Australasian Science: Australia's authority on science since 1938

Nomadic Gnome Solving Weighty Problem

By Magdeline Lum

A gnome is travelling the world to test for subtle differences in gravity.

Kern is a gnome that is travelling the world to highlight a quirk of planet Earth. Gravity changes depending on your location on Earth due to the shape of the planet – it is not a perfect sphere. Earth is more like a potato with a middle bulge than a tennis ball.

This bulge means that the north and south poles are closer to the core than places along the Equator. Throw in additional gravity counterbalancing inertia from the spin of the Earth to the situation and it means that you or Kern would weight more at the poles than in Hawaii.

When it comes to comparing the weights of precise amounts from countries around the world, this can become a problem if the scales used are not calibrated to account for local gravity differences. Hence a Bavarian scale manufacturer, Kern & Sohn, is raising awareness of the issue by sending Kern around the world with a set of precision scales to measure the difference.

So far Kern has travelled to Antarctica, where he weighed in heaviest at 309.82 grams at the Amundsen-Scott Research Station, as well as visiting CERN, Tokyo, Mumbai, Callao and Sydney – with more travels to come. Scientists wanting to get involved in the experiment can get more information at http://www.gnomeexperiment.com, and Kern’s travels can be followed at his online diary at http://kernthegnome.tumblr.com.

Caterpillars Are More Likely to Vomit if Alone
Animals have many different methods of defence – stings, venom and chemical sprays to name a few. The caterpillar of the cabbage butterfly (Pieris brassicae) wards off attackers in a novel way by vomiting partly digested leaf material on its would-be predator. These caterpillars also have another defence mechanism against predators, and that is to live in groups according to the “safety in numbers” principle.

However, some studies have found that the size of a group does not affect the chances of an individual surviving.

Researchers from the University of Liverpool and the University of Bristol have observed that there is a social side to deciding whether to vomit or not. The willingness of a caterpillar to vomit depended on the size of the group it was part of, with the caterpillars more shy about vomiting when living in groups than when alone.

But defensive vomiting is a weapon that must be used with care. The vomiting results in a loss of food, which slows down growth and even lowers reproduction by reducing the number of eggs a female can lay.

Another factor in decision-making is also competition for food. Large groups experience more competition for food and resources, so in large groups it may be more important not to vomit.

The researchers found that the proportion of non-vomiting caterpillars increased as the size of the group became larger. While this is possibly a result of safety in numbers, it could alternatively be due to the presence of “cheats” – caterpillars that do not vomit.

The researchers noticed that some caterpillars did not vomit at all when attacked, and hypothesise that this may be a way of exploiting safety in numbers by leaving the cost of vomiting to other caterpillars with a greater propensity to vomit.

Additional research is needed to confirm this or whether individuals take turns to vomit defensively.