The Problems With Time-Travel (Star Trek/Doctor Who)

[@joshuafrahm8778]

"My advice on making sense of temporal paradoxes is simple: don't even try."- Captain Kathryn Janeway

[@DMSProduktions]

I tried, and got severely punished for it!

[@maxhax367]

you'll just make your headache worse

[@DMSProduktions]

@@maxhax367 True.

[@Vladimir_The_Impaler]

I recommend the light touch theory. Such as over powering household electric wiring causing a minor fire to claim insurance money. As for the fixed points in time, are in my eyes examples are Albert Einstein father of relatively, or his famous letter to Roosevelt. Hitlers fourth Reich. Post media television POTUS Ronald Reagan, time selected him as President cause he had to perform good on Television to keep maintain world order and a smooth transition to a post cold war millennium. These are fixed points in time. Hypothetically speaking the unraveling of the ball of yarn results?,, I foresee two possibilities,, it will all work out in time😉 or its the sound of smalls stones effect,, hence causing a unstoppable avalanches in the mountains resulting in a avalanches everywhere else. Each collapse of fixed points, creates a space time fracturing paradox. The results of which could cause a chain reaction that would unravel the very fabric of the space time continuum, and destroy the entire universe!!!! Granted, that's a worse case scenario🧐. The destruction might in fact be very localized, limited to merely our own galaxy.

[@tastycheddar7958]

The bridge problem is simple; change the gravitational constant of the universe.

[@tsinestexicthdauwraum9082]

Oh? You cant do that? I forget, youre such a... Limited species.

[@JasonGroom]

It's as easy as moving a moon

[@insertnamehere8099]

Ben Muir Hah, I just watched that episode 20 Minutes ago!

[@charlesmurphy1510]

Except the universe has no gravitational constant.

[@Vladimir_The_Impaler]

I recommend the light touch theory. Such as over powering household electric wiring causing a minor fire to claim insurance money. As for the fixed points in time, are in my eyes examples are Albert Einstein father of relatively, or his famous letter to Roosevelt. Hitlers fourth Reich. Post media television POTUS Ronald Reagan, time selected him as President cause he had to perform good on Television to keep maintain world order and a smooth transition to a post cold war millennium. These are fixed points in time. Hypothetically speaking the unraveling of the ball of yarn results?,, I foresee two possibilities,, it will all work out in time😉 or its the sound of smalls stones effect,, hence causing a unstoppable avalanches in the mountains resulting in a avalanches everywhere else. Each collapse of fixed points, creates a space time fracturing paradox. The results of which could cause a chain reaction that would unravel the very fabric of the space time continuum, and destroy the entire universe!!!! Granted, that's a worse case scenario🧐. The destruction might in fact be very localized, limited to merely our own galaxy.

[@MrMuzza008]

What do we want? Time travel! When do we want it? That's irrelevant!

[@AlphaDogTech]

This made me LOL, and may be the funniest thing I've seen in months...

[@MrMuzza008]

Yeah its good. I first heard it from Terminator Genisys, but its probably originally from elsewhere.

[@SeaJay_Oceans]

What do we wanting ? Time Travel ! When Will we want it ? Yesterday !

[@scottmantooth8785]

as Douglas Adams pointed out in his Hitchhikers books (the third one i think) that time travel by its very nature was/would be discovered simultaneously at every point along the space time continuum past present and future...which in as of itself could be considered something of a circular temporal paradox...

[@cosmogoblin]

@@scottmantooth8785 Also I believe it was Adams who explained that all the supposed problems with time travel - killing your grandfather etc - pale into insignificance when you try to figure out the correct tense to speak in!

[@alexwest6469]

To be completely fair in doctor who they more often than not just blame it on a ripple from the time war since it was such a massive scale temporal war

[@GeorgeMonet]

But it really wasn't that large. It was like a month long fight between two people who didn't really do anything.

[@Gothic7876]

That was spread across the universe, with both sides constantly altering events, making the relative time much longer. It was that bad the entire Time War timeline was sealed away from the rest of the timeline

[@MrChupacabra555]

In a recent episode of "Legends of Tomorrow" (about a bunch of time traveling Super-Heroes), the character Constantine finds himself in the same bar as his bastard father, long before he was born. He tries to kick his father so hard in the balls that he becomes unable to sire children, but as soon as he tried, he blinked out of existence, only to reappear a few feet away, confused and startled. One of the other members told him that the universe has a 'Ball Kick Paradox", it simply won't let someone interfere in their own timeline enough to prevent their own birth (of course, this show has made many rules, only to break them later, much like Dr. Who ^_^)

[@Adam-eb8tp]

Did You see, the one, in witch Constantine ancestor was some powerful mage, yet his father was no one, which mean if they (his lineage) had some power in magic and in land, they lost it all a long time ago.

[@scottmantooth8785]

a somewhat inelegant distillation of the temporal causalities that govern the space time continuum but none the less accurate

[@octoberboiy]

Yes, I love sci it movies with this premise. It makes it so that no matter how hard they try, the time traveler can’t interfere with events that affect his existence, to the point where every physically possible event will prevent it from happening.

[@DMSProduktions]

That IS very close to reality!

[@Ozzy_2014]

The original series Who episode Day of the Daleks with the 3rd doctor gets involved with Time traveling Daleks who conquered the Earth after a 3rd world war. The gureilas decided that the peace conference that failed started the war that allowed a weakened Earth to be defeated. They stole the technology of time transference and traveled back in time to the peace conference. They planned to kill the diplomat who brought everybody together believing that he intended to derail the conference deliberately. Instead in their attempt the Daleks detected the time trace and showed up to stop the gureillas and in the process the house where the conference was held was blown up. Destroying the last attempt to prevent the 3rd world war. Thus causing the very war they tried to stop. A predestination paradox was created. Had the guerillas not traveled back, neither would the daleks. There would be no explosion. The conference would go ahead. Peace can reign. The Earth wouldn't have been conquered and there'd be no guerillas to acidently start the war.

[@hokusman100]

"Starfleet had an active branch dedicated to just maintaining continuity." To bad CBS didn't.

[@fivish]

Continuity on set is usually done by a lady with a clip-board!

[@MistedMind]

@Manek Iridius No one mentioned Discovery before you did. There are MANY continuity-errors in the previous Star-Trek TV-shows too.

[@RageUnchained]

@Manek Iridius found the discovery fan boy

[@kaitlyn__L]

@@MistedMind No one except by a very obvious implication, since there's only show originated by CBS currently out anywhere...... unless you feel like TOS and TNG remastered ruined continuity? Like, I agree that all of Trek has had plenty of continuity issues (Data's rank in All Good Things for example). I don't think it's uniquely a thing Discovery had to deal with at all. But the original comment's intent was very clear nevertheless, y'know?

[@henchmen999]

The final episode of STD will be a bunch of Temporal Agents beaming in and deleting everybody.

[@neilprice513]

Another type of "paradox" , invented by Sir Terry Pratchett, may he rest in peace, was for his Discworld book series. It was called "The Trousers of time", basically, it's where you go back in time, but for some reason, go to a "diverging present" or "down the wrong leg" on the return journey and enter a alternate timeline by mistake.

[@DrewLSsix]

You likely couldn’t help but go up the new divergent line, returning to your original timeline is impossible.

[@neilprice513]

@@DrewLSsix Yep, the fact that you traveled back in time in the first place, means that the "Present" you return to isn't the one you came from.

[@DyrianLightbringer]

so... Back to the Future time travel

[@neilprice513]

@@DyrianLightbringer roughly speaking, yes. But the problem is that if you travel back in time, you can't return to the same "present" you came from. The action of time travel means that you have already changed the past before you get there.

[@VulpisFoxfire]

Depends on how you look at it..predestination paradox takes your time travel into account, and the timeline you started in is *already* the result of your meddling in the past.

[@darrenchapman2786]

your bridge collapse problem sounds like a simplified version of Star Trek Voyagers' Year of Hell. with Annorax trying to correct a tragedy in his past but never quite managing the perfect outcome.

