# What's the status of time travel? **URL:** \ **Category:** Factual Questions\ **Created:** [March 3, 2003, 1:23pm UTC](https://boards.straightdope.com/t/whats-the-status-of-time-travel/158746 "2003-03-03T13:23:46Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![jonpluc](https://avatars.discourse-cdn.com/v4/letter/j/fbc32d/32.png) [@jonpluc](https://boards.straightdope.com/u/jonpluc)\ **Post date:** [March 3, 2003, 8:12pm UTC](https://boards.straightdope.com/t/whats-the-status-of-time-travel/158746/21 "2003-03-03T20:12:31Z")
You need the status on time travel?? Wait, let me check…yes here it is…Nope, still impossible. ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [March 3, 2003, 8:15pm UTC](https://boards.straightdope.com/t/whats-the-status-of-time-travel/158746/22 "2003-03-03T20:15:45Z")
The [Visser](http://www.orionsarm.com/eg/v/Vi-Vn.html#Visser_Decay) virtual particles will close the wormhole before you can kill /become your own grandfather. (nice idea about the silver [balloons](http://boards.straightdope.com/sdmb/showthread.php?s=&postid=3020613#post3020613)- have to try that some time) If Time travel can be done, it will change the past, and continue to do so until time travel is uninvented again. You could call this the Hawking/Niven Chronological Protection Conjecture. ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [March 3, 2003, 9:10pm UTC](https://boards.straightdope.com/t/whats-the-status-of-time-travel/158746/23 "2003-03-03T21:10:00Z")
> [@](#): > > \*Originally posted by Beelzebubba \* > \*\*[nitpick] > The flux capacitor does not _generate_ 1.21 gigawatts, it _requires_ this much power to operate. As this is GD, you’d think we could stick to the facts. > > 😃 \*\* As this is actually GQ - not GD as you indicate - and you are being smarmy, you’d think you would check the fine details of your post. 😃 Also, as per the script, the Flux Capacior GENERATES the 1.21 gigawatts. "Marty: The flux capacitor? Doc: It’s taken me almost 30 years and my entire family fortune to realize the vision of that day. My god has it been that long. I remember when this was farm land as far as the eye could see. Old man peabody owned all of this. He had this crazy idea about breeding… pine trees. Marty: This is, uh, this is heavy duty doc. Does it run like on regular unleaded gasoline? Doc: Unfortunately no. It requires something with a little more kick. Plutonium. Marty: uh, plutonium. Wait a minute, doc, are you tellin me that this sucker is nuclear? Doc: hey, keep rolling, keep rolling there, No, no, no, No, this sucker’s electrical, but it needs a nuclear reaction to generate the 1.21 gigawatts of electricity I need." See, the nuclear reaction allows the flux capacitor to generate the 1.21 gigawatts. ---
**Author:** ![Davebear](https://avatars.discourse-cdn.com/v4/letter/d/bcef8e/32.png) [@Davebear](https://boards.straightdope.com/u/Davebear)\ **Post date:** [March 3, 2003, 9:28pm UTC](https://boards.straightdope.com/t/whats-the-status-of-time-travel/158746/24 "2003-03-03T21:28:23Z")
> [@](#): > > \*Originally posted by Chronos \* > \*\*As for why it’s generally believed to be impossible, the classic example is the “grandfather paradox”. \*\* Actually, this is a classic example of fuzzy thinking. No offense intended to you, **Chronos**. I imagine you were just relaying the concept in the most commonly encountered form. But it’s wrong, as presented. The “grandfather paradox”, along with all the other hypothetical paradoxes (not to be confused with a “pair o’ doxies”, hypothetical or otherwise), are reasons why it might be _a bad idea_, not reasons why it’s _impossible_. They do not prevent us from attempting time travel, should it ever be possible. A paradox may be a bad thing, but it doesn’t proactively enforce the laws of math, physics, or Murphy. ---
**Author:** ![ianzin](https://avatars.discourse-cdn.com/v4/letter/i/ed655f/32.png) [@ianzin](https://boards.straightdope.com/u/ianzin)\ **Post date:** [March 3, 2003, 11:10pm UTC](https://boards.straightdope.com/t/whats-the-status-of-time-travel/158746/25 "2003-03-03T23:10:35Z")
To answer the OP, Time Travel was finally perfected in the year 2107. I’m sorry, but I’m not allowed to tell you any more. Wow, it’s just so cute to use this _keyboard_ and the _internet_. I’ve read about these in history books! ---
