SCIENCE NEWS - Coming soon to a pond near you: air moving faster than the speed of sound

Supersonic means faster than the speed of sound, which is about 760 miles per hour in air. That’s a speed limit that can be broken — by jets and bullets, for example, or by the space shuttle as it returns to Earth.

Now, a scientist named Stephan Gekle has found that you can make air move faster than the speed of sound by doing a simple little trick: throw a rock in a pond.

In a recent study, he and his colleagues showed that after a rock drops into a body of water, a tiny jet of air shoots upward faster than the speed of sound.

This isn’t the first time Gekle has explored what happens when a rock sinks through water. In an earlier study, he and his team showed that as a rock falls into a flat surface of water, like a pond, it carves out a tiny tube of air. This tube connects the sinking rock to the air above the pond. The tube doesn’t exist for very long, though — almost immediately, the surrounding water pushes on the sides. This pressure is stronger in the middle than at the ends. As a result, the tube looks like an hourglass, where the middle gets smaller and smaller as the water forces the air out.

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SCIENCE NEWS - Cigarettes might be infectious

The presumption has been that smoking renders people vulnerable to disease by impairing lung function or immunity. And it may well do both. “But nobody talks about cigarettes as a source of those infections", notes Amy Sapkota of the University of Maryland, College Park.

The tobacco in cigarettes hosts a bacterial bonanza — literally hundreds of different germs, including those responsible for many human illnesses, a new study finds. If these germs are alive, something she has not yet confirmed, just handling cigarettes or putting an unlit one to the mouth could be enough to cause an infection.

The idea that tobacco might contain viable germs isn’t just idle conjecture. Several research teams have isolated bacteria from tobacco that they could grow out in petri dishes. Those earlier investigations tended to hunt for — and, when found, attempted to grow — only one or two species of interest, Sapkota says.

Among the large number of germs whose DNA laced these cigarettes were: Campylobacter, which can cause food poisoning and Guillain-Barre Syndrome; Clostridium, which causes food poisoning and pneumonias; Corynebacterium, also associated with pneumonias and other diseases; E. coli, Klebsiella, Pseudomonas aeroginosa and Stenotrophomonas maltophilla, all of which are associated not only with pneumonia but also with urinary tract infections; and a number of Staphylococcus species that underlie the most common and serious hospital-associated infections.

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