[@scottmantooth8785]

that was a strange one to be sure...every calculation resulted in a bigger mess than before

[@QuestionDeca]

The answer, as with all Krenim Temporal Incursions, was to erase the Incursions themselves. The Krenim Timeship could only Remove, never add or restore, and thus could never fix what it had done till it, itself, was removed.

[@danny1229c]

The problem becomes deeper when all those ppl who would have died continue to live and create a ripple that grows so big it could change everything.

[@Vladimir_The_Impaler]

I recommend the light touch theory. Such as over powering household electric wiring causing a minor fire to claim insurance money. As for the fixed points in time, are in my eyes examples are Albert Einstein father of relatively, or his famous letter to Roosevelt. Hitlers fourth Reich. Post media television POTUS Ronald Reagan, time selected him as President cause he had to perform good on Television to keep maintain world order and a smooth transition to a post cold war millennium. These are fixed points in time. Hypothetically speaking the unraveling of the ball of yarn results?,, I foresee two possibilities,, it will all work out in time😉 or its the sound of smalls stones effect,, hence causing a unstoppable avalanches in the mountains resulting in a avalanches everywhere else. Each collapse of fixed points, creates a space time fracturing paradox. The results of which could cause a chain reaction that would unravel the very fabric of the space time continuum, and destroy the entire universe!!!! Granted, that's a worse case scenario🧐. The destruction might in fact be very localized, limited to merely our own galaxy.

[@espalorp3286]

Perhaps there is an alternative to complete alteration as proposed in the bridge scenario? Instead of tragedy, you could have narrowly avoided tragedy. Say 10 cars plunge into the water and their occupants are destined to drown to death. You could have a potential standby team nearby for the event and have them coordinate in such a way that all the occupants are rescued or resuscitated. Instead of complete tragedy occurring, a failure in construction parameters caused the near deaths of 15 or so people who were luckily saved in time. Instead of remembering 9/11 for the towers, it could be remembered for how close the planes came to hitting before the controls were wrestled away in time. Instead of Vasili Arkhipov voting with the rest of the submarine crew to launch the nukes, he could've voted against it and prevented World War III. Oh wait, shit, wrong timelime.

[@mattevans4377]

OR, force the bridge to collapse when no one is on it, but make it look like the original accident. People now improve the design, knowing it is flawed, but also grateful no one got hurt in the first place, because you made sure the collapse happened with no one on the bridge. Win-win.

[@demarcusfaulkner7411]

Proteus well it could be worse.

[@tommywilliamson152]

But what if yiy save the people that would/should have died and one turns out to be tyrant that in the long causes the death of tousands or millions of people; some of which would have made great contributions to the good of mankind b7t are not thers to make those contributions.

[@LtAlguien]

Pfff, yeah sure. Like saving the life of that austrian painter from dying to gas in the War that ended all wars will matter.

[@espalorp3286]

I'm not saying that someone should go back in time to save lives. I'm saying that there are better ways of intervention. The thought of someone potentially going on to murder thousands as a result of survival isn't lost to me. That's timetravel 101. What I'm trying to get across is that there is a more efficient solution (if you so chose to go back) that could not only give people cause for concern, but also avert tragedy. As Matt pointed out, you could have the bridge collapse on its own. But I personally think parking all those empty cars on a busy bridge might arouse too much suspicion.

[@johnnyricardobown2171]

So when Rick brings up the grandfather Paradox, who else immediately thought of that one Futurama episode, where the Planet Express crew ends up going back in time to Roswell, New Mexico? And yeah, predictably Fry's grandfather dies horribly in a atomic bomb test, leading to the hilariously disturbing consequence of Fry, having sex with his grandmother and thereby ensuring his own existence.

[@scottmantooth8785]

yeah...that explains a lot of things about Fry...

[@davidhonez8859]

He did the nasty in the pasty

[@Anonymous-zd1ow]

the bootstrap grandfather paradox

[@Vladimir_The_Impaler]

Lessons in not changing history by Mr my own grandpa,,, screw history!

[@fishbaitx]

Arguably a predestination paradox

[@lunistg]

To quote Ron Stoppable, "Time travel: It's a cornucopia of disturbing concepts"

[@Vanilla0729]

To quote Miles O'Brian: I hate temporal mechanics.

[@ZatoichiBattousai]

To Quote me, It's never gonna ever happen cause it's not scientifically possible, but keep it in fiction!

[@kamenridernephilim]

It especially confusing trying to figure out what tense to use.

[@kimnice]

"Time travel: It's a cornucopia of disturbing concepts" You should watch this German Netflix-show called "Dark". Some of the concepts are truly disturbing and difficult.

[@user2C47]

@@Vanilla0729 _2 Simultaneous Instances_ of Chief O'Brian.

[@HappyBeezerStudios]

To quote simple words: "If time travel is ever invented, it already exists"

[@mr.incorporeal7642]

Honestly, I've always preferred the concept that any time travel immediately creates a new timeline/universe entirely separate from the original one. You know, you can go back and kill your own grandpa without (time-related) consequence, because the moment you stepped out of the time machine you were already in a newly created universe. That's not *your* grandpa you're killing, that's the grandpa of another now non-existent version of yourself. Lets you explore all that fun time-travel stuff, without worrying about the paradoxes that get more and more complicated and convoluted the more you think about them.

[@WAX1138]

Yet the many worlds interpretation of string theory has been disproven many times. Its makes good scifi but in actuality is wasteful and makes anything & everything pointless.

[@MistedMind]

@@WAX1138 "interpretation of string theory has been disproven many times" Oh really? Which sources of this can you name?

[@karlfranzemperorofmandefil5547]

@@MistedMind his statement is incorrect because string theory as a whole was proven to be Incorrect. however the Kopenhagen Interpretation of Quantum physics , which postulates a different many world's theory was never disproven.

[@nicolaiveliki1409]

@@karlfranzemperorofmandefil5547 it's not really that string theory was "disproven". It's more like it doesn't produce predictions that can be falsified, which makes it a non-(scientific-)theory. But it has amazing math, and some very thought provoking concepts which might still prove useful. At least that's how I understood Matt O'Dowd on PBS SpaceTime

[@InternetGravedigger]

personally I think more along the lines of 'when you travel in time, you're no longer in sync with the timeline, and so are unaffected to changes in the timeline.'

[@DecimusEX]

I know this is star trek/doctor who, but Isamov's "End of Eternity" Perfectly addresses this

[@RelativelyBest]

Some notes: A more general definition of the Grandfather Paradox is: You can't go back in time and remove the conditions that made you go back in time. If you think about it, this includes most if not all intentional interferences with the past: If you prevent the bridge collapse tragedy, you would never have the idea to go back and prevent it in the first place since it didn't happen, and so on. (Note that this does not apply to models where this causes alternate timelines.) I think people tend to get too literal about these things: It doesn't _have_ to involve erasing yourself by killing a close relative. Contrary to what some people assume, causal loops are not actually time paradoxes - they are weird and counter-intuitive, but do not violate causality. (I know you didn't claim this in the video, I'm stating it for the record.) This even includes the Bootstrap Paradox, which is an _ontological_ paradox rather than a causal one. The Lucky Charms examples used in this video are actually not very good examples. For the first one, there is no reason to believe the message from the future is the reason you end up sending that message. Future you may simply have realized he forgot to buy Lucky Charms, which was the original reason he sent the message. Then, the version of you who got the message sent the same message simply because he knew he was supposed to. This would actually be an example of changing time while maintaining causality. In the Bootstrap example, the main problem is that the box of Lucky Charms would degrade over time so it would be an older box in every iteration, meaning there will come a point where you can no longer send it back in time which means the event logically can't happen. It works better when time travel simply causes a series of events to occur that circles back around. See Heinlein's By His Bootstraps, which is the origin of the term. On that note: Time loops can in fact have sensible beginnings and endings and don't need to mess with causal events. For example: Say I'm hungry but my local pizzeria closed half an hour ago, so I go back in time one hour and get my pizza. Then I head home just as my other self goes back in time, at which point I just carry on with my life as usual. I'd be an hour older than I should be but at least I'm not hungry anymore. In fact, causing an event that leads to you causing that event is pretty much the definition of a Bootstrap (or closed) causal loop. So, both of your examples were in fact intended to be Bootstrap paradoxes.

