Explain xkcd: It's 'cause you're dumb.
This comic is an inverse version of the origin story of the superhero character Superman.
In the Superman story, Jor-El and his wife Lara notice that their home planet Krypton is about to be destroyed in a giant explosion, so they decide to send their baby Kal-El to Earth to save him - and there he becomes Superman.
In this comic, Cueball and Megan also notice that the planet Krypton is about to explode, but instead of attempting to save a baby from Krypton, they decide to send a baby to Krypton from Earth so that it'll stop annoying them with his crying. This would be a huge overkill for something this small. 
In the fourth panel both spaceships can be seen. The rocket containing the Earth baby arrives at planet Krypton, while the crystal star shaped spaceship containing Kal-El leaves Krypton towards Earth - this is a reference to the version of the spaceship depicted in the 1978 Superman movie, (see trivia section).
In the fifth and last panel we see Krypton explode.
In the Superman movie, Kal-El carries with him a lot of information pre-recorded by his parents. During the very long trip he listens to the recordings, one of which explains that the Sun and gravity of Earth will give him (Kal-El) great powers (this is the way he becomes Superman). The title text is a satirical version of this information, given to the Earth baby during his trip: That Megan & Cueball do not have the faintest idea (or care about) what the sun and gravity of Krypton will do to him - but their best guess at what these mostly will do to him is to "make you out of earshot from Earth", which was their original reason for shipping the baby off in the first place.
- [Cueball and Megan are standing near a telescope.]
- Cueball: The distant planet Krypton is becoming unstable!
- Baby crying (from outside the panel): Waaaaaa
- Megan: That crying baby is really annoying.
- [Cueball and Megan looking at each other.]
- [Spaceship taking off.]
- [Spaceship passing another spaceship on route to distant planet.]
- [Planet exploding.]
- Whereas the Kal-El rocket clearly looks like the one in the 1978 Superman, a movie which is also the origin of the title text joke, the Earth baby rocket looks like any nondescript rocket. It has some features in common with the one used in 1350: Lorenz as can be seen here under the Rocket launch theme - color scheme the same, but different body of the rocket. One could also argue that it resembles some of the various versions of the rocket that brought Superman to Earth as depicted in early comic books - Not that big a resemblance though, due to the very different tip and fins.
- As the nearest stars are several light years away, this comic does of course not make any sense if you look at it from a scientific point of view, but can still do if you don't.
- First of all - how would Cueball be able to see that Krypton is unstable in a telescope - as we at the moment can only just detect planets around other stars.
- And even if he did detect this and immediately shipped his baby away in a close to light-speed rocket, then it would take several years to reach Krypton; at best - more likely to be somewhere between a hundred to a thousand years.
- Plus, because light takes time to travel, Cueball was seeing the planet as it was many years ago, meaning it had been unstable for some time already. So even for the closest star (exclusive of the Earth's sun), it would be 4.3 years to see the instability and then over 4.3 more years for the ship to travel, even with close to light speed travel, for a total of over 8.6 years from when the light left the planet until the rocket arrived there.
- As faster than light-speed travel is impossible according to the current model of our universe this option is not really relevant here.
- During all those years, the unstable planet should still keep together - in spite of being so unstable that Cueball can determine this instability with his telescope on Earth.
- And then the rocket arrives just when Kal-El is being shipped the other way a few moments before the planet explodes. Of course if the arrival of the rocket causes the explosion this would explain the last two events. Kal-El is shipped off at the last moment when his parents realizes an incoming rocket will destroy their planet.
