That still requires a pretty impressive feel for the relative size of oranges and planets though. I would have preferred something like this table:

  2 nm Diameter of a DNA Alpha helix

  4 nm Globular Protein

  6 nm microfilaments

  7 nm thickness cell membranes

 20 nm Ribosome

 25 nm Microtubule

 30 nm Small virus (Picornaviruses)

 30 nm Rhinoviruses

 50 nm Nuclear pore

 100 nm HIV

So 13 nm is on the scale of a very small virus... :)