OK, there's a thread I've been following on the Dates and Dating forum on accelerated decay of 40K (it's
her). Now, this is an idea I've not really come across before, and I'm interested in trying to understand what initially, to me, seems a fairly bizarre concept. And, I've been told quite clearly that to discuss things beyond the limited case of 40K would be "shifting the goalposts", though I can't see any way to logically discuss one isotope without simultaneously discussing all of them. So, here's a thread with nice wide (and I'm happy to have them moveable within reason) goalposts which might help me (and maybe even other people) get my head around this idea.
Let me start by outlining what I think the basic position is:
1) Rocks are observed to have isotopic compositions that include radioactive isotopes and known decay daughters of these.
2) Radio-isotope dating use these isotopic compositions to determine the ages of these rocks.
3) These ages consistently come out as very much older than YEC would predict.
4) It's suggested that at some point in the past the rate of decay of these radio-isotopes was very much faster than that currently observed, making young rocks look old if the current observed decay rate is used.
Now, the problems associated with this position seem to all relate to the physical effects of the accelerated decay. Some numbers were given in the other thread for 40K which showed that even if spread over approximately 2000y the accelerated decay of 40K in sea water would introduce an extra heat input to the oceans equivalent to approximately 20% of the solar energy input. There would be even more heat input to rocks which typically contain mor K than sea water. The accelerated decay of U and Th isotopes would increase this heat input even further.
Additionally, the accelerated decay process would significantly increase the radiation dose rate to humans and other life. The internal radiation dose to the human body is currently about 0.2mSv per year, with external doses due to geology ranging from about 0.2mSv to 0.6mSv per year. So, modern internal and geological dose rates are about 0.5mSv per year, or 1.4μSv per day. For the correct isotopic composition of rocks dated at 1 billion years to be formed in 2000y would require an acceleration of the decay by a factor of 500000. This would increase the dose rate to 0.7Sv per day which would result in certain disability after about 3d exposure, and death within a week.
These calculations assume the same acceleration for all radioisotopes. I don't see any logical reason why there would be significantly different levels of acceleration for different radioisotopes, which is why I don't think introducing different isotopes to the original thread would have been "moving the goalposts". Personally I've no objection to this post being added to the existing thread, as I don't think the goalposts are any different, if the Admins here feel that's more appropriate than starting a new thread.
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