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| Star Formation |
 Title text: It's ok, I still have some nice, cool gas clouds that aren't collapsing. As long as nothing ionizes them, I can continue to enjoy their ... HEY! NO!!! |
Explanation
This comic depicts a simplified model of how structure forms in the universe, then pushes it to an absurd extreme. In cosmology, small density variations in the early universe grow over time: regions with slightly higher density attract more matter via gravity, eventually forming gas clouds, stars, and galaxies. Pressure, driven by temperature, resists collapse, so the evolution of a cloud depends on the balance between gravitational attraction and internal pressure; this is often described by the Jeans instability criterion.
In the first panel, the on-screen narrator (with a passing resemblance to the time-travelling sphere and other speaking dots uses in xkcd), and apparent creator of the universe, describes pressure waves moving through gas and causing it to clump. In the second, the clouds begin to collapse under gravity as more gas falls in. The third panel sees the outcome: as collapse proceeds, the gas heats up (via compression and radiation processes), increasing pressure and eventually sparking fusion. The comic depicts the formation of stars, something that we know this universe has done, with the implication that this was a totally unforeseen outcome for the manipulator or creator of this universe.
The final panel humorously frames this as the narrator lamenting the destruction of their "beautiful clouds," as the process has gone out of their control and produced a star instead of the desired (and perhaps, to their mind, more aesthetically pleasing) gently pulsating clouds.
The title text continues this joke by referencing the importance of ionization. "Cool" gas clouds (low temperature, neutral gas) can remain stable or collapse slowly. If they are ionized (for example, by nearby stars emitting ultraviolet radiation), the gas heats up, increasing pressure and preventing or disrupting collapse. The narrator hopes to preserve some of their own calm, neutral clouds but then reacts in horror as something ionizes them, ruining the delicate balance and ending their ability to "enjoy" stable gas clouds. But this is a natural result of star formation within and around a nebula again unforeseen by the being who apparently set up the circumstances that led to all the cosmic evolution we see. Interestingly enough though, the narrator acts as if there is another diety as well as it, actively causing the ionization. This could be true, or it could be that they are just imagining that the clouds have life - Which is another possibility as well.
Transcript
- [A black dot with star burst all around it is speaking, as indicated with a line from one of the burst lines to the text above it. Around the dot there are four larger and three small clouds. The one to the top right is somewhat larger than the other bigger ones.]
- Dot: I think I did a good job with this universe.
- Dot: Pressure waves dance through gas clouds.
- Dot: They clump together and then pressure pushes them apart.
- [In a fame-less panel the dot comments on the development as the largest cloud from seems to be gathering several other smaller clouds together. The other three larger clouds are still there, but there now seems to be some larger clouds stuck together in the upper right part, with more than ten smaller cloud either on top of these or moving in from all angles.]
- Dot: Oh weird, that big clump of clouds is staying together.
- Dot: Their gravity is overcoming the pressure and more gas is falling in.
- [The dot keeps commenting as the increasingly fragmentary clouds start to fall in streaks towards the original large cloud, which has now been compressed so it is smaller than before, but obviously are many more clouds stuck together. The larger clouds from before have begun to be drawn out and moving towards the larger.]
- Dot: It's not stopping!
- Dot: The heat is rising but the collapse is only accelerating!
- Dot: I messed up bad. I messed up bad.
- [The dot comments on the final result. There is now a shining star in place of the dense field of clouds, radiating strongly in all directions, blowing the few remaining smaller clouds around it, nine in total, away from it.]
- Dot: Noooooooo!!!
- Dot: My beautiful clouds!
- Dot: Ruined! It's all ruined!
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