Respuesta :
Answer:
The radioactive isotopes within these brains typically record the ages of the grains-not the time when the sedimentary rock was formed, making it difficult to date using radiometric dating. The half-life of U-235 is 704 million years.
Explanation:
hope this helps but if i'm wrong then i'm sorry..
Answer:
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Explanation:
Very old rocks would be been formed before said isotopes with short half-lives. We're thinking of a very long geological time. The original rock might be rock C, then years and years later rock Y would be measured. Y can't match C since there's too much unknowns in between.