I keep hearing 4.6 to 4.7 billion years old for the age of the planet. Usually proved by dating meteorites. However, you never hear of anything older than this. Even though it [appears](https://world-nuclear.org/information-library/nuclear-fuel-cycle/uranium-resources/the-cosmic-origins-of-uranium.aspx) that the uranium that we use to date the planet was formed 6.5 billion years ago from the previous generation of stars.
The dust cloud that contained all the material that makes up both the planet and asteroids was here long before that.
So, my question is this, How did we settle on 4.6 – 4.7 billion years old for the age of the planet when all the materials were here long and coalescing before that? Did we just not cosider it a planet before the formation of the sun?
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Edited for corrections and clarity (hopefully). I can’t remove solar system from the subject line.
In: 3
Long 5 year old answer:
Because the Universe is older!! Nearly 10 billion years older at that, and that’s where the dust cloud originated from.
Before the solar system is created, the supposed-to-be star pulls in material from that Dust, and clumps and lumps it together to form the planets and asteroids. This forms this thing called isotopes, which would take a while to explain but just know that we can tell their half-life, or how long it would take for half of it to radioactively decay.
Knowing how long it takes for half of it to decay, we just look at how much radioactive material HAS decayed and how much is left, determining the formation of that particular isotope, as well as the planet/thing it’s on.
I tried to not use big words
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