A history of radiometric dating.

Get your science fix here: research, quackery, activism and all the rest
Post Reply
User avatar
Gfamily
Light of Blast
Posts: 4434
Joined: Mon Nov 11, 2019 1:00 pm
Location: NW England

A history of radiometric dating.

Post by Gfamily » Mon Nov 07, 2022 3:57 pm

Interesting read.
https://physicstoday.scitation.org/do/1 ... 20221104a/

I think I need to think about how precisely this method works
In the isotope dilution method used today, scientists take highly enriched 235U and dissolve it, calibrating the liquid so they know the precise concentration. They add that solution to a similar mixture of dissolved rock, homogenizing the two. By then measuring the ratio of the two uranium isotopes in the mixture, they can learn how many atoms of natural uranium—with its known ratio of 235 to 238—are in the sample.
My avatar was a scientific result that was later found to be 'mistaken' - I rarely claim to be 100% correct
ETA 5/8/20: I've been advised that the result was correct, it was the initial interpretation that needed to be withdrawn
Meta? I'd say so!

User avatar
Boustrophedon
After Pie
Posts: 2518
Joined: Mon Nov 11, 2019 3:58 pm
Location: Lincolnshire Wolds

Re: A history of radiometric dating.

Post by Boustrophedon » Tue Nov 08, 2022 10:43 am

A mass spectrometer will give you a peak, but that doesn't tell you how much of it was in the sample. Give the sample a known amount of U235 then you have a reference peak to compare the U238 in the sample with.
This place is not a place of honor,
no highly esteemed deed is commemorated here,
nothing valued is here.

User avatar
shpalman
Princess POW
Posts: 7396
Joined: Mon Nov 11, 2019 12:53 pm
Location: One step beyond
Contact:

Re: A history of radiometric dating.

Post by shpalman » Tue Nov 08, 2022 11:15 am

Nope, still not convinced. How does adding a known enriched ratio of U235/U238 to the sample help you figure out the U235/U238 ratio in the sample more easily or more precisely than just measuring the U235/U238 ratio in the sample directly?
having that swing is a necessary but not sufficient condition for it meaning a thing
@shpalman@mastodon.me.uk

User avatar
dyqik
Light of Blast
Posts: 6193
Joined: Wed Sep 25, 2019 4:19 pm
Location: Masshole
Contact:

Re: A history of radiometric dating.

Post by dyqik » Tue Nov 08, 2022 2:00 pm

shpalman wrote:
Tue Nov 08, 2022 11:15 am
Nope, still not convinced. How does adding a known enriched ratio of U235/U238 to the sample help you figure out the U235/U238 ratio in the sample more easily or more precisely than just measuring the U235/U238 ratio in the sample directly?
I think it's by giving a "gain" calibration (radioastronomy terminology) and determination of the background to the spectrum, so that you can calibrate the height/area under the peaks due to the sample vs that area due to the background.

User avatar
shpalman
Princess POW
Posts: 7396
Joined: Mon Nov 11, 2019 12:53 pm
Location: One step beyond
Contact:

Re: A history of radiometric dating.

Post by shpalman » Tue Nov 08, 2022 2:09 pm

Oh it's because you want the absolute number of U235 and U238 atoms in the sample, so if you add a known number of atoms of mainly U235 and a bit of U238, you can tell if there were a lot (your spike didn't make much difference) or not many (your spike made a big difference). And you can tell how much of a difference your spike made to the sample from your measurement which is actually telling you how big a difference the sample made to your spike.
having that swing is a necessary but not sufficient condition for it meaning a thing
@shpalman@mastodon.me.uk

KAJ
Fuzzable
Posts: 296
Joined: Thu Nov 14, 2019 5:05 pm
Location: UK

Re: A history of radiometric dating.

Post by KAJ » Tue Nov 08, 2022 2:44 pm


User avatar
shpalman
Princess POW
Posts: 7396
Joined: Mon Nov 11, 2019 12:53 pm
Location: One step beyond
Contact:

Re: A history of radiometric dating.

Post by shpalman » Tue Nov 08, 2022 3:48 pm

KAJ wrote:
Tue Nov 08, 2022 2:44 pm
See https://en.wikipedia.org/wiki/Isotope_dilution
I did.
having that swing is a necessary but not sufficient condition for it meaning a thing
@shpalman@mastodon.me.uk

User avatar
Bird on a Fire
Princess POW
Posts: 9992
Joined: Fri Oct 11, 2019 5:05 pm
Location: Portugal

Re: A history of radiometric dating.

Post by Bird on a Fire » Sat Nov 12, 2022 12:27 pm

IIRC that's also used for stable isotope analysis, at least for trace elements that go in the mass spec. A while since I did any, though, and the uni has a technician to do the fancy physics bits ;)
We have the right to a clean, healthy, sustainable environment.

KAJ
Fuzzable
Posts: 296
Joined: Thu Nov 14, 2019 5:05 pm
Location: UK

Re: A history of radiometric dating.

Post by KAJ » Sat Nov 12, 2022 4:21 pm

Bird on a Fire wrote:
Sat Nov 12, 2022 12:27 pm
IIRC that's also used for stable isotope analysis, at least for trace elements that go in the mass spec. A while since I did any, though, and the uni has a technician to do the fancy physics bits ;)
Yes, that's where I've seen it used. The Wiki article I cited above says
https://en.wikipedia.org/wiki/Isotope_dilution#Applications wrote:... In addition to the use of stable isotopes, radioactive isotopes can be employed in isotope dilution...

Post Reply