- Spring-Loaded Heels Gave Extra Step to Early Humans
- Beautiful Spiral Galaxy Has Oddly Flat Center
- Mars’ Shifty Sand Dunes Knocked Down by Dry Ice
- World’s Most Powerful X-Ray Laser Illuminates Hidden Protein World
- No Link Between Flu Vaccine and Paralyzing Disorder
- New Mexico Bill Seeks to Protect Anti-Science Education
- Clones of Crazy Ant Queens Fuel Global Invasion
- Exoplanet Hunter Finds Bounty of Multi-Planet Solar Systems
- Exclusive: Chat With Exoplanet Guru Geoff Marcy
- Invisibility Crystals Make Small Objects Disappear
Posted: 03 Feb 2011 01:00 PM PST
Stone Age people, unlike their Neandertal contemporaries, had heel bones spring-loaded for long runs, a new study suggests.
In ancient Homo sapiens, as in people today, a short lower heel stretched the Achilles tendon taut, Raichlen's team concludes. That arrangement increased the tendon's spring-like action during running and reduced energy consumption, enabling extended excursions, the scientists report in a paper published online January 26 in the Journal of Human Evolution.
The result coincides with an earlier proposal that bodies suited to endurance running evolved in the genus Homo more than 2 million years ago because they aided hunting and carcass scavenging before spears were in widespread use, beginning sometime after 400,000 years ago (SN: 3/1/97, p. 134).
Raichlen's team also finds that Neandertals, compared to people today, had tall heel bones that put a less energy-efficient spring in their steps while running. Neandertals' tall heel bones possibly stabilized their ankles, giving them an advantage over Homo sapiens in walking uphill and jumping, the researchers hypothesize.
"We can say that energy costs of running differed between Neandertals and modern humans, but our data don't really speak to the question of what happened to the Neandertals," Raichlen says.
Scientists already knew that, relative to Stone Age people, Neandertals weighed more, had shorter legs and had smaller inner-ear canals that would have affected the balance needed to coordinate body movements, all obstacles to endurance running. Raichlen's study "provides a new line of evidence that Neandertals were not as adept at long-distance running as modern humans were," remarks anthropologist Herman Pontzer of Hunter College in New York City.
Reasons why modern humans evolved to run farther than Neandertals are unclear, Pontzer adds. Running prey to exhaustion may have worked better on hot African savannas where Homo sapiens lived than in cold European settings inhabited by Neandertals, he notes. But no heel fossils have been unearthed for any other Homo species, making it impossible to determine when running-friendly, spring-loaded feet like those of modern humans first evolved.
In their new investigation, Raichlen's team calculated rates of oxygen consumption for eight experienced distance runners as they ran on a treadmill for 10 minutes at 16 kilometers per hour (10 miles per hour). On a separate day, an MRI scanner took images of each man's heels and Achilles tendons.
Volunteers displayed short lower heel bones, especially the runners who used oxygen most efficiently while running.
Heel-bone measurements of 13 fossil Homo sapiens that lived between approximately 30,000 and 100,000 years ago resemble those of today's runners, the scientists say. On average, the measurements indicate that the ancient humans expended 6.9 percent more energy while running than their counterparts today did — not a substantial difference, according to the researchers.
Analyses of heel bones of six Neandertals from the same time period indicate that these hominids used an average of 11.4 percent more energy while running than modern athletes did, a statistically notable disparity, Raichlen says.
Energy efficiency while running depends far more on a person's anatomy than on physical training, the researchers say. They used distance runners as a modern comparison group in order to account for any training effects.
Image: An MRI of a distance runner's foot and ankle shows a heel bone sized to pull the Achilles tendon taut, a condition that researchers say applied to Stone Age humans but not to Neandertals. Measurements of part of the heel bone helped scientists determine how easily an individual could run long distances./Elsevier/D. Raichlen.
Posted: 03 Feb 2011 12:30 PM PST
This stunner of a galaxy, called NGC 3621, may look like a run-of-the-mill spiral galaxy. But closer observation shows that it's missing the characteristic central bulge that marks most spiral galaxies.
NGC 3621 is a fairly bright galaxy, easily visible to medium-sized telescopes, that lies about 22 million light-years away in the constellation Hydra.
