Explain SMBC — the wiki for Saturday Morning Breakfast Cereal

This comic features a character drawn to resemble astrophysicist Neil deGrasse Tyson, standing in front of a chalkboard covered with physics equations related to event horizons and black holes. He delivers the line "Once you go black (or further) you'll never go back (to an outside observer)," a physics-themed twist on a well-known innuendo.

The joke plays on the double meaning of "once you go black, you never go back," repurposing the phrase as a description of what happens when something crosses the event horizon of a black hole. In general relativity, once an object passes the event horizon, it can never return -- but crucially, this is only from the perspective of an outside observer. The parenthetical qualifications transform a crude saying into a technically accurate statement about black hole physics. The caption "Professor Tyson discusses Event Horizons" completes the gag by framing this as a straightforward academic lecture.