On Fri, 06 Jul 2007 01:29:17 GMT, Norminn
wrote:

mm wrote:

On Thu, 05 Jul 2007 20:17:01 GMT, "JoeSpareBedroom"
wrote:

What about the suction being added by the pump which sends the water to the
filter?


I believe that even if there were a total vacuum below the water
drain, the maximum pressure would be the weight of the water and air
above the drain. That's the principle of a mercury barometer (except
that there is a vaccum in the tube above the mercury instead of below
it), and if water barometers were made 600 feet tall, that would be
the principle there too.

I don't think suction really exists. All there is is unresisted
pressure, and the pressure is caused by the weight of the atmostphere
(and the water, when something is under water.)

Sort of like centrifugal force doesn't really exist (that is equal and
opossite to the centripetal force, as elementary school science books
sort of said). All there is is inertia that tends to make the
something go straight ahead, perpendciular to its axis of rotation,
not away from teh center of rotation.

Atmospheric pressure in this case is irrelevant.....

You made the article sound upsetting and I didn't look at it. But we
've been discussing water pressure and pumps and partial vacuums, and
if there were no atmospheric pressure, or if it were low like on some
planets, I don't believe the pump would have been able to suck as
much, no more than the atmospheric pressure plus the water pressure.

Even some bigger and more massive planets than ours, have, I believe,
less atomospheric pressure, because that pressure increases as the
mass of the planet inceases, but decreases as the mass of the
atmosphere decreases.

it was the pump that
did the damage.

Atmospheric pressure is invisible, but it's there.

AFter going to to the trouble to warn me about how depressing the
artcile would be, you then had to print some of it below, snippped.