0 to 60 in 3 seconds

YouTube link.

"Holding Nature's land speed record for ten million consecutive years."

The physics of sudden beer foaming

YouTube link. (the video is silent)

From Physics Buzz:

A team of three international scientists has explained the physics behind why beer in a bottle transforms into an overflowing mass of foam when the bottle receives a vertical tap on the mouth, as shown in the video. They will present their work and its applications outside of the bottle at the 66th Annual Meeting of the APS Division of Fluid Dynamics.

Abstract: "A sudden vertical impact on the mouth of a beer bottle generates a compression wave that propagates through the glass towards the bottom. When this wave reaches the base of the bottle, it is transmitted to the liquid as an expansion wave that travels to free surface, where it bounces back as a compression wave. This train of expansion-compression waves drives the forced cavitation of existing air pockets, leading to their violent collapse. A cloud of very small daughter bubbles are generated upon these collapses, that expand much faster than their mothers due to their smaller size. These rapidly growing bubble clusters effectively act as buoyancy sources, what leads to the formation of bubble-laden plumes whose void fraction increases quickly by several orders of magnitude, eventually turning most of the liquid into foam."

Gorillas in the midst (of autumn leaves)

YouTube link.

The physics of giant pumpkins

YouTube link.

Time-lapse views of the sky

YouTube link.

These images come from the American landscape, but similar ones could be obtained at many places on earth where light pollution is minimal; for those interested a list of these locations is posted at the YouTube link and at Neatorama.

If you're going to watch, there's no reason not to click the Full Screen icon.  That's what it's for.

The mixed genetics of American bison

YouTube link.

The video depicts an annual bison roundup at a state park in far southwestern Minnesota near the South Dakota border.  From it I learned that some of the bison who survived the great slaughter of the settlement era have DNA that is "contaminated" with ranch cattle DNA.  Some effort has been made to cull current stock to restore the genetic purity of the remaining animals. 

During the population bottleneck, after the great slaughter of American bison during the 1800s, the number of bison remaining alive in North America declined to as low as 541. During that period, a handful of ranchers gathered remnants of the existing herds to save the species from extinction. These ranchers bred some of the bison with cattle in an effort to produce "cattleo."  Accidental crossings were also known to occur. Generally, male domestic bulls were crossed with buffalo cows, producing offspring of which only the females were fertile. The crossbred animals did not demonstrate any form of hybrid vigor, so the practice was abandoned. The proportion of cattle DNA that has been measured in introgressed individuals and bison herds today is typically quite low, ranging from 0.56 to 1.8%.  In the United States, many ranchers are now utilizing DNA testing to cull the residual cattle genetics from their bison herds. The U.S. National Bison Association has adopted a code of ethics which prohibits its members from deliberately crossbreeding bison with any other species.

A hat tip to reader Lloyd Stanley for bringing the video to my attention.

"Oh, what a tangled web we weave..." - updated

YouTube link.

Filmed in South Yorkshire.  The YouTube comments plumb the depths of ignorance; it's too bad such people can't see the everyday awesomeness of the natural world.

Via Nothing to do with Arbroath.

Addendum:  A tip of the hat to an anonymous reader, who in response to my query in the Comment thread asking why this happens, offered a link to a Metabunk post on this subject which has several embedded videos and photos.  The discussion indicates that these confluent areas are indeed of arachnid origin, but may not be "webs" in the traditional sense.  Rather they may arise from silk spun for "ballooning" (travel) purposes (I probably should change the title of the post):

...there are approximately one million of spiders per acre, (nearly a billion spiders in a square mile) and occasionally a large number of spiders will take to the air ar the same time (probably due to hatching at the same time based on weather conditions). The masses of silk will coat fields, get caught in trees, and sometimes get tangled up and blown into the air...

It was only relatively recently (the 1700s) that people realized the "gossamer" that sometimes coats fields actually came from spider, and was thought to come from evaporated dew...

This silk is not particularly sticky (spiders can spin both sticky and non-sticky silk). But is very light and thin, and when rolled in your fingers it will collapse upon itself, resulting in just a few specks. This can be mis-interpreted as "dissolving", but really it just that the silk occupies very little space to start out with. The silk used for flying is known as "gossamer" silk, and is one the lightest and thinnest of all types of spider silk.

The Leidenfrost Effect is endlessly fascinating

YouTube link.

I've written about it before (see "How to dip your hand into liquid nitrogen") and was delighted to find at Nothing to do with Arbroath the above video, in which students at the University of Bath used the effect to create directional movement by droplets of water.

