# Radiometric dating strength and limitations

Geologists can employ two basic methods to dating rocks and fossils. Relative and absolute geologic dating practices have their strengths and weaknesses. Various dating methods available today have some advantages and some disadvantages which depend on Change in direction and strength of magnetic field. limitations of and extensions to the C dating technique. The level of cosmic rays varies with the sun's activity, the strength of the Earth's geologists, and anybody else who use radiocarbon dates; they test for it and take it.

But doesn't it seem strange that after more thanyears earth's population is still only 7 billion? After all, the population increased from 1 billion in to 7 billion in - a span of just years! Of course, population growth is exponential, but even then the numbers don't add up. Some claim a world-wide catastrophe may have occurred around 70, years ago, reducing the human population to maybe just 1, breeding pairs.

Let's do the maths on these 'catastrophe' figures. Of course, there are many factors that affect r, such as climate, disease, war, standard of living and so on. Typically, population growth rates are between 0. In words, earth's population should be some million, billion, billion, billion. This an impossibly large number when compared to the earth's current 7 billion people.

Either the population growth calculation is hopelessly wrong, or the theory of human evolution is suspect!

This computation appears much more realistic. Scientific Debate Earth dating via ocean sediments, magnetic field decay, atmospheric helium, short-period comets and other techniques point to a young earth. However, the scientifc accuracy of YE claims are frequently challenged e. In order to balance the discussion we should also challenge the currently accepted radiometric dating methods.

## What are some of the limits of radiometric dating techniques?

If these are suspect then the disputed methods take on more meaning. Assumptions and Weaknesses of Radiometric Dating Most rock dating methods rely on the following basic assumptions: The K-Ar method dates rocks by measuring the accumulated Ar It is claimed the advantage of this method is that it circumvents the zero date problem i.

In other words, all Ar in a rock is assumed to have been produced by in-situ radioactive decay of K within the rock since it formed and there was zero Ar in the rock when it solidified. However, this primary assumption has been challenged e. This 'zero Ar' problem has also been identified by Snelling who comments for one research project: Certainly it is known to diffuse easily from deeper rocks under pressure so surface rocks tend to have a higher Ar concentration than would be expected.

This, coupled with the fact that potassium is easily washed out of minerals, suggests this technique can give an artificially high age for the earth and leads some to conclude that: Pitman, Radiometric Dating Methods, ] If we question these techniques, there is an alternative method called isochron dating. The isochron dating method attempts to combat the zero date problem by using ratios of isotopes and samples of different minerals from the same rock.

However, it still relies on certain basic assumptions, and in particular on the assumption that the specimen was entirely homogenous when it formed i.

The method also assumes that all mineral samples will have the same initial Sr to Sr ratio, but this is not always the case. So whilst isochron dating can give a straight line, the slope may have no significance [Vardiman et al]. Constant Decay Rate and Uniformitarianism What about the radiometric assumption of constant decay rate?

### Age of the Earth: strengths and weaknesses of dating methods

Such an assumption rests on the old evolutionary concept of uniformitarianism. In broad terms this means the observed geological features are the result of slow geological forces of the same kind and intensity as those found today. And for radiometric dating it means that the decay constant of the parent has not changed over earth's history.

Scientific justification for this assumption is found for example in Radiogenic Isotope Geology, A. The overall theme is that of a very old earth. In contrast, Humphreys has proposed an accelerated decay higher decay rate early in earth's history, leading to a younger earth. This idea has been rebutted by those who claim there is no known scientific mechanism to produce such a change, see for example Tim-Thompson: Others disagree and say that studies in theoretical physics suggest accelerated nuclear decay can occur e.

Variation in compactified dimensions could affect coupling constants Consequent variation in coupling constants could cause accelerated decay Changes in potential well depth change the alpha-particle wave function Changes in the alpha-particle wave function change decay half-lives Uniformitarianism is also challenged if we invoke the concept of a world-wide flood for which there is much evidence.

Vardiman et al claim that this would result in unreliable radioisotopic dating. They conclude from their research that: The chief reason is that uniformitarianism is not a legitimate model of earth history. Observational evidence supports the recent occurrence of a global catastrophic flood. Classical OE dating radiometric dating is based upon the spontaneous breakdown or decay of atomic nuclei, where a radioactive parent atom decays to a stable daughter atom.

