# Time Travel, Space and Relativity **URL:** \ **Category:** In My Humble Opinion\ **Created:** [July 17, 2022, 12:29am UTC](https://boards.straightdope.com/t/time-travel-space-and-relativity/968066 "2022-07-17T00:29:26Z")\ **Posts on this page:** 15\ **Page:** 6
**Author:** ![Buck\_Godot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/buck_godot/32/6573_2.png) [@Buck\_Godot](https://boards.straightdope.com/u/Buck_Godot)\ **Post date:** [July 19, 2022, 3:00am UTC](https://boards.straightdope.com/t/time-travel-space-and-relativity/968066/101 "2022-07-19T03:00:12Z")
Awesome, thanks for the link. 😁 ---
**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:** [July 19, 2022, 3:08am UTC](https://boards.straightdope.com/t/time-travel-space-and-relativity/968066/102 "2022-07-19T03:08:40Z")
Thanks! I was looking for that earlier but didn’t remember enough to be able to find it. Bookmarked now. ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [July 19, 2022, 3:17am UTC](https://boards.straightdope.com/t/time-travel-space-and-relativity/968066/103 "2022-07-19T03:17:06Z")
> [@Whack-a-Mole](#): > > Thanks! I was looking for that earlier but didn’t remember enough to be able to find it. [My Google-Fu](https://www.google.com/search?q=All+time+travellers+kill+hitler+short+story) is stronger than yours! ---
**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:** [July 19, 2022, 7:35am UTC](https://boards.straightdope.com/t/time-travel-space-and-relativity/968066/104 "2022-07-19T07:35:10Z")
> [@Just\_Asking\_Questions](#): > > Any time travel violates conservation of matter - for a while. > You take your 1000 lb time machine and jump ahead 40 years. For those 40 years, the universe is missing 1000lb of matter. > Or you travel 40 years into the past, and for as long as you are there, the universe has an extra 1000lbs.\* One of the many reasons time travel is a bad idea. If the universe allows both time travel and arbitrarily advanced civilisations, some of those advanced civilisations could persist into the long, dark, energy-scarce deserts of the Heat Death of the Universe. I suspect these advanced civilisations would prefer to be in the energy-rich, dense regions of the early universe; if they have time travel they will come back in time and increase the population, and the mass of the early universe, over and over again. Eventually the early universe will have enough mass to recollapse in upon itself in a big crunch. This is a historical timeline, or series of events, I wouldn’t recommend. Almost every universe that includes time travel seems to end up in chaos, collapse, or inescapable predeterminism. ---
**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:** [July 19, 2022, 2:15pm UTC](https://boards.straightdope.com/t/time-travel-space-and-relativity/968066/105 "2022-07-19T14:15:02Z")
> [@eburacum45](#): > > Eventually the early universe will have enough mass to recollapse in upon itself in a big crunch. That’s a fascinating idea I hadn’t considered. It’s the logical extension of the idea of 400,000 people time traveling to Germany 1932 with rifles. It could go the other way - these far future time travelers might just come back in time and steal some stars. One or two every 15 billion years might be sufficient. Especially if you spread out your stealing to only one from any galactic cluster. It’s probably better to be a race in an empty universe. No threats. ---
**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:** [July 19, 2022, 2:29pm UTC](https://boards.straightdope.com/t/time-travel-space-and-relativity/968066/106 "2022-07-19T14:29:10Z")
If time travel is possible, it has never been discovered, nor will it be discovered in our particular timeline. If it was, our history would be continuously changing and we would have evidence of that occurring. The “best” we can hope for is that in a Many-Worlds Universe, time travel was/will be discovered in timelines other than ours. ---
**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:** [July 19, 2022, 8:40pm UTC](https://boards.straightdope.com/t/time-travel-space-and-relativity/968066/107 "2022-07-19T20:40:18Z")
> [@Tibby](#): > > If time travel is possible, it has never been discovered, nor will it be discovered in our particular timeline. If it was, our history would be continuously changing and we would have evidence of that occurring. Would we have evidence? If the timeline changed then we change with it and will never know. Maybe someone changed time and you winked into existence 10 seconds ago but you’d never know it. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [July 19, 2022, 9:16pm UTC](https://boards.straightdope.com/t/time-travel-space-and-relativity/968066/108 "2022-07-19T21:16:45Z")
