Final answer:
In Sidney's "Sonnet 31," the speaker addresses the moon in the opening line, seeking understanding for his unrequited love.
Step-by-step explanation:
The opening line of Sidney's "Sonnet 31" is addressed to the moon. In this sonnet, Sidney's speaker is Astrophel and he addresses the moon as an entity that he feels can understand his unrequited love for Stella. The poem is part of the "Astrophel and Stella" sonnet sequence, which is known for exploring themes of love and desire. Sidney's use of the moon as a confidant for the lovesick speaker reflects a common poetic device of the time. This use of apostrophe is a common poetic device in which the speaker addresses an absent or inanimate object as if it could hear and respond.