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Author Topic:   Geologists and dating (India Basins Half a Billion Years Older Than Thought)
ChrisS
Junior Member (Idle past 5711 days)
Posts: 5
From: Melbourne, Victoria, Australia
Joined: 08-17-2006


Message 91 of 93 (487015)
10-26-2008 7:35 PM
Reply to: Message 82 by peaceharris
08-15-2008 1:29 PM


Re: data
Sorry! the second half of my post was missing
The amounts of the other isotopes are then easily calculated from their reported ratios wrt 206Pb
207Pb = 112.9 and
208Pb = 34.2
204Pb is negligible
You then use the amounts of 206Pb and 207Pb to calculate the amount of 238U and 235U from the reported 206Pb/238U and 207Pb/235U ratios and obtain a value of 111.76 for 238U and 0.81 for 235U. Mistake no. 2. This is also wrong!
The Pb and the Pb/U isotopic ratios are reported in atomic ratios whereas (although this is not stated in the table). The actual quantities of Pb and U are reported in weight ratios. To convert from one to another the atomic weights of each isotope must be taken into account. Thus the ratio of 206Pb/238U in atomic units must be multiplied by the ratio of their atomic weights ie (206/238)=0.866 to obtain the weight ratio.
Similarly for 207Pb and 238U. The conversion factor is (207/235) = 0.884.
Using the values from Wilde, row 1, Table 1.
206Pb/238U = 0.928 in atomic units
206Pb/238U = 0.928 * 0.866 = 0.803 in weight units, and the value for 207Pb/235U becomes 69.5 * 0.884 = 61.44
So 238U = 206Pb/0.928 = 207.86/0.928 = 258.85 and
235U = 207Pb/61.44 = 1.84
As there are only three naturally occuring isotopes of Uranium the amount of 234U can be calculated from the simple difference between UTotal less the sum (238U + 235U) i.e.258 - (258.85 + 1.84) = -2.69. The slight error is due to the errors in the absolute concentrations of U and Pb caused by uncertainties in the sample weight - something that I imagine is common to all SHRIMP analyses of zircons - and large uncertainties in the concentration of U and Pb, which can, apparently, be up to as much as 20%! As these values are not used in the calculations of age in the concordia method these errors have no bearing on the result and presumably is the reason why no errors are listed in the Table. The Pb/Pb and Pb/U ratios used for age calculation are, however, extremely accurate as Wilde's Table 1 shows.
So your more accurate method is based on a simple algebraic mistake and a missing conversion factor. This hardly inspires confidence in the accuracy of your other model.
Best wishes
Chris

This message is a reply to:
 Message 82 by peaceharris, posted 08-15-2008 1:29 PM peaceharris has not replied

  
peaceharris
Member (Idle past 5675 days)
Posts: 128
Joined: 03-28-2005


Message 92 of 93 (487145)
10-28-2008 1:30 AM
Reply to: Message 90 by ChrisS
10-26-2008 7:26 PM


Re: data
ChrisS writes:
You state that the amount of 206Pb is equal to:-
PbTotal*(1 - 204Pb/206Pb - 207Pb/206Pb - 208Pb/206Pb). Mistake no. 1 - this is wrong!
Thanks for pointing out that mistake. I have removed that paper from the web.

This message is a reply to:
 Message 90 by ChrisS, posted 10-26-2008 7:26 PM ChrisS has not replied

Replies to this message:
 Message 93 by Percy, posted 10-28-2008 9:46 AM peaceharris has not replied

  
Percy
Member
Posts: 22607
From: New Hampshire
Joined: 12-23-2000
Member Rating: 4.8


Message 93 of 93 (487160)
10-28-2008 9:46 AM
Reply to: Message 92 by peaceharris
10-28-2008 1:30 AM


Re: data
peaceharris writes:
Thanks for pointing out that mistake. I have removed that paper from the web.
Whoa, you don't get off that easy.
It's to your credit to acknowledge a mistake, but look what it took to get there. You were evidently willing to believe that generations of radiometric dating scientists had their collective heads up their asses while your amateur scientist efforts were bringing us new insights. You have no record of producing any scientifically valid work, yet in this case you believed you'd shown up an entire field of science. Even when the general flow of your thinking was shown to be flawed you would not relent. It took someone with the time and knowledge to actually examine your calculations and give you chapter and verse about your mistakes before you would relent.
From your kind of thinking springs the most egregious misconceptions about the nuts and bolts of how scientists practice science. It's a cold, cutthroat business. When one scientist produces a paper describing some new findings, other scientists do not just jump on board and congratulate him, and they don't do that because it is a cold, cutthroat business. If that scientist has actually discovered something new and interesting, then things like reputation and grant money and tenure will tend to flow in his direction, and that's reputation and grant money and tenure that won't flow in the direction of other scientists.
So even if scientists did not have a love of science and for getting things right, even just their own self-interest (and vanity) demands that they work hard to make sure that other scientists only get credit for legitimately new and interesting discoveries. That's one reason why legitimate scientific journals have a peer review process, and that peer review process continues after the publication of the paper as other scientists review and test the results to see if they hold up.
I know we'll never see the end of creationists who somehow convince themselves they've found basic scientific errors, but your experience in this thread is extremely instructive, and we should remember and cite this thread in the future when similar situations arise.
Chris, many thanks for going to all the time and trouble.
And Peacharris, again, kudos to you for acknowledging the errors. I encourage you to continue your efforts to find scientific errors, because seeking to correct error is always a good thing. But in the future you might want to pass your work by Chris before going public. When I've submitted papers to peer-reviewed publications I've always had a few colleagues go over them first, maybe Chris could play this role for you.
--Percy
Edited by Percy, : Grammar.

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