It’s very dangerous to jump to the past with a fixed place single source time machine. You don’t know if that past will ever lead to a future with that time machine. Fixed location time machines are the most hazardous type, often leading to time travelers leaping from time period to time period in an attempt to find their way back to their original time line. Travel into the future seems to be impossible with that kind of machine for some reason. Recursive time machines are the safest variety. These time machines travel through time along with their payload. As long as you have sufficient power available you can always get back to your own timeline since your time machine will exist there some day. I would suggest taking some alternate power source when you travel, something like a small steam driven generator with multiple fuel options. Caution! All time travel is dangerous! Only trained experts should travel in time. Do not try DIY microwave transformer hacks to make your own time machine. ---
**Author:** ![mjmlabs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mjmlabs/32/69_2.png) [@mjmlabs](https://boards.straightdope.com/u/mjmlabs)\ **Post date:** [July 19, 2022, 9:33pm UTC](https://boards.straightdope.com/t/time-travel-space-and-relativity/968066/109 "2022-07-19T21:33:07Z")
> [@eburacum45](#): > > If the universe allows both time travel and arbitrarily advanced civilisations, some of those advanced civilisations could persist into the long, dark, energy-scarce deserts of the Heat Death of the Universe. > > I suspect these advanced civilisations would prefer to be in the energy-rich, dense regions of the early universe; if they have time travel they will come back in time … Wasn’t that a gag in some humorous sci-fi? (Knowing my library, likely from Douglas Adams or Terry Pratchett, but maybe not.) “We” travel back in time to loot the past’s resources, only to find that those bastards from the future (also “us”) have already looted them, because (wait for it) _they got there first_. Boffo laffs! ---
**Author:** ![Moriarty](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/moriarty/32/49_2.png) [@Moriarty](https://boards.straightdope.com/u/Moriarty)\ **Post date:** [July 19, 2022, 10:43pm UTC](https://boards.straightdope.com/t/time-travel-space-and-relativity/968066/110 "2022-07-19T22:43:45Z")
> [@Whack-a-Mole](#): > > Maybe someone changed time and you winked into existence 10 seconds ago but you’d never know it. Or last Thursday (my son likes this one). > **[What is last thursdayism?](https://medium.com/mondo/what-is-last-thursdayism-db9d16b4d76a)** > > Short answer > World was created last Thursday. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [July 19, 2022, 10:57pm UTC](https://boards.straightdope.com/t/time-travel-space-and-relativity/968066/111 "2022-07-19T22:57:06Z")
> [@TriPolar](#): > > I would suggest taking some alternate power source when you travel, something like a small steam driven generator with multiple fuel options. Many time travellers get good results with a Mr Fusion. Those work with common household waste, so refueling is usually not a problem. ---
**Author:** ![msmith537](https://avatars.discourse-cdn.com/v4/letter/m/d9b06d/32.png) [@msmith537](https://boards.straightdope.com/u/msmith537)\ **Post date:** [July 20, 2022, 2:06am UTC](https://boards.straightdope.com/t/time-travel-space-and-relativity/968066/112 "2022-07-20T02:06:15Z")
> [@mjmlabs](#): > > > [@eburacum45](#): > > > > If the universe allows both time travel and arbitrarily advanced civilisations, some of those advanced civilisations could persist into the long, dark, energy-scarce deserts of the Heat Death of the Universe. > > > > I suspect these advanced civilisations would prefer to be in the energy-rich, dense regions of the early universe; if they have time travel they will come back in time … > > Wasn’t that a gag in some humorous sci-fi? (Knowing my library, likely from Douglas Adams or Terry Pratchett, but maybe not.) “We” travel back in time to loot the past’s resources, only to find that those bastards from the future (also “us”) have already looted them, because (wait for it) _they got there first_. Boffo laffs! There was an episode of South Park, “Goobacks”, where time travelers from the future were migrating to South Park, with predictable results. ---
**Author:** ![mjmlabs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mjmlabs/32/69_2.png) [@mjmlabs](https://boards.straightdope.com/u/mjmlabs)\ **Post date:** [July 20, 2022, 3:06am UTC](https://boards.straightdope.com/t/time-travel-space-and-relativity/968066/113 "2022-07-20T03:06:02Z")
… OhmygodtheykilledKenny? ---
**Author:** ![JacobSwan](https://avatars.discourse-cdn.com/v4/letter/j/a6a055/32.png) [@JacobSwan](https://boards.straightdope.com/u/JacobSwan)\ **Post date:** [July 20, 2022, 6:36am UTC](https://boards.straightdope.com/t/time-travel-space-and-relativity/968066/114 "2022-07-20T06:36:34Z")
They took ma job! ---
**Author:** ![msmith537](https://avatars.discourse-cdn.com/v4/letter/m/d9b06d/32.png) [@msmith537](https://boards.straightdope.com/u/msmith537)\ **Post date:** [July 21, 2022, 3:29pm UTC](https://boards.straightdope.com/t/time-travel-space-and-relativity/968066/115 "2022-07-21T15:29:33Z")
never mind [Previous page](https://boards.straightdope.com/t/time-travel-space-and-relativity/968066.md?page=5)