# How quickly and pervasively would the “butterfly effect” happen after a time travel intervention? **URL:** \ **Category:** In My Humble Opinion\ **Created:** [December 3, 2018, 7:59am UTC](https://boards.straightdope.com/t/how-quickly-and-pervasively-would-the-butterfly-effect-happen-after-a-time-travel-intervention/825486 "2018-12-03T07:59:21Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![XT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/xt/32/456_2.png) [@XT](https://boards.straightdope.com/u/XT)\ **Post date:** [December 3, 2018, 5:57pm UTC](https://boards.straightdope.com/t/how-quickly-and-pervasively-would-the-butterfly-effect-happen-after-a-time-travel-intervention/825486/21 "2018-12-03T17:57:36Z")
> [@Thudlow\_Boink](#): > > I think the OP’s point is that they’d be different people. If your conception had been timed just a little bit differently, it would have involved different sperm and/or eggs, and thus a different you. Not in a few months or even a few years…after that though, sure. Other things would have greater impacts that would become cumulative over time. It would certainly be a vastly different world, fast forwarding to today, and I’d guess that none of the people alive today would be alive in the alternative timeline. ---
**Author:** ![Pabitel](https://avatars.discourse-cdn.com/v4/letter/p/bbce88/32.png) [@Pabitel](https://boards.straightdope.com/u/Pabitel)\ **Post date:** [December 3, 2018, 7:56pm UTC](https://boards.straightdope.com/t/how-quickly-and-pervasively-would-the-butterfly-effect-happen-after-a-time-travel-intervention/825486/22 "2018-12-03T19:56:57Z")
I go with the many worlds theory. We already have developed time travel several times but the inventor went back and changed something thereby creating yet another “many world” with a new timeline conforming to those events. This all leaves our timeline intact and with no knowledge of time travel because the inventor will never be seen in our world again. ---
**Author:** ![Ashtura](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ashtura/32/2963_2.png) [@Ashtura](https://boards.straightdope.com/u/Ashtura)\ **Post date:** [December 3, 2018, 8:14pm UTC](https://boards.straightdope.com/t/how-quickly-and-pervasively-would-the-butterfly-effect-happen-after-a-time-travel-intervention/825486/23 "2018-12-03T20:14:21Z")
Honestly, I think it would be huge, pretty quickly. Let’s say Hitler’s killed as a baby. The baby boom might never happen, and even if you delayed people a few seconds from doing the deed, whole other sets of people would be here, or never born. Plus, assuming ww2 never happens, potentially millions of people who died would not have. It would be massive, massive changes, for better or worse. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [December 3, 2018, 8:48pm UTC](https://boards.straightdope.com/t/how-quickly-and-pervasively-would-the-butterfly-effect-happen-after-a-time-travel-intervention/825486/24 "2018-12-03T20:48:50Z")
People talking about the impacts of World War II are missing the scale of the problem. Stopping World War II would obviously change everything, but so would just going back, stepping out of your time machine, sneezing once, and then returning. Anyone conceived more than (at most) a week after that event would be the result of a different sperm cell winning the race, and thus a completely different person. And of _course_ if you re-run history with a completely different set of people, the course is going to be different. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [December 3, 2018, 8:59pm UTC](https://boards.straightdope.com/t/how-quickly-and-pervasively-would-the-butterfly-effect-happen-after-a-time-travel-intervention/825486/25 "2018-12-03T20:59:13Z")
> [@Chronos](#): > > People talking about the impacts of World War II are missing the scale of the problem. Stopping World War II would obviously change everything, but so would just going back, stepping out of your time machine, sneezing once, and then returning. Anyone conceived more than (at most) a week after that event would be the result of a different sperm cell winning the race, and thus a completely different person. And of _course_ if you re-run history with a completely different set of people, the course is going to be different. I kinda sorta follow the principle but not this particular example. How is a sneeze going to affect anyone conceived within a week? I could see how if you stop to ask someone directions it could affect the conception of his child, but “anyone” is pretty sweeping especially if you didn’t even sneeze on anyone, and the scope of such impact would be pretty limited geographically. Your sneeze in Hoboken isn’t going to have any impact on that couple who just went to bed in Sydney. ---
