Campfire Habitable Zone
Campfire Habitable Zone
[A campfire is in the middle of the panel in a white area with two areas shaded green to the left and right of the fire. There are also two white areas outside of these green areas. Ponytail is sitting normally on the ground to the left of the fire, with her body fully inside the left green area. She is facing the fire and is holding a stick in both hands. The stick has a marshmallow on the tip and she is holding it over the top of the flames of the fire. Cueball is sitting to the right near the fire, only half inside the green are. He is sitting sideways leaning away from the fire, holding one hand to his head, while his other hand seems to be ready to support him as he is leaning further away from the fire. The arm closest to the fire and his head seems to be very hot as three small smoke-like lines rises from Cueball. Megan is crouching to the right of Cueball, far from the fire outside the right green area. She is supporting herself on one knee and one foot. She is also holding a stick in both hands with a marshmallow on it. She is holding the stick inside the green area to the right of Cueball far from the fire. Four small lines above and below indicates that she is waving the stick up and down. The camp fire is built up of several logs on top of each other, with big flames above it, with smaller flames hanging loose in the air above the main flames. A small dead tree is to the far left and small rocks/stones lie along the ground all the way from left to right interspersed with grass tufts. Below the scene there is a label from which two curved arrows point to the two green areas.] Label: Habitable zone
[Caption below panel:] Astronomers define the Campfire Habitable Zone as the region where you're far enough not to be burned but close enough to roast marshmallows.

This comic plays on the concept of the astronomic "habitable zone" applied at the scale of people sitting around a campfire.
The habitable zone of a star is the range of distances in which a planet might support liquid water, and hence life in the only form that we currently know of (as an allusion to the "not too hot, not too cold, but just right " of the related children's story , the habitable zone is also commonly known as the "Goldilocks zone"). If the planet is too close to the star, then the amount of stellar radiation would be too great, causing the water to boil; too far from the star, and the planet doesn't have enough radiation, causing the water to freeze (although for life to actually exist, the planet itself must also have the right mass in order to maintain a life-compatible atmosphere and meet other such requirements). For our Sun, the habitable zone is estimated to range from about 0.38 to 10 astronomical units, where 1 astronomical unit is the distance from the Sun to the Earth.
Marshmallow toasting is a popular camping activity in which people place a marshmallow (a soft, sugary blob made of gelatin and covered in corn starch) on a stick and over/near a fire. As the marshmallow cooks, the inside becomes gooey while the outside becomes crispy (perhaps slightly charred and maybe even burned, depending on the toaster's preference), making it tastier via caramelization and the Maillard reaction .
In the context of the campfire, a similar "habitable zone" is posited by Randall to exist: a zone which is close enough to the fire such that the person can comfortably toast marshmallows, presumably on a stick of reasonable length (the ones in the comic seem to be about 1.5 times an arm's normal reach), yet far enough such that the person is not uncomfortably hot or even burned by either direct contact with the flames or by exposure to the radiant heat of the fire.
To demonstrate this hypothesis (with the habitable zones marked in green), Cueball is shown sitting outside the right habitable zone on the side of the fire. Even though he is able to toast his marshmallows on the fire due to his being close to it, he will have and is having part of his body scorched, as he is too close (fires can get really hot ). Megan, also on the right, is well outside the habitable zone on the side away from the fire. Although not burned, the marshmallow on the stick she is waving will presumably not toast due to its being too far from the campfire. Ponytail, on the other hand, has found and is enjoying the medium between the plights of both Cueball and Megan by sitting entirely within her (the left) habitable zone, thereby both being close enough to the fire to be able to toast her marshmallows while also staying far enough away such that she will not be burned.
The title text introduces the concept of tidal locking , in which one astronomical body synchronizes its rotation with its orbit around another such that one side always faces the other body (e.g. the case of Earth's moon, which always presents the same face to the Earth). The joke here is that if a marshmallow became tidally locked to the fire, then one side would become more and more cooked, perhaps burnt, while the other side never became toasted at all. This also may allude to the instance in which a marshmallow has begun melting more than you realized and dripped down so far that it no longer responds to your rotation of the roasting stick (the solution to which is to cut your losses and pull the marshmallow out immediately, before it drops into the fire pit).
[A campfire is in the middle of the panel in a white area with two areas shaded green to the left and right of the fire. There are also two white areas outside of these green areas. Ponytail is sitting normally on the ground to the left of the fire, with her body fully inside the left green area. She is facing the fire and is holding a stick in both hands. The stick has a marshmallow on the tip and she is holding it over the top of the flames of the fire. Cueball is sitting to the right near the fire, only half inside the green are. He is sitting sideways leaning away from the fire, holding one hand to his head, while his other hand seems to be ready to support him as he is leaning further away from the fire. The arm closest to the fire and his head seems to be very hot as three small smoke-like lines rises from Cueball. Megan is crouching to the right of Cueball, far from the fire outside the right green area. She is supporting herself on one knee and one foot. She is also holding a stick in both hands with a marshmallow on it. She is holding the stick inside the green area to the right of Cueball far from the fire. Four small lines above and below indicates that she is waving the stick up and down. The camp fire is built up of several logs on top of each other, with big flames above it, with smaller flames hanging loose in the air above the main flames. A small dead tree is to the far left and small rocks/stones lie along the ground all the way from left to right interspersed with grass tufts. Below the scene there is a label from which two curved arrows point to the two green areas.] Label: Habitable zone
[Caption below panel:] Astronomers define the Campfire Habitable Zone as the region where you're far enough not to be burned but close enough to roast marshmallows.
