- Holographic Telecommuting May Soon Be Possible
- Google Sky Adds Galaxy Clusters
- Giant Vicious-Looking Ancient Shrimp Was a Disappointing Wimp
- How Darwin’s Finches Keep Their Species Separate
- Shuttle Launchpad From Space: Discovery Awaits Liftoff
Posted: 03 Nov 2010 12:46 PM PDT
A new holographic display can transmit three-dimensional movies from one location to another almost in real time. If Princess Leia had to send her "Help me Obi-Wan Kenobi, you're my only hope" message from Earth today, it would now be technologically possible.
"We can take objects from one location and show them in another location in 3-D in near real time," said optical scientist Nasser Peyghambarian, and project leader from the University of Arizona in a press conference Nov. 1. "It is no longer something that is science fiction, it is actually something that you can do today."
Holographic movies have been a dream since at least 1966, when the first hologram was transmitted over a television system by Bell Labs. Updatable holographic displays have been around for decades as well; the first was developed by Stephen Benton at the MIT Media Lab in 1989.
The new device projects a color 3-D image onto a sheet of special plastic using a fast-flashing laser. The image can be updated once every two seconds, fast enough to give a sense of movement.
"In the past, other holograms you have seen are static images," said Pierre-Alexandre Blanche of the University of Arizona, lead author of a study in the Nov. 4 Nature describing the device. "Now, with a 2-second lag, it starts to become something more tangible."
The image can also be transmitted over the internet in less than a second, which would allow a near real-time window into distant events, something the authors call "holographic telepresence."
Peyghambarian and colleagues set an array of 16 webcams in a semicircle around the objects they wished to project, which included a model airplane, a vase of flowers and the researchers' heads. Each camera captured the object from a different perspective, making the ultimate image more lifelike.
"If you go to a 3-D movie like Avatar, you would see only two perspectives, one for one eye and one for the other eye," Peyghambarian said. "In our case, we have demonstrated 16 perspectives, but the technology has the potential to show hundreds of perspectives. So it's very close to what humans can see."
The cameras sent the images to another room, where they were encoded into pulsed laser that flashes 50 times per second. Each laser pulse encodes one holographic pixel, or "hogel."
Then the researchers trained the laser onto a newly developed plastic called a photoreactive polymer, which is coated with a material that converts light into electrical charges that create and store the image. The charges move around the plastic in such a way that when light bounces off the material, it reaches your eyes as if it had bounced off the toy plane or the researcher's head.
"With this material, since you can move the charge around, you can erase the hologram and write another hologram on it," Blanche said.
Two years ago, Peyghambarian's team made a similar material that could only refresh the image every four minutes. The images in that material were also disturbed by vibrations and temperature changes, so the screen had to be kept in a highly controlled box.
The new material rewrites every two seconds, a 100-fold improvement, and isn't bothered by changes to its environment, the researchers say.
Beyond entertainment and fighting the Empire, the display could have important medical and military applications, Peyghambarian says.
"Different doctors from different parts of the world can participate [in surgery] and see things just as if they were there," he said. The device could even be used for telecommuting. "People from Europe don't have to come to the U.S. to participate in a conference, it would be as if they were there."
"This is mostly a materials advance," said optical scientist Michael Bove of the MIT Media Lab, who was not involved in the new research but is collaborating with Peyghambarian on another project. "The material is faster and more sensitive than what had previously been reported."
Given the small size of the screen and the two-second lag time, "some people in the field object to the term 'telepresence,'" Bove said.
Blanche agrees that the hologram's lag time is too long. "Quite frankly, it's a bit annoying, and we know that," he said.
For truly real-time video, the image would need to refresh 30 times a second. That would take either a much more sensitive material or a "very big, very nasty" laser, Blanche said. The team hopes to push the material to produce video quality holographs in the next two years, and the technology could be ready for your living room within the decade.
"In two years we improved the speed by a factor of 100. If we can improve the speed by the same factor, we will be over video rate," Blanche said. "It will be done."
Video: Blanche et al. Nature.
Posted: 03 Nov 2010 10:54 AM PDT
Using Google Earth in Sky mode is a fun and interactive way to explore the universe. By importing images from space telescopes like Hubble and the Sloan Digital Sky Survey, Google Sky lets you fly deep into the visible universe for close-ups with planets, galaxies and star clusters.
