Explain xkcd: It's 'cause you're dumb.
Megan has taken or visited an astronomy class and has become more conscious about the vast size of the universe, and our own small place in it. She ponders that she can only observe and learn about the rest of the universe; she cannot explore it directly as she is trapped, presumably by the constraints of gravity, time and human technology.
The sphere she mentions her is a metaphor for the Earth, which is roughly spherical in shape. Note that the figure of the Earth is an irregular shape which can be better approximated as an oblate spheroid or more exactly as a geoid (that is, "earth-shaped").
Her disinclination to make "small talk" with Cueball is a reference to how astronomers (and people of other 'big-science' specializations) can be so focused on their topic that they become disconnected from the simple details of everyday life. This has also been touched upon in 663: Sagan-Man and 786: Exoplanets.
The title text is a continuation of this theme. The name "Society of Astronomers Trapped on the Surface of a Sphere" (or, "SATSS", if you will) follows a common naming practice for scientific communities, Society (or "Association" or "Union") of <Scientists> of <Country, Nationality, or What Have You>.
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- Cueball: How are you?
- Megan: Trapped on the surface of a sphere.
- [A beat.]
- Cueball: That astronomy class has made you suck at small talk.
- Megan: The universe is too big for small talk.
More specifically,a geoid.--Guru-45 (talk) 08:51, 7 August 2013 (UTC)
- Astronomers observe objects in the sky, not the Earth.--Dgbrt (talk) 11:19, 7 August 2013 (UTC)
- Astronomers live on the surface of the Earth, not on the surface of the sky (celestial sphere). 220.127.116.11 13:25, 7 August 2013 (UTC)
Are you sure “Sphere” refers to “hemisphere” and not simply to earth? After all, she’s trapped on earth and not on the celestial sphere. Quoti (talk) 11:24, 7 August 2013 (UTC)
- It's the hemisphere, see my comment above.--Dgbrt (talk) 11:46, 7 August 2013 (UTC)
- I'm assuming you're referring to the "light-sphere" whose origin lies at the astronomer's location, and thus the universe always being bigger than the places he can physically visit. Still though, the statement "They can't travel to the places they observe" isn't accurate. We've been to the moon for instance. And then of course, there are always the unknown unknowns of the universe and interstellar travel. 18.104.22.168 12:19, 7 August 2013 (UTC)
- The fact that we, the human race, have been to the moon is no comfort to anyone who's seen the wonders revealed by the HST (which isn't even suitable for inspecting the moon). We are, indeed, "trapped" here on Earth, into the foreseeable future. — tbc (talk) 13:22, 7 August 2013 (UTC)
- I read it as earth. It's a sphere and we're all trapped on its surface and astronomy classes make you aware of this fact more than your everyday experiences. Also, doesn't "hemisphere" mean "half sphere"? like northern and southern hemisphere of the earth? Peter (talk) 12:48, 7 August 2013 (UTC)
Do we maybe have a reference to 1246? 22.214.171.124 11:37, 7 August 2013 (UTC)
- That comic belongs more to space science than to astronomers.--Dgbrt (talk) 11:46, 7 August 2013 (UTC)
I'm sure the sphere is Earth. We don't live on the surface of the universe. Everybody in http://forums.xkcd.com/viewtopic.php?f=7&t=104172 agrees. 126.96.36.199 13:12, 7 August 2013 (UTC)
"This totally occupies her mind, and she feels frustrated that she can only learn about those mind-boggling places, and not visit them herself." Wow. She must have been in a class? She's "totally" occupied? She's frustrated? (Not wistful, or resigned, or just aware of a fact mind you.) She isn't just thinking about the size of space, but apparently really, really wants to actually travel there. (To where, exactly? What "mind boggling" places? "Space"? Seems rather general.) You got all that deep and specific feeling from just her using the word "trapped"? Looks like reading a lot into things, to me. CFoxx (talk) 15:53, 7 August 2013 (UTC)
- I try to not to make the explanations too dry; they are and should often be interpretations to some extent. On the other hand yeah, you are probably right that I read too much emotion into it. I changed the things you commented on. –St.nerol (talk) 18:29, 7 August 2013 (UTC)