At a glance, it looks like an ordinary classical spiral galaxy. But this new image from the Wide-Field Imager camera on the 2.2 meter telescope at the La Silla observatory in Chile reveals that it's actually a "pure disc" galaxy, lacking a central bulge that marks an ancient galactic collision.
Astronomers think most galaxies grow by merging with other galaxies, a process that over time should build up large blobs of material at the galaxy's center. NGC 3621's surprising flatness indicates that it hasn't had such a close encounter with another galaxy. Recent research suggests that such pancaked galaxies are actually relatively common.
Image: ESO/Joe DePasquale
Posted: 03 Feb 2011 11:00 AM PST
Thought to be encased in a frozen, static crust, the Martian north pole is actually a dynamic place, with sand dunes skidding and sliding in spring.
The dunes were first observed in the 1970s, spotted at edge of Mars's north polar cap. They appeared to be frozen in place. Scientists figured they formed at least 30,000 years ago when Mars's climate was more extreme.
"In one Mars year, we see really fairly substantial changes on the dunes," said planetary scientist Candice Hansen of the Planetary Science Institute in Tuscon, Arizona. Hansen is lead author on a paper in the Feb. 4 Science reporting the new observations. "That was the surprise."
HiRISE has been snapping high-resolution photos of the Martian surface since March 2006, or about two and a half Martian years. Hansen and colleagues examined images of the same location at different times of year, and found that dark sand streaks and new ravines appeared as the seasons changed.
"Because we had all these years of data where no one saw any changes, people developed theories — the dunes are cemented by ice, maybe they're crusted over — theories for why they were not changing," Hansen said. "In fact, they were probably changing all along, and we just didn't have instruments that were good enough to see it."
The changes could be forged by a layer of frozen carbon dioxide — dry ice — changing directly from solid to steam. "This is a very un-Earthly process," Hansen said.
Every winter, Mars's polar cap is sheathed in a thin blanket of carbon dioxide. In the spring, the warming ice layer sublimates, or shifts directly to gaseous form without bothering to melt first.
This sudden shift destabilizes the dunes and triggers avalanches. In the center panel of the images above, the green or blue stuff is bright fresh frost. The dark streaks are escaping sand.
In another surprise, ravines and gullies seemed to disappear from the dunes from one spring to the next. Models of Martian climate predict that the winds should not be strong enough to shift sand grains, and measurements from the Phoenix lander and the Mars rovers Spirit and Opportunity support that idea.
"Everybody may have to sharpen up their pencils and go back to their climate models," Hansen said, though she points out that they only have two Martian summers to compare. "Is this just an oddball year, or is this something that happens regularly? We'll need more Mars years to be able to say."
Image: 1) Science/AAAS. 2) NASA/JPL/University of Arizona.
Posted: 03 Feb 2011 09:30 AM PST
In brilliant bursts of light from the world's most powerful X-ray laser, physicists have taken snapshots of living viruses and see the 3-D shape of proteins frozen in nanometer-scale crystals.
The technique is described Feb. 3 in two Nature papers, and the images are the first biological subjects to be captured by bouncing X-rays off single particles.
"This really lets us see things that were invisible before," said study co-author Marvin Seibert, a Stanford University physicist. "The most important thing is that scientists will be able to solve the structures of new biological molecules."
To get a picture of a protein, researchers typically grow it in large crystals. For some proteins — especially those that span a cell's membrane — this is difficult, even impossible. About 30,000 membrane proteins are found in the human body, but scientists know the shape of only six.
"Growing one of these crystals can be worth a Nobel," Seibert said.
To make images with an X-ray laser, researchers sprayed viruses or individual proteins, frozen into crystals, into the path of an extremely powerful X-ray beam. According to the researchers, it was a billion times brighter than previous X-ray sources. The beam's pulses lasted for quadrillionths of a second, scattering from the subject's surface in the instant before it vaporized.
A camera recorded the scattering patterns, from which the subject's shape could be reconstructed. From the combination of thousands of snapshots, three-dimensional images emerged. (To make the mandala-like image above, of a protein used in photosynthesis, the researchers took three million snapshots and combined the best 10,000.)