**Author:** ![Mr\_Shine](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mr_shine/32/464_2.png) [@Mr\_Shine](https://boards.straightdope.com/u/Mr_Shine)\ **Post date:** [December 3, 2018, 9:16pm UTC](https://boards.straightdope.com/t/how-quickly-and-pervasively-would-the-butterfly-effect-happen-after-a-time-travel-intervention/825486/26 "2018-12-03T21:16:21Z")
> [@](#): > > I kinda sorta follow the principle but not this particular example. How is a sneeze going to affect anyone conceived within a week? I could see how if you stop to ask someone directions it could affect the conception of his child, but “anyone” is pretty sweeping especially if you didn’t even sneeze on anyone, and the scope of such impact would be pretty limited geographically. Your sneeze in Hoboken isn’t going to have any impact on that couple who just went to bed in Sydney. Jim in Hoboken is distracted by your sneeze so he walks little slower for half a step, he is now a little off. Everybody he encounters on his way to work will also move slightly differently and will also be off. Everybody all these people encounter will also be slightly off. Somebody who is slightly off is going to call their grandparents in Adelaide who will then affect everyone around them. It won’t take long before everybody is somewhat off-kilter. Big changes like getting the right lottery ticket from a lucky dip or not will also add localised extra bangs which will again speed up the ripples. ---
**Author:** ![Alessan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alessan/32/465_2.png) [@Alessan](https://boards.straightdope.com/u/Alessan)\ **Post date:** [December 3, 2018, 9:16pm UTC](https://boards.straightdope.com/t/how-quickly-and-pervasively-would-the-butterfly-effect-happen-after-a-time-travel-intervention/825486/27 "2018-12-03T21:16:54Z")
> [@Pabitel](#): > > I go with the many worlds theory. We already have developed time travel several times but the inventor went back and changed something thereby creating yet another “many world” with a new timeline conforming to those events. This all leaves our timeline intact and with no knowledge of time travel because the inventor will never be seen in our world again. Unless we’re the other world, the world he arrived in. ---
**Author:** ![SlackerInc](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/slackerinc/32/275_2.png) [@SlackerInc](https://boards.straightdope.com/u/SlackerInc)\ **Post date:** [December 3, 2018, 10:18pm UTC](https://boards.straightdope.com/t/how-quickly-and-pervasively-would-the-butterfly-effect-happen-after-a-time-travel-intervention/825486/28 "2018-12-03T22:18:49Z")
> [@Thudlow\_Boink](#): > > I think the OP’s point is that they’d be different people. If your conception had been timed just a little bit differently, it would have involved different sperm and/or eggs, and thus a different you. Yes, quite right. > [@septimus](#): > > Although Lorenz coined the term “butterfly effect,” he may have been inspired by [the 1952 science fiction story by Ray Bradbury, mentioned above by **CalMeacham**](https://web1.nbed.nb.ca/sites/ASD-S/1820/J%20Johnston/short%20stories/A%20Sound%20of%20Thunder%20with%20questions%20--Ray%20Bradbury.pdf): Yes, this was always how I thought of it (having read that story at a pretty young age). I didn’t realize this was not a universally agreed-upon interpretation. Of course, in the Bradbury story, it’s actually taken in a direction whose specifics I don’t really buy, despite their “cool factor”. They don’t go with the “many worlds” theory, so they show things as changing even within the time travelers’ lives. They act as though walking on elevated walkways and not touching anything in dinosaur times would not alter the future, when I agree with those who say even a couple sneezes would do it (though I think they might be overestimating how quickly those changes would ripple through). And in that story, the protagonist comes back and finds some of the letters in the alphabet are different, but the same two candidates are running in the election, with the “bad” one winning in the altered timeline. There’s no way so much would be different and simultaneously so much the same. > [@Chronos](#): > > People talking about the impacts of World War II are missing the scale of the problem. Stopping World War II would obviously change everything, but so would just going back, stepping out of your time machine, sneezing once, and then returning. Anyone conceived more than (at most) a week after that event would be the result of a different sperm cell winning the race, and thus a completely different person. And of _course_ if you re-run history with a completely different set of people, the course is going to be different. So you think a sneeze makes every conception, even those thousands of miles away, different within just a week? I am sympathetic to the general thrust of this argument, but you might be a little more radical than I am. I feel like it might take a few months in that case. Although I suppose maybe it would start to get exponential? That’s probably the argument you’d make, and I could see that. I do think history rerun with different people would still get us to a similar point, though. There would presumably be changes in terminology (I love JAQ’s “urban seamripper”), but I’m not convinced we could go so far as to get to the 21st century without nukes, or even without something pretty similar to an iPhone even if it is called something different. I’m open to persuasion on this though. ---
