- Skydiver Aims to Jump from 120,000 Feet, Break the Sound Barrier
- New Evidence of Ice Age Comet Found in Ice Cores
- Bats Use Sun to Calibrate Geomagnetic Compass
- Phew, It Works! Science Begins at the LHC
Posted: 31 Mar 2010 10:28 AM PDT
If you're planning to jump out of a plane at 120,000 feet and break the sound barrier, you need a really fancy suit.
Austrian skydiver Felix Baumgartner has been working with a company that makes space suits for astronauts in an effort to pull off a record setting jump with the Red Bull Stratos project that he hopes will also lead to safer flight suits for future astronauts.
Baumgartner, the Red Bull star who has done everything from crossing the English Channel during free fall using a carbon fiber wing, to BASE jumping off the tallest buildings in the world, is planning to ascend to the stratosphere in a pressurized capsule carried by a massive helium balloon. Once reaching 120,000 feet, the plan is to depressurize the capsule, open the door and step off.
The current record for a skydive was set way back in 1960 when U.S. Air Force Colonel (Retired) Joseph Kittinger jumped from 102,600 feet. In addition to breaking that record, Baumgartner, like Kittinger, is working with several scientists to research new, safer suit designs for pilots and future space travelers. The hope is to develop the next generation of full pressure suits that would help increase survival if the need to bail out of a spacecraft should ever arise at extremely high altitudes.
The new suit being used by Baumgartner is made by David Clark Inc., the same company that made Kittinger's suit as well as full pressure suits for astronauts and military pilots flying at the edge of the atmosphere in aircraft such as the SR-71 Blackbird, the U-2 and the X-15. The suits provide an artificial atmosphere that allows pilots to survive in what would otherwise be a a deadly environment.
For Baumgartner's jump, temperatures are expected to be colder than minus 58 degrees Fahrenheit, and the air pressure will be so low that a condition known as ebullism would kill him if the pressure suit were to fail. The condition is explained by everybody's favorite formula from chemistry class, the ideal gas law. Ebullism can strike at 19,000 feet, but at 120,000 feet, the outside air pressure is less than one pound per square inch, so vapor bubbles in the blood expand causing the blood to basically boil.
Another potential problem is maneuvering during free fall. In order to achieve Mach 1, Baumgartner will have to adjust his position during free fall and a normal suit is too restrictive to allow sufficient freedom of movement. One of the worries is what would happen if a person were to begin tumbling.
Skydivers use their arms and legs to maneuver, but with the limited motion in a space suit, mobility is greatly restricted. The David Clark suit gives Baumgartner more flexibility to move during free fall. So far the Red Bull Stratos team has tested the new suit in wind tunnels, low pressure chambers and several jumps from 25,000 feet. Baumgartner has been fine tuning his "delta" position that he will use to achieve the supersonic jump.
No person has ever broken the sound barrier during free fall, though it is thought if a person were forced to bail out of a spacecraft at altitudes much higher than 120,000 feet, they would achieve supersonic speeds involuntarily. Baumgartner wants to help researchers better understand the possible affects of supersonic speeds on a person falling through the atmosphere as well as the affects on the suit.
Images: Red Bull
Posted: 30 Mar 2010 02:18 PM PDT
A new study cites spikes of ammonium in Greenland ice cores as evidence for a giant comet impact at the end of the last ice age, and suggests that the collision may have caused a brief, final cold snap before the climate warmed up for good.
In the April Geology, researchers describe finding chemical similarities in the cores between a layer corresponding to 1908, when a 50,000-metric-ton extraterrestrial object exploded over Tunguska, Siberia, and a deeper stratum dating to 12,900 years ago. They argue that the similarity is evidence that an object weighing as much as 50 billion metric tons triggered the Younger Dryas, a millennium-long cold spell that began just as the ice age was loosing its grip (SN: 6/2/07, p. 339).
Precipitation that fell on Greenland during the winter after Tunguska contains a strong, sharp spike in ammonium ions that can't be explained by other sources such as wildfires sparked by the fiery explosion, says study coauthor Adrian Melott, a physicist of the University of Kansas in Lawrence.
The presence of ammonium suggests that the Tunguska object was most likely a comet, rather than asteroids or meteoroids, Melott says. Any object slung into the Earth's atmosphere from space typically moves fast enough to heat the surrounding air to about 100,000° Celsius, says Melott, so hot the nitrogen in the air splits and links up with oxygen to form nitrates. And indeed, nitrates are found in snow around the Tunguska blast. But ammonium, found along with the nitrates, contains hydrogen that most likely came from an incoming object rich in water — like an icy comet.
More than a century after the impact, scientists are still debating what kind of object blew up over Tunguska in 1908. They also disagree about whether an impact or some other climate event caused the Younger Dryas at the end of the ice age. But the presence of ammonium in Greenland ice cores at both times is accepted.
"There's a remarkable peak of ammonium ions in ice cores from Greenland at the beginning of the Younger Dryas," comments Paul Mayewski, a glaciologist at the University of Maine in Orono who was not involved in the new study. The new findings are "a compelling argument that a major extraterrestrial impact occurred then," he notes.
Whenever a comet strikes Earth's atmosphere, it leaves behind a fingerprint of ammonium, the researchers propose. Immense heat and pressure in the shock wave spark the creation of ammonia, or NH3, from nitrogen in the air and hydrogen in the comet. Some of the ammonium, or NH4+, ions generated during subsequent reactions fall back to Earth in snow and are preserved in ice cores, where they linger as signs of the cataclysmic event.
