Radiocarbon Dating

a method of dating ORGANIC material up to 8000 years old. There is a small amount of radioactive carbon 14 in the atmosphere which is taken up naturally by plants and animals during life. When the organism dies there is no more uptake of ¹⁴C and it starts to decay, with a HALF-LIFE of 5730 years. A date for the sample is arrived at by comparing the amount of ¹⁴C left with known standards.

Taken from Dictionary of Science

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Radiocarbon dating, or carbon dating, is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 (¹⁴C) to determine the age of carbonaceous materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" (BP), "Present" being defined as AD 1950. Such raw ages can be calibrated to give calendar dates.

One of the most frequent uses of radiocarbon dating is to estimate the age of organic remains from archaeological sites. When plants fix atmospheric carbon dioxide (CO₂) into organic material during photosynthesis they incorporate a quantity of ¹⁴C that approximately matches the level of this isotope in the atmosphere (a small difference occurs because of isotope fractionation, but this is corrected after laboratory analysis). After plants die or they are consumed by other organisms (for example, by humans or other animals) the ¹⁴C fraction of this organic material declines at a fixed exponential rate due to the radioactive decay of ¹⁴C. Comparing the remaining ¹⁴C fraction of a sample to that expected from atmospheric ¹⁴C allows the age of the sample to be estimated.

The technique of radiocarbon dating was developed by Willard Libby and his colleagues at the University of Chicago in 1949. Emilio Segrè asserted in his autobiography that Enrico Fermi suggested the concept to Libby in a seminar at Chicago that year. Libby estimated that the steady state radioactivity concentration of exchangeable carbon-14 would be about 14 disintegrations per minute (dpm) per gram. In 1960, he was awarded the Nobel Prize in chemistry for this work. He first demonstrated the accuracy of radiocarbon dating by accurately estimating the age of wood from an ancient Egyptian royal barge for which the age was known from historical documents.

Taken from Wikipedia

Quantum

(plural quanta) a small amount or unit of electromagnetic radiation which can be thought of as a particle of energy.

Taken from Dictionary of Science

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In physics, a quantum (plural: quanta) is the minimum unit of any physical entity involved in an interaction. An example of an entity that is quantized is the energy transfer of elementary particles of matter (called fermions) and of photons and other bosons. The word comes from the Latin "quantus", for "how much." Behind this, one finds the fundamental notion that a physical property may be "quantized", referred to as "quantization". This means that the magnitude can take on only certain discrete numerical values, rather than any value, at least within a range. There is a related term of quantum number.

A photon, for example, is a single quantum of light, and may thus be referred to as a "light quantum". The energy of an electron bound to an atom (at rest) is said to be quantized, which results in the stability of atoms, and of matter in general.

As incorporated into the theory of quantum mechanics, this is regarded by physicists as part of the fundamental framework for understanding and describing nature at the infinitesimal level, for the very practical reason that it works. It is "in the nature of things", not a more or less arbitrary human preference.

Taken from Wikipedia

TRENDS TO TALK ABOUT

Wine Coolers Aren't Soft Drinks. One 12-ounce (.35 liter) wine cooler contains the same amount of alcohol as a 12-ounce beer, a glass of wine or a shot of hard liquor.

Space Tomatoes. NASA is asking students to plant tomato seeds from space to see how they grow. The seeds were floating around in a satellite for five and half years. They don't think it will be another Attack of the Killer Tomatoes, but "Obviously, if a teacher... says they've got a 25-pound [11 kilogram] purple tomato, you bet we'll go look at it," a scientist told USA Today.

Because It's, Well, There. Can't get away to Yosemite to rock climb this afternoon? Why not try an indoor climbing wall? They're sprouting up all over the United States, and a Youth 90 reporter even found one in the highlands of Scotland. These rock climbing gyms often feature fiberglass walls made to feel like the real thing.

Elvis in Your Garden? A Cincinnati, Ohio, toy company makes a mold that you can put on vegetables while they're growing. After a few weeks your favorite veggies will have one of several faces, including Elvis Presley (not licensed yet) or a "pickle puss" for cucumbers that will be pickled. You can even have a mold of your own face--for $2,500.

Taken from Youth 90 magazine