Today I also found a description of the effect from 1868:

Mr. Davenport informs us, that he saw one of the workmen in the King’s Dockyard at Chatham immerse his naked hand in tar of that temperature [220°]. He drew up his coat sleeves, dipped in his hand and wrist, bringing out fluid tar, and pouring it off from his hand as from a ladle. The tar remained in complete contact with his skin, and he wiped it off with tow...

Mr. Davenport ascribes this singular effect to the slowness with which the tar communicates its heat, which he conceives to arise from the abundant volatile vapour which is evolved ‘carrying off rapidly the caloric in a latent state, and intervening between the tar and the skin, so as to prevent the more rapid communication of heat.’..

The workmen informed Mr. Davenport, that, if a person put his hand into the cauldron with his glove on, he would be dreadfully burnt, but this extraordinary result was not put to the test of observation. 

And found that the eponym comes from a German physician:

"During his lifetime, Leidenfrost published more than seventy manuscripts, including De Aquae Communis Nonnullis Qualitatibus Tractatus (1756) ("A Tract About Some Qualities of Common Water") in which the Leidenfrost effect was first described (although the phenomenon had been previously observed by Herman Boerhaave in 1732)."

Video of the moon rotating

YouTube link.

The technology is explained at NASA's Astronomy Photo of the Day:

No one, presently, sees the Moon rotate like this. That's because the Earth's moon is tidally locked to the Earth, showing us only one side. Given modern digital technology, however, combined with many detailed images returned by the Lunar Reconnaissance Orbiter (LRO), a high resolution virtual Moon rotation movie has now been composed. The above time-lapse video starts with the standard Earth view of the Moon. Quickly, though, Mare Orientale, a large crater with a dark center that is difficult to see from the Earth, rotates into view just below the equator. From an entire lunar month condensed into 24 seconds, the video clearly shows that the Earth side of the Moon contains an abundance of dark lunar maria, while the lunar far side is dominated by bright lunar highlands.

Incredible camouflage

YouTube link.

This moth is Uropyia meticulodina, found in China and Taiwan.  Real Monstrosities has another video showing the moth in flight. 

Via Neatorama.

The Grand Canyon of Greenland

YouTube link.

"Data from a NASA airborne science mission reveals evidence of a large and previously unknown canyon hidden under a mile of Greenland ice.

The canyon has the characteristics of a winding river channel and is at least 460 miles (750 kilometers) long, making it longer than the Grand Canyon. In some places, it is as deep as 2,600 feet (800 meters), on scale with segments of the Grand Canyon. This immense feature is thought to predate the ice sheet that has covered Greenland for the last few million years...

The researchers believe the canyon plays an important role in transporting sub-glacial meltwater from the interior of Greenland to the edge of the ice sheet into the ocean. Evidence suggests that before the presence of the ice sheet, as much as 4 million years ago, water flowed in the canyon from the interior to the coast and was a major river system."

(I do wish people would not say "Artic" Ocean.)

Noctilucent clouds AND the aurora borealis - at the same time

YouTube link.

Filmed by Maciej Winiayczyk in the sky above Caithness.

Hat tip to reader Shaun for alerting me to a related video at the BBC.

How to walk on water - updated

YouTube link.

Waxy, hydrophobic coatings typically make such insects’ points of contact (feet, legs, etc.) water-repellent, and their light weight can be supported by surface tension. Navigating the interface between air and water is more complicated, though, and these creatures have evolved several mechanisms to help. Some, like water striders, use appendages they insert below the surface for propulsion. At 0:49 in the montage above, you can see flow visualization of the vortices generated by a stroke. Other insects release a chemical in their wake that lowers the local surface tension and drives them away via the Marangoni effect.

That last-named one is particularly cool; I presume that's what's happening in the segments labeled "meniscus climbing." 

Addendum:  A hat tip to an anonymous reader for sorting out two of the mechanisms.

The Marangoni effect is shown near the end of the video, but I believe the sections labeled "meniscus climbing" are something different. The insects shown are adopting postures that change the shape of the surface of the water around them, causing capillary forces to draw them up to the top of the meniscus. This can be seen in the side views as dents or peaks in the water where the legs touch, or in the top view as bright and dark spots around the legs in the shadow - bright spots where the water is pulled up and focusing light, dark where it is pushed down and diffusing light. The same forces are used as in the capillary attraction two insects use to stick together at 1:03. The water treader Mesovelia (the first one shown climbing the meniscus) is covered with water-repellent hairs, so it uses special claws to grasp the surface of the water for meniscus climbing. 

