Vikings Left Greenland in the 15th Century

One of the great mysteries of late medieval history is why did the Norse, who had established successful settlements in southern Greenland in 985, abandon them in the early 15th century? The consensus view has long been that colder temperatures, associated with the Little Ice Age, helped make the colonies unsustainable. 

However, new research, led by the University of Massachusetts Amherst and published recently in Science Advances, upends that old theory. It wasn't dropping temperatures that helped drive the Norse from Greenland, but drought.

When the Norse settled in Greenland on what they called the Eastern Settlement in 985, they thrived by clearing the land of shrubs and planting grass as pasture for their livestock. The population of the Eastern Settlement peaked at around 2,000 inhabitants, but collapsed fairly quickly about 400 years later. 

For decades, anthropologists, historians and scientists have thought the Eastern Settlement's demise was due to the onset of the Little Ice Age, a period of exceptionally cold weather, particularly in the North Atlantic, that made agricultural life in Greenland untenable.

However, as Raymond Bradley, University Distinguished Professor of geosciences at UMass Amherst and one of the paper's co- author, points out, "before this study, there was no data from the actual site of the Viking settlements. And that's a problem." 

Instead, the ice core data that previous studies had used to reconstruct historical temperatures in Greenland was taken from a location that was over 1,000 kilometers to the north and over 2,000 meters higher in elevation. "We wanted to study how climate had varied close to the Norse farms themselves," says Bradley. And when they did, the results were surprising.  READ MORE...

Shape Shifting Enabled

Physicists have discovered a new way to coat soft robots in materials that allow them to move and function in a more purposeful way. The research, led by the University of Bath, is described in a paper published on March 11, 2022, in Science Advances.

Authors of the study believe their breakthrough modeling on ‘active matter’ could mark a turning point in the design of robots. With further development of the concept, it may be possible to determine the shape, movement, and behavior of a soft solid not by its natural elasticity but by human-controlled activity on its surface.

Wrapping an elastic ball (orange) in a layer of tiny 

robots (blue) allows researchers to program shape 

and behavior. Credit: Jack Binysh

The surface of an ordinary soft material always shrinks into a sphere. Think of the way water beads into droplets: the beading occurs because the surface of liquids and other soft material naturally contracts into the smallest surface area possible – i.e. a sphere. But active matter can be designed to work against this tendency. An example of this in action would be a rubber ball that’s wrapped in a layer of nano-robots, where the robots are programmed to work in unison to distort the ball into a new, pre-determined shape (say, a star).

It is hoped that active matter will lead to a new generation of machines whose function will come from the bottom up. So, instead of being governed by a central controller (the way today’s robotic arms are controlled in factories), these new machines would be made from many individual active units that cooperate to determine the machine’s movement and function. This is akin to the workings of our own biological tissues, such as the fibers in heart muscle.

Using this idea, scientists could design soft machines with arms made of flexible materials powered by robots embedded in their surface. They could also tailor the size and shape of drug delivery capsules, by coating the surface of nanoparticles in a responsive, active material.. This in turn could have a dramatic effect on how a drug interacts with cells in the body.

Work on active matter challenges the assumption that the energetic cost of the surface of a liquid or soft solid must always be positive, because a certain amount of energy is always necessary to create a surface.  READ MORE...

Fireflies Sync Their Flashes

Swarms of synchronous fireflies are rather like melting ice, or at least that’s how Raphael Sarfati, a physicist, sees it. Ice remains solid until it warms to a certain temperature and becomes a liquid. Likewise, a loose swarm fireflies will flash the lanterns in their abdomens randomly. But when the swarm reaches a certain density, the fireflies begin to blink in unison.

“Above that threshold, it is almost perfect synchronization,” with rhythmic, coordinated waves of light, said Sarfati, a postdoctoral associate at the University of Colorado, Boulder.

The spontaneous synchronization of certain species of fireflies, such as Photinus carolinus in the Great Smoky Mountains in North Carolina and Tennessee, has long baffled humans who observed the peculiar mating ritual, in which blinking males strive to attract the attention of ground-level females. 

Early-20th-century scientists dismissed the phenomenon as accidental or blamed it on puffs of wind or the twitching eyelids of the people who made these reports, according to one 1935 review in Science.

In the past 50 years, scientists collected anecdotal observations of these unified flashes but not enough empirical data to truly study firefly synchronization’s mechanisms.

Now, Sarfati and Orit Peleg, a physicist and assistant professor also at the University of Colorado, have filmed the mating hordes of P. carolinus and mapped their flashing patterns in three-dimensional space. 

Their research, published Wednesday in the journal Science Advances, adds to evidence that the insects sync their flashes, and suggests what may drive that coordination. TO READ THE ENTIRE ARTICLE, CLICK HERE...