Explain SMBC — the wiki for Saturday Morning Breakfast Cereal

The Joke

This is a science-heavy comic set in space, featuring two celestial bodies (drawn as characters) discussing the physics of orbits and gravitational interactions. The comic explains the concept of the "gravitational slingshot" (gravity assist) maneuver, where a spacecraft gains speed by passing close to a massive body and stealing some of its orbital energy.

The characters discuss how the process involves a body of lesser mass passing through the gravitational influence of a more massive body, changing direction and gaining energy. They note that technically the larger body loses a tiny, immeasurable amount of orbital energy in the process. The comic builds to a punchline where a spaceship performs this maneuver, and the celestial body remarks on the "sacrifice" it makes — losing an infinitesimally small amount of its energy so the spacecraft can travel onward.

The final caption references "The Sacrifice" in an ironic, grandiose way.

The Humor

The humor comes from the dramatic, emotional framing of something that is physically real but practically meaningless. When a spacecraft performs a gravity assist around a planet like Jupiter, the planet does technically lose a tiny fraction of its orbital energy — but the amount is so absurdly small as to be completely immeasurable and irrelevant. The comic treats this infinitesimal energy transfer as a noble "sacrifice," giving cosmic grandeur to something that has literally zero practical effect on the planet.

This is a classic SMBC move: taking a real scientific fact and finding the absurd emotional narrative hidden within it.

References

Gravity assist (or gravitational slingshot) is a real spaceflight technique used by NASA and other space agencies. Notable examples include the Voyager missions, which used gravity assists from Jupiter and Saturn to reach the outer solar system. The physics is based on conservation of momentum — the spacecraft gains kinetic energy at the expense of the planet's orbital energy, though the effect on the planet is negligibly small.