While the Chapter 4 was clearly a statement of L'Engle's theology, Chapter 5 showcases her understanding of science. She wrote 'A Wrinkle in Time' while studying Einstein's theory of relativity, which unites space and time in a single space-time continuum like a fabric. This notion appears in the book when, in demonstrating how the group will travel through space-time, Mrs. Whatsit assembles the fabric of her skirt.
The chapter also alludes to L'Engle's personal understanding of time, most clearly articulated in her autobiography 'A Circle of Quiet'. She describes two types of time: Chronos and Kairos. While Chronos is ordinary clock time, divided into hours, minutes, and seconds, Kairos is God's time, in which notions of past and present are inconsequential. When Meg expresses her fears that their mother will worry about her missing children, Mrs. Whatsit assures her that, due to certain properties of time, this will not happen. The children do not travel through linear time on their journey to rescue Mr. Murry. Their quest is circular, involving an escape from ordinary Chronos into the realm of Kairos and then returning to Chronos at a point prior to their departure. L'Engle's creative conception of time resembles the twin paradox and other notions that are a consequence of the theory of relativity. The author further develops the novel's ideas in the chapter and continues to present the reader with insights into Meg's character. Meg's desire to understand everything rationally comes to the fore again. When Mrs. Which lists the great warriors who fought against the Dark Thing, the children add to the list from their knowledge of great cultural and historical figures. Calvin and Charles name religious leaders, painters, poets, and musicians but Meg is able to list only mathematicians and scientists. Her invocation of Euclid and Copernicus reveals Meg's commitment to conquering the world through rational thinking. She has not yet fully accepted the idea of explanations that exceed our logical understanding. Meg is also reminded of the other lessons she has yet to learn. She must learn to be patient in spite of her desire to rescue her father immediately. Also, she must learn moderation and compromise. Indeed, this latter challenge, first verbalised in Mrs. Murry's advice that Meg seeks a "happy medium," and echoed by her twin brothers in Chapter 2, resounds in this chapter as a delightful play on words. Meg and her friends meet a jolly clairvoyant who is, in the most literal sense, a "happy medium." Though this is of course not what her mother had in mind, the medium is a playful realisation of Mrs. Murry's words and perhaps proves Mrs. Murry wiser than she knows. The meeting also serves to connect Meg back to thoughts of her mother and her mother's advice. Although Mrs. Murry cannot be with them, her words' abiding truth lingers with Meg comfortingly.