November 26, 2013
Seahorses belong to the genus Hippocampus, which gets its name from the Greek words for “horse” and “sea monster.” With their extreme snouts, weirdly coiled bodies and sluggish movements produced by to two puny little fins, these oddly shaped fish seem like an example of evolution gone terribly awry. And yet, new research published today in Nature Communications shows that it is precisely the seahorse’s uncanny looks and slow motions that allow it to act as one of the most stealthy predators under the sea.
Seahorses, like their close relatives the pipefish and sea dragons, sustain themselves by feasting on elusive, spastic little crustaceans called copepods. To do this, they use a method called pivot feeding: they sneak up on a copepod and then rapidly strike before the animal can escape, much like a person wielding a bug swatter tries to do to take out an irritating but otherwise impossible-to-catch fly. But like that lumbering human, the seahorse will only be successful if it is able to get near enough to its prey to strike at very close range. In the water, however, this is an even greater feat than on land because creatures like copepods are extremely sensitive to any slight hydrodynamic change in the currents around them.
So how do those ungainly little guys manage to feed themselves? As it turns out, the seahorse is a more sophisticated predator than appearance might suggest. In fact, it is precisely its looks that make it an ace in the stealth department. To arrive at this surprising conclusion, researchers from the University of Texas at Austin and the University of Minnesota used holographic and particle image velocimetry–fancy ways of visualizing 3D movements and water flow, respectively–to monitor the hunting patterns of dwarf seahorses in the lab.
In dozens of trials, they found that 84 percent of the seahorses’ approaches successfully managed not to sound the copepod’s retreat alarms. The closer the seahorse could get to its unsuspecting prey and the faster it struck, the greater its odds of success, they observed. Once in range of the copepod, seahorses managed to capture those crustaceans 94 percent of the time. Here, you can see that method of attack, in which the seahorse’s giant head looks like a floating bit of marine sludge drifting toward the blissfully ignorant copepod:
The way the seahorse’s movements and morphology–especially its head–interact with the water particles, the researchers found, likely take the credit for its exceptional hunting skill. The animal’s arched neck acts like a spring for generating an explosive strike, they describe, while the shape of its snout–a thin tube with the mouth positioned at the very end–allows it to drift through the water while creating minimal disturbance.
To emphasize this pinnacle of engineering, the team compared water disruptions caused by seahorses with those of sticklebacks, a relative of the seahorse but with a more traditional fishy look. Thanks to the shape and contours of the seahorse’s head, that predator produced significantly less fluid deformation in the surrounding water than the stickleback. The poor stickleback possesses neither the morphology nor posture to generate “a hydrodynamically quiet zone where strikes occur,” the authors describe. In other words, while the seahorse may appear a bit odd so far as fishes go, evolution was obviously looking out for that funny but deadly animal’s best interests.
August 29, 2013
A rocky, icy body the size of Rhode Island is playing follow the leader with the seventh planet from the Sun, whizzing along Uranus’ orbit one-sixth of a revolution ahead of the planet. The body, temporarily dubbed 2011 QF99, is the first of its type found to circle with Uranus. Researchers reporting in the journal Science document its detection and show that it is probably not alone
, promising a clearer picture of the ongoing celestial pinball game in the solar system’s outer reaches.
Thousands of similarly positioned bodies are known to exist around Jupiter; they are called Trojans because each is named for a mythological character in the Trojan War. But scientists had believed that gravitational tug around Uranus and Saturn, particularly the pull of Jupiter, made similar companions there unlikely.
What exactly are Trojans? Their story dates back to the 18th century, when a famous mathematician named Joseph-Louis Lagrange wrote an essay on the problem of three bodies, identifying five positions where the gravitational effects of a body orbiting another body (think of the Earth-Moon system as a single body circling the Sun) would allow a third smaller body to stay balanced. When located at any of these five Lagrange Points, the third body would appear stationary relative to the other two. Three of these five positions, called L1, L3 and L3, would be unstable–if the third body drifted just a bit off course from any of these positions, it could never recover from the misstep. L1 and L2 are ideal locations for placing artificial satellites that study the Sun and space, although the spacecrafts’ trajectories have to be constantly tweaked so that they stay at these points.
But at two Lagrange Points, dubbed L4 and L5, the body would be pulled right back regardless of which way it drifted, causing it to swing around the point like a gymnast on a high bar. In fact, multiple bodies–many thousands–could dance around each point within an elongated region of stability that contours to the orbital path of the planet. One of these points sits 60 degrees ahead on that orbital path and another 60 degrees behind.
