Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Inside Singing
These are the vocal folds of a woman singing. Human speech (and song) results from interactions between elastic muscles and aerodynamics. As we exhale, the vocal folds are initially pushed apart, then the flow of air moving past creates low pressure (via the Bernoulli effect) that helps pull the folds together. As the folds close,…
Boulder Sorting on Asteroid Itokawa
Itokawa is a small asteroid visited by the Japanese Hayabusa probe in 2005. Photographs of the asteroid revealed a surface covered in large boulders at high elevations and small pebbles in the valleys. The Brazil nut effect is often invoked to explain size separation in particle mixtures, but Itokawa is so small that any shaking sufficient…
Self-Propelling Drops
Droplets of acetone deposited on a bath of warm water can float along on a Leidenfrost-like vapor layer. The droplets are self-propelling, too, thanks to interactions between the acetone and water. Acetone can dissolve in water, and when acetone vapor beneath the drop gets absorbed into the water bath, it lowers the local surface tension.…
Asperitas Clouds
This short timelapse captures an impressive display of asperitas clouds over Augusta, Georgia. Asperitas clouds, previously known as undulatus asperatus, are a new classification recommended by the Cloud Appreciation Society in 2009. Recently, the World Meteorological Organization indicated they would include the clouds in the their latest Cloud Atlas under the new name. Asperitas clouds…
Using Jets to Find Food
Archer fish are well-known for their ability to hit aerial targets with perfectly aimed jets of water, as we’ve discussed previously. But a new study shows they use a similar technique to form underwater jets that help them uncover food. The researchers found that the fish altered the timing of their jet formation based on…
Bottle Rocket Shock Diamonds
Mach diamonds or shock diamonds can often be seen in the exhaust of rocket engines. Here they’re shown in high-speed video of a bottle rocket’s launch. The rocket’s exhaust exits at a pressure that is higher than the surrounding atmosphere, which causes the exhaust to bulge outward and forms two expansion fans, seen in pink,…
Titan’s Bubbly Islands
Titan, Saturn’s largest moon, is a fascinating world with remarkable similarities to our own. It is the only other world we know of with stable bodies of liquid at its surface. Unlike Earth, frigid Titan’s lakes and seas are filled with methane and ethane. Radar data from the Cassini mission has shown oddly changing shorelines…
Reader Question: Image Credits
kermitsstickylittlefingers asks: Dear Nicole, thanks a lot for your amazing blog which I have been following for years. My name is Julian and I am a PhD candidate working on tree frog attachment at Wageningen University in the Netherlands. Inspired by FYFD, I decided to start a science blog on bioadhesion and biomimetics. With respect to…
Hot Versus Cold
Did you know that you can hear the difference between hot and cold water when they’re poured? Go ahead and give the video above a listen to try it out. I’ll wait. As explained in the video, the viscosity of water changes with temperature – the higher the temperature, the lower the viscosity. In fact,…
Surface Tension’s Pop
Surface tension in a liquid arises from molecular forces. Within a liquid like water, a molecule inside the fluid experiences equal tugs from similar molecules in every direction. A molecule at the surface, on the other hand, experiences the pull of similar molecules only on some sides. The net effect of this imbalance is a…