What are theories of the origin of earth?

Answer 1

It was long thought that the earth and all the planets in our solar ssystem were formed as the sun itself was formed. However, young stars consist almost entirely of hydrogen, and this early theory would not account for the quantity of heavy elements in the earth's crust and atmosphere. In fact, an average star like the sun does not produce very heavy elements at all.

Cosmology explains how the earth was formed. At some stage, a supernova star exploded in the neighbourhood of our sun - within a few million light years from here. Supernovas are formed as giant stars die and are not entirely uncommon. And giant stars, because of their far greater mass, are able to convert their hydrogen into heavy elements before finally dying. Conversion of hydrogen into heavy elements is also well known to nuclear physicists. So, our supernova exploded and sent an enormous amount of heavy elements out into empty space. A very small part of this was captured in orbit around our sun, where it eventually concentrated into the various planets and other bodies that orbit the sun. One of these was, of course, the earth.