Most people don't realise that the Earth's 4 billion age estimate comes from uranium decay and that of similar elements. It is flawed! Here is
why:
The dating comes from the tracking of lead isotopes from the decompostion of uranium 238. 238 decomposes to lead 206, which is really different than
common lead 204. The half life of 238 is 4.5 billion years, so it is safe to say, in 4.5 billion years 238 will turn into half lead 206. This is the
relation that rocks are dated. The amount of 238 and 206 in the sample is compared. The big problem is that 206 can be formed from other processes!
While 238 is decaying, it releases neutrons which bombard surrounding particles, including common lead 204. 204 will absorb these neutrons which
will convert it to 206.
238 isn't a metal but it is a water soluble uranium oxide which can be carried by water to one place to the other, which enriches or depletes said
places, throwing off the dating accuracy again.
Remember there are no independant means outside the pardigm of radioactivity of verifying the age of rocks. Rock samples when dated, present a range
of dates like the bell curve. Some are too old or too young and are chosen subjectively often because they "feel right" in context. Consider the
Mcdougall study in 1976, where the "scatter" of dates conducted by various research groups ranging from 0.52 million to 17.5 million years ago for a
sample of KBS Tuff material used to date the age of Lake Turkana Man fossils. The dates for the KBS were taken all over the place. The date of 2.6
million years arrived for the KBS Tuff sample was eventually chosen, to end the debate because it was apparently "reasonable" to the scientists
involved.
"Reasonable"....piss poor if you ask me.
These crappy assumptions can't and mustn't be applied to a system that that is not understood within the unrestricted world of physics in Nature.
The real fact is the Earth could of been here trillions,billions,millions, or a few 1000 years......the honest truth is nobody really knows but God
himself.
[Edited on 5-15-2004 by Cearbhall]
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I never believed in those kind of dating methods
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Here we go again... 
Cearbhall, no-one has said that U-Pb dating (or any kind of geochemical dating) is one hundred percent accurate. It is based, as all scientific
theories are, on assumptions and inferences, some of which - *gasp* - may be incorrect.
But we act to minimise the chances of a flawed result. Samples used for U-Pb dating are selected carefully, ensuring that no sign of erosion (and
therefore no possible contaminant) are present. Samples are taken from a geographical and chronological range, examined, dated and compared, and then
a picture is formed of "contextualised" samples.
Even at this stage, U-Pb dating isn't relied on by itself, but is checked and compared with other dating methods, geological evidence, and every
other investigative technique we can think of. Only then do scientists put forward an unconfirmed date for the area they are studying.
It's not guesswork. It's not faith. It's based on evidence of one's eyes, and the product of one's intellect. It's called "reasoning based
on evidence".
You should try it.
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