Dating fossils entails making many assumptions, including the idea that the processes operating today have not changed in billions of years of history. This is also known as uniformitarianism. If a global catastrophe such as the Flood of Noah’s day did actually occur, then dating methods that attempt to date things older than that will inevitably come up with wrong dates.

The dates provided by different techniques give different dates, sometimes varying by millions of years. The date that fits most closely with the scientist’s presumptions is the one that is chosen when this occurs. One might argue that since all of the dating methods give ages of millions of years it must be so, but I would argue that with an error rate of +/- millions of years they can’t be trusted at all.

All dating methods also assume that the original quantity is known. If you go into a room and see a guy peeling potatoes, and as he peels them he puts them in a basket, you could watch him and see how long it takes him to peel a potato. Then you could look in the basket and see how many potatoes are in there, and you could determine how long he’s been peeling potatoes, right? Wrong. What if when he started peeling the potatoes there were already several in the basket? You’d have no way of accurately calculating how long he’s been peeling potatoes just by looking at the number of potatoes in the basket. The same goes for these radioisotopic dating methods. Scientists assume they know how much of an isotope was present at the beginning, something that can never be proven.

Check out ICR’s RATE project for a scholarly opinion:
http://www.icr.org/rate/