Although an impact big enough to trigger the Younger Dryas would have generated around a million times more atmospheric ammonia than the Tunguska blast did, the concentrations of ammonium ions in the Greenland ice of that age aren't high enough.
But the relative dearth of ammonium in the ice might simply be a result of how the ice cores were sampled, Melott and his colleagues contend. Samples taken from those ice cores are spaced, on average, about 3.5 years apart, and ammonia could have been cleansed from the atmosphere so quickly that most of the sharp spike might fall between samples.
Image: Aftermath of the Tunguska event.
Posted: 30 Mar 2010 11:16 AM PDT
Bats are nocturnal, but some need sunlight to set their internal compass.
"Recent evidence suggests that bats can detect the geomagnetic field," wrote Max Planck Institute ornithologists Richard Holland, Ivailo Borissov and Bjorn Siemers in an article published March 29 in the Proceedings of the National Academy of Sciences. "We demonstrate that homing greater mouse-eared bats calibrate a magnetic compass with sunset cues."
Previously, Holland showed that interfering with the magnetic field around bats impaired their long-distance navigation abilities. Those findings suggested that while bats used echolocation for short-distance steering, they rely on some geomagnetic sense to guide nocturnal flights that take them dozens of miles from home. The details, however, were hazy.
In the new study, Holland's team captured 32 greater mouse-eared bats. Half of them were placed inside a pair of giant, coiled magnets that created a geomagnetic field misaligned with Earth's, temporarily scrambling their own geomagnetic sense. All were released in an unfamiliar location 15 miles from their home cave.
Bats that were captured at night flew home unerringly, regardless of what the researchers had done. They'd already set their compasses by the sun. But if the bats were captured and magnetically disoriented at twilight, when they would normally be flying around calibrating their compasses, they could no longer find their way home. The bats appear to use the twilight as a point of reference while setting their compasses for the rest of the night.
How the compass works is still a mystery. Some birds use sunset for navigational calibration, but the similarities likely end there. While birds' eyes contain geomagnetically sensitive molecules that are activated by photons, Holland has previously shown that bats don't have this system. Instead, some of their cells appear to be laden with magnetite.
Bats that fly only in the dead of night, such as vampire bats, could provide an interesting comparison, wrote the researchers.
"The cues used by the bats to indicate their position can only be speculated on at this stage," they wrote, noting that ornithologists have argued over the bird compass for decades. "For animals that occupy ecological niches where the sunset is rarely observed, this is a surprising finding."
Images: 1) Greater mouse-eared bat/Gilles San Martin/Flickr. 2) The directions flown by control and experimental control bats when their magnetic fields were disrupted at sunset (above) and after dark/PNAS.
Citation: "A nocturnal mammal, the greater mouse-eared bat, calibrates a magnetic compass by the sun." By Richard A. Holland, Ivailo Borissov, and Björn M. Siemers. Proceedings of the National Academy of Sciences, Vol. 107 No. 13, March 30, 2010.
Posted: 30 Mar 2010 08:58 AM PDT
Early this morning, two proton beams collided in the Large Hadron Collider's 17-mile-long ring at a combined energy of 7 TeV, three times higher than ever before. Finally, the flood of data particle physicists have been anticipating for years for has begun.
"It's a great day to be a particle physicist," said General Rolf Heuer, director of CERN where the LHC is located, in a press release Tuesday. "A lot of people have waited a long time for this moment, but their patience and dedication isstarting to pay dividends."
Getting the LHC started has not been easy. In September 2008 as it was first turned on, physicists around the world celebrated like never before. Just a week later when the LHC suffered a mechanical failure, it silenced the cheering abruptly like a visiting team hushing the home crowd with a buzzer-beating three-pointer.
Several more setbacks pushed the restart back a full year, and when the machine was turned on again, the celebration was more subdued, and until today, the physics world hadn't fully exhaled. The first page of the first chapter has finally been turned.
"With these record-shatteringcollision energies, the LHC experiments are propelled into a vast regionto explore," said physicist Fabiola Gianotti, spokesperson for the ATLAS experiment on the LHC. "The hunt begins for dark matter, new forces, newdimensions and the Higgs boson."
It remains to be seen how quickly the new machine will begin picking off its prey, however. Catching something as mysterious, elusive and possibly nonexistent as the Higgs boson takes more than just high energy. The beams must be calibrated, and recalibrated and tamed into submission. Scientists must get to know the LHC's typical data output before they can successfully find the anamolies that will be evidence of yet unknown particles and phenomena.
In the meantime, physicists continue to work on the well-oiled, well-understood Tevatron at Fermilab in Batavia, Illinois. The LHC's shadow has been lurking ever closer to the previous world-record holder for the highest energy, but the delayed start and slower ramp-up time put the Tevatron scientists into an unexpected overtime period, and they have continued to work hard chasing results — the Higgs boson in particular.
The LHC will run at its current energy for a year and a half, if all goes well. At this point, physicists expect it will have essentially caught up with the Tevatron, and the race will be over. Regardless of whether it has captured the Higgs boson by then, the Tevatron will be benched indefinitely, and the LHC will take a time out for maintenance and then ramp up to its combined collision energy target of 14 TeV.
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