Today on Twitter, I encountered this GIF:
Source: <a class="youtube-link" href="https://www.youtube.com/watch?v=QgNDao7m41M">https://www.youtube.com/watch?v=QgNDao7m41M</a> (4:09)Highly recommend you check that video out.
It shows how much mass is in the super-large black holes that anchor galaxies within space. By extension, too, it shows how many things 20 billion is.
It is, in my opinion, a very good GIF.
Now, black holes aren’t only a reflection of mass, but also of density. Lots of matter in a very compressed space makes a black hole. So as the source video for the above animation makes clear, the Earth could become a black hole— it would just have to be compressed smaller than its Schwarzschild radius, or, specifically, to about the size of a peanut.