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Is the Earth baby the real reason Krypton was destroyed? 126.96.36.199 08:58, 20 June 2014 (UTC)
- It seems that, in this comic, the answer is yes; in the real Superman series the answer is no because there is no Earth baby.188.8.131.52 21:24, 3 March 2016 (UTC)
Is now a good time to mark the shark jump? --184.108.40.206 12:52, 20 June 2014 (UTC)
- Only if this keeps up. Yeah, it's a crappy comic, but I don't think the quality overall has been dropping that much. Everyone has off days. 220.127.116.11 13:58, 20 June 2014 (UTC)
- Jumping the shark is a single event, not a segment of time. In this case it's launching the earth baby. --18.104.22.168 03:30, 21 June 2014 (UTC)
- And you can't identify a "shark jump" until a consistent decline is clearly evident. Then you can look back, and see where things started going downhill. NealCruco (talk) 15:32, 25 June 2014 (UTC)
- And often a "shark jump" is entirely arbitrary and based primarily on the opinion of self-centered wankers who think just because it doesn't make them laugh then obviously it's in an unstoppable nose dive. -Pennpenn 22.214.171.124 05:32, 3 February 2015 (UTC)
Not so bad if you can relate to the anguish of parenting a colicky kid. Sending him to Krypton is an improvement on some of the things I was tempted to do. 126.96.36.199 15:08, 20 June 2014 (UTC)
- Sending a baby off to die is better than things you were tempted to do? You really want to make that claim? 188.8.131.52 16:14, 20 June 2014 (UTC)
- It is a completely reasonable reaction given a culture that murders children in the womb for far, far less.Seebert (talk) 04:05, 23 June 2014 (UTC)
- Please, please, please, let's not turn this comment section into a "hey listen to my important opinion" fight about abortion. 184.108.40.206 21:55, 23 June 2014 (UTC)
- "Please, please, please, let's not turn this comment section into a "hey listen to my important opinion" fight about abortion. I thought that, with Randall seeming to be a liberal, that I could avoid that uncomfortable thing called truth here. Please don't rip rocket-sized holes in my arguments, lest I bring out the hate speech." Did you hit Save before finishing? NealCruco (talk) 15:32, 25 June 2014 (UTC)
- This is a wiki discussion. Not CNN comment board. The comment was not related to the comic and does not indicate the author's support for abortions nor a lack thereof. Perhaps you've entered the incorrect URL. As mentioned in prior xkcd comics, statements about ideas related directly to science are not political by definition. One may attempt to use science for political reasons, but that is not what is being done here. Please end the personal attacks. 15:25, 6 October 2014 (UTC)
It may be a cultural-linguistic thing, but I felt compelled to change "cries" to "crying", in the explanation. Hearing "his cries" is redolent of "Ahoy there!" coming from a person attracting attention in a nautical context, the various distinctive calls of a person selling produce in a street-market or "I'm up here! Get me down!" from a person stuck on the ledge of a burning building. When a baby cries (as opposed to when someone "cries out") you hear him (or her... it's not actually specified) 'crying', not his(/her) 'calling-cries', even though both are indeed similar forms of attracting attention. I've overthought this, of course. 220.127.116.11 15:19, 20 June 2014 (UTC)
(Also, should the baby survive... somehow... would Earth Rock, howsoever sent there, be naturally strenghthening to the child? Assuming similarly transmuted as per the mundane (for native Kryptonians) planetary material beneath their feet was, during the cataclysm... It'd probably depend on which subsection of Superman canon you observed, as they tend to reinvent the 'physics' behind standard green kryptonite, even before adding in the other colours of it...) 18.104.22.168 15:19, 20 June 2014 (UTC)
Can someone explain how this is funny? 22.214.171.124 (talk) (please sign your comments with ~~~~)
- Seriously. Infanticide as entertainment?!! Parents deciding to kill a baby because it's noisy is neither amusing nor an interesting observation. Shame on Randall. 126.96.36.199 16:11, 20 June 2014 (UTC)
- "Infanticide as entertainment?!!" --188.8.131.52 11:26, 21 June 2014 (UTC)
- Given infanticide only being punished after you do it to several infants over 19 years why would any good liberal worry about it in a comic strip?Seebert (talk) 04:05, 23 June 2014 (UTC)
- 184.108.40.206 and 220.127.116.11, just think of it as a post-birth abortion. Does that make it easier to handle? NealCruco (talk) 15:32, 25 June 2014 (UTC)
- What's the best part about dead baby jokes? They never get old. --Dangerkeith3000 (talk) 18:41, 25 June 2014 (UTC)
- What's the deal with the discussion here? Its like some anti abortion person said, look at this comic and make comments and two people showed up. Protip, no one cares what you think. They care about explaining the comic. 15:32, 6 October 2014 (UTC)
- The humor of this comes from the comical reversal of an older story. Try to see the comic not as a joke about "We don't like our baby, let's kill it" so much as a joke about an earth family sending their baby to Krypton.RedHatGuy68 (talk) 03:16, 20 April 2016 (UTC)
What I totally don't get is...when the visual information about Krypton's instability has reached Earth, Krypton has already exploded many years ago. I guess that Kal-El's spaceship is travelling at near-lightspeed, so time-dilation effects cause very little apparent time to pass for Kal-El; so when he arrives he's still a a baby. This assumes that (a) the alien technology allows for extraordinary acceleration while still maintaining survivable conditions for the baby (while Superman can apparently survive extreme conditions, this trait is most probably bestowed upon him only at the end of his journey by the Earth sun), and (b) the he is a male (this primary sexual characteristics are not shown in the movie, IIRC...). An FTL spaceship is out of the question, as this would mean that the Krptonite meteors would also have been travelling at FTL speed.