Other three-body systems have these same balance points, and in 1906 astronomers found an asteroid in the
L4 region of Jupiter’s orbit around the Sun, naming the body Achilles. In the following years, more Trojan asteroids were discovered around Jupiter’s L4 and L5 and, more recently, Trojans have been found along other planets’ orbits, including Mars’, Neptune’s and even Earth’s.
But none had turned up for Uranus or Saturn–until now. As part of a Canada-France-Hawaii Telescope survey designed to search for small bodies orbiting beyond the most distant planet, Neptune, a team of astronomers spotted 2011 QF99 in three images taken an hour apart on the same patch of sky. The object’s brightness suggested it was 60 kilometers across and its orbit pinned it as distant as Uranus, but further observations in 2011 and 2012 distinguished it from a Centaur, an unstable icy body that orbits the Sun and occasionally crosses, but doesn’t follow or lead, planetary orbits. The team’s study showed 2011 QF99 running out ahead of Uranus like a dog on a leash: It was an L4 Trojan.
“A Uranian Trojan was not the focus of our survey,” says Mike Alexandersen, an astronomer at the University of British Columbia. “When we realized what it was, we were like ‘Whoa, wow.’”
Unlike most other known Trojans, which adopted their current positions early during the solar system’s formation, 2011 QF99 was probably first a Centaur and was captured at L4 later on, caught as it leaked inward from more distant reaches. Numerical analyses of the details of the orbit of 2011 QF99 suggest it will remain as a Trojan for 70,000 years before, after a million years or so, it moves beyond the L4 region of stability and rejoins the Centaurs.
2011 QF99, then, is a temporary Trojan. And simulations by Alexandersen and his team, reported for the first time in the new paper, find that 2011 QF99 is not alone. About 3 percent of the small bodies in the outer solar system share an orbit with Neptune or Uranus at any given time. “There are a lot of asteroids and comets flying around the solar system, and a lot of them cross the orbits of planets and only a tiny fraction get captured,” he says. Capture is “
a low probability event. Intuitively, we thought it had an even lower probability.”
While the more permanent Trojans have quite a lot to to say about primordial jostling, the temporary Trojans–including others discovered orbiting with Neptune and Earth–could reveal information on the amount of Centaurs populating the nether reaches, how exactly they got there and what paths they follow.
“Those unstable objects, the Centaurs, often go on to become Jupiter-family comets, many of which approach the Earth and could, eventually, pose an impact threat,” says Jonti Horner, an astronomer at the University of New South Wales who wasn’t involved in the study. “Being able to study those objects when they’re far from the Sun, and therefore not hidden by a cometary coma, can tell us a lot about comets and other objects that can threaten Earth.”
“It’s a really exciting discovery for me, and for other people who look at the solar system’s small bodies,” he added.
Alexandersen, who notes that the risk of impact is extremely low, says the results speak to how much is still left to know about our solar system. He predicts that more will be revealed as astronomers continue to detect smaller and smaller objects. “If there is one 60-kilometer Trojan, then there are probably dozens of one-kilometer Trojans,” he says. “We just can’t see them yet.”
August 22, 2013
Modern archeologists, excavating ancient Egyptian tombs, have often found something unexpected amongst the tombs’ artifacts: pots of honey, thousands of years old, and yet still preserved. Through millennia, the archeologists discover, the food remains unspoiled, an unmistakable testament to the eternal shelf-life of honey.
There are a few other examples of foods that keep–indefinitely–in their raw state: salt, sugar, dried rice are a few. But there’s something about honey; it can remain preserved in a completely edible form, and while you wouldn’t want to chow down on raw rice or straight salt, one could ostensibly dip into a thousand year old jar of honey and enjoy it, without preparation, as if it were a day old. Moreover, honey’s longevity lends it other properties–mainly medicinal–that other resilient foods don’t have. Which raises the question–what exactly makes honey such a special food?
The answer is as complex as honey’s flavor–you don’t get a
food source with no expiration date without a whole slew of factors working in perfect harmony.
The first comes from the chemical make-up of honey itself. Honey is, first and foremost, a sugar. Sugars are
hygroscopic, a term that means they contain very little water in their natural state but can readily suck in moisture if left unsealed. As Amina Harris, executive director of the Honey and Pollination Center at the Robert Mondavi Institute at Univeristy of California, Davis explains, “Honey in its natural form is very low moisture. Very few bacteria or microorganisms can survive in an environment like that, they just die. They’re smothered by it, essentially.” What Harris points out represents an important feature of honey’s longevity: for honey to spoil, there needs to be something inside of it that can spoil. With such an inhospitable environment, organisms can’t survive long enough within the jar of honey to have the chance to spoil.
