Radiometric Dating is Wholly and Demonstrably Accurate, and Definitively Precludes a Young Earth and a Global Flood While Simultaneously Corroborating Evolutionary Theory

​Quite a bit rests on the accuracy of Radiometric Dating in the world of Young Earth Creationism and Flood Geology. This practice taken at face value says blatantly that their ideas of the antiquity of the Earth and the diversification of life are supremely incorrect, full stop. Radiometric Dating confirms that the Earth is some 4.8 billion years old and that transitional forms are separated by vast swatches of time.​
So it shouldn't be surprising that these belief systems go to great lengths to reject radiometric dating as a field (except in the instances when it corroborates biblical history). I aim to cover the many aspects of their claims and faults with the process of dating rocks and fossils, as well as to explain why radiometric dating makes the argument of "Evolution vs Creation (six days)" and open and shut case.​
It is fairly well known in this sub that I am a Theistic Evolutionist. I say this because the primary source I am using for this post is "The Bible, Rocks and Time" a book written by religious geologists Davis Young and Ralph Stearley who accept the allegorical nature of Genesis and argue passionately for the ancient age of the Earth. I recommend it highly for anyone (secular or otherwise) with an interest in geology.​

• Radiometric Dating: An Overview

Radiometric dating is not subjective in any sense. It is simply a method of determining precise dates based on the Physics principle that as time passes atoms of a particular chemical element will spontaneously change into atoms of a different chemical element. This is a firm law in physics: The Radioactive Decay Law. It additionally covers the nature of decay constants and half-lifes and indicates that to our current knowledge: decay rates do not change in meaningful ways in nature on our planet.
Radiometric Dating can be done in a variety of ways and usually involves decay types: beta decay, alpha decay and electron capture.

• YEC attempts to Discredit Radiometric Decay Rates.

The RATE team (an Institute for Creation Research group) was deployed specifically to refute this. And what they found is that decay rates cannot be changed in meaningful ways (that is, significant enough to propose 6000 years) on our planet.
That RATE group has been discontinued since 2005, and in their book on their findings the group of YEC scientists “admit that a young-earth position cannot be reconciled with the scientific data without assuming that exotic solutions will be discovered in the future. No known thermodynamic process could account for the required rate of heat removal nor is there any known way to protect organisms from radiation damage.”
Carl Wieland of AiG (Answers in Genesis, a YEC site) had this to say as well: " When physicist Dr Russell Humphreys was still at Sandia National Laboratories (he now works full-time for ICR), he and Dr John Baumgardner (still with Los Alamos National Laboratory) were both convinced that they knew the direction in which to look for the definitive answer to the radiometric dating puzzle. [new paragraph] Others had tried—and for some, the search went on for a while in the early RATE days—to find the answer in geological processes. But Drs Humphreys and Baumgardner realized that there were too many independent lines of evidence (the variety of elements used in "standard" radioisotope dating, mature uranium radiohalos, fission track dating and more) that indicated that huge amounts of radioactive decay had actually taken place. It would be hard to imagine that geologic processes could explain all these. Rather, there was likely to be a single, unifying answer that concerned the nuclear decay processes themselves"
In all the history of radiometric dating, the maximum change in decay in a laboratory environment was 1.5% in 1999 by altering environmental conditions chemically. To date, no evidence for perturbation in the decay constant of any geologically important radioactive isotope has been found.
This has left a large problem for YEC's. Humphreys of the RATE team makes a tacit admission that the induced accelerated decay that has been experimentally performed (in elements not related to radiometric dating mind you) are "minuscule compared to the million-fold or greater acceleration of decay rates which is required by the evidence for a young Earth". He then suggests "we should not be surprised if we find evidence that God has supernaturally intervened".
So what we have here is the admission that without supernatural intervention the Earth's age appears to be ancient.

