Explain xkcd: It's 'cause you're dumb.
|Cosmologist on a Tire Swing|
Title text: No matter how fast I swing, I can never travel outside this loop! Maybe space outside it doesn't exist! But I bet it does. This tire came from somewhere.
Cueball and a curious child walk through a forest with many small holes or pools. The setting of trees interspersed with these many small pools resembles the Wood between the Worlds, a meta-verse described in C.S. Lewis's The Magician's Nephew; each pool leads into a different universe — one of these is ours, another is Narnia, and the world of the White Witch is also visited through these pools.
The girl asks about the time before the Big Bang. Cueball says he thinks there was no time before — which is implied by most forms of the Big Bang theory. But then they happen upon a cosmologist, Megan, on a swing who has several other theories about the universe.
Simply put, the tire swing is a symbolic representation of our universe. Scientific observations tell us that both space and time began with the Big Bang ~13.8 billion years ago. We don't know if there was such a thing as "before" the universe, or what that might be.
The first 6 panels reference ongoing speculation about where the universe came from and why it even exists in the first place. The last two panels relate to recent observations of the accelerating universe in which galaxies are now receding from each other at higher and higher speeds, due to dark energy.
The swing itself is likely a reference to the Cyclic Model, where the universe expands from a Big Bang, then contracts back in on itself under its own gravity for a Big Crunch, before bouncing outward again in another Big Bang, and repeating the whole process. On the other hand the swing is accelerating as the universe — so it may also be a reference to the entire universe. We are all "trapped" on this swing — and it's accelerating!
The title text references questions about the shape of the universe and what could lie "outside" of it. By the current understanding on physics laws, we can't see outside of the observable universe, but it's likely that the universe is bigger than this observable universe and uniform on large scale. Even though nobody can leave our own universe, Megan bets that such unknown worlds do exist - because this universe is here, and it must have come from somewhere — like her tire.
The shape of our universe was visited soon after in 1365: Inflation where we can see what the outer boundaries of our universe looks like.
- Girl: What was before the big bang?
- Cueball: I think time began with the big bang. So it doesn't make sense to ask what came before it.
- Cosmologist (off panel): Look out
- Cosmologist: WHEEEE Hi I'm a cosmologist on a tire swing!
- Cosmologist: We don't know whether time
- Cosmologist: started at the big bang.
- Cosmologist: It might have!
- Cosmologist: Or maybe not! We don't know!
- Cueball: Oh. OK!
- Girl: ...Your tire swing looks fun!
- Cosmologist: I can't stop!
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- Girl: Won't the swing stop on its own?
- Cosmologist: I thought it would, but it seems to be accelerating.
- Girl: Cosmology sounds pretty confusing.
- Cosmologist: WHEEEEE!
See this TED talk for clue: http://www.ted.com/talks/allan_adams_the_discovery_that_could_rewrite_physics
184.108.40.206 07:54, 7 April 2014 (UTC)
The question "what lies outside our observable universe?" is pretty easily answered with a "the same stuff as inside it, we just can't observe it". The more poignant question is whether the universe as a whole (not just its observable part) has an edge and if so, what lies beyond it. --Koveras (talk) 08:09, 7 April 2014 (UTC)
- The parts of universe which are not observable due to speed of light looks the same as the ones we can observe, sure. Just bigger. But there is nothing in physics saying there can't be something even more "outside". In fact, some theories consider it probable. And what can be THERE? Anything. Dragons. Possibly literally. Unfortunately, according to current physic, we can't PROVE something outside exists, much less look at it. -- Hkmaly (talk) 10:21, 7 April 2014 (UTC)
What's the setting of the first panel? Given the cosmological context, could it be a reference to the Wood between the Worlds from the Narnia series? 220.127.116.11 10:57, 7 April 2014 (UTC)
The puddles/ponds in the first panel mirror "reality", is this a hint for parallel universe(s)? Escher sees three worlds in a pond. http://cache2.allpostersimages.com/p/LRG/7/779/1X5I000Z/poster/escher-m-c-drei-welten.jpg 18.104.22.168 (talk) (please sign your comments with ~~~~)
Someone please rewrite my shunted in assertion about the aforementioned wood. There's a reason for the setting in the first panel, I just can't think of a better place to put it in the explanation.
22.214.171.124 11:43, 7 April 2014 (UTC)
The tire swing also evokes the cosmology field in itself; accepted theories keep changing like the swing, endlessly being replaced by the next one. Ralfoide (talk) 14:19, 7 April 2014 (UTC)
Seems to me Randall is referring to the the A and B theories of time. — tbc (talk) 14:24, 7 April 2014 (UTC)
- Seems to me Randall is referring to Physics and not philosophy. ExternalMonolog (talk) (please sign your comments with ~~~~)
It's possible the tire swing might also be a reference to the idea that the universe is "shaped like a doughnut". 126.96.36.199 16:32, 7 April 2014 (UTC)
Maybe it's important to note that the cosmologist is also portrayed as somebody not serious, and also doing "silly" science? A jab at the state our most serious scientists are, because we know, in a way, so little? Not sure if that's the kind of thing you put here, but it's relevant. 188.8.131.52 17:21, 7 April 2014 (UTC)
- Science is fun. 184.108.40.206 16:36, 8 April 2014 (UTC)
- Maybe some of our most "serious" scientists.
Randall seems to be referring directly to the discovery of dark energy and the perpetual acceleration it gives to the expansion of the universe. "Tire swing" girl directly addresses this when she speaks of her surprise that her momentum increases rather than decays.ExternalMonolog (talk) 00:18, 8 April 2014 (UTC)ExternalMonolog
Maybe I shouldn't be writing here, since I'm a new guy around and I'm not well versed in the ways of this wiki, but it seems to me that aside from all that you've said, the main point of the idea of "Cosmologist on a tire swing" seems to be a parody of the fact that not only does every simple person apears to have a definite explanation for those universal unanswered riddles, (even though "It might have! Or maybe not! We don't know!"), the scientific community also seems to 'swing' between answers constantly as they discovers new clues or evidence. And even though it would seem that having more knowledge would bring them closer to getting the one true answers, it only gets them more and more doubts and questions about the nature of, well, everything (hence the swing not stopping but accelerating). 220.127.116.11 02:39, 8 April 2014 (UTC)
It'd be cool to have the link to the TED talk or something similar about the gravity wave detection and its potential multiverse-ish implications; it seems relevant to the explanation. 18.104.22.168 04:54, 8 April 2014 (UTC)
Georges_Lemaître developed the big bang theory as a Catholic Priest, with the understanding that he would not investigate whether anything happened before that. It was a compromise that allowed the physical threory to work within the context of theology. This gave backing to a desire not to think about what happen before. 22.214.171.124 16:17, 8 April 2014 (UTC)
Although the swinging messes up her hair, isn't the cosmologist Megan? Athang (talk) 21:46, 9 April 2014 (UTC)
- Yes it is Megan, and I have added her name to the explain, and it is thus also clear that it is her not Randall who speaks the title text line. Maybe he agrees with Megan (I bet he does ;-) but that is not given. Kynde (talk) 14:44, 10 April 2014 (UTC)
I'm a little late to the party, but I enjoyed (as a CS Lewis fan) the thoughts about what the puddles represent and would like to add (as a Douglas Adams fan) that the late D.N.A. has a wonderful "puddle quote" about how humans feel our observable universe was build "for us" and that anything beyond what we can see simply doesn't fit our limited view. Obscure, yes. But, is perhaps the only time my cerebrally-challenged self has had something to add. 126.96.36.199 (talk) (please sign your comments with ~~~~)