September 5, 2020 | Issue 58
Science Spotlight
Upside-Down Boats
Set Sail!
We all know boats typically float in water, but did you know a boat can even float underwater? The idea may be more realistic than you think! Physicists at the University of Auckland have managed to float tiny boats on the underside layer of floating liquid.

The science behind why boats float is explained as the downward force of gravity being balanced by the upwards pressure of the displaced water. Previous experiments had shown that liquids with a higher viscosity in a vibrating container can be made to hover. That’s because each time part of the fluid tries to drip down, the shaking provides an opposing force that pushes it back up. That stops the lower surface of the fluid from breaking up and traps a cushion of air underneath.

They keep the object stable on the lower surface where the downward pull of gravity and upward pull of buoyancy are perfectly balanced. It’s not yet clear whether the stunt has any practical uses, but we can't wait for the day till we can float upside down!

Hummingbird Vision May See Outside the Normal Spectrum
About 3,000 years ago, warriors on the riverbanks of the Tollense River in Northern Germany, a great battle was fought. Over the past decades, archaeologists have discovered skeletal remains of hundreds of warriors, giving us further understanding of our prehistoric brothers and sisters.

Many of us grew up with parents (or television ads) telling us that milk is the key to growing up big and strong, but new genetic testing reveals that the Tollense warriors were unable to process fresh milk. None of the warriors had the genetic mutation that allows adults to digest milk, an ability known as lactose persistence that’s common in many ancient Europeans.

One theory is that, at the time, the mutation gradually spread along with the development of agriculture and herding. As these ancient civilizations began utilizing milk, more people were able to build up a tolerance. People able to digest milk would be able to get more calories from their herds than those without, and more of their children would survive to pass on the gene.