Well start out that there are no dating methods that prove a earth millions of years old. Prove to me that there are in your own words. If you cant put it in your own words then you dont understand what you are talking about. - James Brown
Ok James Brown here is a guide to dating methods in my own words...
Scientists use a variety "clocks" to measure geological time. This makes it possible to check the accuracy of any particular clock against others. As they also operate at vastly different speeds, between them, they cover the whole span of the 7 or 8 orders of magnitude we are interested in.
At the fast end of the spectrum of natural clocks we have tree rings or dendrochronology. Annual growth rings in trees reveal distinct patterns based on climate with certain fingerprint sequences of rings that can be recognised and dated exactly. By examining living trees and fossils it is possible to extend tree-ring dating back with certainty for 11,500 years. That is literally yesterday by evolutionary standards but it does pose an interesting quandary for young earthers. It is particularly useful in archaeology. On a similar time-scale sediment layers (varves) in glacial lakes lay down annual layers that can be dated with certainty, as can annual growth layers in coral reefs.
The other dating methods that measure tens or hundreds of millions or even billions of years are mostly radioactive and are accurate to within an error range that is proportional to the timescale concerned. Typically around 1%
Now for the chemistry lesson; Every atom is like a tiny solar system (in the real world it is not so simple but the model is still useful and valid) with a given number of protons clustered together in the nucleus. The exact number defines the element concerned, all atoms of copper always have 29 protons at the heart of every atom, hydrogen has 1, carbon has 6 and so on. Protons have measurable mass and a positive electrical charge.
Whizzing around them like planets in orbit is exactly the same number of negatively charged electrons, which are so tiny as have a mass of zero for practical purposes. Now the clever bit; also in the nucleus and possessing a mass similar to protons and a neutral charge are neutrons. Unlike the protons, the number of neutrons found in the nucleus is not definitive of the element, usually it is slightly more than the number of protons but the number can vary. Elements can exist with different numbers of neutrons and these are called ”isotopes” of the element.
For example carbon exists as 3 different isotopes. Carbon-12 has 6 protons and 6 neutrons in the nucleus of every atom. Carbon-13 must always have 6 protons (otherwise it would not be carbon) but it has 7 neutrons. Carbon-14 has 8 neutrons and we will come back to carbon-14 shortly.
Some isotopes are stable; they are content to remain with the hand they were dealt, but others are unstable where the atoms decay into something else and crucially do so at a very precise and measurable rate. This change is what we call radioactivity.
There are three main types of radioactive decay. In one kind of decay the extra neutrons turn into protons, this means that the mass stays the same but the number of protons goes up by one so that the atoms become a different element; for example sodium-24 decays to become magnesium-24.
In another form of radioactivity the opposite happens, a proton becomes a neutron, so again the mass remains unchanged but the atoms turn into the element one place below in the periodic table.
In the third kind of decay a neutron strikes the nucleus of another atom knocking out a proton and taking its place. The effect on the atom is the same as the example above.
What is vital to understand is that every unstable radioactive isotope decays at its own characteristic rate, which is precisely known. The rate of decay is always “exponential” which means that a fixed proportion decays in a given time. The favoured unit of measurement is half-life. This is the time taken for half of the amount of an isotope in a sample to decay to another stable element.
The half-life of carbon-14 is 5-6000 years, which makes it useful for specimens up to around 50-60,000 years. After that practically all the carbon-14 has decayed. Rubiduim-87 has a half-life of 49 billion years and fermium a mere 3.3 milliseconds.
The point is there are a range of clocks available to cover all of evolutionary time and that they can be used to confirm and correct each other.
Before the advent of radioactive clocks geologists had built up a picture of the sequence of layers of rock that can be readily identified all over the world. Sedimentary rocks like limestone or sandstone consists of layers of mud or sediment laid down on the floor of a sea, lake or estuary. It becomes compacted over ages and hardens to form rock.
These layers had been identified and given names like Cambrian, Ordovician, Devonian, Jurassic, Cretaceous, Eocene, Oligocene and Miocene. The same layers have the same appearance and contain the same sets of fossils wherever they are found. Logically the oldest layers are found below the younger layers and although a complete collection of layers may not be found in any one location, by daisy-chaining and jigsawing your way around the world the relative age of each layer can be known. Apart from where they have been turned on their side or even upside down by movements of the earth's crust these layers are always found in the same sequence. The micro-fossils called foraminifera and radiolaria that are found in each layer is totally predictable and are used by geologists to locate oil. Young earth creationists don't have much success in oil exploration.
