Author: John Timmer

Solar Impulse on the ground in New York City. (credit: John Timmer)

Right now the Solar Impulse aircraft is over the Persian Gulf, approaching Abu Dhabi, its final destination. As Abu Dhabi is also the location that the craft started on its round-the-world flight, its extended journey is near an end. The Solar Impulse flight marks the first circumnavigation of the globe by a piloted solar aircraft.

Bertrand Picard is at the controls, having started the flight in Cairo and taken the craft over Saudi Arabia, Qatar, and the Persian Gulf. The final flight has taken about a day and a half so far and has suffered a lot of turbulence as the desert below it heated up and cooled off.

At the moment, Solar Impulse is making slow loops back and forth offshore, suggesting that the team is waiting for either traffic or weather conditions to improve at its destination. Since it's currently night, it's also possible that the team wants to bring the aircraft down at a time when it will be possible for everyone to see it.

A local honey hunter holds one of his trusty guides. (credit: Claire Spottiswoode)

Humans and wild animals often help each other out, but the relationship is usually accidental. For example, birds of prey sometimes follow farm equipment through fields because the hardware flushes small animals out. Humans don't help the birds intentionally, and we don't gain anything from them. For truly cooperative relationships, you generally have to look to animals we've domesticated.

Generally, but not exclusively. There's an African bird called the honeyguide that helps humans find bees' nests. The humans get the honey, while the birds feast on the wax left behind (the honeyguides were first formally described after they were witnessed eating some candles). Now, new research shows that the birds can specifically respond when a human makes a call that indicates they're interested in finding honey.

Honeyguides inhabit an area of Africa that includes Tanzania and Mozambique. When they're in the mood for beeswax, they approach a human and start making a chattering call. This call is distinct from the call they use to communicate with each other, and it's accompanied by very specific behavior: the bird flits from tree to tree in the general direction of a bee's nest. Once the nest is located and opened, the human comes away with honey and leaves the wax behind for the honeyguide to eat.

Lux, a xenon-based dark matter detector. (credit: Lawrence Berkeley Lab)

Today, the team behind one of the most sensitive dark matter detectors announced its full experimental run had failed to turn up any of the particles it was looking for. The LUX detector (Large Underground Xenon) is designed to pick up signs of weakly interacting massive particles, or WIMPs, when they engage in one of their rare interactions with normal matter. The null result doesn't rule out the existence of dark matter, but it limits its potential properties.

As their name implies, WIMPs don't interact with normal matter often, but sthey hould on occasion bump into an atom, imparting energy to it. LUX provides a tempting target in the form of 370kg of liquid xenon. The detector is flanked by photodetectors to pick up any stray photons from the interactions, as well as hardware that picks up any stray charges knocked loose.

The challenge is to determine which signals are caused by dark matter and which are the product of cosmic rays or the natural background of radioactive decays. To handle the former, the detector is located nearly 1.5km below the surface in South Dakota's Homestake Mine. It's also partly shielded from the radioactive decays of the surrounding rock by an enormous tank of ultra-pure water. Even so, the scientists behind it had to spend time carefully characterizing the background noise. The success of that effort meant that LUX ended up four times more sensitive than it was originally designed to be.

Enlarge / A passage of one of Feynman's lectures, written in individual atoms. (credit: TU Delft)

Last week saw researchers figure out how to make circuitry that's only a single atom thick, and this week we're pushing the physical limits on what we can do with data storage. While the ultimate limit is probably going to be a single atom, a procedure presented in a new paper is slightly less efficient in that it requires the space occupied by two atoms. Even so, and even after accounting for the equivalent of bad blocks in the storage media, the data density is enough to fit the contents of the Library of Congress within a 100 micrometer cube.

The approach, developed by a team of Dutch and Spanish researchers, has so many ingenious features that it's difficult to know where to start describing it all. But since we have to start somewhere, we'll begin with the medium itself.

The researchers first evaporated some chlorine and allowed it to settle on a copper surface. Given enough time, a single-atom layer of chlorine will fully coat the copper surface. But if you cut the process short, you end up with a mix of chlorine atoms and vacant spaces on the surface. With a scanning-tunneling microscope, which registers the electronic state of the surface, you can easily detect the difference between a chlorine atom and the hole where one could be.

Enlarge (credit: SpaceX)

With a number of successful Falcon booster landings behind it, SpaceX is getting ready to try something likely to be a bit more challenging: three nearly simultaneous landings. This doesn't mean SpaceX is upping its launch schedule; instead, the three boosters will all be part of the planned Falcon Heavy vehicle.

Essentially three standard Falcons strapped together, the big rocket will be capable of lifting 54 metric tons into orbit. SpaceX is planning on the first Falcon Heavy test launch later this year. A video posted earlier this year made it clear that those plans include treating each of the three boosters as a regular Falcon once they've separated from the payload. That includes a return flight to Florida or a barge offshore.