Now that researchers photograph single proteins, they have a shortcut to learning their shape, and thus to understanding how they work. Most drugs and diseases target these membrane proteins, so knowing their shape is important.
For the second study, researchers sprayed individual, unfrozen viruses into the X-ray beam, hoping to see their living shape. The subject was Mimivirus, the largest known virus, so immense it's infected by other viruses.
Their pictures (see below) showed a dark region in the Mimivirus center, which is probably its genetic material. In an experiment ongoing now, using X-rays four times more powerful than those in the new study, the researchers are trying to capture the viral genome in 3-D.
If it works, they might be able to see how one virus differs from another, and how they develop over time.
"It's very hot work," said Seibert, "And it is happening literally right now."
Images: 1) Three-dimensional rendering of the X-ray diffraction pattern for a mimivirus' Photosystem I protein./Thomas White, DESY. 2) X-ray diffraction pattern of a single Mimivirus particle./Tomas Ekeberg, Uppsala University.
Citations: "Femtosecond X-ray protein nanocrystallography." By Henry Chapman, John Spence et al. Nature, Vol. 470, No. 7332, February 3, 2011.
"Single mimivirus particles intercepted and imaged with an X-ray laser." By Marvin Seibert, Janos Hajdu et al. Nature, Vol. 470, No. 7332, February 3, 2011.
Posted: 03 Feb 2011 08:15 AM PST
Any speculation drawing an ongoing link between flu vaccination and the risk of a rare, paralyzing neuromuscular disorder has been dashed by a huge study. An analysis of side effects recorded among nearly 90 million people in China who were vaccinated during the 2009–2010 flu season found that only 11 people subsequently were diagnosed with Guillain-Barré syndrome, a rate no greater than what normally appears in the population. The study appears online February 2 in the New England Journal of Medicine.
In 1976, a strain of swine flu showed up in the United States, prompting the manufacture and delivery more than 40 million doses of vaccine against it. The epidemic ultimately never materialized, but studies noted that hundreds of cases of Guillain-Barré syndrome were reported after the vaccination campaign. The vaccine was withdrawn. In 2003, an Institute of Medicine review found that the evidence pointed to an association between the 1976 swine flu vaccine and the syndrome.
IOM found no clear evidence of such a link with subsequent flu vaccines, but some concerns have lingered vis-à-vis flu vaccination.
These fears intensified in 2009 when another swine flu emerged, this time known as the H1N1 flu, and a vaccine was made for it. After mass vaccinations, physician Yu Wang and colleagues at the Chinese Centers for Disease Control and Prevention in Beijing collected data on all adverse effects reported by the 89.6 million people in China who received the flu vaccine in 2009 and 2010. The researchers found an exceptionally low rate of Guillain-Barré syndrome among those who had been vaccinated — less than the background rate in the population.
"This was a generally well-done study given the limitations of a voluntary reporting system," says Penina Haber, an epidemiologist at the U.S. CDC. The results are similar to a U.S. CDC analysis of adverse events for vaccines and provide further evidence of the safety of the 2009 H1N1 influenza vaccine, she says.
Grace Lee, a physician and epidemiologist at Harvard Medical School and Harvard Pilgrim Health Care Institute in Boston, notes that the actual rate of Guillain-Barré syndrome reflected in the Chinese study was based on reporting from a wide network of health officials. "It's hard to be sure the actual rate of events is accurate," she says. But she says that the size of the database probably makes up for any weaknesses in data collection. "It's a great study because this is such a huge population. The utility of this passive surveillance system is that there is sheer power in the numbers to pick up unanticipated adverse events."
Posted: 03 Feb 2011 07:19 AM PST
If educators in New Mexico want to teach evolution or climate change as a "controversial scientific topic," a new bill seeks to protect them from punishment.
House Bill 302, as it's called, states that public school teachers who want to teach "scientific weaknesses" about "controversial scientific topics" including evolution, climate change, human cloning and — ambiguously — "other scientific topics" may do so without fear of reprimand. The legislation was introduced to the New Mexico House of Representatives on Feb. 1 by Republican Rep. Thomas A. Anderson.
