THINK of an atom, and chances are you’ll picture something that looks like a tiny solar system. You’d be wrong, but never fear: researchers have engineered an atom that looks just like you think it should.

When the atomic nucleus was discovered a century ago, the solar system analogy was obvious. The nucleus’s mass and charge would force electrons to circle it, just as the sun’s gravity holds orbiting

planets. But quantum mechanics pooped the party, maintaining that electrons would smear out over large areas of space.

Now Tom Gallagher’s team at the University of Virginia in Charlottesville have trapped electrons and made them parade around a nucleus. Their inspiration came from Lagrange points – regions of space where gravity from different sources cancels out. They

For healthy kids, marry a stranger

MARRYING within the family not only ups the risk that your children will have a genetic disorder, but also makes them more susceptible to some infections.

William Amos at the University of Cambridge and colleagues analysed genetic data from communities in Gambia and India, where marriage within the extended family is common. In Gambian families where children had TB or hepatitis B, parents were significantly more likely to be related than in families with healthy children (Biology Letters, DOI: 10.1098/rsbl.2009.0133). Amos says this is probably because the children have less diversity in the genes giving rise to the immune system.

Children with leprosy in India, however, were not more likely to have related parents. Specific genes affect the risk of leprosy, says Amos, which may drown out the subtler effects of relatedness.

When a roar like a jet engine means lava is on the way

THE low-frequency rumble of a violent volcanic explosion

sounds just like the roar of a jet engine, a similarity which

might tells us what’s going on within the fiery mountains.

Robin Matoza of the University of California, San Diego,

and colleagues measured infrasonic signals from volcanic

eruptions around the globe . When they speeded up

the frequency of the volcano recordings to within the

range of human hearing the distribution of frequencies

closely resembled a Boeing 747 jet engine. “The science

of jet noise is very well understood,” says Matoza.

“If we can understand how this works for volcanoes,

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IN BRIEF

An atom just as you would imagine it achieved a similar effect with an electron by using microwaves to counteract the force of the nucleus. This created an electron pocket like a Lagrange point, which they guided around the nucleus by rotating the microwave source (Physical

Review Letters, vol 102, p 103001). “Besides being a beautiful

piece of physics, it can really tell us a lot about how classical we can make quantum systems,” says Carlos Stroud of the University of Rochester, New York.

we may be able to infer properties of eruption columns.”

They already have a few hints. The sound produced in

engines is partly down to turbulent air near the inner walls

of the engine. The fact that a similar sound is made by

vulcanian and plinian eruptions – two types of blast with

tall dense ash columns – suggests it is created as ash and

gas churn up near the inner surface of the volcano mouth.

Explosive eruptions are far too violent to measure

directly using sensors or aircraft, says Darcy Ogden at

Stanford University in California, so the finding could

be a useful way of discovering a plume’s velocity, density

and pressure.

The recordings could also be used to warn pilots of

eruptions hidden by clouds, says Matoza, whose work will

appear in Geophysical Research Letters.

IN UNCERTAIN times, hedge your bets. That’s what other species do , say Angela Crean and Dustin Marshall of the University of Queensland in St Lucia, Australia.

Many species alter their reproductive strategy when food becomes scarce or other conditions change, but they were thought to change either towards fewer, larger offspring, or more smaller ones. The researchers re-examined five studies that showed such changes and found that in soil mites and damselfish clutches of eggs had actually become more varied, with both larger and smaller eggs (Philosophical Transactions of the

Royal Society B, DOI: 10.1098/rstb.2008.0237). “We think there will be dynamic bet hedging in many other species,” says Crean.

Variety pays when times get tough

12 | NewScientist | 21 March 2009