Siphon on the Moon?
OK, I’m visualizing Cecil’s siphon working on the Moon,
minus the cat and the fish. So, if someone poked
a hole with an icepick in the top of the bend,
it would “break” the siphon just like on Earth?
Why? Because the hole somehow affects the
water’s cohesiveness? I’m skeptical.
Alternatively, it would not “break” the siphon at
all, because the water has so much cohesiveness?
Then why do siphons “break” on Earth?
Why can’t we make “water boogers?” I was taught
that capillary action can draw water to the top of
trees because of water’s adhesion to the walls of
capillary tubes (it forms a concave meniscus) and
not because of any special tensile strength.
When a water siphon stops flowing at 34 feet
(equal to sea level atmospheric pressure) the
two arms of the siphon look to me very much like
water barometers. Apparently “Uncle Al” Schwartz,
the “Usenet physics adept,” regards this as a
curious coincidence. I’m skeptical.
This reminds me of a story that went around during
the 1979 gasoline shortage, about somebody trying
to siphon gas out of an RV and opening the wrong cap.
Better smell that thing before you suck on it,
because I think it’s full of crap.
When Al Schwartz “insisted that water’s tensile
strength remained the conservative explanation”
it didn’t add any credibility for me. Maybe it’s
because I live in Berkeley, but that phrase often
signals me to expect a face full of… uh, highly
implausible stuff, like “impurities and dissolved
gases” that reduce the tensile strength of water
to “the atmospheric case” – except when the siphon
is working, it which case the tensile strength
comes back, apparently.
I’ve read this particular column repeatedly, but
I cannot understand why Cecil “felt entitled to
call this argument a draw.” I’d appreciate a little
more explanation.