It is Vijayadasami today. A day to start/renew. And here I am saying hello to my blog again.
My morning terrace walk today - learned about Squid Games (South Korea's version of Hunger Games) and saw two Green Bee-eaters in the sky. The Bee-eaters did a couple of sorties and were gone, sadly. The parakeets stayed, and a young crow fixed me with an intense and curious stare, following me, up and down the terrace before it flew away out of boredom.
The skies are full of Wandering Gliders, moving east to west, from the coastline, across the city, and made me wonder if that's what had attracted the bee-eaters.
The Wandering Gliders never cease to amaze me, coming with the monsoon winds every year, and moving ceaselessly and tirelessly. I shot a long video of their gliding and wandering on the beach. It doesn't make for good viewing or sharing, because they are in and out of the frame in a second, and there are these tiny squiggles moving across the screen. I marvelled at their two sets of wings, sometimes beating in harmony and other times out of sync for some reason. Lift? Velocity? Hover?
Solving A Dragonfly Flight Mystery
Dragonflies adjust their wing motion while hovering to conserve energy, according to a Cornell University study of the insect's flight mechanics. The revelation contradicts previous speculation that the change in wing motion served to enhance vertical lift.
The Cornell physicists came to their conclusions after analyzing high speed images of dragonflies in action. The insects have two pairs of wings, which sometimes move up and down in harmony. At other times the front set of wings flap out of sync with the back set.
The physicists found that dragonflies maximized their lift, when accelerating or taking off from a perch, by flapping both sets of wings together. When they hover, however, the rear wings flap at the same rate as the front, but with a different phase (imagine two people clapping at the same speed, but with one person's clap delayed relative to the other).
The physicists' analysis of the out-of-sync motion showed that while it didn't help with lift, it minimized the amount of power they had to expend to stay airborne, allowing them to conserve energy while hovering in place.
The research will be detailed in a forthcoming issue of Physical Review Letters. The authors are Z. Jane Wang and David Russell.
Sept 2007
