Celestial Dotmatrix
From ThorxWiki
The sun appears in many positions in the sky... http://en.wikipedia.org/wiki/Sun_path
a snapshot of them over a year, at the same time of day, reveals the analemma http://en.wikipedia.org/wiki/Analemma
but what if you snapshotted different points in the sunpath over the year? You could write a word. (and it should only take six months maximum! ;)
The effect would be that of a dot-matrix font.
So, what should such a celestial dotmatrix "printer" write as it's first message?
"hello, world", of course! http://en.wikipedia.org/wiki/Hello_world_program