Skipping stones across water may seem like an innocent children’s pastime, but the science behind it has helped to win more than one war. Now, researchers at Utah State University’s (USU) College of Engineering are uncovering new insights into the physics of these kinds of water impacts that could have wide applications in the fields of naval, maritime, and ocean engineering.

It may seem strange, but knowing how to skip things off the water is a very important branch of physics. In the 18th century, Admiral Lord Nelson found that by skipping his cannonballs off the waves he could increase their range and impact. More famously, during the Second World War, Barnes Wallis used the principle to create his Bouncing Bomb, which was the secret weapon to destroy the vital dams in Nazi Germany’s Ruhr Valley during the Dambuster Raid in 1943. Read more

They might be fun to look at, but they’re not necessarily good news

Tide pools along the coast of central and northern California are filling up with inch-long, pink Hopkins’ rose nudibranch—a sea slug whose vivid coloring gives it a kind of punk rock appeal.

The Hopkins’ Rose nudibranch, or pink sea slug

Scientists are logging dozens of the creatures per square meter, says the University of California, Santa Cruz. The sea slugs, common to the waters of southern California, have not been seen in such numbers in the colder reaches of the state since 1998.

That was when the last big El Nino events contributed to “periods of warmer-than-usual ocean water and heavy rains,” explains Science Codex. But there’s been only weak El Niño effects recently, and only a 50-60 percent chance of related conditions occurring in 2015. So what’s causing the slew of slugs? Read more

Fluid is ratcheted through a gap between the pump’s teeth

In most pumps, either a spinning impeller pulls liquid in and then essentially “throws” it out via centrifugal force, or a rotor draws it through using peristaltic force. After studying how birds’ flapping wings use fluid dynamics to push air back while moving the animals forward, however, two scientists from New York University have developed a pump that works in yet another fashion – and it has teeth.

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In 1974, just a couple years after the launch of the first Landsat satellite, scientists noticed something odd in the Weddell Sea near Antarctica. There was a large ice-free area, called a polynya, in the middle of the ice pack. The polynya, which covered an area as large as New Zealand, reappeared in the winters of 1975 and 1976 but has not been seen since.

Scientists interpreted the polynya’s disappearance as a sign that its formation was a naturally rare event. But researchers reporting in Nature Climate Change disagree, saying that the polynya’s appearance used to be far more common and that climate change is now suppressing its formation.

What’s more, the polynya’s absence could have implications for the vast conveyor belt of ocean currents that move heat around the globe.

Satellite imagery allowed scientists to find an ice-free area in the Weddell Sea (upper left quadrant) in the Antarctic winters of 1974 through 1976. (Credit: Claire Parkinson (NASA GSFC))

Surface seawater around the poles tends to be relatively fresh due to precipitation and the fact that sea ice melts into it, which makes it very cold. As a result, below the surface is a layer of slightly warmer and more saline water not infiltrated by melting ice and precipitation. This higher salinity makes it denser than water at the surface. Read more

Planners ignore microclimates at their peril: mistakes can mean frozen crops, lower house values and camper vans blown off the highway.

Microclimates are exactly that: phenomena measured on scales of inches to miles. The wind can be gusting to gale force near a ridgetop while only gentle breezes blow in the valley below. A simple garden wall may enable a plant to thrive where it otherwise would have been hard-pressed to survive. Read more