientists have discovered only the second example of a meteorite impact that occurred at the same time as massive volcanic activity, in research published in the Journal of the Geological Society the week of Jan 12. The first time such a coincidence was observed, at the Cretaceous-Tertiary boundary, was the catastrophic event thought to be responsible for the extinction of the dinosaurs, 65 million years ago.
This new event, uncovered after the 17 km diameter Logoisk impact structure in Belarus was precisely dated, is thought to have taken place around 30 million years ago. The crater was dated using argon isotopes, and found to have occurred at a similar time to a period of massive volcanism known as the Afro-Arabian flood volcanism, which started in NW Yemen at around 30.9 Mya, and SW Yemen at around 29.0 Mya.
The impact also coincides broadly with a period of sudden global cooling and sea level fluctuation. The researchers, led by Sarah Sherlock at the Open University, argue that massive volcanic eruptions and meteorite impacts are likely to have coincided much more frequently than has previously been thought, but because the preservation of impact craters on Earth is poor much of the evidence for these coincidences is lost.
This new event, uncovered after the 17 km diameter Logoisk impact structure in Belarus was precisely dated, is thought to have taken place around 30 million years ago. The crater was dated using argon isotopes, and found to have occurred at a similar time to a period of massive volcanism known as the Afro-Arabian flood volcanism, which started in NW Yemen at around 30.9 Mya, and SW Yemen at around 29.0 Mya.
The impact also coincides broadly with a period of sudden global cooling and sea level fluctuation. The researchers, led by Sarah Sherlock at the Open University, argue that massive volcanic eruptions and meteorite impacts are likely to have coincided much more frequently than has previously been thought, but because the preservation of impact craters on Earth is poor much of the evidence for these coincidences is lost.
© Johns Hopkins Medical Institutions
Launching some 500 pounds of reptilian heft into flight required pterosaurs to use four limbs: two were ultra-strong wings which, when folded and balanced on a knuckle, served as front “legs” that helped the creature to walk — and leap.
Launching some 500 pounds of reptilian heft into flight required pterosaurs to use four limbs: two were ultra-strong wings which, when folded and balanced on a knuckle, served as front “legs” that helped the creature to walk — and leap.
Pterosaurs have long suffered an identity crisis. Pop culture heedlessly - and wrongly - lumps these extinct flying lizards in with dinosaurs. Even paleontologists assumed that because the creatures flew, they were birdlike in many ways, such as using only two legs to take flight.
Now comes what is believed to be first-time evidence that launching some 500 pounds of reptilian heft into flight required pterosaurs to use four limbs: two were ultra-strong wings which, when folded and balanced on a knuckle, served as front "legs" that helped the creature to walk - and leap.
Publishing in Zitteliana, Michael B. Habib, M.S., of the Center for Functional Anatomy and Evolution at the Johns Hopkins University School of Medicine, reports his comparison of bone strength in the limbs of pterosaurs to that of birds and concludes that pterosaurs had much stronger "arms" than legs. The reverse is true of birds.
© UCLA
PET brain scans reveal plaque and tangle accumulation in patients with the APOE-4 gene, which increases risk of Alzheimer's.
PET brain scans reveal plaque and tangle accumulation in patients with the APOE-4 gene, which increases risk of Alzheimer's.
UCLA scientists have used innovative brain-scan technology developed at UCLA, along with patient-specific information on Alzheimer's disease risk, to help diagnose brain aging, often before symptoms appear. Published in the January issue of Archives of General Psychiatry, their study may offer a more accurate method for tracking brain aging.
Researchers used positron emission tomography (PET), which allows "a window into the brain" of living people and specifically reveals plaques and tangles, the hallmarks of neurodegeneration. The PET scans were complemented by information on patients' age and congnitive status and a genetic profile.
"Combining key patient information with a brain scan may give us better predictive power in targeting those who may benefit from early interventions, as well as help test how well treatments are working," said study author Dr. Gary Small, who holds UCLA's Parlow-Solomon Chair on Aging and is a professor at the Semel Institute for Neuroscience and Human Behavior at UCLA.
© NASA, ESA, and Q.D. Wang (University of Massachusetts, Amherst) Credit for Spitzer image: NASA, Jet Propulsion Laboratory, and S. Stolovy (Spitzer Science Center/Caltech)
This composite color infrared image of the center of our Milky Way galaxy reveals a new population of massive stars and new details in complex structures in the hot ionized gas swirling around the central 300 light-years. This sweeping panorama is the sharpest infrared picture ever made of the Galactic core. It offers a nearby laboratory for how massive stars form and influence their environment in the often violent nuclear regions of other galaxies.
This composite color infrared image of the center of our Milky Way galaxy reveals a new population of massive stars and new details in complex structures in the hot ionized gas swirling around the central 300 light-years. This sweeping panorama is the sharpest infrared picture ever made of the Galactic core. It offers a nearby laboratory for how massive stars form and influence their environment in the often violent nuclear regions of other galaxies.
This composite color infrared image of the center of our Milky Way galaxy reveals a new population of massive stars and new details in complex structures in the hot ionized gas swirling around the central 300 light-years. This sweeping panorama is the sharpest infrared picture ever made of the Galactic core. It offers a nearby laboratory for how massive stars form and influence their environment in the often violent nuclear regions of other galaxies.
This view combines the sharp imaging of the Hubble Space Telescope's Near Infrared Camera and Multi-Object Spectrometer (NICMOS) with color imagery from a previous Spitzer Space Telescope survey done with its Infrared Astronomy Camera (IRAC). The Galactic core is obscured in visible light by intervening dust clouds, but infrared light penetrates the dust.
The spatial resolution of NICMOS corresponds to 0.025 light-years at the distance of the Galactic core of 26,000 light-years. Hubble reveals details in objects as small as 20 times the size of our own solar system.
