Why did the Universe start off with Hydrogen, Helium, and not much else?

Where the first atoms in the Universe — the progenitors of all the normal matter that makes up everything we know — came from.

“I see a lot of new faces. But, you know the old saying, ‘out with the old, in with the nucleus.’” -The Simpsons

Looking around the Universe today, there’s no doubt that there’s plenty of hydrogen and helium around; after all, it’s the nuclear fusion of hydrogen into helium that powers the vast majority of stars illuminating the entire cosmos!

Image credit: ESA/Hubble, NASA and H. Ebeling.

But here on Earth, hydrogen and helium are only a small part of the world we inhabit. By mass, hydrogen and helium combined make up far less than 1% of the Earth, and even if we restrict ourselves to the Earth’s crust, it’s still just a tiny percentage compared to the other, heavier elements.

Image credit: Gordon B. Haxel, Sara Boore, and Susan Mayfield from USGS / Wikimedia user michbich.