Here are two relevant links - first to the hard science explanation in the esteemed Nature journal, and to a beautifully illustrated companion piece replete with photos by these same authors.  If this post has stimulated your interest, the second link is totally worth your visit.

Thanks again, anon.





Via fuck yeah fluid dynamics.

Seabed patterned circles

Discovered here, at a depth of 80 feet off an island in the Japanese archipelago, these elaborate circles have been attributed to the work of a small puffer fish, whose activity is shown in this video:

YouTube link.

Enhanced mating and reproductive success is one explanation, but one can't overlook the fact that this amazingly detailed circle has 27 segments - a perfect cube, and a number that is present in pi as a self-locating string (i.e. at the 27th place after the decimal), and is the number of books in the New Testament, and the number of bones in the human hand.  As a famous person once said "you can't explain that."

Via the first blog I ever followed - Gerald Vlemming's The Presurfer.

Videomicroscopy of a mosquito bite

YouTube link.

Anyone who has tried to thread an i.v. or insert a Vacutainer needle into a small vein will appreciate the skill demonstrated by a mosquito as its mouthparts probe under the skin searching for the vasculature.

From afar, a mosquito’s snout might look like a single tube, but it’s actually a complicated set of tools, encased in a sheath called the labium. You can’t see the labrum at all in the videos; it buckles when the insect bites, allowing the six mouthparts within to slide into the mouse’s skin.

Four of these—a pair of mandibles and a pair of maxillae—are thin filaments that help to pierce the skin. You can see them flaring out to the side in the video. The maxillae end in toothed blades, which grip flesh as they plunge into the host. The mosquito can then push against these to drive the other mouthparts deeper.

The large central needle in the video is actually two parallel tubes—the hypopharynx, which sends saliva down, and the labrum, which pumps blood back up.

Further details at the incomparable Not Exactly Rocket Science blog at National Geographic.

Ammonium dichromate + mercury thiocyanate + heat = Kraken

YouTube link.

Kraken explained.

Via Neatorama.

Human-powered helicopter

YouTube link.

"On June 13th, 2013, the AeroVelo Atlas Human-Powered Helicopter captured the long standing AHS Sikorsky Prize with a flight lasting 64.1 seconds and reaching an altitude of 3.3 metres. Visit www.aerovelo.com for more details.

The competition was initially opened in 1980, and over the course of the 33 years that followed, dozens of teams from around the world pushed the limits of existing technology in pursuit of this once-thought-to-be impossible goal. This video is a compilation of footage from the record flight, as well as previous test flights."

An interesting design.  I found this diagram at their website:

Virtual evolution

YouTube link.

This video shows results from a research project involving simulated Darwinian evolutions of virtual block creatures. A population of several hundred creatures is created within a supercomputer, and each creature is tested for their ability to perform a given task, such the ability to swim in a simulated water environment. Those that are most successful survive, and their virtual genes containing coded instructions for their growth, are copied, combined, and mutated to make offspring for a new population. The new creatures are again tested, and some may be improvements on their parents. As this cycle of variation and selection continues, creatures with more and more successful behaviors can emerge.

More information here, via Reddit.

Aftermath of the "glacial" event this spring at Lake Mille Lacs

YouTube link.

This spring I posted video of the ice on Minnesota's Lake Mille Lacs moving onshore like fast-moving glacier.  This video depicts the sequelae of the event, including damage to the shoreline and inland.

By the time it was over, the depth of the mini glacier was one to three feet at the edge near the town houses to over 25 feet at the lake shore. Maintenance personal for Izatys Resort said that clean up could take all summer due to the ice moving massive lakeside and underwater boulders onto the shore. 

The center of the earth may be made of crystals

YouTube link.

 "Scientists believe the solid inner core is made of an iron-nickel alloy.

To understand what form it might take under the extreme conditions at the centre of the Earth, Professor Kei Hirose set himself a seemingly impossible challenge: recreate the conditions of the core in his lab at the SPring-8 synchrotron near Osaka, Japan. After 10 years of trying, he has finally succeeded.

He has created an incredibly powerful vice using the tips of two diamonds. Between them he has pressurised a sample of iron-nickel to three million times atmospheric pressure and heated the sample to about 4,500C.

Under these extraordinary conditions, the crystal structure of iron-nickel alloy changed and the crystals rapidly grew in size. "We may have very big crystals at the centre of the Earth, maybe up to 10km," says Hirose. These crystals would all align "like a forest", says Hirose, pointing at the poles."