Honey is also naturally extremely acidic. “It has a pH that falls between 3 and 4.5, approximately, and that acid will kill off almost anything that wants to grow there,” Harris explains. So bacteria and spoil-ready organisms must look elsewhere for a home–the life expectancy inside of honey is just too low.
But honey isn’t the only hygroscopic food source out there. Molasses, for example, which comes from the byproduct of cane sugar, is extremely hygroscopic, and is acidic, though less so than honey (molasses has a pH of around 5.5). And yet–although
it may take a long time, as the sugar cane product has a longer shelf-life than fresh produce, eventually molasses will spoil.
So why does one sugar solution spoil, while another lasts indefinitely? Enter bees.
“Bees are magical,” Harris jokes. But there is certainly a special alchemy that goes into honey. Nectar, the first material collected by bees to make honey, is naturally very high in water–anywhere from 60-80 percent, by Harris’ estimate. But through the process of making honey, the bees play a large part in removing much of this moisture by flapping their wings to literally dry out the nectar. On top of behavior, the chemical makeup of a bees stomach also plays a large part in honey’s resilience. Bees have an enzyme in their stomachs called glucose oxidase (PDF). When the bees regurgitate the nectar from their mouths into the combs to make honey, this enzyme mixes with the nectar, breaking it down into two by-products: gluconic acid and hydrogen peroxide. “Then,” Harris explains, “hydrogen peroxide is the next thing that goes into work against all these other bad things that could possibly grow.”
For this reason, honey has been used for centuries as a medicinal remedy. Because it’s so thick, rejects any kind of growth and contains hydrogen peroxide, it creates the perfect barrier against infection for wounds. The earliest recorded use of honey for medicinal purposes comes from Sumerian clay tablets, which state that honey was used in 30 percent of prescriptions. The ancient Egyptians used medicinal honey regularly, making ointments to treat skin and eye diseases. “Honey was used to cover a wound or a burn or a slash, or something like that, because nothing could grow on it – so it was a natural bandage,” Harris explains.
What’s more, when honey isn’t sealed in a jar, it sucks in moisture. “While it’s drawing water out of the wound, which is how it might get infected, it’s letting off this very minute amount of hydrogen peroxide. The amount of hydrogen peroxide comes off of honey is exactly what we need–it’s so small and so minute that it actually promotes healing.” And honey for healing open gashes is no longer just folk medicine–in the past decade, Derma Sciences, a medical device company, has been marketing and selling MEDIHONEY, bandages covered in honey used in hospitals around the world.
If you buy your honey from the supermarket, that little plastic bottle of golden nectar has been heated, strained and processed so that it contains zero particulates, meaning that there’s nothing in the liquid for molecules to crystallize on, and your supermarket honey will look the same for almost forever. If you buy your honey from a small-scale vendor, however, certain particulates might remain, from pollen to enzymes. With these particulates, the honey might crystallize, but don’t worry–if it’s sealed, it’s not spoiled and won’t be for quite some time.
A jar of honey’s seal, it turns out, is the final factor that’s key to honey’s long shelf life, as exemplified by the storied millennia-old Egyptian specimens. While honey is certainly a super-food, it isn’t supernatural–if you leave it out, unsealed in a humid environment, it will spoil. As Harris explains, ” As long as the lid stays on it and no water is added to it, honey will not go bad. As soon as you add water to it, it may go bad. Or if you open the lid, it may get more water in it and it may go bad.”
So if you’re interested in keeping honey for hundreds of years,
do what the bees do and keep it sealed–a hard thing to do with this delicious treat!
July 12, 2013
A glass of merlot may make the world look rosy, but it can also be a source of frustration for a physicist. The wine pours, splashes and swirls, yet the glass remains stiff as a solid vessel.
Zoom in on the merlot and you’ll see molecules held close together but moving about with no fixed position. Zoom in on the wine glass and you’ll also see this disordered arrangement, but no movement.
On an atomic level, the two forms of matter look the same. Even though a glass is frozen solid, it lacks the rigid crystalline structure found in, say, ice cubes.
Though artisans have been making glass for millennia and scientists have been studying its structure for decades, until now there has been no clear experimental evidence to confirm what prevents liquids that form glasses from crystallizing. In a new paper published online in Science, a team of Japanese researchers used a high-powered electron diffraction microscope to view glass at the tiniest scales yet. At such high resolution they saw what looks to be a basic unit of some glasses–atoms packed in a distorted version of an icosahedron, a three dimensional shape with 20 faces.
