# No-paradox time travel is invented. Should it be shared with the world? **URL:** \ **Category:** In My Humble Opinion\ **Created:** [February 12, 2020, 3:34am UTC](https://boards.straightdope.com/t/no-paradox-time-travel-is-invented-should-it-be-shared-with-the-world/847803 "2020-02-12T03:34:58Z")\ **Posts on this page:** 4\ **Page:** 3
**Author:** ![RickJay](https://avatars.discourse-cdn.com/v4/letter/r/bb73d2/32.png) [@RickJay](https://boards.straightdope.com/u/RickJay)\ **Post date:** [February 20, 2020, 10:03pm UTC](https://boards.straightdope.com/t/no-paradox-time-travel-is-invented-should-it-be-shared-with-the-world/847803/41 "2020-02-20T22:03:22Z")
> [@wolfpup](#): > > Your mere presence in the past profoundly affects it regardless of what you do or don’t do (the butterfly effect) Only in whatever way it already did. That is the point of the Novikov principle. Going back in time will not change the timeline, because it already changed the timeline. You cannot change history. You already changed history. > [@](#): > > so the only way this scenario makes sense is that what you’re dealing with is not so much a time machine as a very advanced form of archeology that allows you to see and hear the events of the distant past without actually being there. But if you travelled back in time, you already were there. ---
**Author:** ![begbert2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/begbert2/32/3357_2.png) [@begbert2](https://boards.straightdope.com/u/begbert2)\ **Post date:** [February 20, 2020, 11:30pm UTC](https://boards.straightdope.com/t/no-paradox-time-travel-is-invented-should-it-be-shared-with-the-world/847803/42 "2020-02-20T23:30:03Z")
> [@Tibby](#): > > The way I see it, unless there is some type of intelligence controlling the physics of our universe, what can be sent back in time needs to be all or nothing, butterfly effect or not. Either you can send anything back, or nothing at all. Otherwise, you’d need an intelligent gatekeeper. > > _No, that elephant can’t travel back in time, he might sit on somebody’s grandfather and that would invoke a paradox. But, Bob can go back as long as he promises to be sneaky and not disturb history._ That doesn’t make sense. > > And, if organic matter can’t go back, then inorganic matter can’t go back either. Because, who’s to determine what the dividing line is? > > _We can send that archaeological spy camera back in time, but not that bomb—heck it might blow up Hitler and then the universe would collapse._ That doesn’t make sense either. > > I would certainly like for advanced archaeology tech to exist whereby we could see and hear the past without physically interacting with it. 4K video resolution and Dolby Digital sound, please! > > It would be great to see a real saber tooth tiger from the comfort of my La-Z-Boy recliner without being eaten by one. Seeing mid-1300’s Europe without catching bubonic plague would also be nice. But, short of magic, how could that happen without something from today interacting with something from the past. > > Maybe some sort of quantum virtual particles can travel back in time without breaking physical law, but surely nothing that can record and send messages back to us. > > To me, time-travel makes no rational sense unless the many-worlds interpretation is correct and infinite time-lines exist. Under the specified time travel model for this thread, it’s not about whether you _can_ send back a bomb, it’s whether you _did_ send back a bomb. If you did send back a bomb, then it appeared in the past. If you didn’t, you didn’t. Look at it this way: in the specified time travel model, the future operates like the past, because it might actually _be_ the past to somebody who just jumped back from there. And the way the past operates is that nobody can change how events played out in the past; they already happened and nobody can change that. If you planted a bomb somewhere yesterday, then that bomb was planted. If you didn’t plant a bomb, then no bomb was planted by you. So, let’s consider Bomber Bob, who if he gets his hands on a time machine will most definitely use it send a bomb back and blow up Hitler. If no bomb blew up Hitler, what does this tell us? That Bob didn’t get his hands on a time machine. (And neither did anybody with similar ideas to him.) Everybody who gets their hands on a time machine won’t blow up Hitler. We know this because there’s documentary evidence that nobody did. This isn’t a disproof of the Bill-and-Ted model of time travel, but it _does_ strongly argue that time machines won’t be distributed to all and sundry in any universe with that model of time travel. Whoever makes a time machine will only give it to people who screw with the timeline in non-destructive ways. So what happens if they try to give a machine to Bob anyway? Or they try to send a bomb back themselves? They’ll fail. At some point the plan to blow up Hitler will fail. Not because of divine intervention, but because they failed. It’s (quite literally) a foregone conclusion that they’ll fail, for one reason or another, in the same way that if you think back to a time you failed at something that failure was, after the fact, inevitable. ---
**Author:** ![RickJay](https://avatars.discourse-cdn.com/v4/letter/r/bb73d2/32.png) [@RickJay](https://boards.straightdope.com/u/RickJay)\ **Post date:** [February 29, 2020, 4:10am UTC](https://boards.straightdope.com/t/no-paradox-time-travel-is-invented-should-it-be-shared-with-the-world/847803/43 "2020-02-29T04:10:57Z")
> [@begbert2](#): > > So, let’s consider Bomber Bob, who if he gets his hands on a time machine will most definitely use it send a bomb back and blow up Hitler. If no bomb blew up Hitler, what does this tell us? That Bob didn’t get his hands on a time machine. Or that he did, but that he had a bad plan. It’s quite plausible he did get his time machine but, apparently, his plan failed. I mean, people AT THE TIME tried to blow up Hitler and failed. Hell, maybe Bob was helping out the July 1944 conspirators. ---
**Author:** ![JRDelirious](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jrdelirious/32/9531_2.png) [@JRDelirious](https://boards.straightdope.com/u/JRDelirious)\ **Post date:** [February 29, 2020, 5:58pm UTC](https://boards.straightdope.com/t/no-paradox-time-travel-is-invented-should-it-be-shared-with-the-world/847803/44 "2020-02-29T17:58:46Z")
> [@Tibby](#): > > The way I see it, unless there is some type of intelligence controlling the physics of our universe, what can be sent back in time needs to be all or nothing, butterfly effect or not. Either you can send anything back, or nothing at all. Otherwise, you’d need an intelligent gatekeeper. > > _No, that elephant can’t travel back in time, he might sit on somebody’s grandfather and that would invoke a paradox. But, Bob can go back as long as he promises to be sneaky and not disturb history._ That doesn’t make sense. > > And, if organic matter can’t go back, then inorganic matter can’t go back either. Because, who’s to determine what the dividing line is? > > _We can send that archaeological spy camera back in time, but not that bomb—heck it might blow up Hitler and then the universe would collapse._ That doesn’t make sense either. > … > Maybe some sort of quantum virtual particles can travel back in time without breaking physical law, but surely nothing that can record and send messages back to us. Which is why for example Baxter/Clarke propose in “Light of Other Days” for a passive viewer a type of anchored-wormhole effect that would alow you to look from your present into the past, so you can behold the events _from your end_. As the two ends of the wormhole are both “present” it does not involve sending anything into the past. [Previous page](https://boards.straightdope.com/t/no-paradox-time-travel-is-invented-should-it-be-shared-with-the-world/847803.md?page=2)