Hi. I have this question that I have problems answering.

H og He make up 98 % of all matter in the Universe. Why dont the Earth and the moon primarly consist of these elements?

Question

Hi. I have this question that I have problems answering. 

H og He make up 98 % of all matter in the Universe. Why dont the Earth and the moon primarly consist of these elements?

sapphiremoon · Answer

The universe is huge. All of that hydrogen and helium mainly exist in stars (of which there are many many more than planets) and interstellar gas. Earth and the moon are made of the things that have the proper state of matter and bonding ability to make them (hydrogen and helium are gases to extremely low temperatures). The 2% of the universe that is carbon-based just so happens to have to be the one in which we live (because being made of hydrogen would be difficult, lol).