1
Postgres geography type is not limited to Earth
It's a little known fact that the PostGIS geography type since PostGIS 2.2 (well was introduced in 2.1 I think but had a bug in it until 2.1.4 or so), supports any spheroidal spatial reference system that measures in degrees. When an srid is not specified, it defaults to using 4326, Earth WGS 84 long lat.