At the end of the year magazines are full of memorials to those we have lost during that year. This year marked the passing at age 88 of author Madeleine L'Engle, who, among other things, provided a wonderfully accessible introduction to the fourth dimension in her children's book A Wrinkle in Time. The clip above is of a tesseract, a fourth dimensional "cube." To see a better image (and one that also that rotates continuosly) click here. I'll put up a post in the future with a bit more explanation of the tesseract. For now, enjoy the image in memory of Madeleine L'Engle and her wonderful stories.