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J. Perelman
"Entertaining physics". Book 2.
Chapter 6. Properties of liquids and gases

WHERE ARE THE WRECKS?

It is widely believed, even amongst sailors, like ships that sank in the ocean, do not reach the seabed and hang motionless in some depth, where the water is respectively sealed by the pressure of the overlying layers.

Opinion is divided, apparently, even the author of "20 thousand leagues under the sea"; in one of the chapters of this novel Jules Verne describes still hanging in the water the wreck, and the other mentions the ships, "rotting, hanging freely in the water."

Whether such a statement?

Some basis for it, as if, there is, as the water pressure in the depths of the ocean really reaches a huge degree. At a depth of 10 m water presses with a force of 1 kg per 1 cm2 of the immersed body. At a depth of 20 m, the pressure is 2 kg, at a depth of 100 m - 10 kg 1000 m - 100 kg. of the Ocean in many places has a depth of several kilometers, reaching into the deepest parts of the Great ocean more than 11 km (Mariana trench). It is easy to calculate, how much pressure should test the water and immersed in her subject at these great depths.

If empty stoppered bottle lowered to a considerable depth, and then extract again, you will find that the water pressure drove the cork into the bottle and the whole bowl full of water. Famous oceanographer John Murray in his book "the Ocean" tells what was done by this experience: three glass tubes of various sizes, with both ends sealed, were wrapped in cloth and placed in a copper cylinder with openings for the free passage of water. The cylinder was lowered to a depth of 5 km When it was pulled out, it turned out that the canvas is filled with nagourney mass: it was shattered glass. The pieces of wood, placed at such a depth, after extraction, was sinking in the water as a brick, so they were crushed.

Naturally, it would seem, to expect that such a monstrous, the pressure should be enough to condense the water at great depths that even heavy objects will not be in it to sink, as it floats iron weight in mercury.

However, this opinion does not substantiated. Experience shows that water, like all liquids, can hardly be compressed. Crushed relentlessly with a force of 1 kg per 1 cm2 water is compressed only on 1/22 000 share of their volume and about as compressed upon further increase in pressure for every kilogram. If we wished to bring the water to the density, so that it floated iron, it would be necessary to condense it 8 times. Meanwhile, for sealing only twice, i.e. to reduce the volume by half, should the pressure in 11 000 kg per 1 cm2 (if only this measure compression has taken place for such a huge pressures). This corresponds to a depth of 110 km below sea level!

Hence, it is clear that to speak of any appreciable condensation of water in the deep oceans is absolutely not necessary. In the deepest of their place water sealed only 1100/22000, i.e., 1/20 its normal density, only 5%*. It's almost no influence on the sailing conditions in different bodies, the more that solid objects immersed in such water are also subjected to this pressure and, consequently, also compacted.

There can be therefore no doubt that sunken ships rest upon the ocean floor. "All that is drowning in a glass of water, " says Murray, " must go to the bottom and in the deepest ocean."

I've heard against this objection. If you care to immerse the glass upside down into the water, he may remain in this position so as to displace the volume of water that weighs the same as a glass. The heavier the metal, the glass may be held in the same position and below the water level, and not sink to the bottom. Similarly, though, can stop halfway up and overturned keel cruiser or another ship. If in some areas of the ship, the air will be tightly locked, then the ship will sink to a certain depth, and there stop.

Not a little because of the ships is sinking upside down - and it is possible that some of them never reach the bottom, staying to hang in the dark depths of the ocean. Rather it would be a slight bump to bring this ship out of balance, flip, fill with water and cause it to fall to the bottom, how could tremors deep in the ocean, where the ever quiet and where not even the echoes of the storm?

All these arguments are based on a physical error. The inverted Cup is not immersed in the water itself - it needs external power to immerse in water, as a piece of wood or an empty stoppered bottle. Similarly, the inverted keel up the ship does not begin to sink, but will remain on the surface of the water. To be halfway between sea level and its bottom, he can not.

* The English physicist has calculated that if the earth's gravity suddenly stopped and the waters became weightless, the level of water in the ocean would rise on average by 35 m (due to the fact that the condensed water would have bought a normal volume). "The ocean flooded least 5 000 000 km2 of land, bound to its surface by the existence of only the compressibility of the surrounding ocean waters" (Berger).

Entertaining physics J. Perelman

 




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