But really, how do scientists figure out how old their dinosaur bones are?
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One of the biggest jobs of a geologist is establishing the absolute age, in years, of a rock or fossil.
Unlike relative dating, which only tells us the age of rock A compared to rock B, numerical dating tells us the age of rock A in x number of years.
In 1905, Ernest Rutherford figured out that we could use radiation to establish the ages of rocks.
By studying how the mass of uranium changed with radioactive decay, Rutherford was able to determine the age of a rock containing a uranium mineral. It meant that scientists could suddenly establish the actual ages of all their rocks and fossils!
That means they don't really know how old their rocks actually are.