Dating fossils and rocks dvd
Was Rb-87 or Sr-87 added to the rock by some unknown process?
Was one of them removed from the rock by some unknown process?
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As someone who has studied radioactivity in detail, I have always been a bit amused by the assertion that radioactive dating is a precise way to determine the age of an object.
The elements rubidium and strontium are found in many rocks. As illustrated above, a neutron in a Rb-87 atom can eject an electron (often called a beta particle), which has a negative charge. We know how long it takes Rb-87 to turn into Sr-87, so in principle, if we analyze the amount of Rb-87 and Sr-87 in a rock, we should be able to tell how long the decay has been occurring.
Their age was measured to be 6.0 /- 0.3 billion years old. Those who are committed to an ancient age for the earth currently believe that it is 4.6 billion years old.
Obviously, then, the error in that measurement is 1.4 billion years, not 0.3 billion years!
If some process brought Sr-87 into the rock, it probably brought different amounts of the atom into different parts of the rock, so the ratio of Sr-87 to Sr-86 won’t stay consistent from one part of the rock to another. He says that there is one process that has been overlooked in all these isochron analyses: diffusion.
If a consistent isochron is generated, however, we can be “certain” that no process interfered with the relative amounts of Rb-87 and Sr-87, so the radioactive date is a good one. Atoms and molecules naturally move around, and they do so in such as way as to even out their concentrations.
Most likely, the effect will be dependent on the age.