- "I try to not to make the explanations too dry" And your efforts are very much appreciated. Hat tip! CFoxx (talk) 15:50, 8 August 2013 (UTC)
- @CFoxx - Absolutely. In XKCD, there are no shades of grey. (really, look for yourself) JamesCurran (talk) 19:43, 7 August 2013 (UTC)
- Heh. :) CFoxx (talk) 15:50, 8 August 2013 (UTC)
Hey, what the hell are you doing? "The sphere she mentions..." is absolutely wrong, the word Sphere appears only at the title and the title text! Megan is just impressed by the vast size of the universe.--Dgbrt (talk) 16:21, 7 August 2013 (UTC)
- And to all you Earth theorists, tell me why Randall mentions astronomers and NOT the entire mankind? And that, after Megan talks about a big universe. Astronomers do not observe the Earth but objects in that big universe, which is from a viewpoint on Earth just a sphere.--Dgbrt (talk) 16:21, 7 August 2013 (UTC)
- One more: Astronomers are not trapped to the surface of the Earth because they use many space telescopes even beyond of earth's orbit. They are also using probes at many planets and more all over the solar system.--Dgbrt (talk) 17:02, 7 August 2013 (UTC)
- Would you please look at the first panel … And just using space telescopes doesn’t mean you’re no longer trapped. Imagine yourself being trapped in a cage with a satellite dish to communicate with a space telescope (well … just imagine that). You’re not going anywhere by using that telescope. I think you confuse “being trapped” with “being limited”. Being trapped somewhere doesn’t mean your observation is limited to that place too. Quoti (talk) 17:54, 7 August 2013 (UTC)
- Ok, I did ignore the first panel, sorry about that. But the Earth is a geoid and absolutely doesn't match the criteria for a sphere. So, like in democracy the mass does win, but I'm still sure I'm right.--Dgbrt (talk) 19:13, 7 August 2013 (UTC)
- She does mention a sphere, so I changed it back. No hard feelings (I hope). –St.nerol (talk) 18:29, 7 August 2013 (UTC)
- I don't mind, but it seems I'm the only astronomer and physicist here.--Dgbrt (talk) 19:13, 7 August 2013 (UTC)
After some more thoughts on this, why nobody (even myself) did raise the idea that Randall talks about both interpretations? Nevertheless, if the sphere is interpreted as the surface of the Earth there is a need to explain the geoid discrepancy to an ideal sphere, as mentioned in the very first post here.--Dgbrt (talk) 19:51, 7 August 2013 (UTC)
- I fixed a sentence on the discrepancy (with some Wikipedia help). Interesting stuff! I think that Megan answers Cueballs question quite literary. How are you? Trapped on a 2-dimensional surface. The 'celestial sphere'-thing seems too far fetched... –St.nerol (talk) 10:54, 8 August 2013 (UTC)
This "a sphere is a surface and has no surface" is too much nitpicking. Wikipedia (http://en.wikipedia.org/wiki/Sphere) talks about calculating the surface area of a sphere. I think "surface of sth" is not very rigorously defined. Often two dimensional manifolds are called surfaces, and a sphere is one, and the surface (different meaning) of the earth is roughly a sphere. What a sphere doesn't have is a border. Peter (talk) 11:54, 8 August 2013 (UTC)
- You are right that the Wikipedia article is not consistent with its terminology. However, the Wp-article on 'ball' mentions that "in informal use, sphere sometimes means ball". Maybe thats where the source of the confusion lies? If she by 'a sphere' means 'the surface of the Earth', then she is saying that she is 'trapped on the surface of the surface of the earth', which seems strange. If she means the entire Earth, however correct, her sentence at least makes sense. –St.nerol (talk) 23:37, 8 August 2013 (UTC)
The is trapped on the surface of this sphere, since you can walk on it forever, without ever leaving itOscar (talk) 12:20, 8 August 2013 (UTC)
The sphere could be referring to a black hole. There is a theory out there that says information that falls into a black hole does not get lost as it is on the surface of the black hole. That's how I read it anyway. -(coconutty) Coconutty (talk) (please sign your comments with ~~~~)
For the Incomplete tag: I have explained the title text, but nowhere in the comic does the firmament come into play. All that is is a fictional sphere representing the sky the ancients and medievals used to make sense of their world. Anonymous 19:48, 9 January 2014 (UTC)
- I'm giving up, but THE SPHERE is still the firmament and NOT the Earth to astronomers! --Dgbrt (talk) 22:52, 9 January 2014 (UTC)