Supporters of science education say this and other bills are designed to spook teachers who want to teach legitimate science and protect other teachers who may already be customizing their curricula with anti-science lesson plans.
"These bills say, 'Oh we're just protecting the rights of teachers,' which on the face of it isn't wrong. But they draw big red circles around topics like evolution and climate change as topics to be wary about," said Joshua Rosenau, a policy and projects director at the National Center for Science Education. "It suggests this kind of science is controversial, and would protect teachers who want to teach anti-evolution and climate-change-denying lessons in classrooms."
The bill is one of five already introduced to state legislatures this year. While more than 30 such bills have been introduced since 2004, only Louisiana adopted one as law in 2008.
Rosenau said House Bill 302 will probably never see the light of day, as New Mexico's representatives have bigger issues to deal with, such as their constituents' financial hardships. If it does come to a vote, however, he said its chances are slim.
"These bills are written in such a way that voting 'nay' on them looks bad. Legislators may vote yes to maintain an agreeable voting record, but they often find ways to kill them procedurally," he said.
The bill's introduction comes at a time when, according to a recent study in Science, only 28 percent of U.S. teachers overtly teach scientific concepts of evolution and 13 percent advocate creationism. Some 60 percent water down teaching evolution to avoid confrontation by students and parents.
"Supporters of anti-science education are trying to give cover to what's already happening out there," Rosenau said.
Anderson did not return Wired.com's phone calls or e-mails in time for publication of this report.
Posted: 02 Feb 2011 01:46 PM PST
The worldwide invasion of Longhorn crazy ants appears to rely on a reproductive trick that allows for incest without the problems of inbreeding.
In the early stages of invasion, queens may have no choice but to mate with male relatives. But when that happens, their eggs can hatch as non-working males instead of workers.
Without workers, the colony quickly starves to death. So longhorn crazy ant queens avoid the problem by producing female offspring who are clones of themselves, and sons who are genetically unrelated clones of their fathers.
"It's an incredibly bizarre system," said study co-author Michael Goodisman, a Georgia Institute of Technology sociobiologist who described the trick Feb. 2 in Proceedings of the Royal Society B. "A queen produces males that are completely unrelated to her, that have none of her genetic material."
Longhorn crazy ants, or Paratrechina longicornis, are so widespread that scientists don't even know where they first came from. They form series of connected colonies, called "supercolonies," that greatly disrupt ecosystems they invade, including human farms and homes.
To discover how crazy ant queens deal with a shortage of mates, Goodisman's team formed 21 laboratory colonies, each with one queen and some workers. After three months, the researchers collected pupae of workers, males and queens, then analyzed their DNA.
Workers had one set of genes each from both mother and father, as normal. But females were exact copies of their queen mother, while males were clones of their fathers.
Because both the queens' offspring are genetically unrelated, they can mate with one another without the consequences of inbreeding.
"It's cheating, in a genetic sense, but this weird system allows [crazy ants] to overcome severe restrictions," said evolutionary geneticist Jürgen Gadau of Arizona State University, who wasn't involved in the study.
The cellular mechanisms of this phenomenon are unknown. Goodisman and Gadua suspect that female copies of genes are destroyed in eggs originally destined to be workers. But however it happens, it appears to be fantastically useful.
"It's a way to skirt the deleterious effects of inbreeding and spread all over the world," said entomologist Kenneth Ross of the University of Georgia, who was not involved in the study.
Images: 1) A longhorn crazy ant worker (Paratrechina longicornis) collected in California./April Nobile/AntWeb.org. 2) A longhorn crazy ant queen (Paratrechina longicornis) collected in Madagascar./April Nobile/AntWeb.org.
Posted: 02 Feb 2011 10:00 AM PST
The planet-hunting Kepler Space Telescope released its second batch of data today, revealing more possible new planets than have been spotted to date. The cornucopia of planetary systems includes a star orbited by six worlds, two of which appear to be watery "miniature Neptunes."
The data cover the telescope's first four and a half months of staring wide-eyed at 156,000 stars near the constellation Cygnus, and watching for telltale winks that signal the passing of an orbiting planet.
The first bundle of data, released last June, revealed 306 target planets, but deliberately held back the smallest and most tantalizing candidates. Now, those promising planets — 1,200 altogether, pending final data analysis — are ready to go public.
