Tuesday, April 27, 2010

Spacecraft Spots Active Volcanoes on Venus

Venus is alive.

Researchers using data from the European Space Agency’s Venus Express spacecraft said they spotted three active volcanoes that recently poured red hot lava onto the planet’s already broiling surface.

The discovery, announced in a paper published Friday online in Science, suggests that Venus — like the Earth — is periodically resurfaced by lava flows, explaining why it seems devoid of craters.

“We estimate the flows to be younger than 2.5 million years, and probably much younger, likely 250,000 years or less, indicating that Venus is actively resurfacing,” the authors write. They were led by Suzanne E. Smrekar of the Jet Propulsion Laboratory in Pasadena.

Venus is only slightly smaller than Earth, but it seems to have evolved rather differently. It is swaddled in dense clouds of carbon dioxide. The pressure at the surface is 93 times the atmospheric pressure on Earth, and the temperature is almost 900 degrees Fahrenheit — enough to melt lead.

The planet shows no sign of the plate tectonics, the continental shifts and rumbles that keep the Earth’s surface fresh and erase impact craters, but satellite mappers have detected nine so-called hot spots resembling the Hawaiian islands, which are higher and hotter than the surrounding Venusian plains.

The Venus Express examined three of these smoldering humps with its Visible and Infrared Thermal Imaging Spectrometer, or Virtis, which can see through the thick clouds on Venus and measure the brightness of surface rocks.

The humps range from about half a mile to a mile high. Rocks in these regions, known as Imdr Regio, Dione Regio and Themis Regio, were anomalously bright compared with their surroundings, suggesting that they were relatively young and unweathered by the corrosive Venusian environment.

Video: http://video.nytimes.com/video/2010/04/09/science/1247467574634/venus-volcano.html

Source: http://www.nytimes.com/2010/04/10/science/space/10venus.html?ref=space

Vital link of Interest


Magnifying the Quantum World

In the 1870s, when Max Planck was still a young German university student, his professor Philipp von Jolly discouraged him from continuing to pursue physics, reportedly saying that nothing was left to discover in the field except for a few minor details.

Undaunted, Planck became a professor of physics at the University of Berlin, and by 1900 had developed a theory that would turn physics upside-down: Electromagnetic energy could only be emitted in discrete packets, or “quanta.” The field of quantum mechanics was born, and its ramifications continue to echo through physics today. Indeed, modern quantum researchers aren’t just filling in minor details; they’re still adding in leaps and bounds to our knowledge of how the world fundamentally works.

Planck’s breakthrough came out of his studies of “black bodies,” idealized objects that perfectly absorb and then re-emit electromagnetic radiation. In reality, nothing can absorb light so perfectly, but many real-world objects, like a hunk of iron, absorb and emit electromagnetic radiation similarly to a black body. As an iron ingot is heated, it begins to emit electromagnetic radiation, energy that travels on a spectrum of frequencies. When it’s quite hot, the ingot turns red—and as its temperature rises further, the ingot will progressively turn orange, then yellow, then white. These are only the frequencies we can see—the ingot, of course, is emitting invisible electromagnetic radiation too, in frequencies like infrared. Planck studied this “black-body spectrum,” and precisely measured how changing temperature affected the radiation a black body emitted. In his work, he came to realize that the emitted radiation didn’t smoothly increase with temperature, but in fact changed in sudden steps. Planck never quite understood the implications of his discovery, but Einstein and other physicists soon began to see its reach. Their conclusion: Everything in the universe—energy, light, particles, and all the macroscopic objects they form and influence—is somehow quantized, and subject to strange probabilistic behavior that defies classical explanations. In the quantum world, objects can be in multiple places at the same time, can simultaneously harbor mutually exclusive states, and can pop in and out of existence spontaneously. Even Richard Feynman, the Nobel-Prize-winning physicist who arguably had a better grasp of quantum mechanics than anyone else in the 20th century, quipped that no one really understood it.

Quantum phenomena are most dramatic in extremes that humans can’t tolerate or perceive, like near-absolute-zero temperatures, or in hard vacuum, or at the scale of atomic nuclei. But this doesn’t mean quantum principles don’t apply to larger objects. Chad Orzel, a physics professor at Union College, blogs about a March study that may document the first observation of a certain type of quantum behavior in an object visible to the naked eye.