**Author:** ![X\_Slayer\_ALE](https://avatars.discourse-cdn.com/v4/letter/x/bbe5ce/32.png) [@X\_Slayer\_ALE](https://boards.straightdope.com/u/X_Slayer_ALE)\ **Post date:** [March 4, 2003, 12:12am UTC](https://boards.straightdope.com/t/whats-the-status-of-time-travel/158746/26 "2003-03-04T00:12:42Z")
As the representative of the Celestial Intervention Agency of Galleyfrea, I place you, **ianzin** , under arrest! Stay at your present temporal coordinates. Do not attempt to activate your trans-temporal device. You are under arrest! ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [August 28, 2018, 9:54pm UTC](https://boards.straightdope.com/t/whats-the-status-of-time-travel/158746/27 "2018-08-28T21:54:08Z")
> [@Earthworm\_Jim](#): > > [nitpick] > The flux capacitor does not _generate_ 1.21 gigawatts, it _requires_ this much power to operate. As this is GD, you’d think we could stick to the facts. > > 😃 Note on inevitable flux capacitor failures, [as reported recently on Boston TV](https://pjmedia.com/instapundit/306027/) as main cause of airplane crash. ---
**Author:** ![Weisshund](https://avatars.discourse-cdn.com/v4/letter/w/ba8739/32.png) [@Weisshund](https://boards.straightdope.com/u/Weisshund)\ **Post date:** [August 29, 2018, 2:35am UTC](https://boards.straightdope.com/t/whats-the-status-of-time-travel/158746/28 "2018-08-29T02:35:01Z")
I suppose forward is in theory possible we move forward now, just at the same pace. If you can move someone at near light speed, send them out 3 years and back not much time will have passed for them btu when they return much will have passed here. or at least that is the theory. If you leave earth in a light speed ship to some distant star, you may still be alive when you get there, but there wont be anyone you know left alive to return to ---
**Author:** ![Measure\_for\_Measure](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/measure_for_measure/32/557_2.png) [@Measure\_for\_Measure](https://boards.straightdope.com/u/Measure_for_Measure)\ **Post date:** [August 29, 2018, 3:00am UTC](https://boards.straightdope.com/t/whats-the-status-of-time-travel/158746/29 "2018-08-29T03:00:21Z")
> [@Chronos](#): > > As for why it’s generally believed to be impossible, the classic example is the “grandfather paradox”. Suppose that I invent a time machine, and go back in time to before my parents were born. I then kill one or more of my grandparents. Now, this means that my parents were never born, and therefore neither was I. But if I was never born, then who was the guy who went back and killed those folks? And if nobody did, then I do exist after all, so why can’t I do it? > > Related to this is the problem of djinns, or effects without external causes. Suppose, for instance, that I’m a little more peaceful in my intentions, and go back to visit Bethoven to discuss his music with him. Of course, I bring along a copy of his famous fifth symphony. But I go back to when he was only still working on the fourth. Well, he takes a look at the sheet music I show him, and he thinks that it’s great. I give him permission to publish it as his own, and a few years later, he does. So where did that music come from? The more general problem is sometimes called the “Changing the past objection to time travel.” It’s not as bad as it looks. Two solutions: the second is more compelling: 1. There are multiple world lines. Grandpa lives in one, dies in another. A: That’s not really time travel. That’s cross multiverse travel, that only appears superficially like time travel. Q: It is! A: It isn’t! 1. True, you can’t go back in time and shoot Grandpa. But you can go back in time and wave at Grandpa, or even yourself. There’s nothing contradictory in that. Ok, what if someone is a great shot and wants to kill their Grandpa? Well who says they could pull it off? From the Stanford Encyclopedia of Philosophy: [INDENT] In order to defend the possibility of time travel in the face of this argument we need to show that time travel is not a sure route to doing the impossible. So, given that a time traveller has gone to the past and is facing Grandfather, what could stop her killing Grandfather? Some science fiction authors resort to the idea of chaperones or time guardians… But it is hard to take these ideas seriously… Fortunately there is a better response—also to be found in the science fiction literature, and brought to the attention of philosophers by Lewis (1976). What would stop the time traveller doing the impossible? She would fail “for some commonplace reason”, as Lewis (1976, 150) puts it. Her gun might jam, a noise might distract her, she might slip on a banana peel, etc. Nothing more than such ordinary occurrences is required to stop the time traveller killing Grandfather. Hence backwards time travel does not entail the occurrence of impossible events—and so the above objection is defused. [/INDENT] Since this is philosophy, there’s more to it of course, discussed here: [Time Travel (Stanford Encyclopedia of Philosophy)](https://plato.stanford.edu/entries/time-travel/) , eg “Another response is that of Vihvelin (1996), who argues that there is no contradiction here because ‘Tim can kill Grandfather’ is simply false (i.e. contra Lewis, there is no legitimate sense in which it is true).” 