I saw the delicate, leaf-like ice crystals in the photo whilst snowboarding in France, they measured from 20 - 80mm and were incredibly fragile. The area they covered in the photo was about 20m2 but we saw other patches close by. The site was at about 1800m.

I refilled my ice cube tray, put it in the freezer.  When I came back a couple hours later, I noticed a slender vertical spike protruding from the center of the ice cube.  What would cause the water to freeze in this manner?

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?

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?

While walking in the Cairngorms, a path had muddy puddles one day, and was frozen the following day. Parts of the path were the mixture of ice, air and gravel pictured. The structures are noticeable, because they collapse when stood on. They are different to any normal frozen puddles, because they are not solid ice, nor are they a layer of ice with water or air beneath. The pictured piece measures about 65x65 mm.

This actually comprises several questions: 1/ Does the survival of polar bears depend on the Arctic Ocean being frozen over every winter?; if "yes": 2/ For how long has the Arctic Ocean been regularly frozen over every year? and 3/ Were there any polar bears before this time and, if so, where and how did they live?

I don't mean ice-creams like frozen juice or something like that. Do you know how to do ice-creams like from ice-cream shop?

New Scientist has teamed up with Discovery Channel's MythBusters to attempt to solve a mystery. Thermite and ice can make an explosive combination, so don't try this experiment at home - watch it safely on the web at www.mythbusters-thermite.notlong.com.

We want to find out why the explosion happens. Thermite is a mainstay of pyrotechnics, comprising a mixture of metal and metal oxide powders that burn at extremely high temperatures in a tightly focused area. Thermite is not, by itself, explosive, but if you ignite a bucket of thermite on top of blocks of ice, there will be an enormous bang once it has burnt through the bucket.

MythBusters presenters Jamie Hyneman and Adam Savage are seeking a convincing scientific explanation of this violent reaction (see Interview: The mythbusters). Can Last Word readers solve the mystery?

See the MythBusters offer the challenge