1580: Travel Ghost

Explain xkcd: It's 'cause you're dumb.
Jump to: navigation, search
Travel Ghost
And a different ghost has replaced me in the bedroom.
Title text: And a different ghost has replaced me in the bedroom.

[edit] Explanation

A "ghost" is a common term for the recording of a player's best actions in a racing game. The recording is used to create a virtual racer that another player can compete against. The previous player is shown as ghostly and transparent, because it is only a recording of a previous game and it does not interact in any way with the game currently being played. Certain models of cycling also use this concept to motivate athletes while training.

A mapping app, such as Google Maps, attempts to plot the fastest route from one place to another, but there's no way to tell which route is really the fastest without testing it. So, Cueball has created an app that will simulate a number of different routes and produce "ghosts" from them. He hopes to use this app to discover the fastest route by competing against his ghosts like a racing game. He brags about this app to his friend White Hat.

However, the comic takes a turn for the absurd when it depicts actual ghosts competing with him, instead of simulations on his phone. Soon enough, he is fired from work because one of his "ghosts" is more punctual than he is. And even worse his children apparently comes to prefer the more punctual "ghosts" over him as this version of daddy never misses their games. (The girls could be the same as those in the 1659: Tire Swing).

In the title text this is even taken into the bedroom, although it is a different ghost than the one preferred by the children. This is likely a subtle reference to euphemisms for sexual climax, such as "arrival", with delayed ejaculation generally preferred.

It should be noted that this app would not guarantee the minimum travel time. The user doesn't find out which route was fastest until after the first ghost has arrived. But as the current traffic situation will have changed by then, that route will not necessarily still be the fastest.

[edit] Transcript

[Cueball, holding a smartphone, is talking to White Hat.]
Cueball: Lots of apps let you plan your trips using real-time bus, train, and traffic data. They try to predict which route will be faster, but aren't always right.
[Cueball continues to talk off-panel. The text is above a map showing three possible routes with an overlaid Cueball on each; the top and the bottom route and Cueball are faded and the middle is black up until the black Cueball. After that this route is also faded. A black point on the right indicates the destination.]
Cueball (off-panel): Instead of just planning, my new app lets you send "ghost" versions of you along different routes, simulating their travel using the real-time data
[Cueball, again talking to White Hat, holding the smartphone down.]
Cueball: That way, you can see which route turned out to be faster in practice,
Cueball: You can also race your past selves.
[Cueball is getting out of his car holding his smartphone in one hand and a briefcase in the other; A faded out Cueball bicyclist is in front of him to the right. At the top there is a caption in a frame:
Cueball: Ugh, lost to the bike ghost again.
[Cueball with his briefcase is outside a door, holding a key card up to a key reader. On the inside of the door Ponytail is facing the door and points toward the faded version of Cueball also holding a briefcase.]
Cueball: Hey, my key won't work
Ponytail: I'm sorry, but we've decided to replace you. This floaty guy is much more punctual.
Cueball: But...
[Science Girl and another girl with wavy long hair, is holding faded out Cueball's hands. The real Cueball is standing to the right, next to his briefcase on the ground. He is holding his hands out towards his kids.]
Science Girl: Our new dad never misses our games!
Cueball: Nooo!

comment.png add a comment! ⋅ comment.png add a topic (use sparingly)! ⋅ Icons-mini-action refresh blue.gif refresh comments!


Racing Ghosts is a refference to Mario Kart ẞ qwertz (talk) 12:50, 21 September 2015 (UTC)

This seems like a bit of a stretch to me. 13:35, 21 September 2015 (UTC)
It's not a reference to Mario Kart specifically (lots of racing games have ghosts), but that's basically what this is doing - translating the concept of racing ghosts to the real world.-- 13:50, 21 September 2015 (UTC)
Well, there are some fitness running apps that support a ghost runner mode, so you run against your best time and get updates if you are in front or behind of your „ghost“. Without actually being able to prove it, I believe (and always assumed) this idea is actually inspired from racing games like Mario Kart. 13:56, 21 September 2015 (UTC)
Also, see https://en.wikipedia.org/wiki/Time_attack#Video_games sirKitKat (talk) 14:11, 21 September 2015 (UTC)

So in the title text, is he being replaced with the ghost who always *ahem* comes last? --SaturNine (talk) 12:53, 21 September 2015 (UTC)

I agree. 13:36, 21 September 2015 (UTC)
Women prefer men that are stuck in traffic?? 19:17, 21 September 2015 (UTC)
Nah - just someone who takes the "scenic" route. 19:50, 21 September 2015 (UTC)
I love that this could be a reference to the move Ghost. Great. -Jeff (talk) 19:51, 21 September 2015 (UTC)

Is this the first time Cueballs children were shown? ẞ qwertz (talk) 17:22, 21 September 2015 (UTC)

I don't know if it's worth mentioning that this appears to be a width-first (route-)search algorithm. A memory-heavy but guaranteed 'perfect' solver of best routing, at every point of choice (from the very first, how you start the journey), all possible/practical travel options are explored (including taking a journey in the 'wrong' direction, or waiting for the non-stop train that is not the first to arrive, to take advantage of connections with faster transport links), in parallel according to the total time (or other measure of efficiency) yet taken on each iteration. Unless any 'ghost' arrives at a node that has already been visited by a 'ghost', when it need not continue. Eventually, the most efficient son-of-a-son-of-a-son...-of-a-son-of-a-ghost will reach the destination, indicating the 'correct' answer. At least within the limits of the split-and-propogate algorithm, and the amount of parallelisation available to devote to the problem. (See also the multiple-overlayed 'searches' performed by two-minutes-of-Nicholas Cage, in the near-climactic scene in the film 'Next' (beware spoilers!).) 22:38, 21 September 2015 (UTC)

