Members of the U.S. Army's First Earth Battalion hoped to bend physics and render themselves invisible, when they weren't trying to kill goats by staring at them. The British Ministry of Defense's Future Protected Vehicle project wants top tech companies to create an invisible tank, possibly using cameras and reflective screens, to use for patrols in Afghanistan.
But researchers working for the U.S. Navy have found a more down-to-earth -- down-to-sea, in fact -- inspiration in the search for stealth: squid.
Scientists at Duke University -- something of a hotbed for this kind of work over the years -- the Scripps Institute of Oceanography and the University of California, Santa Barbara's Marine Science Institute are studying the mechanics of how squid, cuttlefish and octopus use special light-sensitive organs and cells to manipulate light and create "dynamic camouflage."
What does that mean? If you've ever gone scuba diving and encountered a cuttlefish, you may have noticed its ability to change color while matching its surroundings, even while jetting along in the water. Its cousin the octopus can even use muscles in its skin to imitate textures, to appear like algae or a rough ocean-reef rock. These chameleons of the sea, called cephalopods, create a range of special effects not just for hiding, but for attracting mates and catching prey.
Cephalopods cast their illusions primarily with organs called chromatophores -- tiny ink sacs controlled by muscles that release pigments in patterns, in layers under the skin. They are among the most intelligent creatures in the sea, and their pattern-making is so advanced they could "probably play a television show on their backs, if their brains were big enough," says Sonke Johnsen, associate professor of biology at Duke University.
"They make color sort of the way soap bubbles do ... but the neat thing about it is they can actively control it."
With $5 million in funding from the U.S. Navy over the next five years, Johnsen is leading a team of researchers trying to determine, in part, whether dynamic camouflage can be put to use on the battlefield.
"The systems evolved by marine animals in order to hunt, hide and mate over hundreds of million years surpass our contemporary engineering designs for underwater vehicles," says one of the team's studies. "The impact will hopefully affect all branches of the armed forces that have aquatic missions. This includes Special Forces, mine hunting vehicles, the submarine community and a newest generation of underwater vehicles that could all benefit from the option of 'stealth.'"
Not just the Navy is interested, either. The Army; defense contractor Raytheon; and the Pentagon's deep-science think tank, the Defense Advanced Research Projects Agency, have funded or are otherwise also involved in the team's work.
They call their primary research tool a Holodeck. But don't think of it in terms of creating Cmdr. Riker-style fantasies -- this Holodeck is about making the animals feel at home.
"We are able to show the animals any scene we want. We have a camera called an Omnicam that takes pictures in all six directions," Johnsen says.
Six monitors -- in essence, plasma-screen TVs -- surround the Holodeck tank, so the team can create a "fairly seamless representation of the world, like being on a coral reef," says Johnsen.
With scientists studying a variety of ways to achieve invisibility, or at least creating the illusion of it, could cephalopods provide the breakthrough? Think twice before ordering that plate of calamari.
"At the moment, what we are left with are the tricks that animals use," Johnsen says. "They are not true invisibility, but they are very good."