FAQ - Radioactive Age-Dating | Planetary Science Institute
The relative atomic masses given in periodic table entries—like the one for way ; this predictability allows the relative abundance of the isotope to be used as a have isotopes with different half lives, and can thus be used to measure age on. Atoms of the same element with differing atomic weights are called isotopes daughter products most commonly used to determine the ages of. For the others, one can only use relative age dating (such as counting . The number of protons usually determines the element the atom belongs to and it is.
Introduction Radioactivity pops up fairly often in the news. For instance, you might have read about it in discussions of nuclear energy, the Fukushima reactor tragedy, or the development of nuclear weapons. It also shows up in popular culture: But what exactly does it mean for something to be radioactive? Radioactivity is actually a property of an atom. Radioactive atoms have unstable nuclei, and they will eventually release subatomic particles to become more stable, giving off energy—radiation—in the process.
Often, elements come in both radioactive and nonradioactive versions that differ in the number of neutrons they contain.
These different versions of elements are called isotopes, and small quantities of radioactive isotopes often occur in nature. For instance, a small amount of carbon exists in the atmosphere as radioactive carbon, and the amount of carbon found in fossils allows paleontologists to determine their age.
Atomic number, atomic mass, and relative atomic mass Atoms of each element contain a characteristic number of protons. In fact, the number of protons determines what atom we are looking at e. In contrast, the number of neutrons for a given element can vary.
Forms of the same atom that differ only in their number of neutrons are called isotopes. If you want to calculate how many neutrons an atom has, you can simply subtract the number of protons, or atomic number, from the mass number.
The atomic mass of a single atom is simply its total mass and is typically expressed in atomic mass units or amu. By studying other planets, we are learning more about our own planet. The effects of impacts and how they might affect us here on Earth, global climate change Venus vs. Earth and what could happen to Earth in an extreme case, etc. How do you technically define half-life? From Wikipedia, radioactive decay is the process in which an unstable atomic nucleus spontaneously loses energy by emitting ionizing particles and radiation.
This decay, or loss of energy, results in an atom element of one type, called the parent nuclide transforming to an atom of a different type another element or another isotope of the same elementnamed the daughter nuclide.
It is impossible to predict when a given atom will decay, but given a large number of similar atoms, the decay rate on average is predictable. This predictable decay is called the half-life of the parent atom, the time it takes for one half of all of the parent atoms to transform into the daughter. If carbon is so short-lived in comparison to potassium or uranium, why is it that in terms of the media, we mostly about carbon and rarely the others?
Atomic number, atomic mass, and isotopes
This may simply have to do with what the media is talking about. When there is a scientific discussion about the age of, say a meteorite or the Earth, the media just talks about the large numbers and not about the dating technique e. On the other hand, when the media talk about "more recent events," ages that are more comprehendible, such as when early Man built a fire or even how old a painting is or some ancient parchmentthen we bring up the dating technique in order to better validate the findings.
Is there a chemical test for carbon? Again referring to Fig. Since the half-life of Rb87 is When properly carried out, radioactive dating test procedures have shown consistent and close agreement among the various methods.
If the same result is obtained sample after sample, using different test procedures based on different decay sequences, and carried out by different laboratories, that is a pretty good indication that the age determinations are accurate. Of course, test procedures, like anything else, can be screwed up.
Mistakes can be made at the time a procedure is first being developed. Creationists seize upon any isolated reports of improperly run tests and try to categorize them as representing general shortcomings of the test procedure. This like saying if my watch isn't running, then all watches are useless for keeping time.
Creationists also attack radioactive dating with the argument that half-lives were different in the past than they are at present. There is no more reason to believe that than to believe that at some time in the past iron did not rust and wood did not burn. Furthermore, astronomical data show that radioactive half-lives in elements in stars billions of light years away is the same as presently measured.
On pages and of The Genesis Flood, creationist authors Whitcomb and Morris present an argument to try to convince the reader that ages of mineral specimens determined by radioactivity measurements are much greater than the "true" i.Atomic Mass: Introduction
The mathematical procedures employed are totally inconsistent with reality. Henry Morris has a PhD in Hydraulic Engineering, so it would seem that he would know better than to author such nonsense.
Apparently, he did know better, because he qualifies the exposition in a footnote stating: This discussion is not meant to be an exact exposition of radiogenic age computation; the relation is mathematically more complicated than the direct proportion assumed for the illustration. Nevertheless, the principles described are substantially applicable to the actual relationship.
Morris states that the production rate of an element formed by radioactive decay is constant with time. This is not true, although for a short period of time compared to the length of the half life the change in production rate may be very small.
Radioactive elements decay by half-lives. At the end of the first half life, only half of the radioactive element remains, and therefore the production rate of the element formed by radioactive decay will be only half of what it was at the beginning.
The authors state on p. If these elements existed also as the result of direct creation, it is reasonable to assume that they existed in these same proportions. Say, then, that their initial amounts are represented by quantities of A and cA respectively. Morris makes a number of unsupported assumptions: This is not correct; radioactive elements decay by half lives, as explained in the first paragraphs of this post.
There is absolutely no evidence to support this assumption, and a great deal of evidence that electromagnetic radiation does not affect the rate of decay of terrestrial radioactive elements. He sums it up with the equations: He then calculates an "age" for the first element by dividing its quantity by its decay rate, R; and an "age" for the second element by dividing its quantity by its decay rate, cR.
It's obvious from the above two equations that the result shows the same age for both elements, which is: Of course, the mathematics are completely wrong.