Right, now, the company is using either the barge or an on-land site at Cape Canaveral to recover the boosters, with the choice depending on how high and far downrange they travel. And the company wants the option of returning all three to land if the opportunity arises (though two by land and one by sea might be an option). And so the company told The Orland Sentinel that it was asking the government for permission to build two more landing pads near its original facility.

The features we're making in current semiconductor materials are shrinking to the point where soon, they will be just a handful of atoms thin. Unfortunately, the behavior you get from bulk materials is often different from what you see when there are just a few atoms present, and quantum effects begin to dominate. There is an alternative, however: start with a material that is already incredibly small and has well-defined properties. Graphene, for example, is a sheet of carbon just one atom thick, and it's an excellent conductor; a variety of similar materials have been also developed.

It's a big challenge to manipulate these things that are just one atom thick, so it's really hard to put together any sort of circuitry based on these materials. Now, however, researchers have figured out how create a template where single-atom-thick materials will grow to create functional circuitry.

As we noted above, graphene is an excellent conductor of electrons, so the authors of the new paper decided to use it to create wiring. But getting sheets of graphene lined up to consistently create the wiring of even simple circuitry has been nearly impossible. The authors didn't even try. Instead, they took a larger sheet of graphene, dropped it onto silicon dioxide, and then etched away any material they didn't want. The etching involved a plasma of oxygen ions, which burned channels in the graphene that were about 15µm wide.

Early Monday morning, SpaceX achieved a successful launch and landing of its Falcon main stage, which sent a Dragon capsule loaded with supplies to the International Space Station. Unlike most previous attempts, the Falcon was able to return to Florida rather than dropping onto a barge in the Atlantic. The successful landing adds another item to the company's collection of lightly used boosters, some of which are intended to ultimately make return trips to space.

The Dragon capsule is expected to reach the ISS within two days. It contains a typical assortment of supplies and experiments in its pressurized portion. But it also carries a bit of hardware externally: an international docking adaptor, or IDA. The IDA is built to standards that different nations can adopt, allowing their hardware to interact with the system. According to NASA, "the adapter is built so spacecraft systems can automatically perform all the steps of rendezvous and dock with the station without input from the astronauts."

This is the second IDA sent to the Station, the first having exploded in one of SpaceX's rare failed launches.

By the time European explorers reached the islands scattered across the vast distances of the Pacific Ocean, most of the voyaging done by the Polynesians was among local island groups. But the locals seemed to know of places well beyond their shores, which suggested their ancestors not only colonized far-flung islands, but returned to share knowledge of them. Eventually, it became clear that trade had distributed goods among Polynesian communities that later became isolated.

In recent years, modern techniques have revealed the staggering geographic extent of this trade, which included a visit to South America for some takeout sweet potatoes, which were later grown on islands throughout the Pacific. But the temporal extent of the trade remained the subject of debate, with some arguing for a brief burst off exchange, and others suggesting extended trade networks persisted for a while. Now, a paper published in PNAS uses another modern form of analysis argues for at least four centuries of trade.

The work relies on a site in the Cook Islands, which provided a rare archeological resource: an extended series of deposits that contained enough material that researchers could carbon date various layers. Also included were some traditional Polynesian stone adzes, tools made from a specific type of volcanic rock. The researchers behind the new paper obtained small samples from these tools, and used them in another type of modern analysis called mass spectroscopy.

Biology has given robot makers lots of good ideas about how to solve certain problems, like how to squeeze into tight spaces, how to conserve energy for flying, and how to move around without a skeleton. But now it's giving us the raw materials for building a robot—or perhaps more properly a cyborg. Researchers have not only based the design of their robot on animals like skates and rays, but have used muscle cells to power its movements and light-sensitive proteins to replace its circuitry.

Skates and rays (technically batoid fish) are distinct from other cartilaginous fish in that they have a largely flat body plan and generate propulsion by undulating their bodies rather than by flapping fins. This undulation is a very simple way to generate locomotion, but it's highly energy-efficient and lends itself to soft-bodied robotics. It's also relatively easy to steer, simply by alternating the frequency of undulations on the right and left sides of the body. So the builders (a huge US-Korean team) of the new robot used this as inspiration for their new design.

To mimic this type of fish, the authors built the body out of a flexible polymer called PDMS. Internally, they added a flexible metallic skeleton made of gold so that once an undulation was done, the body would flex back into its original shape.

We tend to only pay attention to particle physics when scientists announce that they've found something new. But those discoveries would never get to the announcement stage without the years of grunt work needed to control particles at extremely high energies and record the debris that spews into detectors when those particles collide. This work doesn't get talked about much because it simply sets the stage for discovery rather than containing obvious "eureka!" moments.

The people behind CERN's Large Hadron Collider are in the process of setting a phenomenal stage.

Last year's run was all about taking the LHC to higher energies, which would enable the discovery of heavier particles and make it easier to spot light ones. This year's run was about taking the experience gained last year and using it to produce lots more collisions. So far, everything is going according to plan.