But something's been missing, say astronomers Jiangang Hao and James Annis at the Fermi National Accelerator Laboratory. Google Sky's view of galaxy clusters is fuzzy and incomplete. That's because the program uses low-resolution pictures to speed up image transfer over the web. To have higher resolution images, you need to add in better pictures yourself.
Luckily, Hao and Annis have made this easy. They've loaded about 100 scans from one strip of the sky onto a public server at Fermilab, and made them available in Keyhole Markup Language (.kml files), the Google Earth equivalent of HTML files for web browsers. If you already have Google Earth, the whole thing takes a remarkably simple one-click download.
Posted: 03 Nov 2010 09:57 AM PDT
If anything lurking in shallow Cambrian seas looked like a monster, Anomalocaris canadensis was it. The 3-foot-long, lobe-winged, shrimp-like creature came equipped with two barbed feelers and an armor-plated mouth — parts paleobiologists once thought were ideal for finding and crunching tasty trilobites.
But a new 3-D model of the creature's mouth parts, presented Nov. 1 at the Geological Society of America's annual meeting in Denver, Colorado, may restrict the ancient predator's diet only to mushy meals.
"We found that it's extremely unlikely Anomalocaris could eat most trilobites," said James Whitey Hagadorn, the research team's leader and a paleontologist at the Denver Museum of Nature and Science. "It couldn't close its mouth all of the way, its mouth was too soft to crush trilobite shells."
Jean Vannier, a paleontologist at Université Lyon 1 in France who was not involved in the work, said Hagadorn's conclusions make sense.
"What was the function of the powerful frontal appendages of Anomalocaris? They seem to be directed towards the mouth but there [is] no clear evidence that they might be used for crushing food," Caron wrote in an e-mail. "To me their main function might have been to stir up the bottom sediment."
Hagadorn said the mouth parts are often illustrated as capturing trilobites and other Cambrian critters, but emphasized that little if any research backs up the popular depiction. Instead of eating solid food, Hagadorn suspects Anomalocaris stuck to softer items on the menu 500 million years ago, much the same way modern arthropods such as shrimp, crabs and lobsters do.
"They mostly eat soft things, worms in the mud or soft microorganisms floating in water," Hagadorn said. "We have no positive evidence Anomalocaris did eat this way, but that's not surprising. How are you going to tell the difference between mushed-up worms, mushed-up phytoplankton or mushed-up snails in the fossil record? They're all going to look like mush."
To reconstruct Anomalocaris' ancient mouth parts, Hagadorn and his team examined 400 fossils of the structures, picked the best-preserved ones, then plugged the data into a 3-D computer model. They also did the same for 12 groups of trilobites, "including spiny ones, flat ones, round ones, and so on," Hagadorn said, noting the shell strength was modeled after crab and lobster shells.
"Basically, we tried to capture the full range of prey sizes and shapes as well as predator mouth sizes and shapes," he said.
The computerized model's stress tests showed Anomalocaris' two feelers were very inflexible and the armored mouth, at least for non-juvenile trilobites, would break before the trilobites did.
"There's that, plus no positive evidence in fossilized gut contents, feces or otherwise suggesting that Anomalocaris could eat trilobites or anything else with shells or cuticles," Hagadorn said.
Some trilobite fossils have bite marks and scars resembling Anomalocaris' nibble. Hagadorn suggested that perhaps the creature "ingested things and then spit them out," including hard-shelled trilobites, but never ate them.
Jean-Bernard Caron, a paleontologist at the Royal Ontario Museum in Toronto who was not involved in the work, said that doesn't mean Anomalocaris never ate trilobites, however.
"The animal was likely well-adapted for preying on soft preys," Caron wrote, noting that trilobites did shed their carapace during molting. "It is possible that they could have preyed upon them during that time … and before the carapace mineralized again, thus explaining numerous healed injuries on trilobites."
Paleobiologist Danita Brandt of Michigan State University in East Lansing, who was independent of the research team, joked that "no court of law" could convict a predator of trilobites. But she said Hagadorn's work is an important step in getting there.
"His model takes a lot of the guesswork out of the equation of what Anomalocaris was capable of," Brandt said. "I think what he's done here is fantastic."
Images: 1) Illustration of the bottom of Anomalocaris canadensis, with two feelers and an armor-plated mouth./Wikimedia Commons/Nobu Tamura. 2) Anomalocaris' distinctive pineapple-ring-like mouth, in the open position, with the four cardinal plates visible./Hagadorn et al. 3) Fossils of trilobites, creatures Anomalocaris may not have been able to eat while hard-shelled./Flickr/kevinzim.
