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Still Raw

We actually divorced once over the airplane/treadmill argument. (Preemptive response to the inevitable threads arguing about it: you're all wrong on the internet.)

Explanation

This comic shows Cueball and his significant other undergoing a domestic dispute. The debate is heated, enough to tear apart a romantic relationship, and although the end result is Cueball being thrown out of his other's house, he resolves that he will stand by his point of view no matter what.

Of course, in the last panel, we learn that the argument is over something that should be, in the context of romance, utterly trivial: Cueball has been thrown out simply because he believes that Pluto should never have been a planet.

Pluto was the ninth planet in our solar system between 1930 and 2006, during a time when "planet" had no formal definition. (Jupiter was thought to be the ninth planet from 1807 to 1845.) In 2006, the IAU created a formal definition for "planet"; Pluto didn't make the cut, and it was reclassified as a dwarf planet. The reasons are complicated, but the basic issue is that like Ceres, Pallas, Juno, and Vesta, Pluto is too small to function as a planet in the solar system. A better explanation can be found here. While this is purely an issue of scientific classification, with no real bearing on most peoples' lives, a lot of people have strong opinions on the topic. One on side, people argue that planets should have a consistent and well-defined definition, and Pluto doesn't fit that definition. On the other, Pluto was classed as a planet for long enough that generations grew up thinking of it as one, and having it removed from the list feels wrong to them. The joke is that both Cueball and his partner were both so emotionally invested in this purely academic issue that it caused an intense argument, resulting in Cueball being thrown out of the house.

In the title text, Cueball reveals that they "divorced once" over the airplane/treadmill argument, suggesting that they were married, divorced, and then reconciled at some point. The argument in question is whether an airplane can take off while it is on a treadmill that is opposing its progress (pulling it backward). The question usually leads to arguments, both because the question may be posed ambiguously and because many people don't fully understand how airplanes work. As with the issue of Pluto, this issue is entirely academic (even more so, as it's purely hypothetical), but people can get very emotionally involved. The joke is that becoming emotionally involved with such debates, to the point of damaging their relationship, is nothing new for this couple.

Randall further anticipates that many of his readers will respond with strong opinions of their own about the argument, and pre-emptively shuts it down, saying "you're all wrong on the internet", which is likely a reference to 386: Duty Calls.

This argument does, in fact, have a clear scientific answer, which Randall proceeded to explain. The airplane can indeed take off, because its forward motion is provided by its propeller/jet engine, not its wheels, which are free to spin at any speed. This is borne out by both theory and experimentation (having famously been done by the Mythbusters).