This accessible problem will hopefully lead students into the whole
area of solar and astronomical scales. The internet is full of
sites offering information. Google anything and you'll start a
trail of enquiry.
The methods often take some thinking about and nearly all of them
require the imagination of different viewpoints. Grasping the
methods and especially the required adjustment of perspective will
not be immediate for most students and serves as a useful reminder
that mathematical understanding isn't an "instant" or
"not-at-all" experience.