Posted: 03 Nov 2010 09:47 AM PDT
The shifting songs of Darwin's finches have given new insight into processes that shape the course of evolution, preventing newly forked branches on life's tree from growing back together.
Even though it's biologically possible for Geospiza fortis and Geospiza scandens — the original residents of the Galapagos island of Daphne Major — to interbreed with newly arrived Geospiza magnirostris, the species have stayed separate.
The birds learned to sing new tunes, setting off a behavioral cascade that swept the island in just a few decades: Evolution in action, audible to the naked ear.
The findings, published October 31 in the Proceedings of the National Academy of Science, "throw light on what happens at a crucial stage in speciation," wrote Princeton biologists Rosemary and Peter Grant.
Since the late 1970s, the Grants have worked on Daphne Major, studying descendants of some of the same finches that inspired Charles Darwin's evolutionary theories.
Scattered on isolated islands, Galapagos finch species have diverged from a common ancestor over the last several million years. Enough time has passed for species to become physically distinct, adapted to the unique niches of their home islands.
Not enough time has passed, however, for interbreeding to become impossible. Yet finch species often keep to themselves, even when winds or migratory impulses carry them between islands.
That reproductive separation between geographically overlapping but biologically compatible species — technically known as allopatric speciation — is considered an important phase in species divergence. It keeps species apart long enough for their differences to become absolute. It's happened many times in the tree of life's divergence, but at time scales lost to prehistory.
In their new study, the Grants describe it in real-time.
When they arrived in 1978, G. fortis and G. scandens were Daphne Major's sole finch inhabitants. Five years later, G. magnirostris, arrived on the island. After several decades, a few of the original finches interbred, producing a hybrid that appears destined to become its own species. Yet neither bred with with G. magnirostris. According to the Grants, G. fortis and G. scandens maintained separation through song.
For the finches, as for so many birds, songs — sung by males, learned from their fathers — are a central form of communication. They enable individuals to recognize others of their species, advertising the possibility of reproduction. Each species' song is distinctive.
As it happened, the song of G. magnirostris originally overlapped with the tunes of G. fortis and G. scandens. That's no longer true. Since 1983, their trill rates, frequency and bandwidth have all changed drastically.
What's most intriguing about the change is that it doesn't seem to have a physical origin. The shapes of G. fortis and G. scandens beaks haven't changed, as might be expected. (After all, it was variations in finch beak form that so inspired Darwin.) Nor did their bodies change.
Instead the change was behavioral. The finches quickly learned new songs, demonstrating what researchers call "peak shift." Male finches first sing in imitation of their fathers; as they mature, they add new riffs, and teach those songs to their own sons — who, in turn, riff even further.
Peak shift represents a much more active, dynamic evolutionary mechanism than random genetic mutation. In just a few decades, all across the island, both G. fortis and G. scandens occupied a completely new acoustic space.
The Grants think peak shift may be a common evolutionary phenomenon, responsible for separating similar species for the millions of years necessary to become genetically incompatible.
"Behavioral modification of mate-signal learning, through a peak shift mechanism, without genetic change, may be widespread," they wrote.
Images: Top row, the three finch species on Daphne Major; below, the change since 1983 in the acoustic space occupied by their songs. G. fortis and G. scandens (red and green) now occupy very different ranges from G. magnirostris (blue)./Peter and Rosemary Grant.
Citation: "Songs of Darwin's finches diverge when a new species enters the community: Implications for speciation." By B. Rosemary Grant, Peter R. Grant. Proceedings of the National Academy of Sciences, Vol. 107 No. 44, November 1, 2010.
Posted: 03 Nov 2010 09:22 AM PDT
The Space Shuttle Discovery waits on the launch pad at the Kennedy Space Center in Florida for its final trip into space in this image captured by the GeoEye-1 satellite yesterday. The launch will mark Discovery's 39th journey, and NASA's 133rd shuttle mission overall. One final space shuttle launch is scheduled for Feb. 27, 2011, before NASA retires the shuttle fleet for good.
Discovery is scheduled to take off at 3:52 p.m. EDT on Wednesday, Nov. 3, but the Chicago Tribune reports an electrical glitch may push the launch back to Thursday or later.
Update: Discovery's launch has been delayed to 3:29 p.m. EDT on Thursday, Nov. 4.
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