**Author:** ![clairobscur](https://avatars.discourse-cdn.com/v4/letter/c/839c29/32.png) [@clairobscur](https://boards.straightdope.com/u/clairobscur)\ **Post date:** [December 3, 2018, 11:42pm UTC](https://boards.straightdope.com/t/how-quickly-and-pervasively-would-the-butterfly-effect-happen-after-a-time-travel-intervention/825486/29 "2018-12-03T23:42:14Z")
> [@SlackerInc](#): > > The classic example is killing Hitler, with there being variations from assassinating him in the 1930s to actually killing him as a baby (unsettling though that idea is). > > I find that people usually project out the major historical changes this would cause while assuming the same people would mostly continue to be born unless there was some clear major effect preventing this. I disagree. I think if you went back and assassinated Hitler after he became a well-known world leader, and then went back to the present\*, they would find that virtually no one born ten months or more after the assassination would be the same person. Yes, absolutely agree. Given that we were born because a specific sperm out of millions (or dozens of millions? Don’t know) reached the egg, the slightest change in the father’s day (a slightly different body movement at some point, for instance) would result in someone else (or maybe nobody) being born. Even if you killed a completely anonymous person, newborns would be different people all over the planet within some years and history would change completely as they age. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [December 4, 2018, 12:03am UTC](https://boards.straightdope.com/t/how-quickly-and-pervasively-would-the-butterfly-effect-happen-after-a-time-travel-intervention/825486/30 "2018-12-04T00:03:21Z")
> [@](#): > > So you think a sneeze makes every conception, even those thousands of miles away, different within just a week? I am sympathetic to the general thrust of this argument, but you might be a little more radical than I am. I feel like it might take a few months in that case. Although I suppose maybe it would start to get exponential? That’s probably the argument you’d make, and I could see that. It takes two weeks for weather all around the globe to be completely different. And the weather being different would certainly be enough for different conceptions. That’s just the upper bound for the timescale involved. To be honest, I’m inclined to agree with **eburacum45** that it’d actually only take a time corresponding to the speed of sound. ---
**Author:** ![dorvann](https://avatars.discourse-cdn.com/v4/letter/d/df705f/32.png) [@dorvann](https://boards.straightdope.com/u/dorvann)\ **Post date:** [December 4, 2018, 2:00am UTC](https://boards.straightdope.com/t/how-quickly-and-pervasively-would-the-butterfly-effect-happen-after-a-time-travel-intervention/825486/31 "2018-12-04T02:00:36Z")
My understanding of the butterfly effect is that small random events **can** have an effect on a larger scale not that they **must**. The problem with weather prediction is that there millions of small random events happening on any given day so the cumulative effect of them is what causes the unreliability of forecasting models. So **one** butterfly flapping his wing may effect the weather or it maybe simply be an inconsequential event that won’t effect weather at all. So stepping out of a time machine, sneezing, and then returning is unlikely to cause major changes depending on where it happens. I mean if I went back to 1800 to the South Pole and sneezed, the chances of it having any major effect on the timeline is highly unlikely in my opinion. ---
**Author:** ![SlackerInc](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/slackerinc/32/275_2.png) [@SlackerInc](https://boards.straightdope.com/u/SlackerInc)\ **Post date:** [December 4, 2018, 11:11am UTC](https://boards.straightdope.com/t/how-quickly-and-pervasively-would-the-butterfly-effect-happen-after-a-time-travel-intervention/825486/32 "2018-12-04T11:11:10Z")
The last two posts lay out the contours of a fascinating debate! I’m all the more intrigued because I’m honestly not sure who’s right. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [December 4, 2018, 12:21pm UTC](https://boards.straightdope.com/t/how-quickly-and-pervasively-would-the-butterfly-effect-happen-after-a-time-travel-intervention/825486/33 "2018-12-04T12:21:53Z")
If we’re stepping out of time machines, sneezing, then returning home, maybe we ought to rename it The Gesundheit Effect. ---
