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Old 02-11-2020, 09:34 PM
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No-paradox time travel is invented. Should it be shared with the world?


Imagine that you're hyper-genius friend QUERCUS SHOSANNA reveals to you that she has invented a time machine. Quercus's technique is subject to the Novikov self-consistency principle, (https://en.m.wikipedia.org/wiki/Novi...ency_principle ) meaning that travel in this fashion can never effect a change in history. Trying to avert anything known to have occurred ó weather as trivial as a failed geometry test or as monumental as 9/11 ó will always fail. Both the mathematics of Quercus's theory and experimental evidence (she has already made more than a hundred time travel trips) bear this out. She even takes you back several times so that you can see this for yourself.

Quercus's time machine does not allow for travel into the future of the traveler, only the past. Assuming a traveler chooses to return from their trip (that is neither required nor assured), they always arrive approximately 427 milliseconds after leaving. Additionally, because of the way the machine works, travelers are gravitationalally locked to the nearest planetary body when using it. In other words, they don't have to worry about accounting for the Earth's movement through space when using the machine, as they are unable to leave the Earth in the first place. Again, both the mathematics of Quercus's theory and repeated experimental evidence bear all this out.

Quercus has shared this knowledge and experience with you because she values your opinion. She is considering whether to share this knowledge with the world. How do you advise her on this issue?
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Old 02-12-2020, 01:04 AM
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Is there any reason not to? If you can't change anything, it's more like a VR time viewer than a time machine. Maybe do a little more beta testing with a variety of experts first, but then roll it out.
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Old 02-12-2020, 05:38 AM
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Here's a (possibly opposing?) view: People here-and-now are making decisions all the time, and these decisions are based in part on our knowledge of the past. But our knowledge of the past is incomplete and not always accurate. (Just think of all the secrets our politicians keep and the lies they tell. If the truth were known, other people would be making different decisions.)

So if someone could go into the past and discover stuff for themselves, and could then bring this knowledge back with them (which they might or might not share with others), then they (and perhaps others) will make different decisions than they would have.

I don't know, and won't speculate, whether this is a good idea. But one could ask if it would be a bad thing if this time machine were only available to some people and not equally available to everyone. Can it be good if some people can make decisions based on "insider knowledge" that is not available to everyone?

Of course, that happens all the time already. The Q.S. time mochine will just make it even more so.
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Old 02-12-2020, 06:07 AM
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Novikov's self-consistency principle does not mean that a time traveler can't change things, any more than it means that we ordinary non-time-travelling beings can't change things. It just means that when you change things, they stay changed. Effects can still be caused by a time traveler; it's just that the traveler, when they step into their machine, will already remember those effects (assuming they're something the traveler knows of).

And you tried to get around some of the problems by preventing "travel into the future", except that you removed the parts that are no problem at all, and left in the parts that cause the big problems. Travel into the future is easy, and we already know how to do it.
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Old 02-12-2020, 07:34 AM
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If the world had access to a time machine of this type, society would quickly crumble in a sea of anarchy and criminality.

Imagine all those with evil intent who are kept in check by the fear of consequences for their actions. With a way-back machine, consequences could be easily avoided.

Want to murder someone? Go for it. If the cops start closing in on you, go back in time and start with a clean slate. Do it again if you want. Keep murdering until you get away with it. Not only does the victim in your current timeline get murdered, but all the alternate timeline victims get murdered, too. Thatís a lot of murdering for one person to endure.

Personally, I would consider it excessively inconvenient to be murdered more than once.

This scenario assumes Chronoís interpretation. In the OP version, youíd just have to commit the crime (once or multiple times) and go back further in time each time so that the consequences never catch up to you.
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Old 02-12-2020, 08:38 AM
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If the world had access to a time machine of this type, society would quickly crumble in a sea of anarchy and criminality.

