But did I just turn around too soon?

[sovay]

If there is a single word for the object which casts a shadow, I do not know it, but it should exist.

Comments

[ap-aelfwine.livejournal.com]

Gnomon?

I like this.

[pecunium.livejournal.com]

I was beaten to the answer. The Gnomon is the object which casts the shadow in a sundial/solar clock.