If uranium-238 is formed in a star (supernova), how can it be used to date the age of the earth? Aren’t you dating the age of the supernova? What about earth’s formation creates a marker that can be dated with isotopes?

Question

So how do you get 4.5 billion years by dating isotopes that existed long before the formation of the earth?

​

Edit: I’m not creationist trolling. I believe the #, just trying to learn about the sicence.

In: 180

Answer 1

Certain crystals, when they are formed will concentrate certain materials from the environment. For example, when the gemstone zircon is formed, the crystal soaks up uranium from the earth and rock around it. At the same time, when zircon crystals form they expel any lead impurities.

This makes zircon crystals quite special – they contain a lot of uranium but absolutely no lead.

After the crystal forms, the uranium atoms decay and become lead. The lead becomes trapped in the crystal. You can analyse this type of crystal to measure how much lead and uranium are in it. Because when the crystal first formed it had no lead in it, any lead in the crystal must have come from the uranium. If you know how much lead and uranium are present, then you can calculate the time since the crystal first formed.