Estimating age

A sample of spruce wood taken from Two 2. What is the estimated age of the spruce wood... 

As for the estimated age two chronometric methods, radiocarbon and dendrochronological dating, enable the accurate dating of materials or/and events in the timespan between the present and 10,000 years ago. The... 

Cr 261 is one of the oldest open clusters in the Galaxy, with an estimated age ranging from 7 to 11 Gyr ([5] [16] [4]). The metallicity, derived from both low-resolution and high-resolution spectra, is slightly subsolar ([Fe/H]=—0.2 ... 

L and the D/L ratio approaches zero. After the death of the living organism, proteins start to spontaneously break down. An inter-conversion of the amino acids occurs from one chiral form (L) to a mixture of D- and L- forms following protein degradation this process is called amino acid racemisation. The extent of racemisation is measured by the ratio of D/L isomers and increases as a function of time and temperature. The longer the racemisation process continues the closer to 1 the ratio between the D- and L-forms becomes. If the D/L ratio is <1 it may be possible to use it to estimate age. The D/L ratio of aspartic acid and isoleucine are the most widely used for this dating technique [104]. Dates have been obtained as old as 200 000 years. However, it has been used mainly to date samples in the 5000 100 000 year range. Recent studies [ 105] mention an estimation of the method accuracy to be around 20%. 

Developmental norms should be used to estimate age-appropriate executive functions and intellectual abilities. 

Chromatography with a chiral (optically active) stationary phase is one of the few ways to separate enantiomers. We can estimate ages of fossils up to 500 million years old by measuring the fraction of amino acid that has transformed into the d enantiomer in a fossil.4-5 Amino acids do not have enough vapor pressure for gas chromatography. A volatile derivative suitable for gas chromatography is shown in the figure above.6... 

If you know the half-lives of uranium isotopes and the percentage of lead isotopes in some uranium-bearing rock, you can calculate the date the rock was formed. Rocks dated in this way have been found to be as much as 3.7 billion years old. Samples from the moon have been dated at 4.2 billion years, which is close to the estimated age of our solar system 4.6 billion years. 

Ironically, we have come full circle from Darwin s day. When Darwin first proposed his theory a big difficulty was the estimated age of the earth. Nineteenth-century physicists thought the earth was only about a hundred million years old, yet Darwin thought natural selection would require much more time to produce life. At first he was proven right the earth is now known to be much older. With the discovery of the biological Big Bang, however, the window of time for life to go from simple to complex has shrunk to much less than nineteenth-century estimates of the earth s age. 

A blind test was conducted with a cotton sample 814 days old. A single creep test was performed and the age was estimated. The result achieved was an estimated age of 214 days. This result seems to indicate a rather large error. However, when the datum is plotted, the point is not very far from the curve. In fact, it is quite consistent with the trend set by the data for 47- and 400-year-old samples and suggests that the curve rather than the 814-day datum is incorrect. In view of the limited number of calibration points used to fit the curves, this explanation seems plausible. Consequently, the curve in Figure 8 represents a curve fitted to all cotton specimens measured, including the 814-day specimen. The fitted equations presented here should be used only to evaluate the... 

Complications in the estimation of groundwater ages are not unique to For example, diffusion can create major errors in estimated ages when applying the H/ He method in areas where the groundwater velocity is less than —0.01 m yr. In such cases He will diffuse upwards, and little information regarding travel times will be preserved in the He concentrations (Schlosser et al., 1989). Similar comphcations are inherent in the use of other tracers as well (see, e.g., Phillips, 2000 Sudicky and Frind, 1981 Varni and Carrera, 1998). 

H/ He, CFCs (CFC-11 and CFC-12), and Kr can give insight into the dynamics of ground-water flow systems and the major transport processes that influence the concentration of different tracers. They also illustrate how the use of a multitracer approach using direct water dating methods at a local scale increases confidence in estimated ages. 

Figure 7 The Vostok ice-core record (Petit et aL, 1999). (a)-(c) Carbon dioxide, methane, and oxygen isotope ratios (expressed as 5 0) of oxygen in air extracted from the ice. (d) Hydrogen isotope ratios (expressed as or 5D) in the ice. This record is a proxy for local temperature, (e) Sodium in the ice, a measure of sea salt aerosol deposition, (f) Dust in the ice, a measure of continental aerosol deposition, (a)-(c) are plotted against the estimated age of the iee air (d)-(f) are plotted against the estimated age of the ice.

As accurately as these calculations can be made, however, the behavior of celestial bodies over long periods of time cannot always be determined. For example, the perturbation method has so far been unable to determine the stability either of the orbits of individual bodies or of the solar system as a whole for the estimated age of the solar system. Studies of the evolution of the Earth-Moon system indicate that the Moon s orbit may become unstable, which will make it possible for the Moon to escape into an independent orbit around the Sun. Recent astronomers have also used the theory of chaos to explain irregular orbits. 

Even more surprising is the presence of the diunsaturated acid 18 2 in all coal samples studied. The presence of diunsaturated acids is indeed highly unusual because of their inherent instability under geological conditions. Itihara et al. (42) have reported the presence of 18 2 in a fossil walnut stone of estimated age one million years (Pleistocene), but this appears to be the first report of a diunsaturated acid in a sediment or coal from the Eocene epoch or the Permian period. 

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