With sophisticated geometric tools, the team characterized those distortions, reporting in the paper that they allow the system to “retain dense atomic packing and a low energy state.” Certain arrangements of atoms, the researchers conclude, are the very essence of glassiness because they interfere with the development of a well-organized crystal.
Though the researchers were studying a glass made of zirconium and platinum, not your average windowpane, the results may hold for glasses more broadly. By understanding the ways atoms organize, material scientists can find ways to make new glasses and manipulate the ones they’ve got.
But glass is far from figured out. While the study explains why some liquids form glasses instead of crystallizing, it doesn’t explain why these liquids can become sluggish enough to be solid, says Duke University chemist Patrick Charbonneau.
A large community of scientists have been attempting to resolve the sluggishness since the 1980s, but they can’t agree on the solution and they even argue about the best approach.
One popular strategy takes a step back to try to understand how atoms fill a given space. It treats the atoms in glass as hard spheres packed together. Simple, right? “There is no quantum mechanics, there is no string theory, you don’t have to invoke outer space,” Charbonneau says. And yet even studying glass in this way has proven incredibly difficult because of the complications that come with figuring out what positions so many particles could occupy. On top of the inherent challenge of describing the arrangement of the spheres, the approach is a simplification and it is not clear how relevant it would be for real-world glasses.
Still, Charbonneau appears energized when he talks about such research problems. His glass of merlot is half full, because he believes the last few years have brought immense progress. Scientists, he says, have become more creative in asking questions about glass. Charbonneau’s own research simulates glass in higher dimensions, findings that could have important implications for the degree of disorder in three-dimensional glass. Other researchers are considering what would happen if you immobilized some particles in a supercooled liquid, hoping to illuminate how such liquids achieve a glassy state. Still more are considering atoms in glass as entities that can move on their own, sort of like biological cells. All of these efforts are trying to determine the types of interactions that contribute to the formation of glass, so that scientists will recognize a really good sluggishness theory when they see it.
Despite all this talk about movement, don’t expect your wine glass to flow in any visible way anytime soon. This glass “will last longer than the timescale of the universe,” Charbonneau says. Claims that the stained glass in medieval cathedrals is thicker at the bottom because glass flows are bunk. But exactly why it doesn’t flow still remains a mystery.
June 28, 2013
Every day, it seems, a new exoplanet is found (or, in the case of Tuesday, scientists discovered three potentially habitable exoplanets orbiting one star). But there are loads of hurdles that we’ll have to clear before we ever have the chance to visit them: the massive doses of radiation that would be absorbed by would-be astronauts, the potential damage caused by interstellar dust and gas to a craft moving at extremely high speeds, and the fact that traveling to even the nearest habitable exoplanet would take almost 12 years in a spacecraft traveling at the speed of light.
The biggest problem, though, might be the enormous amount of energy such a craft would require. How do you fuel a spacecraft for a journey more than 750,000 times farther than the distance between the Earth and the Sun?
Based on our current technology for exploring space and potential future approaches, here’s a rundown of the possible ways of propelling spacecraft.
Conventional Rockets: These create thrust by burning a chemical propellant stored inside, either a solid or liquid fuel. The energy released as a result of this combustion lifts a craft out of Earth’s gravitational field and into space.
Pros: Rocket technology is well-established and well-understood, as it dates to ancient China and has been used since the very beginning of the space age. In terms of distance, its greatest achievement thus far is carrying the Voyager 1 space probe to the outer edge of the solar system, roughly 18.5 billion miles away from Earth.
Cons: The Voyager 1 is projected to run out of fuel around the year 2040, an indication of how limited in range conventional rockets and thrusters can carry a spacecraft. Moreover, even if we could fit a sufficient amount of rocket fuel onto a spacecraft to carry it all the way to another star, the staggering fact is that we likely don’t even have enough fuel on our entire planet to do so. Brice Cassenti, a professor at Rensselaer Polytechnic Institute, told Wired that it would take an amount of energy that surpasses the current output of the entire world to send a craft to the nearest star using a conventional rocket.
Ion engines: These work somewhat like conventional rockets, except instead of expelling the products of chemical combustion to generate thrust, they shoot out streams of electrically-charged atoms (ions). The technology was first successfully demonstrated on NASA’s 1998 Deep Space 1 mission, in which a rocket closely flew past both an asteroid and a comet to collect data, and has since been used to propel several other spacecraft, including an ongoing mission to visit the dwarf planet Ceres.