Now here’s the challenge, the fossils we want to date are all found in sedimentary rocks; the radioactive clocks are all found in igneous rocks that did not originate in mud but in molten lava.
When lava or magma comes to the surface of the earth and begins to cool it crystallises. At that moment in time all the radioactive clocks it contains are set to zero. For example it may contain a quantity of the isotope of Potassium called Potassium-40. Over time it will decay to become Argon-40 but at the moment of formation the ratio is 100% in favour of Potassium-40. Exactly 1.26 billion years the ratio of Potassium-40 to Argon-40 will be 50:50. After another 1.26 billion years it will be 75:25 and so on. The same is true of all the other clocks contained in the same rock sample each with their own unique half-life.
Since the same layers of sedimentary rock are to be found all over the world, wherever igneous rock is found above, below or within a layer of sedimentary rock it, and the fossils it contains can be dated. The accuracy of these dates can be confirmed by comparing numerous clocks from numerous samples. Not just the relative ages, but also the actual ages of sedimentary rock layers are now known with certainty.
Of the 118 known elements on earth there are 308 isotopes, 150 of which are stable and 158 unstable; that is they will decay to form other elements. If young earth theories were correct you would expect all of these 158 unstable elements to still exist. In fact only 37 of these have not gone extinct already and every one of these have a half-life greater than 700 million years. When we look at the 121 that have gone extinct, every single one of them has a half-life less than 200 million years. The only unstable isotopes we find on earth are those that have a half-life long enough to survive on a very old planet.
All the radioactive clocks agree at placing the age of the earth at between 4 and 5 billion years. For the earth to only be 6000 years old each of these clocks would have to be fiddled individually to have their half-life adjusted to a radically different rate.
An example of an unstable isotope with a short half-life that still exists in abundance is carbon-14. Unlike the extinct isotopes carbon-14 is constantly being produced in our upper atmosphere when cosmic rays bombarding nitrogen atoms turning one of the protons into a neutron. About 1 carbon atom in a trillion is the 14 isotope. The rate of this process is more or less constant and comparing samples with results from dendrochronology, which is accurate to the very year, minor adjustments can be made.
Carbon-14 is absorbed by plant life, which is then eaten by herbivores and spreads through the food chain. At the moment a living thing dies it ceases to absorb new carbon-14 molecules and those it already contains begins to decay to Nitrogen-14 at a half-life rate of 5,730 years. With modern techniques such as mass spectrometry only a small sample is now required to measure the proportion of carbon-14 to nitrogen-14 in a sample and calculate the date of its demise.
Creationists are fond of telling stories about examples of inaccurate results that are obtained from samples of carbon 14. Firstly it should be noted that carbon 14 is never used to date fossils, its half-life is far too short to be used for that purpose. Secondly, the various factors that cause anomalous results are well understood by scientists. It is not creationists who discovered how to use carbon-14 dating effectively it was scientists who openly publish papers about the intricacies of the process - papers which are then quote-mined by creationists to cast doubt on dates that don't fit with their religious dogma.
Finally, going back to the layers of sedimentary rocks that are to be found all over the earth, each with their own distinct collections of fossils, creationists have their greatest opportunity to attack evolution. If the world could be explained by the action of a creator and the layers of rock by a world-wide flood then we ought to find fossils of all sorts of animals in each of the layers. If evolution is correct then there should be a very precisely ordered sequence of increasing complexity as we search through the layers from the oldest to modern times.
For a theory to be truly scientific it must be falsifiable and nowhere is evolution more vulnerable than her in the hard evidence of fossils. Just one good example of a mammal that died and got fossilised in an undisturbed Cambrian rock layer and the whole structure of evolution comes crashing down.
What we in fact find is that every fossil without exception is exactly where we would expect it to be. New creatures appear only after a given date, never before, no exceptions. Not a single mammal is found anywhere in the lower layers, everything is in exactly the order evolution predicts.
Now go and read the article I linked for you.
