Funny carbon dating
Carbon dating is the most famous form of “radiometric dating”.By measuring the trace amounts of radioactive carbon-14 (so named because it has 6 protons and 8 neutrons) in a dead something and comparing it to the amount of regular carbon-12 (6 protons and 6 neutrons) you can figure out how long it’s been since that sample was alive.So if you grind up a zircon and measure the tiny amounts of lead vs.uranium, you’re measuring how long it’s been since that zircon formed. Radiometric dating generally involves tallying up trace amounts of material, so it’s not the sort of thing you do out in the field; you need a clean lab.Carbon-14 is continuously generated in the upper atmosphere when stray neutrons bombard atmospheric nitrogen (which is what most of the atmosphere is).The reason carbon dating works is that the fresh carbon-14 gets mixed in with the rest of the carbon in the atmosphere and, since it’s chemically identical to regular carbon, gets worked into whatever is presently absorbing atmospheric carbon.
And second, that the elements they were before and after the radioactive decay have different chemical properties. If an atom doesn’t interact chemically in the right way, then it won’t be incorporated into a forming crystal.
There are many different kinds of radiometric dating that are used to date things that are non-organic (which is part of how we determine the age of the Earth).
They each rely on a couple of different (thoroughly verified) principles.
Since uranium-238 (the isotope comprising more than 99% of natural uranium) has a half-life of billions of years, it’s useful for figuring out the age of (among other things) zircons that crystallized billions of years ago. And, not for nothing, it’s also caused a thousandfold increase in lead contamination in the bodies (or bones at least) of everything that breathes and/or eats.
If you’ve ever wondered why gasoline should be “unleaded”: that’s why.
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This is the beauty of fundamental research: you never know what you’ll find when you start poking around.