# Fermi's Paradox and Time Travel. **URL:** \ **Category:** Great Debates\ **Created:** [February 10, 2011, 6:01am UTC](https://boards.straightdope.com/t/fermis-paradox-and-time-travel/570867 "2011-02-10T06:01:44Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![DrFidelius](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/drfidelius/32/3447_2.png) [@DrFidelius](https://boards.straightdope.com/u/DrFidelius)\ **Post date:** [February 16, 2011, 6:09pm UTC](https://boards.straightdope.com/t/fermis-paradox-and-time-travel/570867/41 "2011-02-16T18:09:32Z")
> [@kaylasdad99](#): > > Okay, I can’t resist any longer; I’m tellin’ him. > > **Jim B** , _all_ of us are the time tourists. You, personally, are one of only 435,016 people currently on the planet who originated in this timeline. And you’re the only one on the SDMB. That’s it. You’re being written up for deliberately immanentizing the eschaton. You’ll be lucky if they allow you anywhen downline of the Permian for the next few cycles. ---
**Author:** ![RitterSport](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rittersport/32/6326_2.png) [@RitterSport](https://boards.straightdope.com/u/RitterSport)\ **Post date:** [February 16, 2011, 6:22pm UTC](https://boards.straightdope.com/t/fermis-paradox-and-time-travel/570867/42 "2011-02-16T18:22:32Z")
> [@kaylasdad99](#): > > Okay, I can’t resist any longer; I’m tellin’ him. > > **Jim B** , _all_ of us are the time tourists. You, personally, are one of only 435,016 people currently on the planet who originated in this timeline. And you’re the only one on the SDMB. > [@DrFidelius](#): > > That’s it. You’re being written up for deliberately immanentizing the eschaton. You’ll be lucky if they allow you anywhen downline of the Permian for the next few cycles. This board is teh awesome. _sniff_ ---
**Author:** ![kaylasdad99](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kaylasdad99/32/3398_2.png) [@kaylasdad99](https://boards.straightdope.com/u/kaylasdad99)\ **Post date:** [February 16, 2011, 6:43pm UTC](https://boards.straightdope.com/t/fermis-paradox-and-time-travel/570867/43 "2011-02-16T18:43:09Z")
> [@DrFidelius](#): > > That’s it. You’re being written up for deliberately immanentizing the eschaton. You’ll be lucky if they allow you anywhen downline of the Permian for the next few cycles. Meh. I’ll deal. I remanticipate that as one of the most fun extinction events I’ll have ever will been involved in starting… 🆒 ---
**Author:** ![BMalion](https://avatars.discourse-cdn.com/v4/letter/b/e274bd/32.png) [@BMalion](https://boards.straightdope.com/u/BMalion)\ **Post date:** [February 16, 2011, 6:58pm UTC](https://boards.straightdope.com/t/fermis-paradox-and-time-travel/570867/44 "2011-02-16T18:58:23Z")
Where’s John Titor when you need him? ---
**Author:** ![flight](https://avatars.discourse-cdn.com/v4/letter/f/bbce88/32.png) [@flight](https://boards.straightdope.com/u/flight)\ **Post date:** [February 16, 2011, 7:02pm UTC](https://boards.straightdope.com/t/fermis-paradox-and-time-travel/570867/45 "2011-02-16T19:02:09Z")
> [@kaylasdad99](#): > > Meh. I’ll deal. I remanticipate that as one of the most fun extinction events I’ll have ever will been involved in starting… 🆒 Thank you Dr. Streetmentioner. ---
**Author:** ![DrFidelius](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/drfidelius/32/3447_2.png) [@DrFidelius](https://boards.straightdope.com/u/DrFidelius)\ **Post date:** [February 16, 2011, 7:12pm UTC](https://boards.straightdope.com/t/fermis-paradox-and-time-travel/570867/46 "2011-02-16T19:12:57Z")
> [@kaylasdad99](#): > > Meh. I’ll deal. I remanticipate that as one of the most fun extinction events I’ll have ever will been involved in starting… 🆒 The clam bakes alone will not have been believable if we hadn’t been then for at least five iterations. ---
**Author:** ![kaylasdad99](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kaylasdad99/32/3398_2.png) [@kaylasdad99](https://boards.straightdope.com/u/kaylasdad99)\ **Post date:** [February 16, 2011, 7:17pm UTC](https://boards.straightdope.com/t/fermis-paradox-and-time-travel/570867/47 "2011-02-16T19:17:45Z")
Conceded. But at least you can’t deny me the engrams I’ve already internalized. 😛 ---
