Also, if one lives above or below a road, sirens and other traffic noises often vary with the time of day, etc. The standard explanation is diffraction, but maybe others have additional angles or insights to lend.

With my P7 class which was studying the rain forest, we also looked at the differing rainfalls in Brazil and the UK and the water cycle. One of my pupils noted that part of the water cycle information stated that all water on earth is automatically recycled through the Water Cycle so why do we need to worry about saving water. I tried to reassure him that it was to do with the limited amount of fresh water on the planet but would like some "official" confirmation of this.

Following the recent spell of cold weather, I noticed that there are still piles of dirty snow with sand or grit (but not salt) in them, but all the clean snow has melted.

I was walking along a canal several days ago, and, the UK weather being what it is at the moment, the canal was frozen. However under all the bridges that crossed the canal, whether footbridge or road bridge, the water was unfrozen. What is it about the bridges that stops the water under them from freezing?

I have a very conservative relative who lives in FL.  She now believes that global warming is all a liberal conspiracy plot because the weather report announces snow sometime tonight or tomorrow (she's in Orlando).  I'd like to explain to her that these crazy and unusual weather occurrences are a consequence of global warming, but don't know how.  Please help!

Thanks

On the first night of heavy snow - tues 5th Jan - it was cloudy but the sky was  a very light sepia tone all night - enough to see clearly by. It was much more light than on the subsequent nights which have been partially cloudy with a visible moon. On these nights there was the same amount of snow cover, but less cloud. 

On the sepia night it was lighter than if there had been a full moon.

Having recently moved to Canada from the UK it struck me that everybody has to wear extra clothes to keep warm, but the caribou I saw the other day don't seem to notice the freezing temperatures. Animals that live in the Arctic for example are well adapted to their environment e.g. thick fur or layers of fat, but if humans had not invented clothes where on the planet would we be able to survive?

The ice structure pictured is 14cm long, it formed in a single night in this bird bath, and there is nothing above it that could have dripped to form a stalagmite. The triangular cross-section, and angle of lean also suggest that this did not form in the usual way for a stalagmite.

On the day before, the bowl was full of water and the temperature was a degree or two above freezing, overnight temperatures dropped to -2 C, skies were clear with no precipitation, the structure was fully formed the next morning.

I assume this is in fact an ice crystal, but how, and why, did it perform this gravity defying trick, and why don't we see such structures more often?