The speed at which a dune migrates depends on its size; smaller dunes move faster than larger ones. That speed differential implies that small dunes should frequently collide into and Keep reading
Tag: granular material
The Sand Sea’s End
The northern extent of Africa’s Namib Sand Sea ends where the reddish dunes meet the Kuiseb River and the hard, rocky land on its other side. Within the sand sea, Keep reading
In Search of a Better Espresso
Of specialty coffee drinks, espresso has the most cup-to-cup variation in quality. For those who are not coffee aficionados — such as yours truly — espresso is made by forcing Keep reading
Self-Assembly Under Stratification
Sometimes mistakes lead to great discoveries. After leaving a failed outreach demo overnight, researchers discovered a new mechanism for self-assembling particles. In the initial set-up, a layer of fresh water Keep reading
Recreating Volcanic Lightning
Some natural phenomena, like volcanic eruptions or tornado formation, don’t lend themselves to fieldwork — at least not at the height of the action. The danger, unpredictability, and destructiveness of Keep reading
Martian Landslides
Sometimes there are advantages to studying planetary physics beyond Earth. Mars does not have plate tectonics, vegetation, or the level of erosion we do, allowing geological features like those left Keep reading
Drops That Dig
On extremely hot surfaces, droplets will skitter on a layer of their own vapor, thanks to the Leidenfrost effect. This keeps the liquid insulated from contact with the hot surface. But Keep reading
Shearing Grains
Granular materials, like beads and sand, demonstrate both solid and fluid-like behaviors, which makes them difficult to study. Traditionally, one method for studying how fluids respond to deformation places the Keep reading
Crowds as a Fluid
At a low density, crowds of people can behave like a fluid, which has led to numerous hydrodynamically-based crowd models. At higher densities, though, crowds are more like a soft solid, Keep reading
What Controls an Avalanche?
In an avalanche, grains spontaneously flow when a slope reaches a critical angle, and they continue flowing until they settle at a new, lower angle. Scientists have long debated why this Keep reading