<snip>

Why would your scenario of criminals escaping prosecution via time travel be any worse than their doing so by traveling to countries lacking extradition with the jurisdiction where their crimes occurred?
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Old 02-14-2020, 07:46 AM
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If the world had access to a time machine of this type, society would quickly crumble in a sea of anarchy and criminality.
...
Want to murder someone? Go for it. If the cops start closing in on you, go back in time and start with a clean slate. Do it again if you want. Keep murdering until you get away with it. Not only does the victim in your current timeline get murdered, but all the alternate timeline victims get murdered, too. Thatís a lot of murdering for one person to endure.
Novikov self-consistency specifically rules out alternate timelines. If you go back in time and change something, that change has always been there and is part of the future timeline, even if you didn't know about it when you set off.

For instance you could go back in time, set up a few high-interest savings plans or shares portfolios, and come back to the present to collect the money and the interest. Those bank accounts have always been there, it's just that you need not have known about them before you set off. The invention of Novikov-consistent time travel could cause financial havoc in a fairly short time, by concentrating wealth into the hands of time-travellers.
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Old 02-17-2020, 05:12 PM
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Novikov self-consistency specifically rules out alternate timelines. If you go back in time and change something, that change has always been there and is part of the future timeline, even if you didn't know about it when you set off.

For instance you could go back in time, set up a few high-interest savings plans or shares portfolios, and come back to the present to collect the money and the interest. Those bank accounts have always been there, it's just that you need not have known about them before you set off. The invention of Novikov-consistent time travel could cause financial havoc in a fairly short time, by concentrating wealth into the hands of time-travellers.
See Mack Reynolds' short story Compounded Interest..!
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Old 02-14-2020, 07:58 AM
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If the world had access to a time machine of this type, society would quickly crumble in a sea of anarchy and criminality.

Imagine all those with evil intent who are kept in check by the fear of consequences for their actions. With a way-back machine, consequences could be easily avoided.

Want to murder someone? Go for it. If the cops start closing in on you, go back in time and start with a clean slate. Do it again if you want. Keep murdering until you get away with it. Not only does the victim in your current timeline get murdered, but all the alternate timeline victims get murdered, too. Thatís a lot of murdering for one person to endure.
This is completely incompatible with the OP's scenario.
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Old 02-14-2020, 08:24 PM
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If the world had access to a time machine of this type, society would quickly crumble in a sea of anarchy and criminality.

Imagine all those with evil intent who are kept in check by the fear of consequences for their actions. With a way-back machine, consequences could be easily avoided.

Want to murder someone? Go for it. If the cops start closing in on you, go back in time and start with a clean slate. Do it again if you want. Keep murdering until you get away with it. Not only does the victim in your current timeline get murdered, but all the alternate timeline victims get murdered, too. Thatís a lot of murdering for one person to endure.

Personally, I would consider it excessively inconvenient to be murdered more than once.

This scenario assumes Chronoís interpretation. In the OP version, youíd just have to commit the crime (once or multiple times) and go back further in time each time so that the consequences never catch up to you.
You would have to be awfully eager to commit those crimes, in order to live out your life in a society without conveniences, modern medicine, etc.
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Old 02-12-2020, 08:27 AM
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Novikov's self-consistency principle does not mean that a time traveler can't change things, any more than it means that we ordinary non-time-travelling beings can't change things. It just means that when you change things, they stay changed. Effects can still be caused by a time traveler; it's just that the traveler, when they step into their machine, will already remember those effects (assuming they're something the traveler knows of).

And you tried to get around some of the problems by preventing "travel into the future", except that you removed the parts that are no problem at all, and left in the parts that cause the big problems. Travel into the future is easy, and we already know how to do it.

I'm happy to yield to your superior understanding of the physics. But let's ignore that part. Simply granted that Quercus's machine allows for backwards travel only, not alteration of history, is there any reason to oppose the dissemination of the technique?

As for the elimination of future travel, I did THAT simply because I'm not interested in it.
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Old 02-14-2020, 08:55 AM
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I'm happy to yield to your superior understanding of the physics. But let's ignore that part. Simply granted that Quercus's machine allows for backwards travel only, not alteration of history, is there any reason to oppose the dissemination of the technique?

As for the elimination of future travel, I did THAT simply because I'm not interested in it.
Not to fight the hypothetical . . . but what do you mean by "not alteration of history"?

