3251: Time Machine Conversation

Time Machine Conversation

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Title text: It's possible to do sea navigation without a compass, but you'll have to get some spoilers from the Polynesians.

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Explanation

This is one of 43 incomplete explanations: Spoiler alert! This page was created in the past.[citation needed] Don't remove this notice too soon. If you can fix this issue, edit the page!

The comic points out how though many things are seen as perfectly normal and standard today could seem very strange before their creation. Cueball has used a time machine to travel to the Iron Age and has a conversation with an ancient-times version of Hairbun (who seems to be a farmer, since she's holding a pretty modern-looking hoe and seems to be particularly knowledgable of the 'latest' plow developments). However, he is very surprised to see her not knowing about the compass (a very common tool in the present-day), them not having been invented yet. The magnetic compass was first invented in China around 200 BCE, well after the end of the Iron Age, and it wasn't used for navigation until the 11th century AD. For an Iron Age farmer the concept of a 'weird rock that always points north', as Cueball puts it, would seem quite ridiculous, and the inherent dangers of sea travel might well seem to be insurmountable ones. This subject has been covered before in xkcd.

In his surprise at compasses not having been invented yet, he inadvertently starts explaining them to her and then worries about the impact his words might have. According to common time travel tropes, this interaction might cause a chain of events that will lead to Cueball not existing, or worse, which would create a paradox (if it isn't already already a different kind of paradox through being a pre-existing component of Cueball's original timeline). However, rather than the potential radical impact he might have on history by introducing this concept earlier than should have happened, he appears to be concerned that he may have given her a spoiler for upcoming history[1]. Presumably he feels he has deprived her (or humankind more generally) of the joy that would have come with its eventual discovery.

He is then also concerned that he has managed to 'spoilerise' the concept of 'the spoiler'. The modern meaning of "spoiler" didn't arise until the 1970s, which post-date the Iron Age.^{[citation needed]} Spoiler warnings became common on Usenet newsgroups in the late 1980s. Cueball may have created a temporal paradox by introducing the concept thousands of years earlier, although any such 'change' made to that time might easily have been forgotten again in the two or three thousand years since this encounter. In any event, while telling people thousands of years ago that there was a way to make a compass might have changed history significantly, telling them that there are stories that they would enjoy less if they knew the ending before hearing the story seems less likely to have made a significant impact. It's also likely that, even if the term 'spoiler' was adopted by these Iron Age people, it would long have fallen out of use by the time it came to be invented in the late twentieth century.

Whether or not this was an intentional connection, the stars known by some as "the Plough" (Ursa Major, perhaps more popularly known as "the Big Dipper" in the US) are also useful in finding the northern pole star (not the same star then as now but still in the same constellation), hence potentially linking both of the farmer's initial remarks.

The title text has Cueball about to unleash another spoiler on how to navigate without a compass, but he stops himself before saying it. However, he does still end up accidentally revealing that Polynesians know about it, though whether this was another unintentional slip or a deliberate clue left for Hairbun is unclear. It is thought that so-called 'Polynesian navigation' used other methods of marine navigation (celestial navigation, observation of birds, ocean swells, and wind patterns). However, as the Polynesians lived in the Pacific, which would be difficult to reach from Hairbun's location, and probably unknown to her, the clue is useless. It is unclear where Hairbun is, but it is likely that she is in Europe or the area around the Arabian Peninsula, where the term 'Iron Age' is most relevant, and which are quite far from the Pacific.

The comic is based on shaky ground, as it's not clear how they're able to communicate so easily, unless it's part of the function of the time-travel technology. While humans did have language for thousands of years by this time, it would be very far removed from modern English, yet somehow they understand each other's speech. It also appears that the very existence of time travel is not considered a spoiler for an Iron Age person, or even in any way remarkable to them — this might imply that the farmer is already very well aware of such phenomena (or even that Cueball will later have already visited the same society/farmer at an earlier date), which may be one way to explain apparently fluent conversational American English being spoken.

