A stone’s throw

Even if you throw like a girl, you’re still pretty good at it. Scientists write in a recent issue of Nature, that we trump all our primate relatives when it comes to hurling things around.

Looking at 3D recordings of amateur baseball players’ arm action, they found that the shoulder works almost like a slingshot during a throw. When you pull your arm backwards to prepare, the tendons and ligaments of the shoulder stretch. This action stores energy that, upon release, bolts the arm forward.

Our remarkable throwing ability is thanks to anatomical features that first appeared in Homo erectus about two million years ago. It’s likely that precise, powerful throwing helped our early ancestors to hunt better. Eating more meat meant better brain development, which likely boosted our evolutionary progress – and maybe also our ability to duck.

Neil Roach: The Mechanics of Throwing from The George Washington University on Vimeo.

Cry babies

Understanding babies’ moods is child’s play. Cue gasps from strung-out parents. But according to an article in the journal Infancy, five-month-old babies seem to be able to read their friends’ expressions without trouble.

In the study babies were sat in front of two screens. One showed a video of a happy, smiling baby and the other that of a frowning, sad baby. When the sound of a third baby – either happy or sad – was played, the viewer kept looking at the video showing the matching facial expression. The audio was not in sync with lip movements on the videos, which suggests that the match between facial expression and vocal sound was made without external cues.

Fatal attraction

Being positive is not always a good thing. Especially if you’re an insect flying past a spider web. A study published in a recent issue of Scientific Reports, showed that spiders use static electricity to snatch unsuspecting insects from mid-air. Fast, repetitive flapping lets positive charge build up on insect wings.

Spider webs are generally neutral or negatively charged. To test the assumption that spider webs are drawn to the fly-bys, researchers electrostatically charged dead insects and dropped them into fixed webs collected from a stream nearby. Images from a high-speed camera showed how parts of the spider webs deform, touching the insects in mid-flight. In contrast, there was no attraction to neutral insects. Like a moth to a flame they say...

Other interesting stuff:

Spin doctors. Find out how physics predict the movement of a cricket ball.

Like a fish in the water - how fish learnt to swim.

Article first appeared in TechSmart 119, Aug 2013. Read or download it here.