**Author:** ![ralph124c](https://avatars.discourse-cdn.com/v4/letter/r/8797f3/32.png) [@ralph124c](https://boards.straightdope.com/u/ralph124c)\ **Post date:** [February 17, 2011, 6:49am UTC](https://boards.straightdope.com/t/fermis-paradox-and-time-travel/570867/48 "2011-02-17T06:49:48Z")
“there was a young lady named Bright Who Travelled much faster than light She set out one day, in a relative way… and returned home the previous night” This poem summarizes the absurdity of time travel. Results CANNOT precede actions-time travel means that causality is violated. Time flows in only one direction, and cannot be made to reverse. ---
**Author:** ![Nars\_Glinley](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nars_glinley/32/8177_2.png) [@Nars\_Glinley](https://boards.straightdope.com/u/Nars_Glinley)\ **Post date:** [February 18, 2011, 7:47pm UTC](https://boards.straightdope.com/t/fermis-paradox-and-time-travel/570867/49 "2011-02-18T19:47:54Z")
[Scotty] I can’t change the laws of poetry. [/Scotty] ---
**Author:** ![Czarcasm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/czarcasm/32/4050_2.png) [@Czarcasm](https://boards.straightdope.com/u/Czarcasm)\ **Post date:** [February 18, 2011, 7:57pm UTC](https://boards.straightdope.com/t/fermis-paradox-and-time-travel/570867/50 "2011-02-18T19:57:38Z")
If you travel to the future at a pace faster than it is being created, you might want to hold your breath…because you will be the only matter there. ---
**Author:** ![Grrr](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/grrr/32/146_2.png) [@Grrr](https://boards.straightdope.com/u/Grrr)\ **Post date:** [February 20, 2011, 3:22pm UTC](https://boards.straightdope.com/t/fermis-paradox-and-time-travel/570867/51 "2011-02-20T15:22:06Z")
> [@John\_DiFool](#): > > [Cue the old lady who was apparently on her cell phone in a 1920’s movie](http://cubiclebot.com/videos/time-traveler-spotted-in-charlie-chaplins-1928-film-the-circus/)… **John** , I hope you don’t mind but I’m going to shamelessly steal your link and post it in **IMHO**. cuz’ I want to talk about this and not derail _this_ thread. [Linky](http://boards.straightdope.com/sdmb/showthread.php?t=597838) ---
**Author:** ![Jake](https://avatars.discourse-cdn.com/v4/letter/j/f475e1/32.png) [@Jake](https://boards.straightdope.com/u/Jake)\ **Post date:** [February 20, 2011, 9:20pm UTC](https://boards.straightdope.com/t/fermis-paradox-and-time-travel/570867/52 "2011-02-20T21:20:49Z")
> [@Susanann](#): > > Amazing! It can’t be a cellphone, of course. The technology to support it just isn’t there in 1920. I think it’s just a communication device to talk to the director, like a walkie-talkie or something. Just sayin’. ---
**Author:** ![Czarcasm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/czarcasm/32/4050_2.png) [@Czarcasm](https://boards.straightdope.com/u/Czarcasm)\ **Post date:** [February 20, 2011, 9:29pm UTC](https://boards.straightdope.com/t/fermis-paradox-and-time-travel/570867/53 "2011-02-20T21:29:01Z")
> [@Shakes](#): > > **John** , I hope you don’t mind but I’m going to shamelessly steal your link and post it in **IMHO**. cuz’ I want to talk about this and not derail _this_ thread. > > [Linky](http://boards.straightdope.com/sdmb/showthread.php?t=597838) [Previous linky on same subject.](http://boards.straightdope.com/sdmb/showthread.php?t=583094&highlight=Charlie+Chaplin) ---
**Author:** ![kun11](https://avatars.discourse-cdn.com/v4/letter/k/91b2a8/32.png) [@kun11](https://boards.straightdope.com/u/kun11)\ **Post date:** [February 21, 2011, 12:33am UTC](https://boards.straightdope.com/t/fermis-paradox-and-time-travel/570867/54 "2011-02-21T00:33:33Z")
> [@DrFidelius](#): > > That’s it. You’re being written up for deliberately immanentizing the eschaton. You’ll be lucky if they allow you anywhen downline of the Permian for the next few cycles. Anywhen:p I think I have a new favourite word:D ---
