Earth & The Solar System
All of Earth's atoms have been here for 4.5 billion years since its formation.
Earth is 32% iron, 30% oxygen, 15% silicon. Earth’s crust is 47% Oxygen, 27% Silicon, 5% Iron, along with many others in small proportions.
Our galaxy has a galactic structure of a flat, circular disk with a bulge in the middle. The universe contained mostly hydrogen and helium with a small percentage of other gasses. The other gasses.
In two billion years, the sun will be about 15% brighter than it is now
Accretion is when planets build in size as they collide with hunks of matter that sticks.