**Author:** ![Just\_Asking\_Questions](https://avatars.discourse-cdn.com/v4/letter/j/ba9def/32.png) [@Just\_Asking\_Questions](https://boards.straightdope.com/u/Just_Asking_Questions)\ **Post date:** [December 4, 2018, 2:30pm UTC](https://boards.straightdope.com/t/how-quickly-and-pervasively-would-the-butterfly-effect-happen-after-a-time-travel-intervention/825486/34 "2018-12-04T14:30:15Z")
One could postulate that sneezing is not required. the simple act of being there should be enough. When you arrive in the past, you displace the air there. You cause a slight increase in air pressure, which will radiate out. Stepping on grass alters the local wind resistance. Stepping on snow at the south pole creates a local warm spot, which could lead to melting of the glacier in a cascade effect. My theory about the Guardian of Forever isn’t that some giant cataclysmic war destroyed the civilization on that planet, but someone on that planet used it and did the equivalent of stepping on an ancient butterfly. The Guardian survives because it exists outside of time. And that butterfly effect is “still” affecting the universe, and Earth as well. Earth almost got destroyed. Spock was never born, and some Andorian was the first officer of the Enterprise. It’s just best to stay home. Too dangerous! ---
**Author:** ![Tibby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tibby/32/17030_2.png) [@Tibby](https://boards.straightdope.com/u/Tibby)\ **Post date:** [December 4, 2018, 3:09pm UTC](https://boards.straightdope.com/t/how-quickly-and-pervasively-would-the-butterfly-effect-happen-after-a-time-travel-intervention/825486/35 "2018-12-04T15:09:58Z")
> [@SlackerInc](#): > > The last two posts lay out the contours of a fascinating debate! I’m all the more intrigued because I’m honestly not sure who’s right. I believe there are many events that would lead to profound changes world-wide. Killing baby Hitler being one example. But, I also believe there are many events that would have little to no effect on a large scale. Sneezing on the North pole being one example. It’s the types of events between these two extreme examples where I believe things can go either way. Let’s take, as an example, a guy walking down the sidewalk who in this timeline is going to impregnate his wife in one weeks’ time and she will have a baby named Billy 9 months later. Let’s make an alternate timeline, with the only change being that the guy stops for 15 seconds to look at a bird. He then proceeds on his way to his original destination. Will stopping to look at the bird change the baby in any way? Well, it could—perhaps that 15 second delay causes the guy to be crushed by an anvil that falls from a second floor window as he passes under. Or, if the guy was on his way to impregnate his wife immediately after his walk, I believe his sperm may be arranged a little differently due to the delay causing Billy to be someone else. But, the guy isn’t on schedule to knock up his wife for another week. There will be many events occurring in this guy’s life before he and his wife do the baby-making bumping of uglies. Maybe the first event after his walk was a little delayed, but he got back on schedule for the event after that … and all the events after that were on schedule and unaffected by the bird-watching delay. So, when the couple climb into bed and have sex on the fateful evening, are the 2 timelines out of sync in any way one week after the changed event? Not unless the guy picks that time to tell his wife about the weird-looking bird he saw and she falls asleep. Otherwise, I believe 2 Billies will be born with identical DNA. In this case, the more time between the changed event and the resultant outcome caused self-correction and re-syncing. That’s how I see it, anyway. ---
**Author:** ![SlackerInc](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/slackerinc/32/275_2.png) [@SlackerInc](https://boards.straightdope.com/u/SlackerInc)\ **Post date:** [December 4, 2018, 3:36pm UTC](https://boards.straightdope.com/t/how-quickly-and-pervasively-would-the-butterfly-effect-happen-after-a-time-travel-intervention/825486/36 "2018-12-04T15:36:07Z")
I can’t agree with that. I seriously doubt the same sperm will fertilize that egg (which will be the same) unless his every motion over that week was identical. Even if the change doesn’t occur until partway through intercourse, his ejaculating a millisecond earlier or later, or in a position that is changed by a millimeter, will totally change which sperm (if any) gets to the egg. ---
