Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
When Lava Meets Ice
What happens when lava meets ice or water? Artists and geologists are working together to explore these interactions by melting crushed basalt and pouring it onto different substrates. Ice is their classic example; instead of melting instantly through the ice, the lava is so hot that it creates a layer of steam between it and…
Earth’s Aerosols
The motions of Earth’s atmosphere move more than just air and moisture. As seen in this animation built from NASA satellite data, the atmosphere also transports large amounts of small solid particles, or aerosols, such as dust. Each year the wind carries millions of tons of Saharan dust across the Atlantic, depositing much of it…
Reader Question: Rippling Runoff
Reader junolivi asks: When shallow water (like runoff from melting snow) flows across pavement, it creates small repeated wave-like ripples. What creates that texture and why isn’t it just a steady flow? This is a great question that’s probably crossed the mind of anyone who’s seen water running down the gutter of a street after…
Martian Dust Devil
This photo from the Mars Reconnaissance Orbiter stares almost straight down a dust devil on Mars. Like their earthbound brethren, Martian dust devils form when the surface is heated by the sun, causing warm air to rise. The rising air causes a low pressure area that the surrounding air flows into. Any rotational motion of…
Asteroid Impact
I often receive questions about how fluids react to extremely hard and fast impacts. Some people wonder if there’s a regime where a fluid like water will react like a solid. In reality, nature works the opposite way. Striking a solid hard enough and fast enough makes it behave like a fluid. The video above…
Popcorn Popping
The familiar popping behavior of popcorn is the combination of several events. When heated, unpopped kernels act like pressure vessels, managing to contain their boiling water content until a critical temperature of 180 degrees Celsius. At this temperature, nearly all kernels fracture. Popcorn’s jump doesn’t come from the fracture, though. Most of its acrobatics occur…
How Eyelashes Work
New research shows that eyelashes divert airflow around the eye, serving as a passive filter that reduces dust collection and controls evaporation. Mammal hairs in places like the nose act as ram filters that trap the particles that hit them and which require regular cleaning via sneezing. Eyelashes, on the other hand, prevent dust collection…
Making a Bottle Resonate
If you’ve ever blown across the top of a bottle to make it play a note, then you’ve created a Helmholtz resonator. Air flow across the top of the bottle causes air in and around the bottle neck to vibrate up and down. Like a mass on a spring, the air oscillates with a particular…
Testing a Supersonic Car
How do you test a supersonic car like the Bloodhound SSC in a wind tunnel? With free-flying objects like airplanes, wind tunnel testing is relatively straightforward. Mounting a stationary model in a supersonic flow gives an equivalent flow-field to that object flying through still air at supersonic speeds. The same does not hold true for the…
The Milk Crown
This frequently imitated photograph of a drop of milk splashing was taken by engineer Harold Edgerton in 1934. Edgerton pioneered the application of stroboscopic photography to everyday objects, allowing him to capture images with an effective shutter speed much faster than could be mechanically achieved. The photo captures the crown or coronet of a splash.…