Pros: These engines produces much less thrust and initial speed than a conventional rocket—so they can’t be used to escape the Earth’s atmosphere—but once carried into space by conventional rockets, they can run continuously for much longer periods (because they use a denser fuel more efficiently), allowing a craft to gradually build up speed and surpass the velocity of one propelled by a conventional rocket.
Cons: Though faster and more efficient than conventional rockets, using an ion drive to travel to even the nearest star would still take an overwhelmingly long time—at least 19,000 years, by some estimates, which means that somewhere on the order of 600 to 2700 generations of humans would be needed to see it through. Some have suggested that ion engines could fuel a trip to Mars, but interstellar space is probably outside the realm of possibility.
Nuclear Rockets: Many space exploration enthusiasts have advocated for the use of nuclear reaction-powered rockets to cover vast distances of interstellar space, dating to Project Daedalus, a theoretical British project that sought to design an unmanned probe to reach Barnard’s Star, 5.9 light-years away. Nuclear rockets would theoretically be powered by a series of controlled nuclear explosions, perhaps using pure deuterium or tritium as fuel.
Pros: Calculations have shown that a craft propelled in this way could reach speeds faster than 9000 miles per second, translating to a travel time of roughly 130 years to Alpha Centurai, the star nearest the Sun—longer than a human lifetime, but perhaps within the realm of a multi-generational mission. It’s not the Millenium Falcon making the Kessel Run in less than 12 parsecs, but it’s something.
Cons: For one, nuclear-powered rockets are, at present, entirely hypothetical. In the short-term, they’ll probably stay that way, because the detonation of any nuclear device (whether intended as a weapon or not) in outer space would violate the Partial Nuclear Test Ban Treaty, which permits such explosions in exactly one location: underground. Even if legally permitted, there are enormous safety concerns regarding the launch of a nuclear device into space atop a conventional rocket: An unexpected error could cause radioactive material to rain across the planet.
Solar Sails: In comparison to all the other technologies on this list, these operate on a rather different principle: Instead of propelling a craft by burning fuel or creating other sorts of combustion, solar sails pull a vehicle by harnessing the energy of the charged particles ejected from the Sun as part of the solar wind. The first successful demonstration of such a technology was Japan’s IKAROS spacecraft, launched in 2010, which traveled towards Venus and is now journeying towards the Sun, and NASA’s Sunjammer, seven times larger, is going to launch in 2014.
Pros: Because they don’t have to carry a set amount of fuel—instead using the power of the Sun, much like a sailboat harnesses the energy of the wind—a solar sail-aided spacecraft can cruise more-or-less indefinitely.
Cons: These travel much slower than rocket-powered crafts. But more important for interstellar missions—they require the energy ejected from the Sun or another star to travel at all, making it impossible for them to traverse the vast spaces between the reach of our Sun’s solar wind and that of another star system’s. Solar sails could potentially be incorporated into a craft with other means of propelling itself, but can’t be relied upon alone for an interstellar journey.
Antimatter Rockets: This proposed technology would use the products of a matter-antimatter annihilation reaction (either gamma rays or highly-charged subatomic particles called pions) to propel a craft through space.
Pros: Using antimatter to power a rocket would theoretically be the most efficient fuel possible, as nearly all of the mass of the matter and antimatter are converted to energy when they annihilate each other. In theory, if we were able to work out the details and produce enough antimatter, we could build a spacecraft that travels at speeds nearly as fast as that of light—the highest velocity possible for any object.
Cons: We don’t yet have a way to generate enough antimatter for a space journey—estimates are that a month-long trip to Mars would require about 10 grams of antimatter. To date, we’ve only been able to create small numbers of atoms of antimatter, and doing so has consumed a large amount of fuel, making the idea of an antimatter rocket prohibitively expensive as well. Storing this antimatter is another issue: Proposed schemes involve the use of frozen pellets of antihydrogen, but these too are a far way off.
More speculative technologies: Scientists have proposed all sorts of radical, non-rocket-based technologies for interstellar travel. These include a craft that would harvest hydrogen from space as it travels to use in a nuclear fusion reaction, beams of light or magnetic fields shot from our own Solar System at a distant spacecraft that would be harnessed by a sail, and the use of black holes or theoretical wormholes to travel faster than the speed of light and make an interstellar journey possible in a single human’s lifetime.
All of these are extremely far away from implementation. But, if we do ever make it to another star system at all (a big if, to be sure), given the problems with most existing and near-future technologies, it might indeed be one of these pie-in-the-sky ideas that carry us there—and perhaps allow us to visit a habitable exoplanet.