Watching the excellent series, 'frozen Planet' last night, I was impressed, as always, by the fabulous photography and incredible stories of survival. But what sticks in mind was the 'stalagtite' of ice that drops from the underside of the sea ice to the floor. As it hits the sea bottom, it kills all within its footprint, then the ice loosens and the dead creatures float up to pepper the ice ceiling.

It prompted the question: what would happen if water conformed with the usual rules of expansion and contraction; namely the cooler a liquid becomes, the denser it becomes until it solidifies and its dense-packed structure makes it heavier than the surrounding liquid phase? Obviously, then, it sinks. This rule applies to most natural materials.

Not so water. At 4 deg C it is at its densest, thereafter it becomes less dense so that when it freezes, it floats to the surface. Hence ice floats in lemonade.

If this was not the case, I surmise the following scenario:

Each winter, the pack ice that forms around Arctic and Anartctic regions would fall to the sea bottom, allowing fresh ice to form. As the winter progressed, an accumulation of ice would form, then in the subsequent summer it would remain, eroded somewhat by water temperatures, but nevertheless there for the following winter to add more layers. In a short time, the polar regions would expand as the seas froze from the bottom up. The fecund waters of these regions would become sterile of life, and each year the region of solid ice would expand southwards.

The resulting increase in ice coverage would cause the albedo of the earth to rise significantly thus retaining less sun energy and the advance of the ice would continue southwards until it encountered sea temperatures sufficiently warm to check it. This might leave a small 'tropical' region with fluid water, but then again, with thermal reflection maybe not.

I suggest in a short time the earth would be an ice-locked planet with few interesting features except for massive canyons where shrinkage would cause cracks to form. Life would be difficult, if not impossible, limited only where undersea volcanic activity kept the ice at bay.

As it is, however, water exhibits this peculiar expansion feature, and also in its solid phase is a poor conductor of heat. Hence the snow that should spell catastrophe for land-based polar creatures becomes their means of survival as they nestle in holes to bring up their young.

Lucky old us, eh? Still, it's a big universe, anything can happen...

(Can't find an ironical emoticon will this do?) my website

Missed the point there entirely, old chap my website

OK, I've had another look and I think I've got the point now. What you are saying is that if something did something different to what it does now, the things that are affected by what it does now would be affected in a different way and the world would be a different place.

And if someone set out to make the atmosphere less resistant to microwaves so that - oh I don't know - mobile phones might have a greater range, the the laws of physics as we perceive them now would be changed due to STP having been altered?

Money isn't everything, Harry. Tom Fleck is a lovely read and even though he did need a living, like we all do, I think his world was more romantic in so many more ways than it is today. I wonder what kind of world we'd have now if we hadn't got the written word.