In a recent post Robin van Spaandonk questioned where this figure for the Beta-atmosphere pressure on water came from.
I explained that it arose from the discovery of the PV^6 = a constant relation for water. Now I appreciate that it is very difficult to imagine that there exists such an atmosphere which holds materials together with these enormous pressures and gives them their strength. For that matter it is very difficult for a layman to appreciate that a pressure of 15 psi is acting on every square inch of his body - until perhaps an explosive decompression of his 747 sends him flying out of a window. 8-) I remember well the day that Stinks (our science master) demonstrated the effect of atmospheric pressure on a large rectangular metal can. Some water in the bottom of the can was heated to fill the can with steam and the cap was screwed on. The crunching and squealing of the metal as the can was crushed, as though by some giant invisible hand, impressed us all. It would make a nice demonstration to try the same thing on an obsolete 747 - but thinking about it, the pressure would probably be reduced prematurely by the windows and doors popping since they are designed to withstand outward, not inward pressure. It would be nice if one could arrange a similar demonstration for the Beta-atmosphere - but I can't really see how. There was one thing that occurred to me though. Imagine that water is a ball bearing type gas at STP. One gram-molecule will occupy a bit less than 22 litres. Let's say one gram mass occupies 1024 cc to make the maths easy. At 2 atmospheres we have 512 cc. 4 " " " 256 " 8 " " " 128 " 16 " " " 64 " 32 " " " 32 " 64 " " " 16 " 128 " " " 8 " 256 " " " 4 " 512 " " " 2 " 1024 " " " 1 " Now 1000 atmospheres isn't 3750 atmospheres admittedly - but its the right order of magnitude, and at STP water isn't a gas but a vapour and presumably has quite a bit of Beta-atmosphere pressure on it already. In effect this shows how the "attractive" forces which supposedly hold liquid water together can be seen as negations of the external Beta- atmosphere pressure. No doubt the argument could be refined by working at CPT (Critical Pressure and Temperature) rather than STP. Obviously, the argument is not intended as any kind of proof. It simply gives a feeling for the Gestalt switch involved in moving the active action from the inside of a material to the outside, from a photographic negative, to a photographic positive. Cheers, Frank Grimer
