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Principles of Radiometric Dating. An estimate can be obtained from arguments in nuclear physics, which says that the U/ U ratio may have been when the elements formed. Thus, since. we can write. or. and solve for t. The answer is about 6 billion years. Feb 21, Hi guys, this is one of the questions on an internal assessment that i have to do. it talked about carbon and how it has a half-life of yrs. "In a sample of bone discovered in a Neolithic grave, the amount of radioactive C was found to be only 1of that in living things. How old was. The constancy of radioactive decay rates follows from quantum mechanics, which has also passed every test physicists can create. In short, everything we know in chemistry and in physics points to radiometric dating as being a viable and valuable method of calculating the .
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An improved age for Earth's latest magnetic field reversal using radiometric dating. The Earth's magnetic field periodically reverses such that the north magnetic pole becomes the south magnetic pole. You've got two decay products, lead and helium, and they're giving two different ages for the zircon. He received his Ph.D. in physics from University of Texas at Dallas. For many people, radiometric dating might be the one scientific technique that most blatantly . Apr 22, Take potassium-argon dating. Potassium 40 decays into argon 40, a gas, which can diffuse through lava and escape. Newly formed igneous rocks has essentially no argon
All suomi. All Gallegan. Thus, if we start out with 1 gram of the parent isotope, after the passage of 1 half-life there will be 0.
Some examples of isotope systems used to date geologic materials. If we divide equation 4 through by the amount of 86 Sr, then we get:. Note also that equation 5 has the form of a linear equation, i.
How can we use this? In nature, however, each mineral in the rock is likely to have a different amount of 87 Rb. Thus, once the rock has cooled to the point where diffusion of elements does not occur, the 87 Rb in each mineral will decay to 87 Sr, and each mineral will have a different 87 Rb and 87 Sr after passage of time.
Learn about different types of radiometric dating, such as carbon dating. Understand how decay and half life work to enable radiometric dating. Play a game that tests your ability to match the percentage of the dating element that remains to the age of the object.
The discordia is often interpreted by extrapolating both ends to intersect the Concordia. Pb leakage is the most likely cause of discordant dates, since Pb will be occupying a site in the crystal that has suffered radiation damage as a result of U decay.
U would have been stable in the crystallographic site, but the site is now occupied by by Pb. An event like metamorphism could heat the crystal to the point where Pb will become mobile. Another possible scenario involves U leakage, again possibly as a result of a metamorphic event.
U leakage would cause discordant points to plot above the cocordia. The Age of the Earth A minimum age of the Earth can be obtained from the oldest known rocks on the Earth. So far, the oldest rock found is a tonalitic Gneiss metamorphic rock rock from the Northwest Territories, Canada, with an age of 3.
Radiometric dating is a means of determining the age of very old objects, including the Earth itself. Radiometric dating depends on the decay of isotopes, which are different forms of the same element that include the same number of protons but different numbers of neutrons in their atoms. Feb 17, Ive been poking about on the internet again (as you do) and found a whole load of stuff by creationists about the problems with carbon 14 radiometric dating. Specifically they report (with some glee) that coal has been found to contain measurable amounts of carbon14 which it . Radiometric dating is very reliable in theory - the decay of radioactive materials is very-very predictable. But like any other bit of experimental physics "the difference between practice and theory is small in theory but large in practice." It's especially tricky for Carbon14 dating (which most recent stuff relies on).
This gives us only a minimum age of the Earth. Is it likely that we will find a rock formed on the Earth that will give us the true age of the Earth? From the Pb-Pb isochron equation 11 we can make some arguments about meteorites.
Physics radiometric dating
First, it appears that meteorites have come from somewhere in the solar system, and thus may have been formed at the same time the solar system and thus the Earth formed. If all of the meteorites formed at the same time and have been closed to U and Pb since their formation, then we can use the Pb-Pb isochron to date all meteorites. First, however, we need to know the initial ratios of the Pb isotopes. We recognize two major types of meteorites: Fe- meteorites and stony or chondritic meteorites The Fe meteorites contain the mineral troilite FeS that has no U.
Since the mineral troilite contains no U, all of the Pb present in the troilite is the Pb originally present, and none of it has been produced by U decay. We can then determine the Pb ratios in other meteorites and see if they fall on a Pb-Pb isochron that passes through the initial ratios determined from troilite in Fe-meteorites.
The slope of this isochron, known as the Geochron, gives an age of 4. K-Ar Dating 40 K is the radioactive isotope of K, and makes up 0.
Thus the ratio of 14 C to 14 N in the Earth's atmosphere is constant. Living organisms continually exchange Carbon and Nitrogen with the atmosphere by breathing, feeding, and photosynthesis. When an organism dies, the 14 C decays back to 14 N, with a half-life of 5, years. Measuring the amount of 14 C in this dead material thus enables the determination of the time elapsed since the organism died.
Radiocarbon dates are obtained from such things as bones, teeth, charcoal, fossilized wood, and shells. Because of the short half-life of 14 C, it is only used to date materials younger than about 70, years. Other Uses of Isotopes Radioactivity is an important heat source in the Earth. Elements like K, U, Th, and Rb occur in quantities large enough to release a substantial amount of heat through radioactive decay.
Thus radioactive isotopes have potential as fuel for such processes as mountain building, convection in the mantle to drive plate tectonics, and convection in the core to produce the Earth's magnetic Field. Initial isotopic ratios are useful as geochemical tracers. Such tracers can be used to determine the origin of magmas and the chemical evolution of the Earth.
Short-lived isotopes Isotopes made during nucleosynthesis that have nearly completely decayed away can give information on the time elapsed between nucleosynthesis and Earth Formation.
Ratios of stable, low mass isotopes, like those of O, S, C, and H can be used as tracers, as well as geothermometers, since fractionation of light isotopes can take place as a result of chemical process.
We can thus use these ratios of light isotopes to shed light on processes and temperatures of past events. Viewed 3k times. Sven Sven 3 3 silver badges 6 6 bronze badges.
It can be answered with just a "yes. It would be much better if you included some specific objections that have been made and asked whether they are valid, and why. I asked specifically about reliability and limitations with the assumption, that the method itself is valid.
Keep in mind that we much prefer questions that show that the poster put some effort into formulating them, which yours doesn't.
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