Seen and heard
Weird and wonderful stories from the world of physics
Keeping a lid on it
Closing the lid on your favourite board game box can take a while as it slides down the base to close. This so-called “telescoping” cardboard box – where the lid barely overlaps with the base – is commonly used to hold or ship a variety of objects from board games and footwear to mobile phones. Such boxes are cheap to make and while the economic and environmental aspects have been well studied, the physics never had. To make amends, Jolet de Ruiter from Wageningen University and colleagues carried out experiments on commercially available boxes and 3D printed models to investigate the fluid dynamics of the sliding box lid (Phys. Rev. Fluids 7 044101). The researchers used low-Reynolds-number fluid flow to derive a theory for the flow of a thin film of air in the gap between the lid and base. They then compared this to experiments to find that the fastest way for the box lid to close is not based on a conventional straight lid-base configuration but for the lid to have a slight angle – just a few degrees – relative to the vertical base. If this design ever hits the shelves, we can thank the researchers for thinking outside the box.
Fishy finding
It has long been known that fish can count, at least to four, but new work shows they can apparently do much more. Researchers led by Vera Schluessel from the Institute of Zoology at the University of Bonn showed cichlids and stingrays a collection of geometric shapes such as four squares. If these objects were coloured blue, it meant “add one”, while yellow meant “subtract one”. The animals were then shown two new pictures – one with five and one with three squares. If they swam to the correct picture (i.e. to the five squares in the “blue” arithmetic task), they were rewarded with food. If they gave the wrong answer, they went away empty-handed. Over time, the sea creatures learned to associate blue with an increase of one and yellow number with a decrease of one. To see whether they had internalized this mathematical rule, the researchers then set the fish calculations they had never seen before – and in most cases the fish gave the correct answer (Sci. Rep. 12 3894). The researchers say it is not known where they acquired the ability – perhaps they learned about it in their, er, schools?
Equation head-to-head
What is your favourite physics equation and how well would it stand up in the court of public opinion to other equations? That pressing question has now been answered thanks to the Perimeter Institute for Theoretical Physics in Canada. Beginning in mid-March, they began running an online single-elimination tournament that pitted famous physics equations against each other with the winners and losers decided by a public vote on Twitter. The tournament started off with 16 equations that were winnowed down to a final between Maxwell’s equations and Noether’s theorem. Following a gruelling battle royale, Noether’s theorem came out on top with 59% of the vote. Don’t tell us you don’t know what it is.
Rising to the challenge
A key ingredient to any good dough is yeast. It produces bubbles via a biochemical process that causes the dough to rise and develop into a light and airy treat. But how can people who are yeast intolerant still enjoy a good pizza crust? Researchers from the University of Naples Federico II in Italy (of course) set about finding out. They made a yeast-free dough out of water, flour and salt and placed it in an “autoclave” – a pressurized, heated tank. They then dissolved gas into the dough at high pressure, with bubbles forming in the dough as the pressure is released slowly during baking. After many unofficial taste tests, they found that the technique worked (Physics of Fluids 34 033109). “We had a lot of fun applying things we know well to delicious polymers, instead of our typical and sometimes boring smelly plastics,” notes study author Rossana Pasquino. The researchers say they hope pizzerias can get a slice of the action and use the technique in their kitchens.