World Water Day
Today is World Water Day. One article on the BBC News pages today was about how people in remote villages in Tanzania are using very simple methods to sterilise their water supplies. People in the West often do this through the use of chemicals which are expensive, bad for the environment, and not easy to get hold of in the middle of the African bush. One method you may have used if you have ever been camping somewhere off the beaten track is boiling. Put a pan of water over a high heat and let it boil for a while, killing off any nasty bugs which may be in it. What they have been doing in Ndolela village is using sunlight to do the same job.
They bottle the water they get from either the intermittent piped supply or the local well and leave it in the sunlight on a roof which has been painted black. The light from the Sun heats up the water to a moderate temperature and the roof absorbs sunlight and re-radiates a significant fraction as heat which adds to the overall heating. The prolonged heat combined with the exposure to ultra-violet rays over the day kills off anything nasty living in the water. This simple method of purification has made life easier for the people in remote villages like this and helped reduce illness due to stomach complaints often caused by bad water.
OK, so it's not really astronomy, but it's still science.