Time travel is a recurring theme on xkcd.

Transcript

[Cueball is on the left with a ghostly halo around him. Hairbun is on the right, holding a hoe vertically.]

Cueball: Oh hi! Guess my time machine works. How's life in the Iron Age?

Hairbun: Not bad. Developing new kinds of plows.

Cueball: Cool.

Hairbun: And my brother was just lost at sea.

[Only Cueball is shown, with Hairbun out of the panel.]

Cueball: I'm sorry.

Hairbun [from outside the right side]: It's OK. I think sea navigation is probably impossible.

[Cueball and Hairbun are both shown again.]

Cueball: Oh yeah, you don't have the compass, right?

Hairbun: The what?

Cueball: The weird rock that always points north?

Hairbun: What are you talking about?

[Cueball and Hairbun are both shown. Cueball holds his hand to his chin.]

Cueball: It does sound ridiculous when I say it out loud. Anyway, spoilers for the magnetic compass. Sorry.

Hairbun: What's a spoiler?

Cueball: ...Spoilers for the concept of a spoiler, too.

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Discussion

Spoilers for boats. 64.201.132.210 21:25, 27 May 2026 (UTC)

The barman says "Sorry, we don't serve time-travellers". A time-traveller walks into a bar. 81.179.199.253 21:31, 27 May 2026 (UTC)

Before explanation/transcript --OceanLord (talk) 21:38, 27 May 2026 (UTC)

Cool I’ve never been early enough to see an explanation-less comic also help me I’ve never commented before did I mess it up :( 73.148.10.13 (talk) 21:47, 27 May 2026 (please sign your comments with ~~~~)

You messed up slightly -- you forgot to sign your comment with 4 tildes. Barmar (talk) 21:48, 27 May 2026 (UTC)

Like this tilde tilde tilde tilde 82.13.184.33 (talk) 09:02, 28 May 2026 (please sign your comments with ~~~~)

(That's not necessarily helping...)

If you can't find it on your keyboard (or it's awkward... I have to tap a bit of my on-screen keyboard twice to get to the 'secondary set of other characters' layout that features it), you can copy-and-paste it from somewhere else (hmmm... It is usually is mentioned in a comment at the top of a recent Talk page -- edit: and it still is... sorry, went looking for when it vanished, but it never had ...must have been sticky scrolling that stopped me panning up enough to see it... Anyway, it's the "Please sign your posts with" thing at the top of the page. You can copy-paste the four tildes from there, if anyone ever finds it easiest to do that for any reason).

Or, click on the penultimate button in the button-bar immediately above this (as I write) editing window. Has a scrawly 'signature'-like image in it (like the Bold button has a bold B, italics has an italic I, etc) and it will give you "<hyphen><hyphen><tilde><tilde><tilde><tilde>" wherever your cursor is in this textbox (assuming you don't have a custom signature, as a registered user, the effective text of that may appear instead). The hyphens/etc are't strictly important, though a newline starting with two hyphens used to be a standard "this line is the start of a signature" marker in more civilised days. But I'll leave them in here, so you can see how they precede the (more vital, for conversation readability) who-I-am and when-I-posted information that the four-tildes generates for me. --82.132.238.245 12:23, 28 May 2026 (UTC)

It was necessarily not helping ;o) 82.13.184.33 13:07, 28 May 2026 (UTC)

https://en.wikipedia.org/wiki/Polynesian_navigation Sebastian --88.217.185.170 21:50, 27 May 2026 (UTC)

i think it should be "this page was created in the past" not "this page was created in the future". im changing that (its more like present here cause its 22:15, 27 May 2026 (UTC))

Aren't they all created in the past by the time we read it? Barmar (talk) 22:22, 27 May 2026 (UTC)

It could have been created in the future and then sent back in time. 82.13.184.33 15:07, 28 May 2026 (UTC)