- Whatever. By the time a spaceship from Earth arrives, even if it travels at near-lightspeed, Clark Kent will most probably be facing retirement already (after turning a crank for many years, of course).
- I don't think that Randall thinks THAT much about the comics he makes. Besides, Cueball's line is that the planet is BECOMING unstable. I believe that in some of the comics Jor-El, Superman's father, notices the planet's instability long before they launch Kal-El. And Cueball's telescope is not very big (And sort of weirdly drawn), which might suggest that the planet is not hundreds of thousands of light years away. What I think is more confusing is the discussion about the possibility of the Earth baby causing the destruction of Krypton. If a small rocket entering the atmosphere of a planet causes it to go Kablooie, the world probably wouldn't last very long anyway. That should be removed.RedHatGuy68 (talk) 03:16, 20 April 2016 (UTC)
Btw, having Superman turn a crank instead of having him fight crimes would not necessarily mean that Lex Luthor would have had success with his evil plans. Mr. Bond, James Bond, had proven numerous times that he can stop any criminal who attempt to achieve world domination or at least extreme wealth via over-convoluted plans. Yep, I mean, if you could build powersats, you'd immediately achieve wold domination via your monopoly for "free and clean energy", so why bother with criminal plans? Any, if you are smart enough to build powersats, but cannot resist the temptation to use them for over-convoluted criminal plans, should yout net able to think about the option to give your Legion of Doom at least basic training in marksmanship?
But I think I'm getting carried away. --18.104.22.168 16:25, 20 June 2014 (UTC)
I actually thought this was more brilliant before I saw the second ship (rather: noticed that the crystal was a ship). I thought the gag was that some human, in attempting to resolve a crying baby (we've all been there, and if you haven't, don't knock it) actually created Superman (the shuttle destroys the unstable Krypton, and the baby is flung back). If anyone does think that this comic is gruesome, then stop reading it: your efforts could be rewardingly employed by criticizing "Cyanide and Happiness" instead. I love the quirkiness Randall! 22.214.171.124 16:45, 20 June 2014 (UTC)
Am I alone in thinking (NCC-1701) moviebombed the 1978 film? See 'version depicted' in explanation. 126.96.36.199 20:06, 20 June 2014 (UTC)
I think the depth of the cartoon is Newton's "Every action has an equal and opposite reaction" Nathan Hillery (talk) 14:01, 21 June 2014 (UTC)
Scientific objections? But everything about Superman is already scientifically implausible anyway. Jim E (talk) 19:53, 21 June 2014 (UTC)
Regarding the following quote under trivia: "As faster than light-speed travel is impossible according to the current model of our universe this option is not really relevant here." FTL is entirely (theoretically) ppssible, its just travel *at* lightspeed that is impossible. 188.8.131.52 01:32, 29 June 2014 (UTC)
- More importantly, FTL is an everyday thing in the DC universe. Our real-world science says the telescope is impossible, and so is Superman; the idea of just accepting those but drawing the line at FTL is more than a little silly. 184.108.40.206 02:16, 25 September 2015 (UTC)
- "Our real-world science says the telescope is impossible"  220.127.116.11 16:41, 1 July 2016 (UTC)