Murmurations of starlings, the purposeful motion of some bacteria, and the stopping and starting of traffic on a busy motorway are all examples of collective motion that have been studied by physicists. Now, we can add the flocking of sheep to this list.
Luis Gómez-Nava, Richard Bon and Fernando Peruani have just published a paper in Nature that looks at the roles of leaders and followers in driving the motion of flocks of sheep. Based at universities in France, the researchers combined observations of flocking with mathematical models to show that the collective motion of sheep is governed both by the movement of a lead animal and how other animals in the flock respond. Furthermore, the trio found that individual sheep alternated between leaders and followers in a seemingly random way.
As a result, the trio concludes that the collective motion of sheep is governed by both hierarchical and democratic processes within the flock. Something to think about the next time you are on a country walk and come across a field full of sheep.
Modelling fish
Some fish are famous for their collective motion, which is often used to confuse predators. But that is not the focus of research done by mathematicians at the UK’s Aston University, who have created new models of how creatures such as fish reduce their drag as they move through water or air.
Paul Griffiths and colleagues focused on the onset of turbulent flow around a moving object, which is known to increase drag significantly. One thing that fish use to reduce drag is the slime that covers their skin. By understanding how this and other natural drag-reducing techniques work, the Aston researchers hope to reduce the drag on vehicles – and therefore the amount of energy they require to move. So who knows, maybe we will see slime covered cars in the future.
When you buy packaged food, the label should tell you where the food has come from and what it contains. But food packaging constitutes a large chunk of the waste we produce – so wouldn’t it be nice if we could do away with packaging and still know the provenance of food?
Smart cookies
That is the plan of Yamato Miyatake and colleagues at Japan’s Osaka University, who have developed a way of creating QR codes in cookies. A 3D printer was used to create patterns within the bulk of the biscuits – and the codes can be read by shining light through the cookie. As a result, the team says that information about the food is available throughout its journey from the bakery to your pantry.
“We realized that the insides of edible objects such as cookies could be printed to contain patterns of empty spaces so that, when you shine a light from behind the cookie, a QR code becomes visible and can be read using a cellphone,” explains Miyatake, who is now at Bosch Japan.
There is much more about the research here.