“Visible” may be a stretch. The object in question is a fork-shaped device fabricated from aluminum nitride and sandwiched between sheets of aluminum. It’s about 40 microns long, or roughly the width of a human hair. You wouldn’t be able to see it at all if you looked at it from the side, because it’s just one micron thick. Still, since quantum behavior is typically observed at the scale of a single atom or subatomic particle, this research represents an astonishing leap: The device is composed of about 10 trillion atoms.

Orzel says the researchers, led by Aaron O’Connell, cooled the object to its “quantum ground state,” at 0.025 degrees above absolute zero. At warmer temperatures, the device has some resonance, meaning it mechanically oscillates back and forth a bit like a tuning fork. At this experiment’s chilly temperatures, the device still oscillates, but only due to unavoidable quantum effects that cannot be subtracted. Hence, it resides in its quantum ground state. Now, classical physics would say that as the device’s temperature gradually increases, its resonance should smoothly increase, too. O’Connell’s team was able to show instead that the object resonated in discrete intervals. Its resonance was, in other words, quantized.

The resonance itself is not visible; instead this had to be measured indirectly by coupling the resonator to another device, a loop of wire the team fabricated to act as a “qubit,” a register for a single unit of quantum information. This arrangement allowed the researchers to induce resonance in two different ways. They could energize the qubit, which in turn caused the resonator to oscillate, or they could apply microwave radiation to the resonator, and observe the oscillatory response in the qubit. In each case, the resonance occurred only at frequencies predicted exactly by quantum theory.

Greg Fish, a science writer and computer science graduate student, says that this research could also lead to innovations in quantum computing. Because the state of a quantum resonator can’t be directly detected, it leads to a classic conundrum: If an object can be in one of two states, and if we don’t know its state, then it can be said to be in both possible states at the same time. For a computer, this ambiguity can lead to tremendous number-crunching power, because it means that instead of a binary 1 or 0 as in a classical computing “bit,” a qubit can simultaneously embody multiple probabilistic states. And since there are many more than just two possible probabilities, a quantum computer could theoretically process much more information in a given interval of time than a classical computer could. The O’Connell team’s project, therefore, can be seen as a test-run for a quantum computer integrating many resonators like the one in their device. In theory, Fish says, a quantum computer can be as much as 50,000 times faster than a modern supercomputer at solving some types of mathematical problems.

In just over a century, quantum theory has moved from being an abstract curiosity to a powerful driver of technological development, with implications not just for theoretical physicists, but nearly every branch of science. As new developments are unveiled, watch for discussion and analysis on ResearchBlogging.org.

Source: http://seedmagazine.com/content/article/magnifying_the_quantum_world/

Sunday, April 25, 2010

Ice Fishing For Neutrinos From the Middle of the Galaxy

About 25 million years ago, Earth parted in the southeast corner of Siberia. Since then, countless rivers have converged on the gaping continental rift, creating the vast body of water known as Lake Baikal. Surrounded by mountains, this 400-mile-long inland sea has remained isolated from other lakes and oceans, leading to the evolution of unusual flora and fauna, more than three-quarters of which are found nowhere else on the planet. Russians regard it as their own Gal├ípagos. The lake contains 20 percent of the world’s unfrozen freshwater—or just a little less during the severe Siberian winter when, despite its enormous size and depth, Baikal freezes over.

On one such winter’s day, I found myself on the lake near the town of Listvyanka, which is nestled in a crook of the shoreline. I was in an old van that was trying to head west, not along a coastal road—for there was none—but over the ice. The path, however, was blocked by a ridge. It looked like a tectonic fault: Two sections of the lake’s solid surface had slammed together and splintered, throwing up jagged chunks of ice. The driver, a Russian with a weather-beaten face, peered from underneath his peaked cap, looking for a break in the ridge. When he spied a few feet of smooth ice, he got out and prodded it with a metal rod, only to shake his head as it crumbled: not thick enough to support the van. We kept driving south, farther and farther from shore, in what I was convinced was the wrong direction. The van shuddered and lurched, its tires crunching on patches of fresh snow and occasionally slithering on ice. The ridge continued as far as the eye could see. Suddenly we stopped. In front of us was a dangerous-looking expanse littered with enormous pieces of ice that rose from the lake’s frozen surface like giant shards of broken glass.

