Dating billion year old rocks
The best-known radiometric dating system is provided by 14C, or carbon 14, a rare isotope of carbon produced naturally by cosmic rays and anthropogenically by nuclear bombs.
It decays to nitrogen (14N) with a half-life of 5,730 years.
If these assumptions that underlie radiometric dating are not true, then the entire theory falls flat, like a chair without its four legs.
The second fatal flaw clearly reveals that at least one of those assumptions must actually be wrong because radiometric dating . Helens, we watched rocks being formed in the 1980s, but when sent to a laboratory 10 years later for dating, the 10-year-old rocks returned ages of hundreds of thousands to millions of years.
By using all of these methods to cross check each other, we can date rocks.Similarly, some rocks return radiometric “ages” twice as old as the accepted age for earth.Most rocks return conflicting radiometric “ages.” In these cases, researchers select results that match what they already believe about earth’s age (see the section Brand New Rocks Give Old “Ages” for details of this study and several others like it).The uranium provides two reliable chronometers: 238U decays to lead 206 (206Pb) with a half-life of about 4.5 billion years (the age of the Earth), while the rarer isotope 235U breaks down to 207Pb with a half-life a bit longer than 700 million years.By counting how many atoms have decayed we know how old the rock is.