Whales communicate through bone calls

Baleen whales emit extremely lowfrequency vocalisations that can travel extraordinary distances underwater.

Regulators have been trying to create laws to limit the amount of human-made noise the whales are exposed to, but it has proved difficult because no-one knows exactly how the marine mammals hear.

Now Californian researchers have shown that the skulls of fin whales have acoustic properties that capture low frequencies and direct the energy to their ear bones.

In 2003 a young fin whale beached in California and, despite efforts to save it, the youngster died.

But the researchers were able to recover its head, which they placed in a CT scanner to create a three-dimensional computer model.

San Diego State University (SDSU) biologist Ted Cranford said models suggested bone conduction was likely the predominant mechanism for hearing.

The fin whale’s skull now resides in the university’s Museum of Biodiversity. An MRI study suggests psychopathic, violent offenders have abnormalities in parts of the brain related to learning from punishment.

The University of Montreal’s Sheilagh Hodgins said that one in five violent offenders was a psychopath. ‘‘They have higher rates of recidivism and don’t benefit from rehabilitation programmes.’’ Using MRI scans, Hodgins and colleagues compared psychopathic offenders to nonpsychopathic offenders, and a sample of healthy non-offenders.

They found ‘‘structural abnormalities’’ in both grey matter and specific white matter fibre tracts in those offenders with psychopathy. Pregnant women are more likely to quit smoking if financial rewards are offered, a study in the British Medical Journal has found. In the United Kingdom alone, an estimated 5000 foetuses and babies die from mothers smoking during pregnancy each year.

More than 600 pregnant women who smoked were split into two groups – one group received shopping vouchers as motivation for quitting smoking. The incentive was in addition to usual smoking cessation services, including face-to-face appointments, support calls and 10 weeks of nicotine-replacement therapy.

After 12 months, 15 per cent of the women who had been offered financial incentives had stayed away from cigarettes, compared to four per cent in the control group. Fossilised remains of four ancient snakes, dated between 140 and 167 million years old, are nearly 70 million years older than the previous record. the sudden appearance of snakes in the fossil record 100 million years ago had been thought to indicate ‘‘explosive radiation’’ - a rapid increase in the number of species in a short period.

University of Alberta’s Michael Caldwell said the findings, published in Nature Communications, suggested instead that there was a gap in the fossil record where no snakes had been found. Duncan Steel (duncansteel.com), a Wellington-based space scientist whose first book, Rogue Asteroids and Doomsday Comets, spawned the Hollywood movies Armageddon and Deep Impact, both of which were about comets hitting the Earth, responded:

In a single passage through the inner solar system a typical comet loses mass equivalent to about a one-metre surface layer.

For a large comet perhaps 10 kilometres in size, like the wellknown Comet Halley, a consistent reduction of mass at that rate would imply that the comet might make 10,000 such passages before it was all gone. Comet Halley’s orbit last for about 76 years, and so it could continue to follow its present path for almost a million years before it decays to nothing.

Such a timescale estimate we call a physical lifetime. We also sometimes see comets break into fragments, and those may soon disappear, marking the comet’s death.

In fact the lifetimes of comets in the inner solar system are mostly limited by close encounters with the planets. A comet may hit a planet or, more likely, one of the giant outer planets may gravitationally throw it onto a path taking it out of the solar system and into interstellar space, never to return. This we term a dynamical lifetime.

The closest observed passage near the Earth by any comet in history was by Comet Lexell in the late 18th century. It was diverted by Jupiter into a trajectory bringing it near our planet, but on its next approach to Jupiter it was thrown on to a much larger orbit, and we’ve not seen it since.

Comets have multiple tails. There is generally a bluish gaseous tail pointing away from the Sun, and that is called the ion tail. There is also a fan-shaped tail of small solid particles spread behind the comet’s path, and that is the dust tail.

Meteor showers occur when our planet passes through such elongated dust tails. For example, each year in the first week of May and the third week of October we witness meteor showers due to tiny grains that were once part of Comet Halley.

Comets appear quite bright due to the vast clouds of vapour that surround their solid nuclei. Such a cloud we call the coma. Typically a cometary coma is about 100,000km across and so can reflect a lot of sunlight back to our telescopes.

Often comets are first spotted when they pass the distance from the Sun that is three times as great as the Earth-Sun separation, because at that point the flux of sunlight is sufficient to cause the ice on the surface of the nucleus to start vaporising. The coma then rapidly develops and the comet is easy to find.

However, there are other ‘‘ices’’ in comets – such an solid ammonia, carbon monoxide and dioxide, methane, and various other organic chemicals – which will vaporise further from the Sun, making it feasible to discover a comet when it is perhaps out near the orbits of Jupiter or Saturn.

Humankind has recorded apparitions of Comet Halley 30 times so far, since at least 240BC. Another object named Comet Encke was not discovered until 1786, but has returned a record number of times because it takes only 40 months to orbit the Sun, never venturing outwards as far as Jupiter.

Send questions to Ask-A-Scientist, PO Box 31-035, Christchurch 8444, or email questions@ask-a-scientist.net