[@SuperShesh2]

“I hate temporal mechanics” The most easily quoted quote ever

[@harveygranger3209]

I Am advent watcher of this channel and I will say that it is definitely one of my top 5 channels that I watch faithfully. Saying that I have watched this episode at least 10 times and I love the examples for time travel that u make. Even a complete novice that watches this with no understanding of time travel or a watcher or either show will come away with a pretty good understanding of time travel. I love the channel and I love Rick so please keep up the great work.

[@Kitsula]

Huh. That example reminds me of the Silver Bridge disaster in Point Pleasent, West Virginia, USA which had a fatal flaw and the disaster lead to sweeping legislation, changes in construction, inspections of old bridges, and so on. It's also the event that is tied up in Mothman lore and some lore said that it chased/fightened/delayed a bunch of people that night who would have been on the bridge at the time so that it ended up being fewer people than expected on the bridge when it collapsed - more cars with fewer people in them and heavy trucks. Interestingly enough pretty much the same entity supposedly showed up as the 'Freiburg shrieker' (Black color, winged, red glowing eyes) in Freiburg, Germany in 1978 where it scared off a number of miners before a mine collapse. Red Eyed Angel? :p

[@ZatoichiBattousai]

In the Netflix show "Dark", the machine used in the time tunnel is stuck in a Bootstrap paradox loop. It gets repaired each time, at least. (Stuck in a 30 year repeating loop.)

[@scottmantooth8785]

the indie movie Primer is also rather good with this topic

[@crashmatrix]

Solution for the bridge: ensure no lives are lost by ensuring a /very/ expensive piece of equipment is being transported over the bridge at the time of collapse. Motivations to fix the fundamental problem are never addressed more quickly when money is lost, likely ensuring the structural problem is found and fixed all the same. But the point stands, some events 'must' occur, insofar that large scale changes to the timeline could equally result in an unintended grandfather paradox in the end. Every 'fix' (kill hitler, save the bridge, etc) increases the risk of creating a paradox. As for the network of twine on the wall, that's a really nice way of visualizing 'fixed points'. I look at it differently though. Imagine spacetime as a stretchy/rubbery medium in which time travel incursions ripple out. There is some inertia to cause such a ripple. Small ripples (minor tweaks to the timeline) don't radiate out very far, and require little energy/effort to initiate. Larger ripples may leave longer lasting changes, and require all the more initial 'energy' to catalyze. Fixed points are those events that would alter most everything on the fabric, with an almost insurmountable resistance to causing them in the first place. In stead of the entirety of spacetime changing from that point out, the fabric finds another local fold and dissipates the 'wave' of change, keeping it mostly the same as when you started.

[@theldraspneumonoultramicro405]

solution to the bridge problem: i would take inspiration from a real world event where a architect student discovers a critical flaw in the Citicorp tower, now called 601 Lexington in new york, a flaw that could send the towering skyscraper falling down and wiping out nearly a entire city block, the construction was already well on its way and the building was actively in use on its lower floors that had been completed, they had to do emergency reconstruction day and night. just like that time, i would wait for the bridge to be well on it's way to completion, perhaps even wait for it to be completed and opened for use before pointing out the flaw, as the bridge is actively being used and no one knows when it will collapse, fixing it will become a VERY dire emergency as to avoid a disaster, this situation would also create a critical need for new regulations to be put in place to avoid construction of such flawed bridges again. this may not work in all scenarios, but at the very least, that bridge wont be collapsing anytime soon. now, this is however not the scenario i would worry about the most, the one thing i would worry about the most here is people using time travel to intentionally sabotage things to cause disasters to take place, like for example, someone going back in time to put that flaw there in the bridge with the intention to have it collapse causing unknown amounts of dead, hell, i myself would probably be guilty of something like that myself, intentionally creating scenarios that lead to disasters with potentially hundreds if not thousands of deaths, all for the purpose of taking out a singular or a handful of individuals that i have determined to be bad and in need of removal before they become a problem.

[@Kenadian2006]

I see you snuck a Steins;Gate reference into there.

[@Chief_Miles_OBrien]

And I see you saw that reference as well.

[@harbingerofsarcasm2510]

I think your bridge analogy is best exemplified by the Voyager episode Year of Hell, the Krennim captain trys for centuries to correct his own corrections to time each time adding more variables and making it harder to get the desired effect.

[@dugclrk]

Then in the end, the whole two part episode is completely forgotten by by crew as it never happened. Another reason I hate time travel episodes.

[@Beacuzz]

Don't ever ask how old the thing in the bootstrap paradox is. EVER! Your poor brain will explode!

[@xaivierallen4020]

Most of the time it is infinity or 1 second

[@Shadowkey392]

I was aware of the Bootstrap and Grandfather Paradoxes, abs also the Causal Loop. As for the bridge problem, I’d probably just let it happen; better to leave the timeline as it is than to risk making it worse.

[@matthewday7565]

The Orville did one as well, also fitting the trope of "Nice job breaking it, Hero"

[@qdllc]

No. In Angels Take Manhattan, the Doctor couldn't go back to that time period because of the time lines being scrambled. It's not established WHEN Rory and Amy were sent by the surviving angel, but it was a "fixed point" because if the Doctor went back to see them, he might inadvertently impact their known deaths and burial in New York. As he pointed out earlier, you can't change your own history once you know what it will be. This explains why the Doctor traveled without "reading a history book" in The Girl That Waited. His "ignorance" of what specifically happened somewhere give him latitude to mess with time as he knows when something is a fixed point and when it is not. Foreknowledge basically restricts his freedom to interact in events.

[@JakkFrost1]

It was specifically stated in the episode that the Doctor couldn't go back to that time anymore because everything was "scrambled" (I forget the exact wording used offhand). Hell, he had trouble getting through the _first_ time, at the beginning of the episode, when they were going to rescue River. Your logic makes little sense, because the Doctor has visited MANY people whose time of death is already well known. He's even tried to prevent some notable deaths.

[@LightLMN]

@@JakkFrost1 With some considerable effort he did get through. What makes the ending so definitive is because Amy chooses to follow Rory, entering/making a fixed point in history (a detail that is mentioned in-story: "You are creating fixed time! I will never be able to see you again!"), permanently locking the Doctor (and River) out of ever seeing or travelling with her ever again.

[@DyrianLightbringer]

what I never understood is why the Doctor didn't just travel to say... 1940s New York. He sees Amy and Rory's tombstones read their ages upon death, but not the dates of their deaths. He could easily go to New York at any point OTHER than the scrambled time period, visit, or even pick them up, have more adventures, and return them to New York later on. All that their thombstones confirmed was that they died in New York and were 84 and 87 years old when they died.

[@LightLMN]

@@DyrianLightbringer Are you familiar with the Reverse Series 7 theory? That for the Doctor, the first half of the series plays backwards? There's a few points that suggest he tried visiting them, the first being in opening scene of The Doctor, the Widow, and the Wardrobe tying directly into parts of The Name of the Doctor. During the course of Name, the Doctor attempts to go to Trenzalore, a place he should never ever go, and he has to (IIRC) disable some safeguards to do it. Despite this, he can't materialise safetly and arrives in orbit, and has to disable the engines and fall into the atmosphere just to get anywhere. In the Not-Narnia episode, the Doctor is in orbit above Earth on an exploding spaceship, and falls into the atmosphere. No TARDIS in sight. The TARDIS is on Earth's surface somewhere. But the time period is exactly December 25th, 1938. The exact year Rory was first sent back to during Angels Take Manhattan. Perhaps he was trying, and that's why he was there: the TARDIS refused to get any closer, stranding him in orbit after the HADS system (later used in Cold War of the same series) activated, and that's how he knew/worked out how to "land" Trenzalore under similar restrictions. Afterwards, he ended up resigned to never seeing them again, but found his loophole by visiting their 2012(?) selves living in London, eventually leading through the slow goodbye of Power of Three/Town Called Mercy, and leading into Asylum of the Daleks. It's one theory at least.