To me, that seems to mean, "no change in anything, no matter how small" (which you imply in your OP).

While, how can one be in a place without effecting it? Displacing molecules that weren't displaced before.

A problem with popular "history is fixed, but we're going to time travel anyway" stories is that they only focus on a few specific outcomes as being fixed. Things that happen to be in the history books. The problem is that "history" is literally everything that happened, not just the things that have been recorded or that we have direct evidence of in the present. There is no way for a person to be in a place they weren't before, and have zero impact on the history of that place.
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Old 02-14-2020, 11:31 AM
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Not to fight the hypothetical . . . but what do you mean by "not alteration of history"?

To me, that seems to mean, "no change in anything, no matter how small" (which you imply in your OP).

While, how can one be in a place without effecting it? Displacing molecules that weren't displaced before.
But they WERE displaced before, because the time traveler displaced them.
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Old 02-12-2020, 09:01 AM
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I am always happy to help Quercus with the practical and ethical deficits which commonly accompany genius. In order to answer her truthfully I must know what she knows about this tech and the theory behind it. Once this is done, the only question is whether to strangle Quercus or abandon her in the distant past using her own machine. Time travel of this sort brings only knowledge. Knowledge contributes to insight and thus power. Should Quercus share this tech? To even pose this query is madness, for to do so is to share power. Infantile.
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Old 02-14-2020, 08:58 AM
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And, all that is to say, I'm not sure what time travel looks like in this context. If the traveler can't interact in any way with any matter or substance of the past (which doesn't sound like time travel at all), then what benefit or use is this tech to begin with? How do you even know you've time traveled, if you can't prevent photons from reaching the blade of grass behind you by intercepting them with your eyes?
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Old 02-14-2020, 09:01 AM
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Somewhere I read a short story on something similar - it was a view-only time-machine, so no problems with changing the past. Now that I think about it, I've read two stories like that, one may have been Dangerous Visions.

It was ruthlessly controller/suppressed by the government because it was the ultimate surveillance app (in one story - the other imagined what society would be like if it was generally available) - the past is the instance that happened just before now, so given the desire to look, you could basically use it to watch anything real-time.

At any rate, it would completely upend current view of privacy - I could pop into the Oval Office and listen to the president at will. I think general access to such devices would lead to a more open society. Not sure if that would be a good thing or not - certainly no way to know, since we can't use it to future travel.

Last edited by Folacin; 02-14-2020 at 09:03 AM.
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Old 02-14-2020, 09:26 AM
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I think most people are misunderstanding the mechanics of the Novikov consistency principle. Your time travel actions would already be part of history, even before you do it. It’s not that you can’t change anything, it’s that your changes have already had the effects on your current timeline.
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Old 02-14-2020, 10:27 AM
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I think most people are misunderstanding the mechanics of the Novikov consistency principle. Your time travel actions would already be part of history, even before you do it. Itís not that you canít change anything, itís that your changes have already had the effects on your current timeline.
That's right; that is what consistency means in this context. It doesn't mean that you can't go back in time and do things; it just means that the things you do are already part of history. So you could go back and open some high interest accounts, but they would already be part of history before you set off.


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Somewhere I read a short story on something similar - it was a view-only time-machine, so no problems with changing the past.
..., it would completely upend current view of privacy - I could pop into the Oval Office and listen to the president at will. I think general access to such devices would lead to a more open society. Not sure if that would be a good thing or not - certainly no way to know, since we can't use it to future travel.
We've discussed the view-only time machine in a recent thread, about whether it would kill religion. My own opinion about this was that it would not, but it might kill certain religions that are based on lies. It could also kill certain political movements that are based on lies too.

Don't forget that we can travel into the future, using current technology, just by waiting for things to happen in the normal way.
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Old 02-14-2020, 10:36 AM
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I don't know for sure my bitter enemy George is alive, but don't have any reason to believe him dead. Can I go back and kill George? A world with a dead George is not incompatible with the way I understand the world to be at the moment.
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Old 02-14-2020, 11:29 AM
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That is possible. You do not know if you will be successful, but you do not know you won't.
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Old 02-14-2020, 11:41 AM
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Even a view-only time machine would have huge negative consequences.
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Old 02-14-2020, 01:14 PM
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Even a view-only time machine would have huge negative consequences.
Welcome to the fishbowl.
Asimov's The Dead Past, one of the stories I was trying to remember.