"We're just opening up the treasure chest," said exoplanet expert Daniel Fabrycky of the University of California, Santa Cruz, a member of the Kepler team. "There's lots of nice planetary systems there for the taking."
"We think this is the biggest thing in exoplanets since the discovery of … the first exoplanet."
Kepler finds planets by watching for their host stars to dim slightly as the planet crosses, or transits, in front of the star. By measuring the amount of light the planet blocks, astronomers can figure out how big the planet is. So far, Kepler has found planets ranging from many times the radius of Jupiter to just 1.4 times the radius of Earth.
But most of those planets were solo performers. Until today, Kepler-9, which has one Earth-sized world and two Saturns, was the only known star with more than one transiting planet. Among the most exciting systems revealed today is a family of six planets circling a sun-like star named Kepler-11.
Those planets were detected because they gravitationally tug each other to and fro. If a star has just one planet, it should grow brighter or dimmer like clockwork as the planet transits. But adding more planets mean the transits are never on time.
Multi-planet systems are especially valuable because the deviations from clockwork let astronomers compute the planets' mass, a measurement that would normally require hours or days of observations with the biggest telescopes on Earth.
"We think this is the biggest thing in exoplanets since the discovery of 51-Pegasi b, the first exoplanet, back in 1995," said astronomer Jack Lissauer of the NASA Ames Research Center in a press teleconference Jan. 31. The system is described in a paper in the Feb. 3 Nature.
In order for all six planet-crossings to be visible from the vantage point of Earth, the planets must all lie in a plane flatter than a CD, Lissauer says.
The five inner planets all orbit the star once every 46 days or less, and the outer planet orbits once every 118 days. If this system were dropped into our solar system, all the planets would be closer to the sun than Venus.
Compared to Earth, the planets are remarkably light for their size. The five inner planets range from 1.97 to 4.52 times Earth's radius and 2.3 to 13.5 Earth's mass. The outer planet, whose radius is 3.66 times Earth's, is too far away for its mass to be completely determined, but astronomers know it is less massive than Jupiter.
These planets are unlike anything in our solar system. From the planets' masses and radii, astronomers can calculate their density, a clue to composition. Although the planets around Kepler-11 are fairly small, they're all much less dense than Earth, making them more like mini-Neptunes than super-Earths. The inner two could be mostly water, with a thin atmosphere of hydrogen and helium. The farther-out planets may have much thicker hydrogen and helium atmospheres that comprise up to 20 percent of the planet's mass.
Planetary scientist Jonathan Fortney, a coauthor of the paper describing Kepler-11, suggests imagining these planets as a "marshmallow with a ball bearing in the center," where the thick atmosphere makes up most of the volume, but not much of the mass."
If you could stand on the surface of these planets, "you would not be able to see the sky," Fortney told Wired.com in an email. "The hydrogen-dominated atmospheres that we are talking about are extremely thick. You literally would be 1/2 to 2/3 of the way down into the planet, and the atmosphere would be opaque."
How such strange planets formed, and how they ended up in such a tightly packed configuration, is a puzzle.
"This is sending me back to the drawing board," Lissauer said. "It's just totally unexpected to be able to get a planetary system where planets can be this close to one another, that there can be so many of them, that they can be so flat. It's really a sense of extremes there."
The new data dump includes an abundance of other multi-planet systems, including one with 5 planets, 8 quartets, more than 100 doubles and triples.
Of the 1,235 new planet candidates, 68 are Earth-sized, 288 are super-Earth sized, 622 are similar to Neptune, and 165 are as big as Jupiter. 54 of the candidates orbit in the habitable zone, the right distance from their stars to sustain liquid water.
One of those candidates is smaller than Earth. Four are super-Earth-sized, and most are Neptunes or Jupiters. But all the moons of those Jupiters would also be in the habitable zone, noted Kepler science principal investigator William Borucki of NASA Ames Research Center in a press conference Feb. 2.
"For your Christmas vacation you could go from one moon to another, and have a vacation on that different moon," Borucki said. "I'm not saying that happens every day, but it's possible."
