77076479
submission
TaleSlinger writes:
Researchers from University of Bristol, UK found that boulders strewn 200m above sea level on Cape Verde, off the west coast of Africa, were ripped from cliffs below and washed up there by a tsunami between 170m and 270m (550-850ft).
Researchers at Columbia University's Lamont-Doherty Earth Observatory dated the tsunami at 73,000 years ago.
Its interesting that this is about the same time as the Mt. Toba Eruption and about the same time humans nearly became extinct.
68081193
submission
TaleSlinger writes:
MIT researchers have discovered a new mathematical relationship — between material thickness, temperature, and electrical resistance — that appears to hold in all superconductors. They describe their findings in the latest issue of Physical Review B.
The result could shed light on the nature of superconductivity and could also lead to better-engineered superconducting circuits for applications like quantum computing and ultralow-power computing.
“We were able to use this knowledge to make larger-area devices, which were not really possible to do previously, and the yield of the devices increased significantly,” says Yachin Ivry, a postdoc in MIT’s Research Laboratory of Electronics, and the first author on the paper.
“None of the admitted theory up to now explains with such a broad class of materials the relation of critical temperature with sheet resistance and thickness,” says Claude Chapelier, a superconductivity researcher at France’s Alternative Energies and Atomic Energy Commission. “There are several models that do not predict the same things.”
Chapelier says he would like to see a theoretical explanation for that relationship. But in the meantime, “this is very convenient for technical applications,” he says, “because there is a lot of spreading of the results, and nobody knows whether they will get good films for superconducting devices. By putting a material into this law, you know already whether it’s a good superconducting film or not.”
67836243
submission
TaleSlinger writes:
Astronomers may finally have detected a signal of dark matter, the mysterious and elusive stuff thought to make up most of the material universe.
While poring over data collected by the European Space Agency's XMM-Newton spacecraft, a team of researchers spotted an odd spike in X-ray emissions coming from two different celestial objects — the Andromeda galaxy and the Perseus galaxy cluster.
"The signal's distribution within the galaxy corresponds exactly to what we were expecting with dark matter — that is, concentrated and intense in the center of objects and weaker and diffuse on the edges," [assuming that dark matter consists of sterile neutrinos] study co-author Oleg Ruchayskiy, of the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland, said in a statement.
"With the goal of verifying our findings, we then looked at data from our own galaxy, the Milky Way, and made the same observations," added lead author Alexey Boyarsky, of EPFL and Leiden University in the Netherlands.
Researchers have proposed a number of different exotic particles as the constituents of dark matter, including weakly interacting massive particles (WIMPs), axions and sterile neutrinos, hypothetical cousins of "ordinary" neutrinos (confirmed particles that resemble electrons but lack an electrical charge).
The decay of sterile neutrinos is thought to produce X-rays, so the research team suspects these may be the dark matter particles responsible for the mysterious signal coming from Andromeda and the Perseus cluster.
66411675
submission
TaleSlinger writes:
Scientists following two different lines of evidence have just published research that may help resolve "Darwin's dilemma," a mystery that plagued the father of evolution until his death more than a century ago.
Life appeared when the earth was tens of millions of years old, but evolution didn't go into high gear until the "Cambrian Explosion", nearly a billion years later. The two papers propose complementary theories that help explain this. The first suggests that scientists have long overestimated the amount of oxygen in the earth's atmosphere in the pre-Cambrian era just before the "explosion." The second suggests suggests that very dramatic changes driven by the tectonic breakup of the so-called "supercontinents" of the pre-Cambrian era could have caused an extraordinary leap in oxygen levels of both the ancient oceans and the earth's atmosphere.
These two studies fit neatly together, suggesting that a world deprived of oxygen could have changed relatively quickly into an incubator for new life in shallow ponds spread across the continents and fed by waters rich in nutrients. Perhaps that set the stage for the explosion, which may have been five times the evolutionary rate seen today.
66277395
submission
TaleSlinger writes:
One of the great theories of modern cosmology is that the universe began in a "Big Bang", but the mathematical mechanism by which this occurred has been lacking. Cosmologists at the Wuhan Institute have published a proof that the Big Bang could indeed have occurred spontaneously because of quantum fluctuations. "The new proof is based on a special set of solutions to a mathematical entity known as the Wheeler-DeWitt equation. In the first half of the 20th century, cosmologists struggled to combine the two pillars of modern physics— quantum mechanics and general relativity—in a way that reasonably described the universe. As far as they could tell, these theories were entirely at odds with each other.
At the heart of their thinking is Heisenberg’s uncertainty principle. This allows a small empty space to come into existence probabilistically due to fluctuations in what physicists call the metastable false vacuum.
When this happens, there are two possibilities. If this bubble of space does not expand rapidly, it disappears again almost instantly. But if the bubble can expand to a large enough size, then a universe is created in a way that is irreversible.
The question is: does the Wheeler-DeWitt equation allow this? “We prove that once a small true vacuum bubble is created, it has the chance to expand exponentially,” say the researchers.
50654153
submission
TaleSlinger writes:
From Nature:
Ashfordi's team realized that if the bulk universe contained its own four-dimensional (4D) stars, some of them could collapse, forming 4D black holes in the same way that massive stars in our Universe do: they explode as supernovae, violently ejecting their outer layers, while their inner layers collapse into a black hole.
In our Universe, a black hole is bounded by a spherical surface called an event horizon. Whereas in ordinary three-dimensional space it takes a two-dimensional object (a surface) to create a boundary inside a black hole, in the bulk universe the event horizon of a 4D black hole would be a 3D object — a shape called a hypersphere. When Afshordi’s team modelled the death of a 4D star, they found that the ejected material would form a 3D brane surrounding that 3D event horizon, and slowly expand.
The authors postulate that the 3D Universe we live in might be just such a brane — and that we detect the brane’s growth as cosmic expansion. “Astronomers measured that expansion and extrapolated back that the Universe must have begun with a Big Bang — but that is just a mirage,” says Afshordi.
