Hold A Buoyant Sphere Like A Ping Pong Ball Underwater And Let It Go, And You’ll Find That The Ball

Quantum tunnelling

Tunneling is a quantum mechanical effect. A tunneling current occurs when electrons move through a barrier that they classically shouldn’t be able to move through. In classical terms, if you don’t have enough energy to move “over” a barrier, you won’t. However, in the quantum mechanical world, electrons have wavelike properties. These waves don’t end abruptly at a wall or barrier, but taper off quickly. If the barrier is thin enough, the probability function may extend into the next region, through the barrier! Because of the small probability of an electron being on the other side of the barrier, given enough electrons, some will indeed move through and appear on the other side. When an electron moves through the barrier in this fashion, it is called tunneling.

Quantum mechanics tells us that electrons have both wave and particle-like properties. Tunneling is an effect of the wavelike nature.

The top image shows us that when an electron (the wave) hits a barrier, the wave doesn’t abruptly end, but tapers off very quickly - exponentially. For a thick barrier, the wave doesn’t get past.

The bottom image shows the scenario if the barrier is quite thin (about a nanometer). Part of the wave does get through and therefore some electrons may appear on the other side of the barrier.

Because of the sharp decay of the probability function through the barrier, the number of electrons that will actually tunnel is very dependent upon the thickness of the barrier. The current through the barrier drops off exponentially with the barrier thickness

Source: nanoscience.com | Images: x | x | x

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A small Japanese puffer fish is the creator of one of the most spectacular animal-made structures. To impress the female puffer fish, the male labors 24 hours a day for a week to create a pattern in the sand. If the female finds his work satisfactory, she allows him to fertilize her eggs. She then lays them in the middle of the circle, leaving the male to guard the eggs alone.

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Swirling swarms of bacteria offer insights on turbulence

In the bacterial world, as in the larger one, beauty can be fleeting. When swimming together with just the right amount of vigor, masses of bacterial cells produce whirling, hypnotic patterns. Too much vigor, however, and they descend into chaotic turbulence.

A team of physicists led by Rockefeller University fellow Tyler Shendruk recently detected a telling mathematical signature inscribed in that disintegration from order to chaos. Their discovery, described May 16 in Nature Communications, provides the first concrete link between turbulence in a biological system and within the larger physical world, where it is best known for buffeting planes and boats.

Amin Doostmohammadi, Tyler N. Shendruk, Kristian Thijssen, Julia M. Yeomans. Onset of meso-scale turbulence in active nematics. Nature Communications, 2017; 8: 15326 DOI: 10.1038/NCOMMS15326

When swimming together, bacteria produce swirling patterns that can disintegrate into turbulence as they speed up. Credit: Kristian Thijssen

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Native Gold with White Quartz

Eagle’s Nest Mine, Placer County, California