1. Addenda: The Steins;Gate franchise applies a hybrid model of time travel. ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [August 29, 2018, 6:13am UTC](https://boards.straightdope.com/t/whats-the-status-of-time-travel/158746/30 "2018-08-29T06:13:41Z")
> [@Leo\_Bloom](#): > > Note on inevitable flux capacitor failures, [as reported recently on Boston TV](https://pjmedia.com/instapundit/306027/) as main cause of airplane crash. That darn flux capacitator [sic], always failing when you least expect it. ---
**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:** [August 29, 2018, 6:21am UTC](https://boards.straightdope.com/t/whats-the-status-of-time-travel/158746/31 "2018-08-29T06:21:30Z")
> [@Measure\_for\_Measure](#): > > Ok, what if someone is a great shot and wants to kill their Grandpa? Well who says they could pull it off? From the Stanford Encyclopedia of Philosophy: [INDENT] In order to defend the possibility of time travel in the face of this argument we need to show that time travel is not a sure route to doing the impossible. So, given that a time traveller has gone to the past and is facing Grandfather, what could stop her killing Grandfather? Some science fiction authors resort to the idea of chaperones or time guardians… But it is hard to take these ideas seriously… Fortunately there is a better response—also to be found in the science fiction literature, and brought to the attention of philosophers by Lewis (1976). What would stop the time traveller doing the impossible? She would fail “for some commonplace reason”, as Lewis (1976, 150) puts it. Her gun might jam, a noise might distract her, she might slip on a banana peel, etc. Nothing more than such ordinary occurrences is required to stop the time traveller killing Grandfather. Hence backwards time travel does not entail the occurrence of impossible events—and so the above objection is defused. [/INDENT] Since this is philosophy, there’s more to it of course, discussed here: [Time Travel (Stanford Encyclopedia of Philosophy)](https://plato.stanford.edu/entries/time-travel/) , eg “Another response is that of Vihvelin (1996), who argues that there is no contradiction here because ‘Tim can kill Grandfather’ is simply false (i.e. contra Lewis, there is no legitimate sense in which it is true).” > > 1. Addenda: The Steins;Gate franchise applies a hybrid model of time travel. Lewis clearly stole this from an old Superboy comic, where he goes back to save Lincoln but is thwarted. I hope he gave the comic a reference. The problem is that if she failed she could try again later, and again, and again. And sometimes the presence of an additional factor is likely to change the past. The only stable situation is one where there is no time travel. See Asimov’s **End of Eternity.** Anyhow, the real proof against time travel is the lack of ticket stubs dropped by time travelers at significant events. ---
**Author:** ![Wendell\_Wagner](https://avatars.discourse-cdn.com/v4/letter/w/8491ac/32.png) [@Wendell\_Wagner](https://boards.straightdope.com/u/Wendell_Wagner)\ **Post date:** [August 29, 2018, 6:37am UTC](https://boards.straightdope.com/t/whats-the-status-of-time-travel/158746/32 "2018-08-29T06:37:10Z")
tonbo0422, I’m not sure why you brought up in the OP the matter of playing the grooves of ancient pottery to hear the sounds of what was happening when the pottery was made. There’s nothing about doing that that remotely challenges present science. It may be very difficult, but it’s just as much a part of present science as playing the grooves of a record. Time travel, on the other hand, requires a major revision of modern bases of physics. ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [August 29, 2018, 7:58am UTC](https://boards.straightdope.com/t/whats-the-status-of-time-travel/158746/33 "2018-08-29T07:58:41Z")
