16 | NewScientist | 23 March 2013

WITH a pull so strong not even light escapes, a black hole is defined by its gravity. But now a model that ignores gravity is proving surprisingly useful.

Black holes are where big ideas in cosmology, such as gravity and quantum mechanics, collide. That makes them great for testing new theories. “A black hole is a bit like the hydrogen atom of quantum gravity,” says Samuel Braunstein

of the University of York, UK.His team modelled a minimal

black hole, defined only by having an inside and an outside. To their surprise, this object reproduces a lot of the features of real black holes that are thought to rely on gravity, including Hawking radiation – via quantum mechanics (Physical Review Letters, doi.org/ktd).

This chimes with suggestions

Dizzy star caught in a deadly spin

IT IS cursed, doomed to spin faster than any of its peers. Cruelly, the dense white dwarf star could also be headed for a violent demise unlike anything we’ve ever seen.

Catalogued as RX J0648.0-4418, the star takes just 13.2 seconds to whirl once on its axis. Sandro Mereghetti of the Institute of Astrophysics and Cosmic Physics in Milan, Italy, thinks the object got its spin by siphoning material from its partner, the ageing star HD 49798. The extra mass hit the dwarf at an oblique angle, spinning it up.

As HD 49798 runs out of nuclear fuel it will swell again, feeding more mass to the dwarf until it reaches a critical limit. Depending on its chemistry, the star might then explode as an exceptionally bright supernova or collapse into a smaller, faster-spinning millisecond pulsar, an event that has not been witnessed before (arxiv.org/abs/1302.4634).

The world’s giant squid are one big happy family

IT’S a small world after all for giant squid. The first genetic study of global squid populations shows that the mysterious animals are very similar to each other, even though they live so far apart. The finding suggests that their young are dispersed thousands of kilometres by powerful global currents.

M. Thomas Gilbert of the University of Copenhagen in Denmark and colleagues sequenced the mitochondrial genomes of 43 giant squid (Architeuthis dux) samples from all over the world. The genomes were unusually similar, with only 181 genetic base pairs out of 20,331

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in brief

Gravity-less black hole works wonders that gravity is not a fundamental component of the universe but an emergent property of quantum mechanics, just as waves are an emergent property of water molecules. The toy black hole also dodges the recently discovered black hole firewall paradox, an inconsistency between quantum mechanics and general relativity that arises in most models. “Instead of being a cutesy picture, it’s a fantastic contender for the real physics,” says Braunstein.

varying between the individual squid (Proceedings of the Royal Society B, DOI: 10.1098/rspb.2013.0273). Other widely distributed animals show much more variation.

The genetic evidence suggests there is a single, global population of giant squid. But studies of adult squid suggest that individuals confine themselves to small pockets of the deep ocean, whether this be in Japan or Florida. So how come they seem to be so closely related?

Gilbert thinks squid larvae are the explanation. They could travel thousands of kilometres from their place of birth, carried on global ocean currents. He says the larvae, brought to the surface by upwellings, may feed on plankton and other small animals. When they have grown, they dive into the depths and find a nutrient-rich area that has plenty of large prey, where they can settle down.

PIRATE perch are unsmellable, thanks to a unique chemical camouflage that dupes many animals they prey on. Other animals boast a similar talent but can only fool a single species.

William Resetarits of Texas Tech University in Lubbock created small ponds and put fish in some of them. He found that beetles and tree frogs avoided ponds containing fish, unless the fish were pirate perch (The American Naturalist, doi.org/ks8).

Nobody knows how the perch do it. They might give off fewer scent chemicals, or might use another chemical to mask them.

Other animals in dark, still habitats where scent is a giveaway could have evolved similar camouflage, says Resetarits.

Fish dons chemical invisibility cloak

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