[@Croftice1]

@@DyrianLightbringer The difficulty of that task aside, let's look at it this way: if he picked them up in 1940's NY and they were a fixed point (the awareness of their tombstones), what would happen, if said "fixed points" died on an adventure somewhere? Would he be able to return them to their fixed death point? Wouldn't that create a paradox? How could they die in like 1940something, when they died with the Doctor somewhere, lets say on a different planet? You know, he can do anything, but he can't assure their safety 100%. If he can't keep them safe forever, how could he be sure not to create a paradox by allowing their deaths outside of their fixed point?

[@amanofmanyparts9120]

Terminator Genisys: What do we want? Time travel! When do we want it? It doesn't matter!

[@johnilarde8440]

The Doctor: *fixes bowtie* listen here you little shits!

[@gagaplex]

Can't agree. This bit about not knowing the outcomes or generating a less than optimal outcome by saving lives reminds me too much of the following: Imagine you spot a child about to die in a burning building. Do you try to save them? Now, the answer seems obvious: Yes! But perhaps this child will grow up to be a serial killer or the next great dictator. You don't know what the long-term outcome of saving the child will be. Does that change what the moral choice of action would be? I think not. We should save when we are able to save.

[@JaredLS10]

Rick, just came across this video. As expected it was another solid one. Just wanted to say props to you on donating the earning of this video to cancer research. I got into Doctor Who late and it was maybe a year after I saw Journeys End that I heard Elizabeth Sladen had died of cancer. Anyways, keep up the good work.

[@Martin-xd4jl]

I always liked that Blink is one of the best Doctor Who time travel stories, in spite of the fact that time travel in almost every other episode of Who doesn't even slightly work like that.

[@FranciscoTChavez]

I always saw the fixed points in time like wave node points on a plucked guitar string. The string itself is a timeline. As the string waves back and forth, the timeline itself is constantly changing. Yet, the node points don't move and are therefore fixed. Points on the time line that are closer to the fixed points can't move as much, so while they may not be fixed, the also won't (or can't) change as much. This is what I normally use as the basis of my explanation for the flow of time in Doctor Who.

[@kallistiX1]

Your Bridge Problem may have a simple solution: the traveler was always responsible for the leap forward in technology in the first place.

[@eeduranti]

As a temporal investigator I hate it when people try to claim a predestination paradox.

[@redapol5678]

Except that he wasn’t. Unless you’re suggesting it’s also a grandfather paradox. Ok now my head is hurting

[@charlesmurphy1510]

All actions during time travel produces a paradox. If the traveller corrected the flaw and the tragedy never happened then why would the traveller come back to the past to correct a flaw that never happened?

[@pfarnsworth84]

@@eeduranti Why? How do we know he didn't invent the thing?

[@AuxCart]

Bridge problem? Fabricate the conditions that trigger the collapse in a safer time. Unoccupied or significantly less occupied. Bonus points for nearby press.

[@jeremyjohnson4285]

Very nice

[@WildBluntHickok]

My favorite "thinking about time travel" moment was from an Avengers comic. They explained how Dr Doom's time machine in Fantastic Four issue 5 was the first time machine that could change the past (due to a special "doom circuit"). Then they went over every still-active time travel anomaly, and ended the presentation with "if I could I'd go back in time and assassinate Doom before he invented the Doom Circuit...of course for that to work I'd have to use a Doom Circuit, so..." Everyone in the room laughs at that, except the group's resident alternate reality traveller Miss America. She gets this haunted look and says "don't even joke about that. I've seen timelines where the Avengers tried that. It was like spaghetti. Spaghetti that screams."

[@jeffmartyn6743]

On top of the paradoxes, there is also the moral component. Let's say that you have a nephew who is 7 years old, and you decide to change something important 8 years ago. The ripple effect of change, whether destructive or constructive would still be a change in future events. The odds of a specific egg being fertilized by a specific sperm is so astronomical that you might as well buy a powerball ticket and announce your imminent retirement as expect the same nephew to be born. Now, in the Dr Who example, Fate would dictate that this individual would be born as normal for some wibbly wobbly fate reasons, unless of course the father got killed for reasons. However assuming a completely chaotic system, you have prevented that 7 year old from ever being conceived. Is this murder? What if instead of this nephew, you get a niece a year after the nephew was supposed to be born, this 6 year old niece is now existing where she hadn't before in the previous time line. Does that erase the burden of pre-conception murder, and how would it be defined? Assuming only the time traveler is aware of this, no one would know. On a similar level, people's personalities and attitudes toward life are an accumulation of experiences and circumstances presented. If you stopped someone from climbing a mountain and take up mountain bike riding instead of climbing, they might be the same person with an athletic drive, but their personality and strategy to physical adventure is different, possibly resulting in a different enough personality that you might not recognize that individual anymore compared to the original. Paradoxes must be avoided, but morality in time traveling is so socially complex that someone might suffer from psychological distress from the experience. In the end, a time traveler would have to accept that everything beyond the moment of change is going to be completely different from what he knew, and any and all changes are both "his/her fault" and "not his fault" as events would play out according to the new variables. Yes the traveler set in the new chain of events, but he would only be responsible for the initial change to life's variables, how everyone else reacts to those new variables would be difficult to take credit for.

[@rjonboy7608]

Wouldn't the very act of entering a place and interacting with the people (for better or worse) be altering them? Yet that is what humans do day in and day out. I could choose to meddle in a marriage, distressing generations of a family. I could drive carelessly and run down somebody's child. I could be a horribly obnoxious racist pig and hurt people. Or I could be polite and decent and helpful. Everything I do alters those I interact with as they interact with me. It's a great sci-fi notion of timelines and do-overs and all that, but as far as I can tell each individual experiences each moment only once whether time is experienced normally or not. I'm not sure if I could time travel to a period in my own past, because I have already experienced that time. It is fixed for me.

[@BigJeremyBeyer]

You ignored Stargate. They had an episode, 1969, where they accidentally time travelled. Before they entered the Gate, Hammond gave Carter a folded note and told her not to open it. Then a young Lt Hammond found the note after the team was arrested. It was written to himself, telling himself to help the team. After he finds the note by him to him, he keeps the note in a desk for 35 years or so without telling anyone about it. The day of the accidental time travel, he pulls that note out of his desk and gives it to Carter, telling her not to open it. She then ends up arrested and in the custody of a young Lt Hammond, who finds the note by him to him telling him to help the team. He keeps the note in a desk without telling anyone about it until...... Wait..... WHO WROTE THE NOTE!?!?!?

[@redshirtveteran5688]

Brad Wright?

[@BigJeremyBeyer]

I admit that took me a moment 😂

[@RageUnchained]

@@BigJeremyBeyer let's not forget that time they buggered the timeline so bad that the closest they could get it back had fish in O'neill's pond. Or the time Shepard was stuck in the future and had to travel back with help from hologram ghost McKay

[@ScaryBaldMan]

To the Bridge scenario: Instead of directly intervening in the bridge construction, you go to a time slightly before it, and release a "paper" or "news" about how that particular bridge design is flawed, describe the better design, and push for regulations to enforce that design. You save the lives, and you ensure the safer design is put into place.

[@35milesoflead]

I Was thinking a similar thing about going back to be the engineer's tutor for an hour. Or even in his class at school.

[@AdamantLightLP]

Yes but what if the changes (specifically the innovations) were brought about only because the engineer lost a loved one in the incident? Sadness and problems are powerful forces in driving people. Far stronger and more lasting lessons.

