Explain SMBC — the wiki for Saturday Morning Breakfast Cereal

The Joke

A wizard (resembling a children's TV show host) enthusiastically tells a group of kids that they're going to shrink down to the size of a virus to investigate the human body. The kids cheer excitedly. In the next panel, the wizard casts his spell ("Abra kazam!") and then notices the kids are gone, asking "Kids? Kids? Hey, why is everybody asphyxiating?"

The final panel shows a newspaper headline: "WIZARD FAILS TO ACCOUNT FOR MICROFLUIDICS" with a subheading about facing the death penalty.

The Humor

The comic parodies the premise of shows like "The Magic School Bus," where characters shrink to microscopic sizes to explore the human body or other scientific environments. The joke is that in reality, shrinking humans to the size of a virus would be immediately fatal. At that scale, the physics of fluids change dramatically — air molecules would behave like a thick, viscous liquid rather than a breathable gas, a phenomenon described by microfluidics and low Reynolds number physics. The children would be unable to breathe and would essentially drown in air. The wizard's crime is not malice but scientific illiteracy — he forgot to account for the physics of being very small. The newspaper headline treating this as a criminal matter adds to the humor, as does the deadpan observation that the wizard "failed to account for microfluidics."

References

• Microfluidics: The study of fluid behavior at very small scales, where surface tension and viscosity dominate over inertia. At the scale of a virus, air would behave more like a viscous liquid.
• Reynolds number: A dimensionless number that describes whether fluid flow is smooth (laminar) or turbulent. At very small scales, the Reynolds number is extremely low, and fluid dynamics behave very differently from our everyday experience.
• The Magic School Bus: A popular children's educational media franchise in which a magical school bus shrinks to explore the human body and other environments, blithely ignoring the physics problems this would create.