One of the article's central ideas is that scientists have determined the
Earth is 4.5 billion years old.
How does the author introduce this
central idea?

This may not be completely right but I would say that

the author intoduced this central idea by first stating about scientists then by mentioning the main idea about earth.

I hope this helps! Have a amazing day everyone! :D

it being an ocean esketit where we droppin

answertemperature;