The driver seemed to be contemplating going around them to look for thick ice that would let us reach our destination, an underwater observatory operating in one of the deepest parts of the lake. But if he did that, we’d get even farther from the shore, and it would take just one punctured tire to strand us. The sun was little more than an hour from setting, and the temperature was falling. I couldn’t ask the driver if he had a radio or a phone to call for help, since he did not speak a word of English and the only Russian phrase I knew was do svidaniya. The last thing I wanted to say to him at this point was “Good-bye.”

Thankfully, he decided to turn around. We drove along until we came upon vehicle tracks that went over some ice covering the ridge. The driver swung the van westward and cleared the ridge, and soon we were racing across the lake at a speed that turned every frozen lump into a speed bump. The van’s front rose and fell sickeningly, rattling the tools strewn around on the front seat. I worried that the ice would give way and we would plunge into the frigid waters below. But it remained solid, and the van, despite its appearance, was in fine mechanical fettle, its shock absorbers holding firm. In the distance I spied a dark spot on the otherwise white expanse. As we approached, the spot grew to its full size, revealing itself as a three-foot-high Christmas tree. We still had 20 miles to cover, and the sun would soon disappear below the icy horizon. But now that we had found the Christmas tree, I knew we were fine.

I had first seen the tree two days earlier, with Nikolai (Kolja) Budnev, a physicist from Irkutsk State University, and Bertram Heinze, a German geologist. We were headed to the site of the Lake Baikal neutrino observatory, which lay deep beneath the ice. We had just driven onto the lake from the shore near Listvyanka when Heinze asked, “When does the ice start breaking?”

“Sometime in early March,” Budnev answered. My heart skipped a beat. It was already late March, and we were on the ice in an old, olive-green military jeep. “Sorry, sometime in early April,” Budnev corrected himself. Phew.

For more than two dec­ades now, Russian and German physicists have camped on the frozen surface of Lake Baikal from February to April, installing and maintaining instruments to search for the elusive subatomic particles called neutrinos. Artificial eyes deep below the surface of the lake look for dim flashes of blue light caused by a rare collision between a neutrino and a molecule of water. I was told that human eyes would be able to see these flashes too—if our eyes were the size of watermelons. Indeed, each artificial eye is more than a foot in diameter, and the Baikal neutrino telescope, the first instrument of its kind in the world, has 228 eyes patiently watching for these messengers from outer space.

The telescope, which is located a few miles offshore, operates underwater all year round. Cables run from it to a shore station where data are collected and analyzed. It is a project on a shoestring budget. Without the luxury of expensive ships and remote-controlled submersibles, scientists wait for the winter ice to provide a stable platform for their cranes and winches. Each year they set up an ice camp, haul the telescope up from a depth of 0.7 mile, carry out routine maintenance, and lower it back into the water. And each year they race against time to complete their work before the sprigs of spring begin to brush away the Siberian winter and the lake’s frozen surface starts to crack.

What is it about the neutrino that makes scientists brave such conditions? Neutrinos—some of them dating back to right after the Big Bang—go through matter, traveling unscathed from the time they are created and carrying information in a way no other particle can. The universe is opaque to ultraenergetic photons, or gamma rays, which are absorbed by the matter and radiation that lie between their source and Earth. But neutrinos, produced by the same astrophysical processes that generate high-energy photons, barely interact with anything along the way. For instance, neutrinos stream out from the center of the sun as soon as they are produced, whereas a photon needs thousands of years to work its way out from the core to the sun’s brilliant surface.

Neutrinos therefore represent a unique window into an otherwise invisible universe, even offering clues about the missing mass called dark matter, whose presence can be inferred only by its gravitational influence on stars and galaxies. Theory suggests that over time the gravity wells created by Earth, the sun, and the Milky Way would have sucked in an enormous number of dark-matter particles. Wherever they gather in great concentrations, these particles should collide with one another, spewing out (among other things) neutrinos. It is as if a giant particle accelerator at our galaxy’s center were smashing dark-matter particles together, generating neutrinos and beaming them outward, some toward us...

Source: http://discovermagazine.com/2010/mar/15-ice-fishing-for-neutrinos-from-middle-of-galaxy

Monday, April 19, 2010