Explain xkcd: It's 'cause you're dumb.
 Squirrel cosmology
The joke is that these particular squirrels are ambitious but misguided, like the characters in the myth of Icarus and Daedalus, or the Tower of Babel. The squirrels' understanding of astrophysics is lacking, regarding the distance to the sun and appropriate transportation to reach it (in addition to the need to resist the sun's heat and exist in the vacuum of space). It can be seen as a joke about how limited the knowledge of humans still is regarding many advanced topics of science. The idea of taking a balloon to the moon or the sun might not have been immediately rejected even a few hundred years ago. And the fanciful notion of a sun filled with acorns (the ultimate object in a squirrel's reality) is reminiscent of many early human ideas about heaven and celestial objects, even the common old myth that the moon might be made out of cheese.
The title text reveals that "halfway to the sun," 75 million kilometers from all known acorns in our universe, the airborne squirrel jeopardizes the entire mission because he wants to test if the balloon itself is full of acorns. Basic observational skills will tell anyone that acorns do not float, but the idea follows the logic stated by the squirrels: If the sun, being so magnificent, must be full of acorns, then a balloon powerful enough to take a squirrel to the sun must also be powered by something amazing, like acorns. This also reflects on the implied impulsiveness of squirrels, that the squirrel's curiosity would cause him to take an action that would leave him stuck in outer space (presuming he has made it that far already).
In the real world helium balloons cannot escape the stratosphere. Perhaps the squirrel only thinks he's halfway to the sun. Or maybe the acorns in the balloon are pushing on the quantum vacuum virtual plasma.
Alternate hypothesis: this scene is almost identical to a scene found in the recent movie Kingsman: TSS.
 Squirrels in xkcd
Squirrels are often used in xkcd and What if? comics as a way of avoiding reality. Maybe Randall is going through a tough time this week.
It is commonly believed that real squirrels use their tails as parachutes, although as yet "there have been no observational studies on the aerodynamics of free-falling squirrels."
- [There are three squirrels. One is suspended from a balloon. The other two are sitting on the ground, looking up at it.]
- Squirrel to the right: Once you've chewed a hole in the sun, shoot the balloon to fall back to earth, then pull the parachute ripcord to land.
- Squirrel tied to balloon: Are you sure it's full of acorns?
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- Squirrel to the right: Look how bright and magnificent it is! What else could be in there?
Reminds me of the Ice Age squirrel Mikemk (talk) 06:02, 25 March 2015 (UTC)
- Also reminiscent of the star wars scene in Kingmen 22.214.171.124 06:16, 25 March 2015 (UTC)
- Um ya, like why didn't those balloons have a pressure release valve instead of blowing up? A relatively cheap device could have aided that character immensely.Jarod997 (talk) 12:47, 25 March 2015 (UTC)
- Clunky prototype? (And/or they want the maximum amount of elevation. Any presseure release valve would give a safe(r) ceiling of operation lower than the "just before the pop" one they theoretically have, as is. It's still a design-flaw, though, if there's no effective warning of balloon failure, and you're now left swinging on the other, on-the-edge-of-failing, one. And now with only half the lift. Yeah, clunky. Yeah, I've thought about this a little, already.) 126.96.36.199 13:06, 25 March 2015 (UTC)
- Though as soon as the first balloon popped you'd start loosing altitude - due to half of your lift disappearing. So the question comes up - how did the second balloon pop? ;) And as a side note - if you catch the pan around the control room right after our hero dispatches the nerd villain, you'll see a corpse with a head. Jarod997 (talk) 13:27, 25 March 2015 (UTC)
- Obviously there was a squirrel... ;) 188.8.131.52 21:40, 25 March 2015 (UTC)
I think the squirrels are just a vehicle for the joke, which is poking fun at "obvious" conclusions based on personal beliefs. 184.108.40.206 06:48, 25 March 2015 (UTC)
- Absolutely - the current first line of explanation fails, as squirrels being stupid is not a joke. 220.127.116.11 07:18, 25 March 2015 (UTC)
"...due to the expansion of the acorns inside." I love you guys. 18.104.22.168 07:57, 25 March 2015 (UTC)
- We know 22.214.171.124 08:54, 25 March 2015 (UTC)BK201
This comic puts me in mind of the simplistic plot points and devices of a lot of modern scifi movies ... poking fun at them the same way as "Scorcher" from Tropic Thunder does ...--126.96.36.199 09:30, 25 March 2015 (UTC)
I'd say the squirrels are a stand-in for ancient humans. Their understanding of the world and what is obvious reflects their pre-scientific state of knowledge. Their interests as squirrels have affected their conclusions, just as humans have projected their interests on what they interpret the sun to be (source of acorns instead of a sun god). I'm pretty sure the "halfway to the sun" part refers to a point where they think they're halfway but probably aren't even close to leaving the atmosphere, drawing parallels again to ancient human assumptions (the sun and moon are small orbs that are just high in the sky). 188.8.131.52 (talk) (please sign your comments with ~~~~)
- Alternatively, it might be referring to people assuming the sun is golden in some literal fashion. What else could the sun be made of, if it's so gloriously radiant and stuff? 184.108.40.206 13:02, 25 March 2015 (UTC)
Agreed. Or possibly replace "ancient" with "superstitious" - or even nothing at all for that matter to apply to humans in general - and I'll agree with you even more. 220.127.116.11 09:47, 25 March 2015 (UTC)
I think it's also worth mentioning that the real sun is "full of" hydrogen and helium. The same is true for real squirrel lifting balloons. 18.104.22.168 (talk) (please sign your comments with ~~~~)
It's possible that the comic is a commentary on the human condition, constantly reaching out for some grand goal, that is both unreachable, and even if reached is shown to be far less grand then previously thought. 22.214.171.124 15:26, 25 March 2015 (UTC)
I don't think the squirrel in the picture is actually halfway to the sun. I think the title text is a hypothetical future event, and that the description is overthinking things. 126.96.36.199 16:50, 25 March 2015 (UTC)
Is it a possibility that the squirrels represent the government or similar entity? Mikemk (talk) (please sign your comments with ~~~~)
Not quite sure i like the explanation about acorns obviously not being able to contribute to flying. Not because i think they can, but because the exact same argument could be used for a jet engine on a plane as those are also heavy. 188.8.131.52 (talk) (please sign your comments with ~~~~)
- maybe the acorns are pushing on the quantum vacuum virtual plasma? 184.108.40.206 23:34, 25 March 2015 (UTC)
I seriously suspect this has something to do with 1356: Orbital Mechanics 220.127.116.11 10:06, 26 March 2015 (UTC)
I think that the balloon of the title text is a reference to earth herself : the analogy must be natural to a squirrel believing the sun is an accorn field...
I am fairly sure this comic is to mock humanity's tendency to assume what they first think of to be fact. This could also be about religion but I probably shouldn't mention that. Too many fights. The Goyim speaks (talk) 14:18, 26 March 2015 (UTC)
I think Randall's squirrels are cute. A Montrealer 18.104.22.168
00:35, 27 March 2015 (UTC)