today
8:30 a.m. Audubon Society Field Trip See Event Description
read >9 a.m. Arcata Farmers' Market Arcata Plaza
read >9:30 a.m. Discovery Walk: Unknown Waterfront See Event Description
read >9:30 a.m. Manila Dunes Restoration Manila Community Center
read >10 a.m. Manila Dunes Guided Walk Manila Community Center
read >10 a.m. Library Book Sale Humboldt County Library
read >10 a.m. Dia de los Muertos and Mexican Folk Art Sale Private Eureka home
read >10 a.m. Final Arcata Farmer's Market Arcata Farmers' Market (off the plaza)
read >11 a.m. Donlin Foreman Dance Workshop Dell'Arte
read >2 p.m. Humboldt Coastal Nature Center Draft Trails Plan Walk Stamps House
read >5 p.m. Bati Zado and Show Redwood Raks World Dance Studio
read >6 p.m. The Tumbleweeds Chapala Cafe
read >6 p.m. Ali Chaudhary (jazz duo) Libation
read >6:30 p.m. Not Evil, Just Wrong Humboldt Area Foundation
read >7 p.m. Guitar Stan (country) Old Town Coffee & Chocolates
read >8 p.m. Guitar Orchestra of Barcelona Arkley Center for the Performing Arts
read >8 p.m. Stones in His Pockets Arcata Playhouse
read >8 p.m. A Christmas Carol North Coast Repertory Theater
read >8 p.m. Donna Landry Swing Dance Moose Lodge
read >8 p.m. North Coast Wind Ensemble Fulkerson Recital Hall at HSU
read >8:30 p.m. The Last Minute Men (international) Cafe Mokka
read >9 p.m. Ian McFeron Band (folk rock) Six Rivers Brewery
read >9 p.m. The Michael Paul Band WAVE @ blue lake casino
read >9 p.m. The Generatorz (classic rock) Central Station Cocktail Lounge
read >9 p.m. Taxi Bear River Casino
read >9 p.m. VJ Itchie Fingaz Pearl Lounge
read >9 p.m. Jack Ruby Presents + Blue Street + Acufunkture (DIY rock) Jambalaya
read >9 p.m. 2nd Annual Scorpio Bash The Red Fox Tavern
read >10 p.m. Music by DJ Sidelines
read >10 p.m. DJ Icy Hot Aunty Mo's Lounge
read >10 p.m. Jemimah Puddleduck (rock) Humboldt Brews
read >10 p.m. White Manna + Midday Veil + The King Salmon Duo (rock) Jambalaya
read >11 p.m. Radio Moscow (psychadelic blues) + Mosquito Bandito (one-man surf/garage) The Alibi Lounge and Restaurant
read >previous columns
Aug. 7, 2008
Osmosis is Awesome
Sap drips from the leaves of my indoor banana plant. ...
read >July 31, 2008
Concretions
Meter-sized spherical rocks decorate Bowling Ball Beach three miles south ...
read >July 24, 2008
Arms Race & Species
Herpetology, the study of amphibians and reptiles, sheds much light ...
read >Photos
Growth and Decay
By Don Garlick
Begin with one bacterium capable of dividing each hour. After 10 hours there will be 1,024 bacteria (2^10). That's an example of geometric, or exponential, growth. If the colony is confined to a small jar of food, and half that food is converted into those 1,024 bacteria in 10 hours, you can imagine their leader declaring: "Do not concern yourselves. There remains as much food in this jar as we have consumed during our entire past history of 10 generations." His audience will be unpleasantly surprised when the food is gone after just one additional hour, at which point there are 2,048 hungry bacteria.
A useful relationship between percentage growth rate, or annual interest rate, and the doubling time is the 70 percent rule: (Growth Rate) x (Doubling Time) = 70 percent. For example, a 7 percent annual interest rate would double your money in 10 years. The math is related to the natural logarithm of 2, equal to 0.693, approximated by 70 percent.
Exponential decay, the mirror image of growth, is pertinent to nuclear technology, nuclear medicine and geologic dating. Decay Rate multiplied by Half-life = 0.693. For example, Tritium (Hydrogen-3), illuminating your watch dial, has a half-life of 12 years, so the probability of any one atom decaying within any one year is 0.693/12 yr = 0.058/year. Half of the Earth's original inventory of Uranium-238, with a half-life of 4.5 billion years (the age of the Earth) has been converted into Lead-206. The original inventory of fissionable Uranium-235, with a half life of 0.7 billion years, is 99 percent decayed into Lead-207. Modern uranium is only 0.7 percent U-235 and needs to be enriched for use in weapons or power stations. Among its many fission products is Iodine-131, with a half-life of eight days. This isotope accumulates in the thyroid, causes thyroid cancer, and is used in treating thyroid cancer as well as hyperthyroidism. Patients receiving iodine radiotherapy should stay away from children.
Geologic history is quantified by a dozen independent radiometric dating methods in addition to the U-Pb methods. The one creationists love to criticize is Carbon-14 dating. C-14, a trace constituent in the atmosphere and hence plants, is produced from atmospheric nitrogen by cosmic rays and decays back into N-14. Because daughter nitrogen cannot be distinguished from abundant background nitrogen, radiocarbon dating must be calibrated by measuring the C-14 remaining in wood of known age, determined by counting tree rings. Anyway, C-14, with a half-life of 5,730 years, is barely detectable in objects older than 45,000 years. The Earth is 100,000 times older than that.
As an existential exercise, plot on my diagram the percent of food remaining in the bacterial colony during the last three hours of its existence.



















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