When did the earth started?

Answer 1

Modern scientific thought says the Earth is about 4.5 billion years old.

Many religions have much shorter estimates. The Abrahamic religions (Judaism, Christianity, and Islam), for instance, put it at around 6000 years ago. The more rational explain the discrepancy in one of several ways (for example, that "the Earth was without form, and void" should be read "the Earth became without form, and void," pushing nearly all of that 4.5 billion years into the first sentence of Genesis); the less rational just ignore it and assume scientists don't know anything.

Among other things that scientists "don't know anything" about, there's atomic decay (which is the primary evidence that the Earth is 4.5 billion years old). This has the side effect of making the fact that atomic bombs work as predicted anyway at least as big a miracle as anything attested by humans in The Bible/Torah/Quran.

Answer 2

It is unknown but geologists predict around 150 million years ago