[@GeorgeMonet]

But then why would you go back in time if in your timeline the change was made in a way that removed the impetus for going back in time?

[@cricketol]

how I would fix the bridge issue. Make it collapse during construction to fix all the above issues

[@WAX1138]

Then why would one go back in time to fix something that never became a problem. Thus you never go back to fix the thing you went to the past to fix in the first place.

[@cricketol]

@@WAX1138 you would have went back but your time line never played out time is not a line but a branch of choices go left instead of right or go right instead of left. That's overly simple yes but out comes would change non the less

[@WAX1138]

The many worlds interpretation of string theory has been disproven many times. While it makes interesting scifi it is ultimately a wasteful use of energy and makes everything pointless. That said modern string theory does not support it, so there are not multiple versions of the universe and there is only one timeline. But I don't expect you to now this bc "magnets how do they work" and its not entertaining enough for you.

[@cricketol]

​@@WAX1138 thats nice and all about string theory but thats BS anyway ( bad science ) im not talking about string theory. its based on the idea of the infinite universe no beginning and never ending. there is no need at have multiple versions of the universe you would be in the same one just displaced in its time. time can branch out in to multiple places its all the same time just different areas of it time is infinitely long and infinitely wide and about your red herring fallacy does not strengthen your argument. ps. i dont fallow there religious ideas religious. so please keep on topic i dont make off the wall comments on your pic/name. no need to its irreverent to the topic. whats next my grammar or lack there of?

[@WAX1138]

@@cricketol ok enjoy your entertainment.

[@jeckjeck3119]

My friend, this is your best video yet. I just love the research you have put in all this. Bravo!

[@LarryThePhotoGuy]

The Star Trek TNG episode: "Cause and Effect" in which the Enterprise is caught in a temporal loop was fine until the end of the show. Enterprise encounters a "temporal anomaly," a ship from the past emerges and impacts them, the Enterprise is destroyed. The explosion sends the ship back in time i.e. resetting time. A temporal loop is created. The crew manages to detect their situation in the surrounding tachyon field and send themselves a message; thereby avoiding the explosion and escaping the loop. OK; fine so far. But then in the final scene, they discover that 17 days have passed while they were caught in the loop and they reset their clock. This made NO sense. NO additional time should have passed. Their clock should not have had to be reset. I was peeved!

[@Guy-zf5of]

this guy really to the time to study time travel. i couldn't have asked for a better explanation

[@Awestefeld6612]

As per the bridge accident there is another problem. People could die whose offspring make great contributions to the future. Or people might never be born due to the non-collapse. wheels within wheels.

[@fightingfalcon777]

I think one of the most confusing paradoxes is the predestination paradox, the one where a past event is dependent on a person from the future coming back and creating that perfect causal loop. It’s incredibly similar to the bootstrap paradox, but the common example for predestination is going back in time to discover you’re your own great-grandparent

[@DrewLSsix]

People never seem to actually get what the concept of a paradox is supposed to do, everyone thinks it’s some cinematic crisis like fading away in Back to the Future.

[@fightingfalcon777]

DrewLSsix Oh, for sure. Like you said, they think of it more as a crisis, rather than this event that is by nature a contradiction/doesn’t make sense

[@RageUnchained]

I find the best example of explaining a predestination paradox is this: Your parents die in a hit and run automobile accident when you are a child, you crawl from the wreckage and memorize the features of the car. Obsessed with preventing this tragedy you resolve to spend your life to save them, by building a time travel device. You succeeded and you travel to the year in question but you arrive 10 minutes later than expected. As you are racing towards the intersection where the crash occurs so you can place your care in the road, put the hood up and feign disabled causing your parents to slow and avoid the hit and run. you race to the scene and as you come to a four-way stop, you slam into a car spinning it off the road and rolling it. Realizing that any impact you have on the timeline will be devastating you flee the scene. In the rear view mirror you witness the only survivor crawl from the wreckage, you as a child memorizing the features of the car that killed your parents and resolving to make sure it never happens. Thus completing the loop. Your parents died because you witnessed them died, the action you take to prevent the tragedy becomes the cause because it was in reality always the cause, no time traveling you trying to save mom and dad, no car to spin their car into a ditch and roll it.

[@RedDwarfNerd]

Thanks so much for this video Rick, it's really helping me to get my head around some of the Paridox's in Red Dwarf, cheers! 👍👍👍

[@Awestefeld6612]

Need an update to this episode with DC's Legends of Tomorrow and Flash TV shows.

[@RealBadGaming52]

Timeless and Legands of Tommorrow litterly changes history with reckless abandom becasue a hstorical charicter was forgton due to race or gender.

[@nanoguy0]

@@RealBadGaming52 o be

[@RealBadGaming52]

@@nanoguy0 ??????

[@nanoguy0]

@@RealBadGaming52 I have no recollection of writing this comment

[@phyllismitchell9851]

Your explanation regarding the bridge was excellent. I never thought about how the interference cancels out the redesigning process AND the brings in the possibility of the flawed design to be done on s more widespread manner with disastrous repercussions. One still mourns those who initially died in the original though.

[@TheT7770ify]

Destroy the bridge myself just before construction is complete. That way they spot the error and no one dies

[@eds1942]

You get arrested for the incident in the alternate universe. And that universe will have to cancel out matter of equal mass to yourself. Meanwhile, the past was unaffected in your own universe.

[@WAX1138]

Then why did you go to the past in the first place?

[@jkrolak7978]

You then hit the 2nd part of that problem, what of those who were destined to die that day? And then multiply that by the generation of children who are now born due to that kind act. Do they create a better future or worse? Did one marry someone they normally wouldn't have met preventing them from a fated destiny. Sometimes the kindest thing is exactly the wrong thing made 1000x worse as the events ripples out from the action. (In Star Trek: look at what happened when Dr. McCoy saved Edith Keeler. Who might not even had walked in front of that truck had Kirk and Spock not been there and then greeting an old friend.) You've got good intentions, we know what destination uses them as paving stones.

[@RRW359]

Collegehumor did a video about that involving 9/11.

[@Krahazik]

@@jkrolak7978 Was wondering if any one would mention that episode.

[@eeduranti]

What about the Philip Fry version of the grandfather paradox. My personal favorite bootstrap paradox is the watch form Somewhere in Time (also my favorite "chick glick").

[@cosmogoblin]

Great video! One of my favourite books is Isaac Asimov's "The End of Eternity", which addresses the bridge problem. The Eternals travel through time (but not before the 27th century, when the first time machine was created), altering history to improve the lives of humans. They have a policy to cause the "Minimum Necessary Change" required to achieve the "Maximum Desired Response" - they'll misplace a scientist's notes, or burn out a circuit in a diplomat's car, resulting in a calculated butterfly effect to avert a catastrophe or unwise invention. This way, they minimise the disruption to the timeline - but a major plot point is considering whether such disruption can be ethical at all.

[@jeremyanderson5828]

Man, I hated end of eternity. They were just so limited in their vision for people trying to control the destiny of mankind.

[@EmperorZelos]

your concern is captured in the story "The end of Eternity"

[@Shadow-iv9ft]

There's a good short story that goes over the strange effects of a bootstrap paradox: All You Zombies. It's pretty cool, although the implications aren't as fun to think about...

[@DJDaisho]

and actually all you zombies(hats off heinlein) was translated into a movie called predestination, and they actually did an amazing job with it . . . got all the details in, most likely because it was a short story XD . . . love heinlein

[@christophervanoster]

You’re getting ahead of yourself man. The Vulcan science directorate has determined that time travel is impossible

[@virginiaconnor8350]

Yet, Cdr. T'Pol has admitted that going back to 2004 Detroit has tempered her view of time travel.

[@paulmooney4654]

I think a good solution to the bridge problem would be to limit as many people as possible from using the bridge at the time of its collapse. True the building regulations may not be completed as quickly if the collapse was less of a tragedy but the engineer should still learn his mistake. Great video btw.

