Please explain and analyze "Go and Catch a Falling Star," a poem by John Donne.
The rhyme scheme of the poem sticks to: ababccddd. The meter and rhythm of the poem is closest to tetrameter, using mostly iambs (a metrical foot that is an unstressed syllable followed by a stressed syllable) but the poem is not limited to this and uses other metrical feet as well. Following the first stressed syllables ("Go" and "Get"), note the iambs. The stressed syllables are in bold:
Go and catch a falling star,
Get with child a mandrake root,
In the first stanza of this dramatic monologue or love poem, the speaker addresses an unknown listener. He challenges the listener (auditor) to do impossible things: catch a falling star or teach him to hear mermaids singing. The speaker changes the meter to signify the change from the challenge to find these impossible things to a challenge to find something seemingly more possible: an "honest mind." His wish is to find an honest mind to avoid envious thoughts.
In the second stanza, it becomes clear that the speaker has felt envy because he has been rejected by a woman, or because he has a cynical attitude about women in general. He tells his listener that no matter what you've seen and where you've travelled, you have never seen a woman who is beautiful (fair) and loyal (true).
In the last stanza, the speaker asks his listener to inform him if he ever finds such a woman. But the speaker retreats to his cynical outlook that even if his listener is ever to meet a loyal and beautiful woman, by the time his listener sends him word of this discovery, the woman will have betrayed to at least two or three men. (Using the modern spelling):
Though she were true when you met her,
And last, till you write your letter,
False, ere I come, to two, or three.
Notice that in each stanza, the speaker sets up his propositions in consistent (relatively) tetrameter. The propositions in the first stanza are the impossible challenges, the strange things his listener might see in a lifetime of journeys (2nd stanza), and the possibility of finding a true and fair woman (3rd stanza). When Donne uses those shorter lines toward the end of each stanza, he states his cynical conclusions. By shortening the lines, he emphasizes this defeatist or cynical conclusion that things such as an honest mind and a true and fair woman are impossible: "Yet she / Will be / False . . . "
A small addition: some are confused by the line, "and find/what wind/serves to advance an honest mind." At the time the poem was written, the cutting-edge technology toys were accurate clocks—or if you were VERY rich, a pocket watch—the mechanisms of which were "advanced" or driven by winding up a spring within the case. Donne is saying something akin to, "discover what makes an honest mind tick!"