**Author:** ![phreesh](https://avatars.discourse-cdn.com/v4/letter/p/9fc29f/32.png) [@phreesh](https://boards.straightdope.com/u/phreesh)\ **Post date:** [December 4, 2018, 4:22pm UTC](https://boards.straightdope.com/t/how-quickly-and-pervasively-would-the-butterfly-effect-happen-after-a-time-travel-intervention/825486/37 "2018-12-04T16:22:51Z")
> [@Chronos](#): > > People talking about the impacts of World War II are missing the scale of the problem. Stopping World War II would obviously change everything, but so would just going back, stepping out of your time machine, sneezing once, and then returning. Anyone conceived more than (at most) a week after that event would be the result of a different sperm cell winning the race, and thus a completely different person. And of _course_ if you re-run history with a completely different set of people, the course is going to be different. I’m not sure I agree with you. There is something to be said for the ‘sweep of time’. Hitler didn’t factor in World War I, which set the stage for a desperate and angry Germany. Arguably, SOMEONE would have set that match on fire, even if Hitler was never born. And inconsequential things happen all the time. Like, ALL THE TIME. Things may be different, but the ‘averaging’ of events would tend to bring larger movements together regardless of the introduction of a sneeze or not. ---
**Author:** ![Ashtura](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ashtura/32/2963_2.png) [@Ashtura](https://boards.straightdope.com/u/Ashtura)\ **Post date:** [December 4, 2018, 4:51pm UTC](https://boards.straightdope.com/t/how-quickly-and-pervasively-would-the-butterfly-effect-happen-after-a-time-travel-intervention/825486/38 "2018-12-04T16:51:18Z")
> [@phreesh](#): > > I’m not sure I agree with you. There is something to be said for the ‘sweep of time’. Hitler didn’t factor in World War I, which set the stage for a desperate and angry Germany. Arguably, SOMEONE would have set that match on fire, even if Hitler was never born. > > And inconsequential things happen all the time. Like, ALL THE TIME. Things may be different, but the ‘averaging’ of events would tend to bring larger movements together regardless of the introduction of a sneeze or not. Right, but even if WWII still ended up happening, but in a slightly different way, it still would cause massive changes. Certainly having a whole different leadership with likely at least slightly different timelines would result in massive changes. ---
**Author:** ![Quimby](https://avatars.discourse-cdn.com/v4/letter/q/22d042/32.png) [@Quimby](https://boards.straightdope.com/u/Quimby)\ **Post date:** [December 4, 2018, 7:10pm UTC](https://boards.straightdope.com/t/how-quickly-and-pervasively-would-the-butterfly-effect-happen-after-a-time-travel-intervention/825486/39 "2018-12-04T19:10:54Z")
I have it on good authority that someone stepped on a butterfly hunting a Dinosaur and that’s how Trump won in this timeline. ---
**Author:** ![ExTank](https://avatars.discourse-cdn.com/v4/letter/e/35a633/32.png) [@ExTank](https://boards.straightdope.com/u/ExTank)\ **Post date:** [December 4, 2018, 10:49pm UTC](https://boards.straightdope.com/t/how-quickly-and-pervasively-would-the-butterfly-effect-happen-after-a-time-travel-intervention/825486/40 "2018-12-04T22:49:19Z")
> [@Cheesesteak](#): > > I don’t believe in the idea of a Clockwork Universe. If a time traveler were to go back to a particular date, I think it has the effect of restarting the timeline from that date, and all events that follow may be different based on natural randomness of action. > > For example, if the timeline were restarted before a game of Monopoly, would every subsequent throw of the dice be identical from the first playing? I see no reason why it should be. If it was, then one should be able to predict every throw of that game from the initial conditions, since that is exactly where we are resetting the timeline. > > Some things may stay the same, if you restart the timeline in 1975, Microsoft might still wind up a big deal, but there’s little chance for Google since the two founders would have been babes, and it’s unlikely that they would come together many years later to create the same company as the first time around. This. The chance of any one specific individual emerging from any given reproductive act may not be “Lottery Odds,” but it’s probably in the ballpark. For example, killing baby Hitler via time travel doesn’t get the Austro-Hungarian Empire out of the Balkans, but Gavrilo Princip probably doesn’t get to take the shot at Archduke Ferdinand. Still, the Serbian movement might still get him, using someone else willing to be a martyr for the cause, and you might still have WWI; the politics/culture/social pressures were still there. SO let’s say WWI goes ahead, along the same general lines as original timeline. Does the Triple Entente still win? Does Kapitänleutnant Walther Schwieger of the U-20 still sink the Lusitania, bringing America into the war? After all, he may (probably) now has a different weapons officer, and maybe this time his firing solution is off, and misses the Lusitania. Or, being low on fuel (like in the original timeline), he instead decides to return to port for resupply, thereby missing the Lusitania entirely. Neat fodder for alt-history fans. [Previous page](https://boards.straightdope.com/t/how-quickly-and-pervasively-would-the-butterfly-effect-happen-after-a-time-travel-intervention/825486.md?page=1) [Next page](https://boards.straightdope.com/t/how-quickly-and-pervasively-would-the-butterfly-effect-happen-after-a-time-travel-intervention/825486.md?page=3)