[@charlestownsend9280]

In reality the grandfather paradox couldn't actaully happen, say you used a gun, the gun would miss fire, probability would narrow to only allow events that don't break causality and because you've already physically observed and existed in the future where it didn't happen (non physical observations have different rules). Causality loops are basically the only way to actually change time without breaking other rules, as long as you tell your new past self to go back and make the changes. The biggest problem with time travel that is always overlooked is changing small things that can ripple into huge changes that aren't predictable (think of a river during rain, all the drops create ripples, those ripples bounce off of each other making new patterns but remove one rain drop and over time the pattern would have completely changed). Morally if you change time you will be wiping people from existance for your own needs and one could argue whether it is right or wrong. Saying this i love time travel in scifi, especailly doctor who. As for star wars, i agree that it has a fixed timeline but i think that is more due to the force and how it influences the star wars universe as an invisible guiding hand.

[@4G12]

This is why it's a bad idea for even those with God like power to mess with the timeline. Too many possible unforeseen consequences.

[@davidwuhrer6704]

Who cares? If time can be altered, then those are all just parallel alternatives. New pasts and new futures get created and converge all the time. Just pick one you like.

[@kanebunce3791]

Tell that to the many beings beyond the multiverse in DC Comics. Not that doing so would do any good. Many of them do not care even when they do understand. Or some are doing because of what you say.

[@QuestionDeca]

There was this old show/movie I half remember, but what they did was... abductions. They took the people recorded as dying, made body doubles capable of withstanding the era's scrutinization (and decaying naturally) {Dead Clones basically}, and in the example I remember, kidnapped an entire aircraft mid flight, replaced the deceased recorded with the body doubles, then returned the plane to the past to let it crash as it was recorded as doing. I honestly don't remember why, but as seen by your own play of a Time Displaced Captain in Star Trek Online this is basically one of the few ways to allow a tragedy to play out while still saving the lives involved, and if you think about it, it doesn't really react too badly with paradoxes as at worst you'll start a bootstrap that solves itself (the corpses, a dropped tool at worst). Time doesn't like things going back, but it doesn't give a wit about things moving forward, and that's kind of key, you're just moving the people forward in time, not removing them or changing times course in regards to yourself.

[@keithtorgersen9664]

Your comment about the episode Blink opens another can of worms- how the Weeping Angels can seemingly randomly deposit people in random timelines without creating numerous time paradoxes, even ones that may threaten the existence of the angels themselves.

[@KatrinaLeFaye]

You really need to take a very detailed view of the Farscape series. Not only good Science Fiction and characters, but delves deeply into these issues itself, i.e. paradox, consequences, ripples in time, etc. I think it is the best dealing with such of any sci-fi series.

[@XanderKHD]

There is another work around for time travel to work without the risk of paradoxes and keeping temporal stability: The Multiverse Theory, basically stating there's a universe for EVERY possible outcome. For example, let's say you go back in time and kill your grandfather. When you travel back to the future, you don't travel to your own future, but a future in another universe fitting the criteria of the events you played in the past. This means the original timeline is still existing, it's just that you've traveled to another universe that fits the criteria you created from alterations in the past.

[@Ozzy_2014]

Based on Everret Wheeler's many worlds theorem.

[@XanderKHD]

@@Ozzy_2014 Pretty much, ensuring that something like a paradox won't lead to a complete collapse of the space-time continuum. BUT, this also brings about a kind of moral issue: If there's a universe out there for EVERY single choice that was, is, and can be made, does that mean that we are destined to carry out criteria to fit with the model of a universe, and that our choices are irrelevant? Personally, I think a degree of ignorance is helpful in this instance, as it helps to focus on the present of your choices instead of thinking you don't have any choices that are meaningful, in that the universes that are alternate choices don't come into play, UNTIL the choice is made. :)

[@scottmantooth8785]

you're making the assumption that your grandfather (pending) is not a better shot than you and had not been previously warned by an alternate version of himself of your arrival and when to expected it...you would be walking into a temporal ambush...

[@the_kraken6549]

0:59 Badge is transported in and the Tardis rematerializes. Nice touch.

[@tk9102]

Bill and Ted: Grandfather Paradox the movie. I love it though

[@MiddleAgedGuy73]

I love the range of things you watch and cover! I do think Star Wars time travel is somewhat fluid though as Asoka was dead until she was pulled through time. Of course I've barely started the video so perhaps you address things, you're fairly thorough. If you're ever in Oakland California I'd love to pick your brain a bit!

[@skywise001]

For the bridge Id go back early enough to start little whispers about the quality of the product in the bridge. My theory being that they will recignize the material is fine but notice the flaws. Then hype up the shocking and horrifying neglangence to get the momentum going on improvements. Altering time because you want to is one of the worst reasons to do it. Thats why I like the concord of time travel in Trek and the Timelords (before they were killed or not maybie) in their universe. BTW I love your yarn analogy - it works perfectly. Star Trek also uses the string theory of universes a lot of time. Its where the Mirror Universe comes from. The MU also serves as a great warning to not play with timelines.

[@kanebunce3791]

I am glad you showed Rip Hunter. After all, the Time Masters are very much DC's version of the Time Lords. There is a lot of similarities - especially in the Arrowverse.

[@SLagonia]

There's another serious issue with the bootstrap parodox - The Lucky Charms grows a year older in every cycle. Since its an infinite cycle, they should be infinitely old and would have broken down.

[@dperry19661]

I think the sci-fi network continuum got it right. Time travel happens on an alternate timeline. Like on back to the future, Biff asked Marty why he wasn't in Switzerland. Because the Marty that belonged in that timeline was at the European boarding school. Broke ass Marty was screwed, he made his timeline cease to exist. That 4x4 wasnt his it was rich marty's along with that home and that family.

[@480JD]

So where did Rich Marty go?

[@dperry19661]

@@480JD thats the whole problem......once you skew the tangent , you just skewed up

[@davidhonez8859]

@@480JD the same place old Biff went, into nothingness

[@frantisekvrana3902]

3:10 There is another issue with this one. Material objects being looped make the loop unstable. After thousands of cycles, your fingers wear through the box, it falls and spills, ending the cycle. If I was to solve the bridge dillema, it depends on how I learned about the bridge. I would not travel back in time to alter history. If I got there in other way and just happened to spot the fault, I would orchestrate a few trucks filled with dirt to pass over it, faking corpses inside the trucks. The bridge collapses, nobody dies.

[@whade62000]

Something I always point out about "paradoxes": if even a single atom travels back in time, the reality that had 1 extra atom has replaced the one that didn't. Ergo, it is paradoxical. This is easy to see even without going into detail on the hell it plays with physical laws like conservation of energy and whatnot. The idea that you can waltz around in the past as long as you don't affect "important" personal or historical events is a human illusion, we tend to assign more importance to what affects mankind or us personally and ignore the rest, but obviously physics doesn't care about human history, but WILL care about a bit of energy displaced and breaking a fundamental law. Which also means that paradoxes (at least the way they are typically presented) are impossible because if you could travel into the past in the first place and it wasn't impossible, you've already overcome all the paradoxes. In fact "paradox" is better defined as something that makes something impossible in the first place, rather than something that punishes you if you do something.

