[net.physics] No, not a PERPETUAL motion machine

wasser_1@viking.DEC (John A. Wasser) (05/03/85)

>In some places of the world, the Bay of Biafra is one, sunlight causes
>heating and evaporation which results in first tens of feet of
>water being more saline and warmer than the water several hundred feet down.
>
>Take a 200 foot long pipe and suspend it vertically with its top end
>about ten feet below the surface. Now start and upward flow in the pipe.
>As the less saline water warms by thermal conduction through the wall 
>of the pipe it becomes less dense than the more saline water on the 
>outside of the pipe. This density difference then maintains the flow 
>once started.
>
>Is this a perpetual motion machine?

	No.  If you check the first paragraph is attributes the
	conditions to SUNLIGHT.  When the sun stops shining, no
	more water flow.  (I don't mean "at night", I mean "when
	the sun stops shining"... you did say PERPETUAL didn't
	you?)

		-John A. Wasser

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