: How exactly do you differentiate between
: "appears" and "is visible to the naked
: eye"? Presumably, to someone with a very powerful
: telescope (which may or may not exist on Mythworld),
: the comet would "appear" long before it was
: "visible to the naked eye".
The comet appears in the sky. The sky is everything within sight of the person looking above. If it doesn't matter if the comet is visible, then it would always be present, so to speak, and it only becoming visible once every millinia is obsolete.