**Author:** ![Naxos](https://avatars.discourse-cdn.com/v4/letter/n/50afbb/32.png) [@Naxos](https://boards.straightdope.com/u/Naxos)\ **Post date:** [February 21, 2011, 12:44am UTC](https://boards.straightdope.com/t/fermis-paradox-and-time-travel/570867/55 "2011-02-21T00:44:04Z")
> [@Jim\_B](#): > > I don’t know if Fermi’s Paradox is the right term, but seems to apply here: If time travel is possible (a _big_ “if” I realize), then where are all the tourists from the future? I’m sure others have pointed out that time travel may have a starting point in a future time t + A where t is now and A is some future time. So time tourists can go from t + A + T to any time B \>= t + A But time flexibility may be observational and not physical. Meaning, no physical body can go in the past or in the future in time, but that a human, or an object, can _observe_ the past and/or the future. ---
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [February 22, 2011, 10:05pm UTC](https://boards.straightdope.com/t/fermis-paradox-and-time-travel/570867/56 "2011-02-22T22:05:37Z")
> [@Steve\_MB](#): > > If time travel into the past prior to the creation of the time machine is possible and the outcome of events is not fixed, there is a risk of altering history in a way that erases the machine from existence. As the number of trips increases, the probability of this approaches one: Exactly. Time travel is trivially easy and there are hundreds of different ways to travel back in time. But there exists the remote trillion-to-one possibility that none of these methods were discovered. Everytime anyone travels back in time, they change history. What with time travel being so easy, history is constantly being changed all the time. It gets changed millions of times - billions of time - trillions of times. Then at some point, history chances upon the remote possibility that time travel was never discovered. And that’s when it all stops and no further changes occur. ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [February 23, 2011, 9:34pm UTC](https://boards.straightdope.com/t/fermis-paradox-and-time-travel/570867/57 "2011-02-23T21:34:30Z")
Another possibility is that something like Cantor’s Diagonal applies to alternate timelines: there are infinitely more timelines where time travel does not take place then timelines where it does. So even if time travel is possible, the chances of observing it happening approach zero. ---
**Author:** ![Voyager](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/voyager/32/133_2.png) [@Voyager](https://boards.straightdope.com/u/Voyager)\ **Post date:** [February 23, 2011, 11:40pm UTC](https://boards.straightdope.com/t/fermis-paradox-and-time-travel/570867/58 "2011-02-23T23:40:31Z")
> [@DrFidelius](#): > > That’s it. You’re being written up for deliberately immanentizing the eschaton. You’ll be lucky if they allow you anywhen downline of the Permian for the next few cycles. - pulls out my “Don’t Let **Them** Immanetize the Eschaton” button from the Our People’s Underworld issue of National Review from 1967 or so. \* ---
**Author:** ![jackdavinci](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jackdavinci/32/3259_2.png) [@jackdavinci](https://boards.straightdope.com/u/jackdavinci)\ **Post date:** [February 23, 2011, 11:48pm UTC](https://boards.straightdope.com/t/fermis-paradox-and-time-travel/570867/59 "2011-02-23T23:48:39Z")
The leading three theories are: 1. Branching universe - time travel just brings you to a different part of the multiverse 2. Range problem - there are several theoretical models of time travel that only work as far into the past as the time travel was created (since it’s like a door or tunnel). 3. Time cops - time travelers are carefully regulated. ---
**Author:** ![The\_Tao\_s\_Revenge](https://avatars.discourse-cdn.com/v4/letter/t/73ab20/32.png) [@The\_Tao\_s\_Revenge](https://boards.straightdope.com/u/The_Tao_s_Revenge)\ **Post date:** [February 24, 2011, 1:41am UTC](https://boards.straightdope.com/t/fermis-paradox-and-time-travel/570867/60 "2011-02-24T01:41:57Z")
Another possibility is a time barrier. A natural or artificial point in time that can’t be traveled through, though travel on either side is possible. Pass that and suddenly all the tourists show up. [Previous page](https://boards.straightdope.com/t/fermis-paradox-and-time-travel/570867.md?page=2)