After an electrical storm, the water in my father's small fish pond is crystal clear, having previously been full of green algae. Similarly, my parents' drinking water comes straight from a nearby reservoir and often contains organic matter, but a storm also appears to clean it up. What could cause this?Michelle, Johannesburg, South Africa(Image: enrika79, stock.xchng)
With climate change, earthquakes, volcanic eruptions and other natural disasters to contend with, where on the planet is the safest place to live?Michael Leonard, Stoke-on-Trent, Staffordshire, UK(Image: Pyroclastic flows at Mayon Volcano, Philippines, 1984, United States Geological Survey)
My partner recently brought home a large snapper that was caught off the coast of Adelaide, South Australia. When we had finished devouring the delicious fish I noticed that the skeleton had some unusual deformities on the backbone (see photos) in the form of three hard, bony spheres.My partner claims not to have seen anything like it before, and my rudimentary internet search produced no pictures of fish skeletons with similar features. Can someone tell whether these are a normal part of the snapper morphology or an abnormality?Tegan Laslett, Adelaide, South Australia
Driving along in the car the other day, my four-year-old son asked why things that were closer to us were moving faster than those further away. What should I tell him?Milton Inverdale, London, UKThanks for a vast number of answers to this question, many of which were probably more suited to undergraduate level than to a four-year-old. However, one notable group of wags insisted on sidestepping the answer at all costs.Among these was the inevitable "Ask your mother", from Tony Turner of Tuross Head, New South Wales, Australia.Stephen McIntosh of Hull, UK, suggested: "You are far too intelligent for a four-year-old... have a lolly."More encouraging was the answer from Dave Oldham of Northampton, UK, who offered: "If you can ask a question like that at four years of age it won't be many more years before you can explain it to me."And congratulations to Peter Gosling of Farnham, Surrey, UK, for his unashamedly literal view of the world. His advice was: "I think you should tell your son that it is illegal for him to be driving at four years old." - Ed
From the top of Blackpool Tower (approx 150 metres) on the UK's west coast, can you see the curvature of Earth along the Irish Sea horizon? I thought I could, but my friend disagreed. If I'm wrong, how high would we have needed to be?Mark Ford, Bolton, Lancashire, UK
One of my faculty colleagues, Michael Runtz, took this photo (left) of ice bubbles in Cranberry Lake in Ontario. How did the bubbles form in this amazing fashion?James Cheetham, Department of Biology, Carleton University, Ottawa, Ontario, Canada
About a year ago I brought back a bottle of glacial meltwater from Alaska. It was frozen when I collected it and once melted looked perfectly clear. A few months ago, I noticed something that looked like a small clump of hair at the bottom of the glass, which has been growing slowly ever since (see photo, left). I have not removed the bottle top since I collected it.Can anyone tell me what it is and, if it is alive and growing, where is it getting its nutrients from?Sam Lessing, by email, no address supplied
While making a cake I cracked three eggs from a box of half a dozen and all three had double yolks. A few days later I used the three remaining eggs, and two of them were doubles. This column once told us how to spot eggs that have double yolks (12 December, 1998) but not how they arise. Why do some eggs have double yolks and what is the probability of getting eleven yolks from a standard box of six eggs?Chris McManus, London, UK
On a beach in Malaysia I saw small balls of sand in patterns around some holes (see Photo). I couldn't see an animal inside any of the holes. So what makes these patterns, and how are they formed?Romayne Gallagher, Vancouver, British Columbia, CanadaClearly patterns of small balls on the beach is a common sight. So too are their creators. We've received reports from northern Queensland in Australia, Borneo, Goa in India, and Zanzibar. Here are two possible culprits - Ed
I took this photograph looking east while in the Drake Passage between Chile and Antarctica. It seems to show a foggy rainbow. What caused it?Annette West, Lincolnshire, UK