"'North Star'? I guess I'm not familiar with that. What's a 'north'? ... Primary direction, you say? So it's the direction the sun appears every morning?" 2604:2D80:AB87:B700:5456:ED28:D284:B682 23:08, 27 May 2026 (UTC)

They would have been quite familiar with the fact that the Little Bear remained in the same direction all night every night. Though, to avoid confusing them, remember that during the Iron Age, the polar point in the sky would have been closer to Kochab (Beta Ursae Minoris) rather than Polaris (Alpha Ursae Minoris) RegularSizedGuy (talk) 03:43, 28 May 2026 (UTC)

Welll... The Little Bear spun every night, around the (at any given time in history) polar point. Any small amount of interest in the patterns and (if patient, noticable) motion of the stars in a suitably clear night sky would reveal the roughly marked (or rather more unmarked, for those more antipodean) hub of the 'spinning firmament' to which everything (except birds, clouds, 'hairy stars', shooting stars, 'wanderers' and of course Sol and Luna... but pretty much everything else!) seems to be stuck to.

The path of the Sun and the Moon around (or at least close to!) the ecliptic is more important for its seasonal variation. Where the Sun is rising/setting (depending upon your interpretation, either of these could be your prime focus), ever-cycling across the year, is more a time clue (for a given location) than an accurate direction (and possibly latitude) clue when trying to derive your culture's core elements of navigation.

Which is not to say that Sun-chasing (or waiting to see where it popped up, then going that way) might not be part of your over-the-horizon navigation planning, but you had to be wise to the fact that sometimes that would lead you more towards one or othe tropic line than it might do the equator (if you're between the tropics - or varying degrees closer to eventually spiralling in towards the equator if you're currently beyond either tropic).

The presence/absence of some asterisms (either seeing if they appear over the horizon or knowing whether or not they should be in the current night sky at all) might usefully substitute for, or enhance, the concept of the annually changing solar-sunset/-sunrise position, with enough aquired (experienced/learnt) knowledge of these cycles, and clearly it (and posssibly other paleolithic lifehacks) worked well enough for enough proto-polynesian families to make enough successful journeys across enough of the Pacific to have settled so many places so far apart, and likely was also useful for far less expansive trade-routes in other parts of the world where sailing (or walking) in roughlybtue right direction was good enough most of the time, so long as you weren't unlucky and/or perhaps knew how to recognise and avoid particularly troublesome coastlines/etc.

But each culture's travellers probably made use of whatever they had at hand, whether it was lodestones or oases or just following the tracks/milemarkers laid between neighbouring settlements by those already established there. 82.132.238.245 12:23, 28 May 2026 (UTC)

People had been tracking the sun for thousands of years - building megaliths and celebrating solstices, I am sure they had concepts of direction. Lodestones are noted in Greek writing and may have been known earlier. Long distance navigation was also solved in the Bronze Age, in fact you cannot have bronze without shipping tin or copper from one of the few known mines. Definitely no more than a C for History. 92.19.86.70 06:39, 28 May 2026 (UTC)

Surely they would understand the concept of things, like food, being spoiled? Dogman15 (talk) 00:16, 28 May 2026 (UTC)

Agree. Iron-age dad tells a campfire story to his youngest kid, but the chatty older sister blabs out the best parts ahead of time. The concept of spoilers is as old as language, only the English word for it is recent. --2A02:3100:592D:4A00:EE74:8796:90E5:BDAE 13:33, 29 May 2026 (UTC)

I honestly think there should be a category for things common now yet ridiculous then. I've seen 4 comics with that theme already, and there must be more GSLikesCats307 (talk) 09:37, 28 May 2026 (UTC)

The concept of the spoiler probably would only be relevant to someone with a recreational viewpoint and relatively free access to information, something that wouldn't have been common, or even possible, until recent times, except perhaps in limited circumstances with those who were very wealthy and influential. In other cases, such as with the example in the comic, such information would have been highly desirable to pretty much anyone with the ability to understand it and utilize it, and instead it would have been a Disruptive innovation. SammyChips (talk) 16:35, 28 May 2026 (UTC)

