The Earth was never flat. It started off as a tiny sphere of gas and dust and over time gobbled up more gas and dust until it became the size it is now.
Planetary formation is one of the key studies in astrophysics at the moment, because we still aren’t entirely sure how planets form all the way.
Great question,
Ryan
It’s always been round! A planet would really struggle to support itself under its own weight if it was flat, and would start to curl down at the edges, until it became round anyway.
But when the solar system was first forming, it came from what was probably a pretty flat-ish disk of dust and gas, called a proto-planetary disk. That material clumped together to form the sun and the planets – growing like snowballs as Maggie said. Observations have been made lately of another solar system which is just beginning to form from a disk of dust and gas – have a look at the image on this webpage: https://apod.nasa.gov/apod/ap141110.html
The planets are gathering up material, making gaps in the disk.
Comments
Abu.D15 commented on :
thank you
Ry commented on :
Not a problem 🙂 keep asking great questions!