When a liquid is dropped onto a smooth plate that is heated to a specific temperature well above its boiling point, boiled vapor will get trapped underneath the remainder of the droplet insulating it from the hot plate, allowing it to dance around the plate like oil on a wet surface in what is known as the Leidenfrost effect
. Intriguingly, surfaces that are grooved into the shape of a saw blade will cause droplets suspended by the Leidenfrost effect to predictably skitter in the direction of the groove, allowing University of Bath undergraduate students Carmen Cheng and Matthew Guy to build a fascinating maze. [more inside]
For millennia, man has yearned to block the sun (with black plastic balls).
If an un-covered public water reservoir contains bromide, sunlight will combine the bromide with the chlorine used for reducing bacteria -- thus poisoning the water with carcinogenic bromate. Blocking the sunlight is the answer, but building a permanent cover for a huge reservoir is very costly. The solution for LA-area reservoirs, a few years ago: cover the entire water surface with millions of floating "bird balls"
, in effect turning the reservoir into a 10+ acre ball pit. [more inside]
Where's the EPA on this?
Apparently, this stuff is everywhere
, but I haven't heard one word
on its dangers until now. Christine Whitman
, be slient no longer!