Quanta Physics World  November 2020

Seen and heard

Weird and wonderful stories from the world of physics

Tumble triers

(Courtesy: Rachael Miller)

Every time you do a clothes wash, you’re inadvertently creating polluting microfibres, which spew out in the wastewater from your washing machine. But could there be another domestic culprit? Kirsten Kapp from Central Wyoming College and Rachael Miller from the Rozalia clean-ocean project certainly think so, pointing the finger at tumble dryers. Now you might think that hunting for microfibres from a dryer is impossible – surely they all just fly away? But living in a part of the world that sees cold winters, they hit upon a cool idea. Using dryers in Idaho and Vermont, Kapp and Miller tumble-dried two pink polyester fleece blankets that had been soaked in water – and then looked for incriminating fibres that had landed in the snow. The highest concentration of microfibres was found on snow within 1.5 m of the vents, although several locations about 9 m away also had lots too (PLOS ONE 15 e0239165). Hoping their work “inspires researchers to investigate exactly what factors concerning dryer design, installation and settings, increase or reduce shedding”, as Miller puts it, the duo also wants to “educate consumers about the potential effects that dryer use has on our environment”. Let’s hope they don’t get the cold shoulder.

Irrational orbit

One of the most remarkable things about the plethora of known exoplanets is that many orbit right up close to their stars while travelling at extremely high speeds. K2-315b is no exception, moving at a blistering 81 km/s in a tight orbit around a cool star that is about one fifth the size of the Sun. The exoplanet itself appears to be about the same size as Earth, but is expected to have a surface temperature of about 180 °C – about the right temperature, apparently, to bake a pie (Astrophys. J.160 172).  So when Prajwal Niraula from the Massachusetts Institute of Technology and colleagues found – using NASA’s Kepler Space Telescope’s K2 mission and the SPECULOOS ground-based telescopes – that K2-315b takes just 3.14 Earth days to orbit its star, no guesses what they dubbed their new finding. The “π planet”, of course.

These shoes aren’t made for walking

Most conventional running shoes have a “toe spring” – a gentle upward curve of the sole towards the tip of the shoe. While this makes stepping more comfortable and easier, Harvard University’s Daniel Lieberman and colleagues have found that a toe spring can weaken the foot’s ability to push off the ground. In their experiment, 13 participants walked barefoot and in four pairs of custom-made sandals on a treadmill equipped with force plates and an infrared camera system (Scientific Reports 10 14643). While shoes make it easier to walk, the extra comfort, the researchers claim, could be associated with a range of foot problems including plantar fasciitis – a painful condition affecting the tissue that connects the heel to the toes. “We like comfort,” Lieberman told the Harvard Gazette. “That’s why we sit in chairs and take elevators.”

Pitch perfect

(Courtesy: PIXNIO (CC0) )

“The knuckleball is perhaps the most enigmatic pitch in baseball,” write Nicholas Nelson and Eric Strauss from California State University in Chico in a new preprint (arXiv:2009.05140). This type of pitch involves the ball slowly rotating as it speeds towards the batter. But because a baseball has prominent seams that disrupt airflow around the ball, the aerodynamics of the ball alter as it rotates – changing its trajectory and making it very hard for a batter to anticipate the motion of the ball and hit it effectively. Conversely, it is also a very difficult pitch to throw because tiny changes in technique can have huge effects on outcome. In the strike-ing new research, Nelson and Strauss have now developed a model of the knuckleball and shown that the motion of the ball is indeed chaotic .The duo’s model predicts that the position of the ball when it reaches the batter can vary by as much as 1.2 m for typical initial conditions used by knuckleball pitchers. This variation can take the ball well outside the strike zone – where the pitch must be – showing why the knuckleball can not only be dangerous for the batter but the pitcher too.