Why is the explanation clearly written by an LLM? Half the explanation has nothing to do with anything the comic is about, like time travel paradoxes are not involved at all. 2A00:23C6:AB94:B601:BFF5:69F3:97C5:4571 22:05, 28 May 2026 (UTC)

I think you're mistaking authorship by a (non-coordinating) committee of opinionated and self-identifying 'experts' (I would include myself in that group, BTW) for an authorship by some ineffably complex random-text-generator that has merely been prodded to try to produce patterns of apparent meaning not unlike what many, many different realworld contributors might give. But, more seriously, read the page history look at how it has been edited. It didn't at all just appear due to a single (copypaste from) synthetic source. It's clearly mostly anthropogenic in nature, for most of the the additions, removals and rearrangements that you clearly now feel you want to remove, add to and/or further reshuffle to your own satisfaction.

As to whether time travel paradoxes are involved in this comic... Cueball is (selectively!) worried that he's been giving too much information away, for pretty much that reason (even if his thoughts start to drift away regardint the essential nature of them), so I would think it's perfectly ok to mention some of the the other possibilities (that just by being there he's creating a paradox... either destructively so or creating an ontological-bootstrap one), in passing. Cueball is off on something a bit something to do with binge-watching something, and comically missing the point about everything else thathis Time Travel Tech might have left him involved with.

But you can edit it down, if you wish. That's how wikis work. Though don't be surprised if someone edits it back up again (with or without LLM 'assistance', thought I'd prefer without myself). 81.179.199.253 23:37, 28 May 2026 (UTC)

Yeah it annoyed me too, so I've edited it out a bit. It's still there, but I've made it clear now it's not the subject of the comic GSLikesCats307 (talk) 09:11, 29 May 2026 (UTC)

Made it more neutral, since there's clearly a disagreement on what the comic is mainly 'about' (and it can be 'about' more than one thing at once. 82.13.184.33 10:37, 29 May 2026 (UTC)

You don't need a magnetic compass, or Polynesian knowledge, if you have a Viking sunstone. Whatever that is. Martin (talk) 03:41, 29 May 2026 (UTC)

You'd still need Scandinavian knowledge. It'd be an aid to navigation (as with using an Uunartoq-style sun-disc, perhaps together) to interpret. And (except for areas of c9nfused magnetic declination) a north-pointing-stone (once you know which bit of the stone points north!) is comparatively simple to read a direction from. As with "that bit of starry sky" knowledge. But navigation by solar position (and its best crepuscular proxy, by lunar position plus shape, if the Moon is visible even though the necessary stars are not) has to involve a bit of additional knowledge of when you're observing that, and what adjustments to expectations that implies.

It's all a little more complicated than just using the moss on the trees to close enough find north (or, in modern urban areas, the satellite dishes on the houses to identify south) ...in northen climes, at least. That still needs the knowledge that it can be done, but isn't hard to take on board and use as a quick fix.

Understanding how to get to or from any particular polynesian archipelago, without ending up drifting (aimlessly, or at the very best, misaimed) across far too much of the Pacific, would need a bit more experience and perhaps advice learnt from a prior master-sailor. And tgose that would go viking might not need quite so much additional knowledge 'just' to find the east coast of the Angles' land, but they'd definitely need something like it to get to Iceland or Greenland without too much hit-and-miss. 82.132.238.245 04:58, 29 May 2026 (UTC)

There may be an intentional ambiguity in "my brother was just lost at sea". Cueball seems to interpret it as "lost, perished, dead", explaining the "I'm sorry". But Hairbun may have meant that the brother just temporarily lost his orientation (was "lost" for a while). This would explain why Hairbun seems to be so relaxed about it ("it's ok"). --88.113.67.59 13:42, 29 May 2026 (UTC)
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