• The Heat Problem for Accelerated Decay

Let us for a moment grant Young Earth Creationism accelerated decay. What would happen if we were to compress 4.8 billion years of radioactive decay into 6000 years?
A Tufts University Geologist did the math
At the time of Adam and Eve according to YECs, the surface of the Earth would be 70,000 degrees C for every square kilometer. At the time of Jesus's birth, assuming a generous geothermal gradient we would be at 400 degrees C for every square kilometer.
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• Woodmorappe (YEC) and "Fallacies"

John Woodmorappe has given some input on Radiometric Dating as well (although he does openly admit he doesn't at present have an answer for the ancient Bristlecone Pines). He has three fallacies which he uses to "combat" Radiometric dating methods. Let's review his fallacies here.
A) CDMBN or "Credit Dating methods for frequent success, but Blame Nature for failures"
Woodmorappe seems to have this idea that geology is constant and without anomaly. He sees thousands upon thousands of correct and corroborated dates (through multiple methods) each year, but if a single date is strange and geologists remark that it may be a new phenomena it's suddenly fallacious. This is precisely what happens in Evolutionary Theory or Paleontology when a date changes. It's only okay in non-origin related science for change to occur.
B) ATM or "Appeal to Marginalization"
Woodmorappe essentially repeats the first "fallacy" and notes that blaming anomalous circumstances is a cop out of sorts. He points to Rb-Sr dating (despite that this method has been largely abandoned for methods with less room for error, for example, SHRIMP for isotope analysis). He completely disregards the very nature of geology: to understand anomalies. Not to mention once anomalies are understood and accounted for, the margin or error shrinks.
C) ATT or "Appeal to Technicalities"
Human error is not a factor in Woodmorappe's world.​
All three of these "fallacies" amount to one statement: "If incorrect dates are obtained, even rarely, the method must be thrown out entirely."​
On Discordant Dates
The crux of the argument from a YEC perspective appears to hinge on discordant dates. Four U-Pb methods can yield four dates, and may be unique from a K-Ar age obtained from the same rock. To them, this seems suspect at worst and faulty at best. And from a laymen perspective this is somewhat reasonable. But the simple truth is that these methods are not measuring the same event, and were not intended to do so. K-Ar in this case measures the cooling time of the particular crystalline sample, while the U-Pb or Sm-ND methods are measuring the "whole-rock" isocron. Thus these dates SHOULD be discordant.
At worst, discordant ages suggest that geology could be understood more thoroughly and perhaps aren't as precise as we might wish.
Occasionally (of the hundreds of thousands of tests) discordant dates have occurred that have not been understood. That is, we cannot readily attribute them to human error or known anomaly. This should grant YEC's little solace however, as almost invariably these dates are millions too billions of years old even in their discordancy.
There has, to my knowledge and research, never been a rock body which has yielded a date in the millions and a date under 6000 years. They are almost invariably ALL ancient.
Complaints notwithstanding, YEC's ignore the fact that concordant dates make up the vast majority of samples tested. Meteorites of iron and stone, individual or clustered and from all over the globe have been dated with Rb-Sr, Pb-Pb, Lu-Hf, Re-Os, Ar/Ar and EVERY kind of isochron and have ALL yielded dates of 4.4-4.6 billion years.
Or consider the terrestrial samples. Here are the dates given by various methods for the Isue Greenstone Belt in Western Greenland on varying rock types in a sing;e location:

U-Pb and Rb-Sr : 3.66-3.77 billion years
Sm-Nd: 3.74 billion years
Pb-Pb: 3.81 billion years
U-Pb and Pb-Pb: 3.70 billion years
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You should see this and get the idea that this rock formation as a whole was probably completely formed around 3.7 billion years ago!
Corroborated by other methods
The rock dates using varying elements corroborate one another, but in addition to this they are ALSO matched up against Ice cores, dendochronology and ancient coral reefs. Here, they match as well.
Or perhaps we can look at how the movement of plate tectonics match as well!
We can also look at:
The Oklo Reactor
The Galapagos Bottleneck
The Holocene Oak Chronology

Closing Thoughts and TL;DR
Radiometric Dating has withstood immense scrutiny due to it's implications and has come out on top each and every time. It has proven itself, via basics laws in Physics, to be an accurate means of determining the age of rock (and thus our world) and is a very succinct means to deny YEC as a hypothesis. 
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