> [@Wendell\_Wagner](#): > > tonbo0422, I’m not sure why you brought up in the OP the matter of playing the grooves of ancient pottery to hear the sounds of what was happening when the pottery was made. It should be noted that [tonbo0422](https://boards.straightdope.com/sdmb/member.php) last visited the SDMB in 2006, so he’s not likely to answer you. ---
**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:** [August 29, 2018, 1:04pm UTC](https://boards.straightdope.com/t/whats-the-status-of-time-travel/158746/34 "2018-08-29T13:04:33Z")
> [@Weisshund](#): > > I suppose forward is in theory possible > we move forward now, just at the same pace. > > If you can move someone at near light speed, send them out 3 years and back > not much time will have passed for them btu when they return much will have passed here. > > or at least that is the theory. It’s a theory in the sense that gravity is a theory. Time dilation has been proven experimentally. GPS depends on it. ---
**Author:** ![Wendell\_Wagner](https://avatars.discourse-cdn.com/v4/letter/w/8491ac/32.png) [@Wendell\_Wagner](https://boards.straightdope.com/u/Wendell_Wagner)\ **Post date:** [August 29, 2018, 1:14pm UTC](https://boards.straightdope.com/t/whats-the-status-of-time-travel/158746/35 "2018-08-29T13:14:42Z")
Well, maybe tonbo0422 is a time traveler from the far future who went back to 2003 to start this thread. To tonbo0422, 2003 and 2018 are so long ago that the two years are almost the same amount of time in the past. tonbo0422 has decided to experiment with ancient methods of recording, first checking out pottery grooves and then online message boards. Both are incredibly primitive to tonbo0422. ---
**Author:** ![Omar\_Little](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/omar_little/32/269_2.png) [@Omar\_Little](https://boards.straightdope.com/u/Omar_Little)\ **Post date:** [August 29, 2018, 3:16pm UTC](https://boards.straightdope.com/t/whats-the-status-of-time-travel/158746/36 "2018-08-29T15:16:00Z")
Time traveling zombies would be a great idea for a movie! ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [August 29, 2018, 6:09pm UTC](https://boards.straightdope.com/t/whats-the-status-of-time-travel/158746/37 "2018-08-29T18:09:24Z")
> [@Weisshund](#): > > I suppose forward is in theory possible > we move forward now, just at the same pace. > > If you can move someone at near light speed, send them out 3 years and back > not much time will have passed for them btu when they return much will have passed here. > > or at least that is the theory. > > If you leave earth in a light speed ship to some distant star, you may still be alive when you get there, but there wont be anyone you know left alive to return to It is not theory. That is how it works. Indeed the GPS system in orbit around the earth needs to take relativistic time into account in order to provide accurate data for the system to work. In other words, they are moving through time at a different rate than you and I are and they need to account for that difference. Interestingly the clocks on the satellites run faster than those on earth. Because they are moving so fast that slows their clocks down but that is overwhelmed by them being further out of earth’s gravity well which means their clocks speed up. Their speed slows the clocks down by about 7 microseconds/day while being further out of the gravity well speed them up by 45 microseconds/day so the net result is they run 38 microseconds/day too fast. If not compensated for your reported location would be off by about 10km each day. ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [August 29, 2018, 7:49pm UTC](https://boards.straightdope.com/t/whats-the-status-of-time-travel/158746/38 "2018-08-29T19:49:49Z")
> [@Measure\_for\_Measure](#): > > 1. True, you can’t go back in time and shoot Grandpa. But you can go back in time and wave at Grandpa, or even yourself. There’s nothing contradictory in that. > > Ok, what if someone is a great shot and wants to kill their Grandpa? Well who says they could pull it off? From the Stanford Encyclopedia of Philosophy: [INDENT] In order to defend the possibility of time travel in the face of this argument we need to show that time travel is not a sure route to doing the impossible. So, given that a time traveller has gone to the past and is facing Grandfather, what could stop her killing Grandfather? Some science fiction authors resort to the idea of chaperones or time guardians… But it is hard to take these ideas seriously… Fortunately