"All of these new Kepler discoveries, not just the six-planet system but all of them, are showing us that there is a bounty of low-mass planets around other stars," said astronomer Debra Fischer of Yale University, who was not involved in the Kepler observations. "We can see more securely that these low-mass planets not only exist, but they're much more numerous than the big gas giant Jupiter like planets."
The new trove of observations also brings Kepler closer to its main goal: Finding Earth-sized planets that orbit in the habitable zone, where they might host life.
"We can be pretty sure we will find rocky planets in the habitable zone, because of how the numbers are coming out for smaller and smaller planets," Fabrycky said.
Theorists who study planetary formation and dynamics will be eager to jump on the data immediately, said exoplanet expert Sara Seager of MIT.
"Kepler is making people's dreams come true. It sounds kind of corny, but it's really true," she said. "It's changing exoplanet science as we know it."
Images: NASA/Tim Pyle
Posted: 02 Feb 2011 10:00 AM PST
Almost exactly fifteen years ago, astronomer Geoff Marcy addressed a stunned American Astronomical Society at a meeting in San Antonio to announce the discovery of two new extrasolar planets. With those planets, 47 Ursae Majoris b and 70 Virginis b, Marcy brought the grand total of known exoplanets up to three.
Marcy, now a professor at the University of California, Berkeley, and his team went on to discover 70 of the first 100 exoplanets, pioneering techniques subsequently used to find and describe more than 400 planets — and counting. On Feb. 2, a massive release of data from the planet-hunting Kepler project announced the existence of 1200 new planetary "candidates," with full planethood status awaiting final data analysis.
An artist's rendering of 47 Ursae Majoris b, Marcy's first planet and the second planet ever found around a sunlike star.
Marcy's talk at this year's AAS meeting in Seattle focused not on individual discoveries, but on trends that only emerged with piles of planets. The numbers hint that solar systems like ours are not so common.
Wired.com caught up with Marcy at the meeting to talk about the early days of the exoplanet hunt, how success can spring from failure and finding the elusive exo-Earth.
Wired.com: Why exoplanets? You started back when there weren't any. How did you get into this?
Geoff Marcy: You want the real answer? It's personal. After I got my PhD at Santa Cruz, I was really lucky and I got a post-doctoral fellowship at the Carnegie Institute of Washington, which is in Pasadena.
And in brief, my research wasn't going very well. A Harvard astronomer criticized my PhD thesis. And I felt pretty bad. Everyone seemed smarter than me. I felt a little bit like an impostor, like they haven't figured out that I'm not as smart as them, that I'm not really smart enough to be a scientist. I thought okay, well now the jig is up. Maybe my career is over.
But I still have a year and a half on my post-doc! I remember one morning in my apartment in Pasadena, as I took my shower, thinking, I can't suffer like this anymore. I've got to just enjoy myself, do research that really means something to me.
So I thought, what do I care about? I would love to know if there were other planets around other stars.
This was a question that nobody was asking. It was 1983, and nobody was even talking about planets. Even our own solar system was considered boring at the time.
"Of course the real question isn't whether there are habitable Earthlike planets. It's how common are they? Are they one in 100, one in 1000, in in a million? How far do we have to travel to find the nearest, lukewarm, rocky planet with an atmosphere?"
So by the time I turned off the shower, I knew how I was going to end my career. I quickly realized that this was kind of a lucky moment. By knowing that I was a failure, I was free. I could just satisfy myself, and hunt for planets — even though it was a ridiculous thing to do. At that time, I hadn't heard of anybody actively hunting for planets.
Wired.com: How did people react when you started doing it?
Marcy: They were embarrassed for me. I might as well be looking for little green men, or how the aliens built the pyramids in Egypt, or telekinesis. Even professional astronomers at that time associated planets around other stars with science fiction.
It's very hard to imagine that now. Look at this meeting. We have probably 500 talks and posters on extrasolar planets. It's hard to put yourself in a mindset in which planets were considered the lunatic fringe. But that's what it was.
Wired.com: Did you have a plan?
Marcy: George Herbig was my advisor at Santa Cruz. I learned from him how to measure Doppler shifts in stellar spectra. I thought, I will try my best to measure Doppler shifts so precisely that I can see the wobble of a star due to any planets.
Wired.com: Was that a new idea?