[@genostellar]

My answer to the bridge problem is simple. Reduce the death toll secretly, or change it from having been deadly to harmful. The lesson is still learned as people are still hurt, so the upgrade are made, but the payment isn't as bad and nobody is the wiser. The causal loop paradox (otherwise known as the predestination paradox) is one that should be self-destroying upon completion. If you have an event that takes place only because someone traveled back to the past to get it started, then one of two situations happens. Either the paradox is stable, such as with relaying an idea and thus cannot degrade, or it's unstable, such when you give an item to the past, which is then given to the past again, then again. This would complete an infinite number of times in the same moment, presumably, but realistically it would complete as many times as it takes for that item to degrade to the point where it would be destroyed, or at least no longer be given to the past. Those glasses that Kirk was given and then sold in the past, supposedly to be gifted to his past self at some point in the future, should have turned to dust the moment he sold them, or sooner. The way that I solve most time paradoxes is simply by removing any concept of the past. The universe exists in an ever-changing 'now' with no past to travel to and time isn't a real thing that exists, only change. Thus, any time travel to the past would involve reconfiguring matter into a previous configuration, which necessarily involves adding energy to the system. In this way, you'd actually be bringing the past to you by having things look as they did in the past, however it would exist in the future of when you were before. Thus, you could kill your grandfather before your parents were born, but it would have no effect on you because this isn't really your grandfather, he just looks and acts like him.

[@StarCrazedMike]

I've always had a bit of a theory regarding the temporal agents and their willingness to interfere with "temporal events" (or rather, peoples' question of the lack thereof): All the instances we see involving a temporal agent from the future interfering with events in some manner boils down to a simple element. One of the "locuses" of whatever temporal event is set in their local timeline. For instance, when Braxton goes back to erase Voyager from existence it is because of a Temporal explosion that occured in his century. Basically, a prior temporal event was causing destruction in their native timeline which would need to be protected of course. Then we start to go microscale, where they were only willing to reveal themselves and enlist the help of Seven of Nine when Braxton (from their native timeline) had gone back to interfere with the past. Therefore, it is likely that since they are incapable of correcting all paradoxes that have occurred throughout time they would only focus on ones that are detrimental to their current timeline. In order for their current timeline to have existed, all previous temporal paradoxes that had no interference from their organization. This is the actual huge temporal importance of the temporal accords, they essentially were creating a fixed point in history in order to be able to maintain a stable timeline moving forward that would ultimately be safer for all living beings. Essentially, all the paradoxes and problems that were caused up until that point that they inherited they "wiped the slate" with the Temporal accords. They would have strict guidelines on how the technology was to be used and it would likely not been a unilateral decision making process either (i.e. a timeship captain couldn't just decide on his own to go back in time, he would have had to have been sent). I think this is the reason it can be so dangerous for these agents to travel backwards themselves. I imagine Braxton is an example of this, where he makes the unilateral decision to go back in time to erase Voyager (since he "apparently" no longer had a governing authority anymore to consult, I personally believe he was a brash Captain that once he made the decision to go back once it doomed him personally in the temporal scheme of things by being a part of the paradox itself. Sorry that sentence was trash, but I'm sure you guys get how messed up it is trying to explain perception of time. Anyways, in a nutshell to try and use your ball of yarn analogy... I think it's quite apt except that it's kind of like one giant ball that is "the big thread" of "important time", while it's kind of knotted together with strands from other paradoxes and loops that were created along the way leading to the temporal accords. But time leading up to the temporal accords then begins to entwine together to form a rope that begins to hold itself together. Before it was splayed and coming from all over the place because it was unstable, and messing with these stages prior to the point of convergence could (as noted) affect it's very ability to converge. They don't fix these paradoxes (like what Janeway caused by going back in time to bring Voyager home) because they can't. This paradox is in a sense an integrated part of their history. I've always had a cute imagining where we as the audience are actually temporal agents peeking back into events to gain an understanding that were not "recorded in history" (such as Yesterday's Enterprise). If you've read all this, thank you for your time. I'll admit some all natural herbal remedies helped me write this, so it's probably longer and more convoluted than I hoped... But I hope I tickled your noodle a bit.

[@garrysmith9515]

The Grenfell Tower fire could be a good example of this. The event was tragic, and lives were needlessly lost. However, some good will come of it eventually. Not least of all, updates and better enforcement of existing laws and regulations will make builders think twice before using inferior cladding to save a few bucks, as well as incentivizing them to think in longer terms or risk fines/imprisonment/etc... BUT! If someone went back in time(say, for example, the child of one of the victims) and stops the fire from happening to save their parent, it could cause all sorts of issues. Especially ones involving future buildings with similar cladding, thus exacerbating the already existing issue.

[@BainesMkII]

Bootstrap with a physical object has an often overlooked issue. (Though some stories do address it to a degree.) The object being transferred will age, and thus the object you take back is not the same state as the object you received. Depending on how you define time travel as working, there is a further issue in that the object will accumulate age with every loop. Even if you receive a fresh box of Lucky Charms, you'll be sending back a year old box of Lucky Charms, which means you receive a year old box of Lucky Charms (not a fresh box), which means you send back a two year old box of Lucky Charms, which means you receive...

[@jeckjeck3119]

Maybe it stops aging due to it being a part of paradox?

[@BainesMkII]

@@jeckjeck3119 Wouldn't make sense for the paradox itself to magically make an object immune to aging, indeed it would have to be immune to all forms of change, presumably to a sub-atomic level. No energy in or out, no decay (whether biological or atomic), no viruses sneaking in, no dirt or dust accumulating, nothing that would change it in any fashion. Like I said, some stories cheat matters with some other form of time adjustment, such as a character being reborn or de-aged through some other means before the "back to the past" moment occurs.

[@jeckjeck3119]

@@BainesMkII So it becomes like Jack? No regeneration, but a fact that can not be changed.

[@MrEscape314]

Didn't happen the way they describe if you actually read the original, Bootstrap. He creates a new version of a hand written book, by hand copying it before it travels back in time. This the book is only as old as the time from copying to travel back until its worn down and copied.

[@BainesMkII]

@@MrEscape314 Yes. You receive a book; then ultimately send back an identical recreation of the book as it was when received. That works fine enough for a story. But when you sit down and think about it realistically, you aren't sending back a truly identical copy. And if the copy being sent back doesn't have to be truly identical, then how much leeway is allowed? Can you send back a book where you've rewritten some of the sentences? What if you smudge some pages, or use different paper? Does writing the next copy in crayon cause a collapse of space-time? If you allow for the idea that time self-stabilizes itself, adjusting or updating to fit the new reality of the book, then you've simultaneously opened a door to resolve the paradox. You've now got the possibility of, some unknown number of iterations back, a true origin of the original book. (As well as an origin of the loop itself; a timeline where no time travel had yet occurred.) Time has just, over potentially countless iterations, reached a fairly stable circumstance where you create an on-the-surface functionally identical copy of the book and send it back. (Even here this isn't necessarily truly stable, nor indeed is the book being sent back even necessarily the original origin of the loop.)

[@oliverewarthopkins7818]

The most epic example a paradox in Star Trek that I can think of in Trek is the paradox with the Borg.

[@TheZamaron]

For Star Trek time travel, we have seen paradoxes like First Contact, and that if you change history you change the future also First Contact, but we’ve also seen that alternate timelines exist alongside the main one, so the ray thing to do is just nod your head and don’t think too much about it.

[@AngelicaLeDang]

I Think it is best to let things play out on its own and learn from them or else humanity of a person will not develop or evolve

[@ducknorris233]

There are mini alternate universes on our world. Laws are often enacted after a catastrophic event like a bridge collapse, theater fire, child being injured etc. But in some communities they never had the catastrophic event so they never enacted the law or ordnance to prevent it the future. You can see this in action when visiting another city or state that has seemingly peculiar laws.

[@emporer15]

Solution to causal and bootstrap loops: An original you in a future timeline created the message or object to bring back along with the information to your past self of the exact instructions of what to do to sent it back in time along with the same instructions to go with it. This creates an origin point that will continue to loop.

[@prometheuslxi3125]

I always thought of it as that one theory that I can never remember the name to but it goes like if you go back in time to prevent something from happening your actions or inactions are what caused the event in the first place

[@MysteriousMose]

I think the best argument against history-changing is from the Trek episode with the time-travelling historian. Basically, 'why should I meddle to save people who, for me, have already all been dead for centuries either way?'

[@Kingramze]

The problem with a physical object (like a box of lucky charms) being part of a loop is that the physical object will continue aging and deteriorating throughout each loop. Information is immutable, but even a block of stone would wear more with each loop until it's eroded by handling and time.

