You can't hold to an old earth theory without also holding to basic flaws in your argument if you are to believe in creation at the same time.
1. The universe, the earth, and all that is created therein has an appearance of age, so that it is impossible to date beyond the date of creation.
2. All methods of dating were vastly distorted by the Flood if you are to believe the Biblical account of the Flood.
3. Dating methods such as Carbon 14 have never proven accurate beyond more than 2,000 years and yet it is the most common used method of dating not the ones that you have mentioned.
4. All dating methods have inherent flaws in them which even the Bible points out in the law of uniformitarianism.
5. Most people who believe in an earth that is millions of years old also try to justify it by saying that the days of creation are allegorical meaning that one day is as a thousand years or even more. The argument is irrational, as plants and insects, as well as other creatures cannot live through a thousand years of darkness. If a thousand years of light, then a thousand years of darkness. "And the morning and the evening were the___day.
6. If its the gap theory one believes in, then the problem of death raises its ugly head. Death and sin came via Adam's sin, and not before. The Bible is clear on that. The Gap Theory puts death before Adam. That is unbiblical.
All of these have to be taken into account if one is to say that they are to believe in Creation and an old earth at the same time.
I majored in Geology and I will say that radioactive decay is not an unreliable source or methodology of dating certain types of materials that cover the gamut from igneous rocks to carbonaceous fossils.
I will also say that there are no Cretaceous or Jurrasic period creatures of the reptilian or any species that have their original remains intact. Their bones, have been replaced with precipitated minerals from the soils that buried them.
When a T-Rex bone is chipped out of strata, you are not holding in your possession, a piece of calcium-rich bone with old marrow within. It is but an image of what was the shape of the original bone, that has been replaced with all kinds of precipitated minerals that solidified.
As for stalagtites and mites............There are those that form over relatively short periods, and those that take eons to form. It all goes back to the degree of chemicals/minerals and their level of concentrate in solution.
We have icicles overnight, but the ones that normally are found in limestone caves are not overnight wonders. The very solutions that drip off of and onto these tites and mites are measured to determine the rate of build-up and can be accurately determines at to their age or time of formation up to present.
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U235 is a rare Isotope of Uranium. It is found in igneous rocks both of those extruded in the open air and magma that cools deep beneath the earth and is not revealed until later via erosion.
The moment magma or rock is melted, and starts to cool, the internal clock of isotopic decay starts.
Isotopic U235 starts randomly breaking down to PB106 or what would be called Lead 206.
Lead 206 is also an unusual isotope of lead that is not formed in nature as a 206. Why? Because it only comes from the decay of U235. Now scientists many, many years ago measured accurately the decay rate of U235 to Lead/PB106. All the U235 that is found in an igneous rock and is formed at the birth of that magma starts to tick down or decay to 106PB. So here's the half life of U235 = 4.5 billion years! This means that if you find a piece of Granite(Interior cooled magma/lava) or extruded magma(surface erupted magma/lava), you can take a sampe of that rock and isolate both the U235 content and the PB106 content and determine it's age as you have isolated type of ticking atomic clock via decay isotopes within.
So if lab testing of a piece of granite indicated that the ratio between U235 and PB106 isotopes count is 10:1, then you have determined that 1/10 of the U235 has decayed to Pb106. So if the 1/2 life of U235 is 4.5 billion years; I.E. you would have 50% U235 and 50% Pb106 in that piece of Granite and it would be determined to be roughly 4.5 billion years old.
Well, there hasn't been any 50/50 U235-Pb106 ratios found in igeous rocks on earth.
But lets look back at the 10:1 ratio of Uranium to Lead that I used as an example of Granite that is tested. Now we see through testing that 1/10 of the U235 decayed to Pb106. So here's the simple math. So how many 1/10's are in 1/2........=yes 5/10's........So 5/10's Pb106 would mean we have a 4.5 billion year old piece of igneous rock.
Our sample that is 1/10 Pb106 would be 1/5 of 4.5 billion years.......= 900 million years.
Atomic clocks: They are the most accurate time pieces in the world. They operate on the basis of isotopic decay.
When you are measuring on the atomic level you are dealing decay of elements to other states with mine boggling radomness that evens the scales of accurate measurment.
Even Carbon 14 measurements work on the same principle. When something organic is created it also has an internal clock of isotopic decay that happens with such precision of mind boggling proportions. Carbon 12 and Carbon 14 are both isotopes.......12 being the most common. Never the less there is a decay of 14 that has a determined half life just like U235 to Pb106.
So Carbon dating is good to about 60,000 years.
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Those here that question or say that isotopic decay is not reliable must present evidences where this atomic phenomena that God has laid out in His orderly universe does not work.
Yes, God can intervene in time.......Just as He gave Joshua additional time in battle keeping the sun from going down.
Other than those miraculous interventions, Chemistry, Physics, and science in general keeps reveally the orderliness of God's creation. Quantum Mechanics and Calculus work hand in hand, where scientists can mathematically predict compounds because of the undertanding of the various know elements atomic structures and how they interact with one another.
Even our earth's life sustaining position in the universe is a 1 in bezillion odds chance that it could have occured by chance. The distance that the earth is from the sun, from other planets, the Moons distance and orbit, the size of the sun, the distance from other starts, galaxies, it's magnetic field, it's speed of rotation, it's mass, had to all be so precise that the odds of all of these elements to make a perfect environment for life on this terrestrial ball is beyoned measure in odds of it happening.
Yet, science is finding out more and more about how there is order in Creation, not crazy randomness. Our God is a predictable, as revealed in scripture. We cannot read His mind, but we "know" that He is god, Holy, reliable, loving, forgiving, merciful, and all-life sustaining towards His creation.