Are you aware if such an app exists in real life? I'd be interested in trying to program one (albeit with less tangible ghosts). LowHangingFruit 14:19, 22 September 2015 (UTC)
This is an extremely easy algorithm to program (I have taught it while teaching AP (high school) computer science), however it isn't an algorithm that will likely be useful to you since it has exponential time complexity. In other words, if there are more than a trivial number of possibilities to be examined, finding the solution through this algorithm would not finish before you were dead. For those of you who are about to say that if we could run a huge bunch of these possibilities in parallel: merging the results, memory management, context switching, and similar things, even if they could be done in constant time would still mean a constant amount of time for each of an exponential set of possibilities. 22:29, 22 September 2015 (UTC)tomb
Can anyone give me a (couple) Wikipedia articles to read, so I can understand this comment? I'm really interested. 18:53, 23 September 2015 (UTC)
Well, Breadth-first searching is probably your first step, then hit the appropriate sidebar for other methods. ('m a particular fan of the A* (A-Star) method, myself, but that's more probably due to my Dwarf Fortress addiction... ;) 14:29, 25 September 2015 (UTC)

Will his children have half-siblings that are fathered by the ghost that has replaced him in the bedroom? Or are ghosts infertile? 04:07, 22 September 2015 (UTC)

Doesn't light do this according to some theory, sending out "investigation waves / photons" to determine the quickest way to get anywhere? I'm no expert on this, just some food for thought... 11:57, 22 September 2015 (UTC)

Not really - or at least not real. There may be some "potential photons" in some attempts to describe some quantum-based theory ... but there will certainly be no investigation photons after wave collapse. -- Hkmaly (talk) 12:12, 22 September 2015 (UTC)
Yes, really. He's doubtless talking about the Pilot Wave interpretation of quantum mechanics [[1]] -- which is controversial but still mainstream, not crackpot gibberish; it was proposed/championed by the illustrious Boehm and Bell. Feynman and his advisor also worked on a similar theory. 23:41, 26 September 2015 (UTC)
"Everything we call real is made of things that cannot be regarded as real." - Niels Bohr. (Whether or not he's ultimately right, it's an explanation.) 13:48, 22 September 2015 (UTC)

If the simulations explore all travel possibilities, how long will it be until bike ghost gets run off the road by bus ghost? Or flattened by texting driver ghost? 12:30, 22 September 2015 (UTC)

This reminds me of an Android (and probably iOS) game "Does Not Commute" which takes the classic 'ghost competitor' behaviour (note:, below, that it's a common thing) and makes them solid. You run (different) 'missions'/commutes across the playing arena with a succession of new vehicles, each time finding that all your previous commutes are happening, simultaneously, creating obstacles and hazards. You can collide with (or end up being run into by) another vehicle, replaying the path you set it upon in a previous round, and this causes you to rebound. (But there's no 'kickback' when contact is made with your prior 'self', which sticks solidly to its pre-played path. Thus no need to deal with contradictions and temporal paradoxes by deflecting a past-self thus potentially changing the entire arena (for good or bad) for every other attempt you made, trying to avoid everything else.) Worth a dabble, perhaps, but don't get addicted to it! 13:48, 22 September 2015 (UTC)

There's actually a very similar mechanism in the game Canvas Rider, where the best times on a track (it's a bike racing game with stick figures) can be clicked and a ghost that takes the same path with the same speed as those people appears and moves while you do. In fact, they actually look somewhat similar to the ghost in panel 4. 13:17, 22 September 2015 (UTC)

I strongly suspect this also references the concept of the Oracle machine as it relates to the NP hardness of the traveling salesman problem. TSP is in the complexity class NP Complete, and part of the most common proof that it is NP hard involves showing that it reduces to a polynomial time algorithm (and hence potentially practically computed) if there exists an oracle that can tell you if a route is optimal (the fastest) in constant time. I have never edited here before and don't know all the etiquette, so I leave it to a more experienced editor to consider this in the main article. The "ghost" would then be related to the Oracle because many real world "oracles" (as in fortune tellers or weird tripping priestesses of Apollo) claim to get answers by talking to ghosts. 22:17, 22 September 2015 (UTC) tomb

I'm also thinking there may be a worthwhile pun in there about the movie Ghost Dad, though I haven't found a suitable setup for that punchline. 21:50, 25 September 2015 (UTC)

Now I want goggles that let me enter my running pace and let me race my ghost. Forever alone. 09:43, 28 September 2015 (UTC)

I don't get how that one ghost has replaced him in the bedroom, since the ghost comes faster than he does! HE HE. 01:15, 5 February 2016 (UTC)

Where in the comic does it say or reference that he lost his job? 16:51, 24 October 2016 (UTC)

Personal tools


It seems you are using noscript, which is stopping our project wonderful ads from working. Explain xkcd uses ads to pay for bandwidth, and we manually approve all our advertisers, and our ads are restricted to unobtrusive images and slow animated GIFs. If you found this site helpful, please consider whitelisting us.

Want to advertise with us, or donate to us with Paypal?