Marcy: No, it wasn't a new idea. Every astronomer knows about using Doppler shifts to measure binary stars. People knew that, if you can detect binary stars, you ought to be able to detect even lower-mass companions, i.e. planets.
But the daunting part is that stars don't get pulled very strongly by little planets. Even in our solar system, Jupiter pulls on the sun so that the sun moves by a mere 10 meters per second. That's human running speed.
Wired.com: What was the hunt like in the early days?
Marcy: This was a great, lucky thing. Have you heard of the Mount Wilson 100-inch telescope? With which Hubble discovered the expansion of the universe? Well, by the time I got to the Carnegie Institute of Washington, nobody was using that telescope. Why? It was located 4 inches from downtown L.A. The sky was bright, and the only thing you could do was spectroscopy of bright stars. And that's what I wanted to do.
Wired.com: What do you actually do, when you measure Doppler shifts? I know the basic picture, the planet's gravity tugs the star back and forth. But what does that look like? Can you draw it?
Marcy: Suppose I go to the telescope, and what we actually plot on the computer screen is the amount of light, versus pixel number.
So you take a picture, and pixel #498 has a certain amount of light form the star, and pixel #499 has a different amount of light. Each pixel captured a slightly different wavelength than the previous pixel.
What you get when you make a graph of how much light there is at each of these pixels, you get a spectrum that looks something like this:
The amount of light from the star should be pretty constant, because stars are like light bulbs, except that there are certain atoms that absorb light at certain wavelengths.
If I come back a month later, what I hope to see is this: The whole spectrum is reproduced, but shifted over.
Now, stars shouldn't do that. A star should just sit there in space. Why would it change? The reason is that there's an unseen planet that yanks, and the star comes at you and away from you and at you and away from you.
The problem is, displacement here is grossly exaggerated. The actual displacement is only one one-thousandth of a pixel. It's like taking a picture of a snail, and then taking a picture one second later, and hoping to see the motion of the snail. Snails are too fast, actually.
How can you detect a motion as small as one one-thousandth of a pixel? A pixel is supposed to be the indivisible unit, it's like the atom of a digital camera. How can you detect something smaller than a pixel?
If a spectral line spans several pixels, you can ask where's the actual center of that line. It might not be right smack in the middle of one of the pixels. It might be offset. How could you tell? The pixel to the right has a little more light than the pixel to the left. You can see that it's off center.
If you measure the amount of light in the neighboring pixels, the amount of light varies ever so slightly. You can really see that an arbitrarily tiny Doppler shift can be detected by measuring the amount of light in each of those pixels.
Wired.com: So we've been talking about how this worked 30 years ago, when you were starting. How is it different now?
Marcy: [Laughs] It's the same. It's fundamentally the same. Except I'm now dedicated to the Kepler project, which makes life one enormous step easier. Kepler finds the planets for us that are transiting their stars. In the old days, we pointed at stars blindly. Out of every 100 stars, only two or three had planets. Very bad odds.
Kepler changes all that. Now, when I point the telescope, and I'm using the Keck telescope in Hawaii, I know there's a planet there because Kepler said so.
Wired.com: What do you think is the most important outstanding question in exoplanets?
Marcy: There's two, and they're real, real obvious: Are there habitable Earths? Kepler is poised to answer that.
Of course the real question isn't whether there are habitable Earthlike planets. It's how common are they? Are they one in 100, one in 1000, in in a million? How far do we have to travel to find the nearest, lukewarm, rocky planet with an atmosphere?
The second question is: How common is intelligent life in the galaxy? There too, we have a shot at answering it, but it's a longer shot.
That one, my honest feeling about it is, yeah, we need missions to Enceladus and Mars and Titan. NASA will send spacecraft in the next few decades to these obvious destinations, moons with geysers and liquid methane lakes.
But there ain't no intelligent life on Titan. There might be single celled life, and I can't wait if they find it. But we're still going to want to know, does ET have a home out there?
What we need are big radio telescopes that hunt for radio signals. It's not that much of a secret. But we don't have the cultural, political will to fund a serious radio telescope to answer a question that every six-year-old asks.