[@Kingramze]

One possible solution to the bridge problem would be to cause the bridge to fail when it is not in use - and do so in a way that mimics the original cause of the failure. It may not get the public exposure of the original destruction as lives wouldn't be lost, but it would lead to an investigation that would discover the flaws and lead to the same regulations. Whether the regulations would be implemented at the same speed or be of the same quality would primarily depend upon the severity of the flaws. Since there were no public deaths, a legislative solution might be slower to respond, but it would still make sense for anyone currently working on such a bridge design to adapt their designs immediately according to the recommendation of the investigators.

[@gmartuch]

stargate also has a few episodes about TIME TRAVEL. sg1: 1969 (episode), Window of Opportunity, 2010 (episode), Moebius part 1 and 2; sg1 movie: Stargate: Continuum; Stargate: Atlantis: Before I Sleep, The Last Man; and Stargate Universe: Twin Destinies.

[@dugclrk]

Time travel will never happen as it's completely impossible. With the exception of Dr. Who, I hate, hate, hate time travel in sci-fi shows. I just makes everything moot. Time travel would create alternate realities every time even one little thing changed, so what would be the point? Your original timeline is still there and now there is another, a whole new universe created by one time traveler.

[@DrewLSsix]

Time travel is not impossible. It’s actually measurable and there are several mathematically supported routes to accomplish it.

[@dugclrk]

@@DrewLSsix Not sure I believe this. Is it at the atomic level will genuine mass or just information that has time traveled. I'm not referring to the space time relativity but genuinely having something go BACK in time.

[@AdamantLightLP]

Not to mention, those tragedies are in the past, they are important to our history and our development. Changing them is a bad bad bad idea. But as you said, I agree it's impossible. Mathematically they have some models for it, but it requires impossibilities to exist.

[@AdamantLightLP]

@@pupip55 that's kind of really simplified, and still pretty wrong.

[@AdamantLightLP]

@@pupip55 I've looked into it quite a lot. It's nothing but thought experiments and mathematical models that again, require impossibilities. It's not happening, and our world is far better off for it.

[@spluff5]

The answer to the bootstrap paradox is that the lucky charms will keep cycling around until they expire and its no longer something you wanna give to your past self. Then you just have a regular beaching time line-style paradox.

[@echemh]

An example I like to use is of the famous shipwreck Titanic. Very tragic, but look how much good came out of it. Laws and regs were changed to make sure it wouldn't happen again.

[@alexanderglass2057]

My solution to the bridge problem. Say to the engineer “‘ay mate! Don’t you think it is good practice to over engineer your bridges, you never know what is going to be traveling across it in the future.” And if he doesn’t see that as common sense I’ll straight out tell him I know what will be on it in the future and he needs to overengineer it and hopefully he becomes an advocate for over engineering everything to do with people, either for fear of a time traveler getting on his case or because he genuinely sees it as common sense.

[@koodude2313]

It's not like you'll get away with making a change. They're watching. Always watching....

[@shmee123ful]

When I get my next pay I'll see if I can get those books

[@dmkatelyn]

My favorite temporal mechanics explanation comes from Andromeda, the late 90s space opera that looks to heavily inspire Discovery Season 3. The title character, the Andromeda Ascendant, gives the crew a crash course in time travel explaining the two prevailing ways it can play out: "Our timeline is contiguous to this one" where everything happens as the history the characters know says it does (Trials and Tribulations, DS9) and therefore not faithfully reenacting history exactly has disastrous outcomes, or "multiple possible futures" in which each alteration creates a new timeline (Star Trek 2009) in which case alterations are the problem of another timeline. In a lot of sci fi it's clear that both exist side-by-side as the story demands, usually the former is what happens in the actual time travel stories where the latter justifies multiverse stories.

[@jeremyanderson5828]

And this is where I like to envision different types or qualities of time machines allowing access to different types of time travel. Although, it could be hard to imagine or describe how a non multiverse machine could work in a multi verse.

[@voodoo1069]

If you could either use the knowledge of when the bridge will fall or cause the bridge to fall in away that wouldn't look like someone did it. Then set it up so the lose of life is much smaller or non with minor problems to traffic and access to the bridge before it falls. No one can tell the butterfly effect from this but it should still allow the impact of the event to carry most of the weight it would of other wise had and still have an event that would cause you to come back to change.

[@HeavyMetalMouse]

An interesting consequence of the ethical argument on offer: Going back to prevent something bad happening is most often undesirable because it prevents the progress that event would have inspired; when you have time travel, choosing not to prevent the tragedy is an *active* choice, not merely a 'nonchoice'. It is like seeing a person standing on railroad tracks with a train visibly coming, and choosing *not* to warn the man, or help him get out of the way - you still had the ability to act, and made a choice of what to do about it, ultimately deciding that one choice was 'better' than the other. If, then, you find that it is superior to 'let bad things happen', what is to stop that from being ethically equivalent to it being superior to *make* bad things happen in such a way that they can teach lessons or spur progress? If we place ethical value on a group's ability to make their own destiny based on what happens to them, then surely given them *more* opportunities to do this is more ethical. Experiencing a few hundred years of peace and cultural stagnation? Time travel in there to rock the boat a little and get them going again, for their own good! Even attempting to derive some 'natural ethical value of non-interference' becomes problematic, because at what point is an event considered 'natural'? You yourself acquiring time manipulation was a natural consequence of the events of your history, so are not the things you cause to have happened just as 'natural' as anything else? If a disaster only happens within the timeline because of the *choice* someone makes, based on their intentions for future events, is that a natural event, or does the act of choice make it an imposed disaster to correct? What is the difference between: an asteroid impact on a planet; a similar asteroid traveling back in time through a wormhole to impact the planet; or you getting in your timeship, going back in time, grabbing a nearby rock, and hucking it at the planet?

[@BrettCaton]

The lucky charms gets older on each loop, creating divergent futures. This is a problem that is almost always forgotten - the loop has a subjective time element. The object ages along, and even the best possible material will decay.

[@seanrea550]

How i would deal with the bridge problem, allow the bridge to be built as is. Calculate when the problems could be found by inspection or demonstration predicting the collapse. New flaw is found and regulations put in to play to counter. It hold have to be a precise process to do right which would make it difficult. In essence finding the secondary nexus of events that bypasses the original tragedy.

[@the_kraken6549]

One way to address the bridge hypothetical might be to find a time before it collapsed where it was empty for long enough to get a few heavy enough vehicles across (with secret self driving technology form the future, which seems like you could bring with you?), to collapse the bridge on purpose. Not sure how you would disguise the fact no one died tho.. Maybe if you could find or create a point like this where it was unstable enough for just one really heavy truck to do it, you could fake your own life, and then death to make it seem like you were the casualty.

[@DONTFMEGUY]

A spit second before the bridge collapses, teleport everyone about to die to a far away location. Have them live out their lives outside the eye of history. Meanwhile history proceeds as if everyone dies and mankind learns the lessons from the bridge collapse

[@jeremyanderson5828]

Yeah, just freejack them already.

[@MisterHavoc]

You missed a very obvious, and well done (imo anyway) answer of the "Lucky Charms" paradox! There's a multi-part episode that binds multiple SEASONS together in Babylon 5 (Season 1: Babylon Squared, Season 3: War Without End 1 & 2). It even explains the 2000 year old Minbari history of Valen, the "Minbari not born of Minbari that the universe had delivered to them in their hour of need."

[@jm823]

When it comes to the "bridge paradox" I wouldn't interfere, I would let those that died die for the sake of future continuity, but if there was a individual whose death would greatly impact humanity ex:a cure for "insert cure" I would interfere in as much as to deviate said individual away from that situation even if if this cure occurred decades down the road.

[@TheMyrmo]

"I am YOU from the future. There's no TIME to explain!" /me shoots putative future me "I think you just shot future you." "If he was really future me, he would have known that was going to happen."