quote:Or is the nature of water dependant on the physical laws of our universe?
It is dependent on how electrons arrange themselves, ie atomic theory. Because the hydrogens bond on one side of the oxygen atom (think mickey mouse) this causes a slight negative charge on one side and a slight positive charge on the other side of the water atom. When ice forms the water molecules line up in a hexagonal pattern, nose to tail. Kind of like magnets sticking together. The open structure of ice crystal is less dense than water which causes ice to float.
Water is no more fine tuned than any other chemical known to man since all chemicals follow the same rules as water.
quote:Ice sinking could actually cause the oceans to be warmer than they are because it would cause more mixing of the water as the thawed bottom ice water would rise to the surface and the ice blocks sank. This would add convection heat transfer into the system.
Also, we can't forget about the reflectivity of floating ice. Icebergs and floating ice reflect solar energy back out into space. If, for instance, the northern polar ice cap was at the bottom of the ocean the world would be warmer than it is now. Also, surface winds blowing over unfrozen water is warmer than surface winds blowing over ice that is well below 0 celcius (unfrozen sea water is always warmer than about -2 celcius I believe).
quote:I don't think the proposition that life can only arise in water-based environments was as much off the mark as has been suggested;
I don't think it's far off the mark either. Water is probably the best solvent for life, and it makes a stable byproduct for metabolism. I just have a hard time with the "fine-tuning", anthropic argument.
quote:On sulphur, don't the worms around black smokers use a sulfur-based metabolism?
The worms are filter feeders. They feed on autotrophs, some of which metabolize sulfur.