A few years ago, science and tech media began reporting on the phenomenon of “spacetime foam,” alternatively called “quantum foam.” Though it has only recently received media attention, it is not necessarily a new theory; in fact, it’s been around since the theory of relativity has been clashing and intersecting with quantum theory: decades. The issue until recently, however, was that scientists could not figure out what space was filled with. Energy and mass that we predicted would be in certain places was found not to be there—it was “effectively hidden.” To explain this phenomenon, physicists and astronomers have hypothesized that this “emptiness” isn’t smooth, but actually full of “messy” stuff: that “spacetime might not be the trampoline-like plane scientists once envisioned. Rather, it might be a foamy mess of bubbles, each containing mini-universes living and dying inside our own.”

Conceptually, quantum foam feels difficult to grasp, but read articles about it and I promise you’ll almost understand it. There’s also a great book about it as well: Geons, Black Holes, and Quantum Foam.

One scientific press release describes spacetime foam in this way: “At the smallest scales of distance and duration that we can measure, space-time – that is, the three dimensions of space plus time – appears to be smooth and structureless. However, certain aspects of quantum mechanics, the highly successful theory scientists have developed to explain the physics of atoms and subatomic particles, predict that space-time would not be smooth. Rather, it would have a foamy, jittery nature and would consist of many small, ever-changing, regions for which space and time are no longer definite, but fluctuate.”

Fictional accounts of microverses—universes within universes—have existed since long before the development of quantum foam theory. A strong theme within such stories has been radical empathy, a call to recognize the beings who inhabit the smaller universe. Notably, microverses aren’t any more far-fetched than the existence of multiple universes. Researchers speculate that these universes could interact at the quantum level, and one researcher even says interaction at higher than quantum levels “is no longer pure fantasy.”

Dr. Seuss’s Horton Hears a Who is a familiar example of an encounter between the “big” everyday world and a tiny world. Although Whoville is in this iteration a “world,” or more likely a planet, it is symbolically close enough to the theme for us to assume it’s a kind of “closed system” universe (plus, if this Whoville is the same as the Whoville of How the Grinch Stole Christmas, it would appear that Whoville is part of a larger world-system). The story’s moral, that we should extend ethical recognition to beings “no matter how small,” is similar to other literary references to tiny universes. The story uses sound as a method of contact between the two worlds, with a small child in Whoville providing the decisive extra decibels to attract the attention of the skeptics in the bigger world.

Arthur C. Clarke’s The Wall of Darkness jumped emphatically into quantum foam many years before others did, and in fact did so before the public really had the opportunity to contemplate the theory at all. The Wall of Darkness is considered part of the genre of “Mathematical [Science] Fiction” and takes place in a universe consisting of one star and one planet. The planet intersects with an impenetrable wall, inspiring two men to attempt to scale the wall to see what is beyond it. Like the Seuss story, the Clarke work is fundamentally about barriers. Unlike the Seuss story, The Wall of Darkness articulates the quantum reality of multiple universes and suggests a somewhat absurd method of contact.

The idea of tiny universes is provocative for many reasons—universes smaller than ours suggest the existence of universes larger than ours, and even the possibility that we are ourselves a tiny universe inside a bigger one. (We might even ask how this could not be true if quantum foam is an actual thing?). Even more provocative, as suggested by Horton Hears a Who and The Wall of Darkness, is the potential of communication or contact past our own universe and with the wholly other.