Explain xkcd: It's 'cause you're dumb.
In this comic, which I believe Randall created just to put in "BRB, Killing Hitler", Black Hat creates a one use time machine. Cueball selects the most common suggestion for Time Machine usage "Killing Hitler". Black Hat finally relents and goes to kill Hitler, however, he goes to the year 1945, when Hitler is already in his bunker. Hitler has already committed his atrocities and the war was already turning against him. Later in 1945, he reportedly died by suicide in that very same bunker. The joke in here being that he didn't save any lives or prevent the Holocaust or a global war by killing him in 1945 because he went back in time too late. He needed to go earlier, before his rise to power, like 1932. This is also the point of the image text, which states that you cannot travel back in time unless you know what you will occur.
- [Black Hat and Cueball stand in front of a double door, which bears the label 'TIME door'. Black Hat has his hands on his hips.]
- Black Hat: I finished my time machine, but it's one-use only.
- Cueball: You gotta kill Hitler.
- [Close-up of Black Hat, one hand palm upward.]
- Black Hat: You are you so obsessed with this Hitler guy? We have all of time we could explore!
- [Close-up of Cueball with both hands palm upward.]
- Cueball: He's evil incarnate! He murdered millions and sparked global war! Everyone agrees -- if you get a time machine, you kill Hitler.
- [Black Hat enters the now open Time door as the other man looks on..]
- Black Hat: Fine, fine, I get it! Calm down. - BRB, killing Hitler.
- [Black Hat returns and shuts the door, the other man has outstretched arms.]
- Black Hat: There. Done. Are you happy?
- Cueball: Thank you.
- Black Hat: He was in some kind of bunker. 1945 was loud!
- Cueball: NO!
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Actually, I think the joke here is that Black Hat actually did end Hitler's atrocities, but that history is not actually changeable. Hitler's "suicide" was actually Black Hat killing him. This is then layers with the impossibility of changing history. This would imply that anyone that wants to stop Hitler before he rose to power will be circumvented.
UnaSalusVictis (talk) 01:26, 25 November 2012 (UTC)UnaSalusVictis
- According to all reasonable time travel theories, this makes sense. You cannot go into the past to change things, because the future that exists is a future where you were in the past - you just didn't know it yet because it was in your future. This also applies to the future. Your knowledge of the future cannot possibly change it because your foreknowledge exists in this future. If your foreknowledge made that future not happen, then there would be no need to change it. But the future and the past account for the fact that you were there to change things, even before you ever knew you would be. Ergo, any attempt to change the past will merely result in causing the past to result exactly as it did before. The catch-22 of time travel stories. You can have a fatal flaw, or a fatally uncompelling story. But, all that said, this is a cartoon and not necessarily reliant on reasonable time travel theory.18.104.22.168 07:07, 23 June 2013 (UTC)
- That's exactly my opinion on this topic! Look at this video (Mercedes vs Hitler in the past): [] ~~Muessigb
- But say you could predict what the future would look like if you did nothing (or did not yet have that knowledge). Then by obtaining that knowledge you could then do something you would not have done otherwise and thus change the potential future. With a powerful enough simulator, you might get a good idea of what would happen if no one knew about it, and then decide if something should be changed based on this information. This is what happens in the book Lightning. I do not believe this can be done, but as the future has not happened yet, I do not see the same problems as with traveling back in time. Of course having a good guess of the future is not the same as traveling to it... If you did that, then changing it after you had been there would be troublesome. See for instance Back to the Future 2 and the book mentioned above. --Kynde (talk) 12:44, 6 January 2016 (UTC)
True, killing Hitler before he rose to power and committed all his atrocities would cause a Grandfather paradox... Cueball invented the time machine and send Black Hat back because he wanted Hitler dead, but if Hitler died before that, there would be no reason to invent the time machine and send Black Hat back which ergo cause the initial trip to kill Hitler not possible and ergo Hitler couldn't die before he rises to power and committed his atrocities. 22.214.171.124 01:40, 5 December 2012 (UTC)
- Just for the record, it was Black Hat who invented this time machine! --Kynde (talk) 12:51, 6 January 2016 (UTC)
Maybe in the original timeline, Hitler's atrocities extended beyond 1945. When Black Hat went back in time and assassinated Hitler in 1945, a new time-line was created. When Black Hat returned to the current date, he returned to a different timeline than the one he left. In this timeline (ours), Hitler died in 1945, and because this timeline is based on that fact, Cueball thinks that Black Hat has not changed anything, when in fact, Black Hat's actions created the new timeline. -- mwburden 126.96.36.199 15:00, 7 December 2012 (UTC)
- Except that Hitler would have already been killed in 1945 by Black Hat, only it would have been thought beforehand to be Hitler killing himself as, until the time machine is invented, you wouldn't think that people from the future would be coming from the future to assassinate the opponent. People would assume that Hitler killed himself as that is more plausible than an assassin killing him and then vanishing without a trace. -- Mulan15262 (talk) (please sign your comments with ~~~~)
- Also Cueball would not know that anything had happened if anything had been changed, as his an everyone else life would have changed, and most people born say a few years after the start of the way, would probably not have been born, because everyone else would have done something different if World War II had never happened, and many more people would have lived back then, to make the chance that your parents meet and fall in love much less. And even if they still did, they might have had their children at a different time in their lives! And just a few seconds can matter in which cell will enter the egg...--Kynde (talk) 12:51, 6 January 2016 (UTC)
- The only flaw in that logic is that there's really no way Hitler would have survived the Russian invasion. He was in a bunker, killing himself, because his whole nation and army were crushed. He would have been put on trial and no doubt executed, if not shot by the first soldier who saw him. -HavokTheorem 188.8.131.52 04:30, 9 October 2013 (UTC)
- Thank you for this answer. My faith in explainxkcd contributors was declining rapidly until I reached your comment. 184.108.40.206 20:20, 30 January 2014 (UTC)
- Actually you only think that because Black Hat prevented Mecha Hitler. 220.127.116.11 17:54, 16 December 2015 (UTC)
Was the explanation always as bad as it appears now?? It's awful. 18.104.22.168 01:34, 1 February 2014 (UTC)
First off, in a previous time line he could have escaped to a Moon Base to rebuild his army and destroy the world and Cueball just does not remember that history, just the one where Hitler dies in the bunker. Second, there are many forms of logical time travel. You could jump to a different Now 70 years ago and kill Hitler (assuming he exists) and then come back. Your timeline would not have changed, but the other Now would have a future without Hitler. The good or bad that is achieved is the same, but you get no benefit other then the joy of killing Hitler. And you really should seek professional help for that.--22.214.171.124 18:52, 20 May 2014 (UTC)
- In many stories where this idea is used, you actually go to this alternative time yourself, so when you return the world you return to would be the one where Hitler died. Maybe you were never born in this world, but as you are from another dimension where you did get born, then you can exist in this world instead. --Kynde (talk) 12:51, 6 January 2016 (UTC)
Did Randall at least partly choose Hitler because of the old rumour that he wasn't actually dead (Because hearing the news of his death may have seemed incredulous, and because his body was removed by the Soviets, who never openly revealed information to the West). Sorry about the wordiness of this comment, I hope you'll be able to comprehend it. 126.96.36.199 (talk) (please sign your comments with ~~~~)
- I recommend this short story on time travel: Wikihistory. My favourite quote: "everybody kills Hitler on their first trip". Brilliant, short and nerdy.
- --Lou Crazy (talk) 16:37, 28 September 2015 (UTC)
You are all assuming that the time machine actually works. Why? 188.8.131.52 21:50, 9 November 2017 (UTC)