The clash between OE dating millions or billions of years and YE dating thousands of years centres on the decay constant K. As discussed, OE dating rests on the evolutionary concept of uniformitarianism and an assumed constant decay rate for all time. But this is not necessarily so. The Decreasing Speed of Light: InAlbrecht and Magueijo proposed a reduction in 'c' over time as a solution to cosmological puzzles.

For example, theories in which light is traveling faster in the early periods of the existence of the Universe have been recognised as an alternative to the 'big bang' inflation scenario, see Pedram and Jalalzadeh. So, rather than 'c' being constant with time, it has been proposed that the product 'hc' where here 'h' is Planks Constant and 'c' is the speed of light in a vacuum should be considered constant, see Setterfield.

Even in recent times, hundreds of measurements of 'c' since show a small but statistically significant decrease i. See also speed measurments and discussion. The Effect of Changes in 'c': As just noted, some in the scientific community now claim that the radioactive decay 'constant' K can be changed i.

In particular, Setterfield has shown that K is strongly related to 'c'. So if the speed of light slows down, then the radioactive decay rate also slows down, link. It is argued like this: The energy of emitted particles from the nucleus is related to the velocity of light through the relativistic expression for kinetic energy, and the half life of a radioactive atom is related to the energy of the ejected particle by means of the empirical relation called the Geiger-Nuttal law.

Through these relations we can deduce that if the speed of light is slowing down, then the radioactive decay rate is also slowing down. It follows that radioactive decay rates were much higher in the past.

## The Weakness of the Principles of Geologic Dating

In other words, when 'c' was higher, atomic clocks ticked more rapidly and 'atomic time' ran fast. So standard radiometric dating must be corrected for this early accelerated decay ratereducing millions of years to thousands!

From an Old Earth to a Young Earth? The current scientific argument for an old earth is popular especially in the media and education whilst the concept of a young earth as held by Creationism is given low profile and so seems relatively weak.

For example, non-radiometric dating techniques using ice cores do indeed appear to date the earth well in excess ofyears. But there are several factors in favour of a young earth.

These are largely ignored by mainstream science but could be the key to the massive discrepancy when it comes to dating the earth.

Biblical Earth Changes The Bible records two dramatic, worldwide physical changes to the earth: Physical changes to the earth at the Fall of Man Physical changes to the earth during the Flood At the Fall of man the whole of creation, including the earth, was suddenly subjected to corruption or decay Rom 8. Man suddenly had a limited lifespan Gen 2.

Debunking Creationism: "Radiometric Dating Is Unreliable!"

Also, at the Flood there were catastrophic geological changes, see for example geological evidence for the flood and scientific evidence. Some see these physical events as being related to changes in physical laws e. In short, the earth's order is deteriorating with time, and "the earth is wearing out like a garment" Isa This concept seems to be supported by theoretical physics, which suggests that a decrease in the speed of light, c, see Is the Velocity of Light Constant in Time?

Physical changes are also suggested from the biblical accounts of man living to over years prior to the Flood Gen 5followed by an exponential decrease in age after the Flood. Some suggest this could be from a significant increase in radioisotopes in the atmosphere after the Flood. So you can never have perfect running conditions and certain parameters will change over time, this is just the nature of high-tech machinery.

A small shift in a parameter can affect your final outcome. So some analytical limitations can be the beam intensity, counting statistics, dead-time and so on. These are parameters you can control and will affect how accurate and precise your age-dating is.

Don't worry what those parameters mean, just understand they are machine-based. Natural limitations encompass those as a result of nature. For example, you may want to date the same zircon crystals using the U-Pb method.

In order to do this, you need to measure various isotopes of uranium U and lead Pb. Though, when you come to do this measurement you find that uranium concentrations are very low in your sample on the order of a few parts per million. This low concentration will mean your counting statistics will not be as robust and may result in decreased precision.

Another limitation is the length of time a decay series can be used for. Another example, you may want to use. Lets say the object is a million years old but as the scientist measuring this object we don't know that and we go to measure it using the C method.