Sandra Cisneros's poem "Once Again I Prove the Theory of Relativity" is from her third book of poetry, Loose Woman (1994). The poem is a celebration of romantic love. The female speaker imagines how excited and delighted she would be if her lover were to return. She lets her mind and heart contemplate all the things she would do for him and how well she would treat him and relates how beautiful he is. She says she would dote on him and make sure she fully got to know him before he departed again, as she knows he would.

Cisneros is noted not only for her poems but also for her novels and short stories. She typically portrays strong, independent women of Mexican American heritage, who refuse to conform to traditional male expectations of how women should behave and what their place in society should be. "Once Again I Prove the Theory of Relativity" is not exactly a typical Cisneros piece, since it does not emphasize the Chicano or feminist aspect of her work. Instead, it is a heartfelt expression of the ideal of romantic love. It reveals the heightened perceptions and intensity of sensual and emotional responses that such love calls forth. It also expresses the realization that in such intense experiences of love, whether they last or not, lie the seeds of creativity and art.