there is a better response—also to be found in the science fiction literature, and brought to the attention of philosophers by Lewis (1976). What would stop the time traveller doing the impossible? She would fail “for some commonplace reason”, as Lewis (1976, 150) puts it. Her gun might jam, a noise might distract her, she might slip on a banana peel, etc. Nothing more than such ordinary occurrences is required to stop the time traveller killing Grandfather. Hence backwards time travel does not entail the occurrence of impossible events—and so the above objection is defused. [/INDENT] Since this is philosophy, there’s more to it of course, discussed here: [Time Travel (Stanford Encyclopedia of Philosophy)](https://plato.stanford.edu/entries/time-travel/) , eg “Another response is that of Vihvelin (1996), who argues that there is no contradiction here because ‘Tim can kill Grandfather’ is simply false (i.e. contra Lewis, there is no legitimate sense in which it is true).” This can be simply stated as: “You can’t go back in time to kill your Grandfather, because you didn’t. If you had, you would have. But you didn’t, so you won’t and didn’t.” Or another way to put it is that any changes to the past have happened already. They aren’t changes to the past, they’ve always been the past. If you go back in time and step on a butterfly, you already stepped on that butterfly. Another theory is that you can travel into the past and change the past and this creates a whole new timeline. This happens all the time, but no one notices because when the past is changed it is the new present. So people go back to stop Hartler, then they go back to stop Schneider, then they go back to stop Xrrph, then they go back to stop #\*!)(\<. Then eventually somebody goes back in time and makes a change that coincidentally results in the time machine never being invented. This is the timeline we live in. Time travel is possible, but it’s never going to be invented, because if it was someone would eventually change the timeline enough that time travel would never be invented, and that’s the only stable timeline. ---
**Author:** ![davidm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/davidm/32/225_2.png) [@davidm](https://boards.straightdope.com/u/davidm)\ **Post date:** [August 29, 2018, 8:25pm UTC](https://boards.straightdope.com/t/whats-the-status-of-time-travel/158746/39 "2018-08-29T20:25:55Z")
> [@Lemur866](#): > > This can be simply stated as: “You can’t go back in time to kill your Grandfather, because you didn’t. If you had, you would have. But you didn’t, so you won’t and didn’t.” Or another way to put it is that any changes to the past have happened already. They aren’t changes to the past, they’ve always been the past. If you go back in time and step on a butterfly, you already stepped on that butterfly. > > Another theory is that you can travel into the past and change the past and this creates a whole new timeline. This happens all the time, but no one notices because when the past is changed it is the new present. So people go back to stop Hartler, then they go back to stop Schneider, then they go back to stop Xrrph, then they go back to stop #\*!)(\<. Then eventually somebody goes back in time and makes a change that coincidentally results in the time machine never being invented. This is the timeline we live in. Time travel is possible, but it’s never going to be invented, because if it was someone would eventually change the timeline enough that time travel would never be invented, and that’s the only stable timeline. And this would explain the Fermi paradox. The only stable timeline is one where no civilizaton lasts long enough to figure out time travel. This does not bode well for us. ---
**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:** [August 29, 2018, 8:41pm UTC](https://boards.straightdope.com/t/whats-the-status-of-time-travel/158746/40 "2018-08-29T20:41:09Z")
Back when the LHC was firing up, it had a number of setbacks and failures due to a variety of perfectly mundane but nonetheless odd and quirky failures. Some physicists suggested, mostly-facetiously, that a full-power LHC would destroy the Universe somehow or another, and so we were only seeing the a priori improbable timelines where it didn’t reach full power. [Previous page](https://boards.straightdope.com/t/whats-the-status-of-time-travel/158746.md?page=1) [Next page](https://boards.straightdope.com/t/whats-the-status-of-time-travel/158746.md?page=3)