Pancake or Oatmeal Universe What's for Breakfast?
Image credit: Public Domain
Over its lifetime, the universe started out fairly smooth, but has grown lumpy.
Data from the COBE satellite show what's been called a smooth, early universe – with measured variations in the cosmic microwave background (CMB) radiation of only 1 part in 100,000! At that very early time, the universe was like the surface of a pancake. If you glance at a pancake it looks smooth, but differences in texture can be seen if you look more closely.
The universe today is more like a bowl of oatmeal, with real "lumps" and clumps of matter and energy. Objects like planets, stars, galaxies and galaxy clusters are the "lumps" which are easily detectable. Even with these lumps, the overall universe is much smoother than was predicted by the original Big Bang. This problem has been solved by inflation.
While the early universe was extremely smooth compared to today, those tiny lumps in it were vital. Through the action of gravity, they led to the much bigger lumps we see today, the ones that make our very existence possible.