The telescope called the Allen Telescope Array, which is our greatest hope, is struggling. And for what? It costs $100 million. NASA's budget is $19 billion. Less than one percent of NASA's budget in just one year is enough to fund this marvelous, epochal, Nina, Pinta, Santa Maria – why aren't we doing this?
Wired.com: Can I play Devil's advocate for a minute? We have the James Webb Space Telescope, which is struggling, and it hasn't even flown yet. And then you have the average person on the street, who we're trying to convince to care about that in the first place. We're still trying to get health care to a lot of people. $100 million could solve a lot of other problems.
Marcy: I'm just talking about within NASA's existing budget. How will you spend that money that's going to get spent anyway on something to do with space? We only need 1 percent of one year's budget to make our search for extraterrestrial intelligent life happen. I think that's worth thinking about really hard.
Image: 1) NASA. 2) Debivort. 3) Wired.com. 4) NASA/Kepler. 5) The SETI Institute. Video: View Space.
Posted: 02 Feb 2011 07:33 AM PST
Professor Snape beware — invisibility cloaks aren't just for the microscopic anymore.
Using natural crystals, two independent research teams have designed "carpet cloaks" that can abracadabra 3-D objects as big as an ant or a grain of sand seemingly into nothing. Up to now, making things invisible has relied on tiny structures called metamaterials. These fabrications are often a mix of stacks and crisscrosses of nano-sized metals and other materials that can guide electromagnetic rays, such as microwaves or infrared and visible light, around objects. If researchers tweak metamaterials just right, they can make tiny things disappear — at certain light wavelengths and from certain angles, at least.
But now two teams, including an MIT group that published its results in Physical Review Letters in January and another from England and Denmark that published Tuesday in Nature Communications, didn't bother with metamaterials. They adopted calcite prisms, a type of naturally occurring crystal, to build carpet cloaks. Carpet cloaks aren't true now-you-see-them-now-you-don't apparatuses. The bottom of the cloaking device is notched with a small triangle that looks like a bent mirror. Thanks to the optical properties of metamaterials or, in this case, calcite, the bent mirror can look like a flat plane when viewed from some angles. Anything hiding in the notch vanishes.
This low-tech design sidesteps some of the limitations of metamaterial invisibility cloaks, says Ulf Leonhardt, a physicist at the University of St. Andrews in Scotland who was not involved in either study. His landmark 2006 paper in Science helped to launch invisibility research. Because metamaterials require intricate sculpting by lasers or other tools, scientists can make them only so big. Harry Potter would need to be more than paper-thin to hide under early carpet cloaks. The calcite shields, on the other hand, can disappear objects 1 to 2 millimeters tall. Metamaterial designs "liberated the imaginations," he says. "Now, it's time to come back to reality."
But with such tricky optical sleight of hand, reality may seem like a misnomer. With the right type of light, calcite prisms can bend laser beams in different directions based on the crystal's orientation. Light enters the cloak — a triangle or trapezoid made of two prisms glued together — and bounces off the bent mirror at the bottom into the second prism, then out. By the time the beams leave the cloak, they look like they changed direction only once, says George Barbastathis of MIT, coauthor of the Physical Review Letters article. His team used the cloak to hide a small metal wedge. "Putting calcite on top of the wedge, the light goes back into the same direction that it would have with a flat mirror," he says. But it's not just the same direction — the light looks exactly like it bounced off a flat mirror. The metal wedge vanishes.
"It's not a Harry Potter cloak," says Shuang Zhang, a physicist at the University of Birmingham in England and one of the Nature Communications study coauthors. The cloak works only under one light polarization. And while it works at all angles, it's not three-dimensional. It only cloaks when Zhang aims the light source dead-on at the crystals. But, he says, scaling up to 3-D isn't too big of a leap from 2-D. Zhang imagines similar technology one day concealing submarines on the sea floor.
Leonhardt says the future of optical legerdemain lies not in hiding things, but in revealing them. He uses the same geometric tools to design better microscopes. "We use similar ideas not to make things disappear but to make them visible," he says.
Now that's something Professor Snape could get behind.
Image: A piece of pink paper vanishes under a new invisibility cloak developed by MIT researchers./Baile Zhang and G. Barbastathis/SMART Centre.
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