5 assumptions of radiometric dating
This does not mean that all rock samples are unreliable, but it is possible to account for a process which throws off the data for metamorphic rocks.For example, with Uranium-lead dating with the crystallization of magma, this remains a closed system until the uranium decays.
One assumption that can be made is that all the lead in the sample was once uranium, but if there was lead there to start with, this assumption is not valid, and any date based on that assumption will be incorrect (too old).Carbon dating, with its much lower maximum theoretical range, is often used for dating items only hundreds and thousands of years old, so can be calibrated in its lower ranges by comparing results with artifacts who's ages are known from historical records.Scientists have also attempted to extend the calibration range by comparing results to timber which has its age calculated by dendrochronology, but this has also been questioned because carbon dating is used to assist with working out dendrochronological ages.There is no reason to expect that the rate of decay of a radioactive material is largely constant, and it was almost certainly not constant near the creation or beginning of the universe.As early as of 1673, John Ray, an English naturalist, reckoned with alternative that "im the primitive times and soon after the Creation the earth suffered far more concussions and mutations in its superficial part than afterward". Atoms consist of a heavy central core called the nucleus surrounded by clouds of lightweight particles (electrons), called electron shells.
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However, the nucleus has a strong positive charge and the electron shells have a strong negative charge.