Copper corroding in the sea, Grasshopper life span, Faucet invention
Does copper corrode in salt water? I plan to build a salt-water hot tub and wonder if the heater copper pipes will corrode in
the "marine" environment. Bert, Albuquerque, New Mexico
Seawater leaves copper-nickel alloys practically intact. General corrosion rates for 90-10 and
70-30 copper-nickel alloys range between 2.5 and 25 microns per year. That's not much: 25
microns — only twice the thickness of a human hair — in a whole year.
 Native copper. Photo by Jonathan Zander, courtesy of Wikipedia.
Copper pipes will easily last the lifetime of a hot-tub heater, especially if the copper is a
copper-nickel alloy.
What protects the alloys? An oxide film forms on copper's surface,
which stops further corrosion quickly, much like the chromium oxide film that
keeps stainless steel shiny. The film can make the copper look brown,
greenish-brown, or brownish-black.
The film gets better with time. In flowing water, the corrosion rate decreases continually over at least a 14-year period.
That's the answer, but there's more about copper:
- Copper beads, found in Iraq, date back to 9000 BC.
- Egyptian metal workers first cast copper to shape in molds ( c . 4000 BC), reduced ores to metal with fire and charcoal, and
intentionally alloyed copper with tin to form bronze ( c . 3500 BC).
- Copper got its name from the Romans, who called it the "ore of Cyprus" since Cyprus supplied almost all Rome's copper. In Latin,
that's aes Cyprium. The Romans soon shortened that to cyprium and later corrupted it to cuprum and finally we anglicized it to
"copper".
- The greatest known deposit of copper is in rock formed by volcanic activity in the Andean Mountains of Chile.
- Copper, present in humans as a trace element, helps catalyze hemoglobin formation in our blood.
- Almost all coins contain copper.
- In World War II, the Germans laid mines in shallow waters, even in the Thames Estuary. Magnetic sensors detected when a ship's steel
hull passed above and triggered the mines. The exploding ships were devastating allied and neutral shipping. Copper to the rescue.
Workers simply attached a copper strip around the hull and connected the strip to ship's power. A current passed through the strip,
neutralized the ship's magnetic field, and defeated the mines.
- Policemen are called "cops" or "coppers" because their uniforms used to have copper buttons.
Further Reading:
Copper through the ages,
Copper Development Association
What is the average life span of a grasshopper? Chessnie
 A young grasshopper (approx
0.7 in or 17mm) on a grass stalk. Taken in Swifts Creek,
Victoria, Australia by Peter (aka Fir002).
"Hmmm...this actually is tougher than you'd think," muses Jeffery A. Lockwood, entomologist
professor at the University of Wyoming.
Aging and natural lifespan generate much interest among researchers these days but information is scarce.
Lockwood hazards an estimate: about a year.
Females lay eggs in mid to late summer. The eggs spend the autumn and winter
dormant in the soil,
about ten months. A typical grasshopper hatches, goes through five molts (called nymphal instars), and
becomes an adult after the fifth molt. Each of the nymphal stages lasts five to ten days, depending on
temperature. So a grasshopper takes about 25 to 50 days to become an adult after hatching. Counting in life as an egg, the grasshopper is
about 11 months old when she reaches adulthood.
Now, the tricky part: life as an adult. She takes ten to 14 days to reach sexual maturity and mate. She lays an egg pod every week or so
until she lays one to three pods. Then she dies. So she lives about 30 days as an adult. Adding in time as an egg and spent in nymphal
stages we get a 12-month life span.
Of course, a bird or other predator could eat her before then. Grasshopper mortality rates indicate she has a 50 % probability of dying
within 50 days after she hatches. This says nothing about the chances some parasite will lay eggs inside the original grasshopper egg,
killing her before she hatches.
Further Reading:
U of Wyoming: Grasshoppers of the west
U of California, Berkley: Crickets and grasshoppers
Who invented the water faucet? "zipper" Buffalo, New York
That simple machine we take for granted is a valve, whose origins goes back into prehistory. Perhaps a clever human decided to
control the flow of a stream or river by blocking its flow with large stones or a tree trunk and thus hit upon the notion.
However the idea sprang into being, it ranks with the invention of the wheel. People could now regulate water flow. Early Egyptians and
Greeks devised valves to divert water for drinking and crop irrigation. The Romans advanced these ideas enough to deliver water to
individual buildings. Their plumbing had plug valves (stopcocks) and check valves to prevent backflow.
 Modern
tap mechanism. Tap photo by Angie of Sawara, Chiba-ken, Japan.
Drawing courtesy of Wikipedia.
A plug valve is a conical plug with a hole. By turning the plug the hole is either lined up with the pipe so water flows or set at right angles
to block flow.
In the early 1500s, Leonardo da Vinci designed canals and irrigation projects that used valves. He left sketches illustrating his ideas. In
1705, Thomas Newcomen invented the first industrial steam engine. That generated new interest in valves since Newcomen needed better
valves to contain high steam pressures built up in his engines. In February 1870, J.H. Davis filed a patent on a globe valve — the familiar
faucet with the round handle. Soon after, in April of that year, F. Manz filed a patent for a beer faucet.
(Answered Oct. 11, 2002; updated Dec. 4, 2007)
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