And it would have huge consequences, negative in the short term. Hard to say how society would adjust to it. In the other story I recall (but not the name of), things were fine - there was just no expectation of privacy. Humans are an amazingly malleable species.
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Old 02-14-2020, 01:22 PM
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Asimov's The Dead Past, one of the stories I was trying to remember.

And it would have huge consequences, negative in the short term. Hard to say how society would adjust to it. In the other story I recall (but not the name of), things were fine - there was just no expectation of privacy. Humans are an amazingly malleable species.
Whether or not there are privacy issues depends on whether your machine actually sends you into the past, or whether it's a viewer. If it's just a viewer there are massive privacy issues, but if you actually get physically sent it's no easier to sneak into somebody's house and peek into the shower yesterday than it is to do it today.

Actually, not that I think of it, it is easier - or rather safer, because you know you won't get caught. You might fail utterly (and in fact will probably fail to get anywhere near the house, because your clumsy butt would have been seen by the neighbors and wasn't), but if you know you weren't detected/arrested yesterday you can make as many slapstick attempts as you like with no risk of anything worse than an accidental karmic death that leaves your body rotting undetected in the chimney for weeks.
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Old 02-14-2020, 01:56 PM
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Actually, not that I think of it, it is easier - or rather safer, because you know you won't get caught. You might fail utterly (and in fact will probably fail to get anywhere near the house, because your clumsy butt would have been seen by the neighbors and wasn't), but if you know you weren't detected/arrested yesterday you can make as many slapstick attempts as you like with no risk of anything worse than an accidental karmic death that leaves your body rotting undetected in the chimney for weeks.
I read the OP such that the time machine is a TARDIS, but is stuck on Earth - so I could use it to materialize directly to an location.
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Old 02-14-2020, 05:48 PM
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I read the OP such that the time machine is a TARDIS, but is stuck on Earth - so I could use it to materialize directly to an location.
My assumption was the phone booth time machine from Bill and Ted's Excellent Adventure/Bogus Journey, movies that are extremely blatant about the fact that they use the "you can go back and interact, but everything you do had already happened even before you even decided to go back in time" model being discussed in this thread.

And be it phone booth or police box, neither are short enough to fit in a room with eight foot ceilings without putting a hole in the roof. If you're using one of those machines you're not going to materialize inside their house or anywhere else close enough to peek in their windows without attracting a lot of attention. And even if your time machine is a wristwatch, you're still physically there - you have a distinctly nonzero chance of being observed while peeking. If doing so would have got you caught, when you hadn't get caught, that means that either you will be (aka were) successfully stealthy - or that events transpired to prevent you being there at all.

And that's just peeking at somebody showering. A decent set of security cameras and security guards would be sufficient to completely stymie time travelers attempting to infiltrate after the fact into anyplace that didn't see them there before, and of course if nobody extra was seen infiltrating events in a closed area then there's nothing for a later time traveler to do. Hordes of thousands weren't recorded visiting the Last Supper, so time traveling tourists will be out of luck.

They could probably visit some of the sermons, though. BYOLAF.

(Pretending that the bible is factual.)
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Old 02-15-2020, 09:14 PM
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In the other story I recall (but not the name of), things were fine - there was just no expectation of privacy.
That's probably "I See You" by Damon Knight.
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Old 02-14-2020, 12:25 PM
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In order to really understand the hypothetical, we would need to know how the Novikov self-consistency principle is enforced. Either there are going to have to be severe restrictions on the application of the time machine, or else there are going to be severe restrictions on free will.

So what happens if a person sets the time machine to a place where he historically wasn't? Does the machine simply fail? In that case I would imagine that there would be a lot more failures than there are successes. Also if you do succeed in going back but try to act ahistorically what happens.

The easiest solution to this is a look but don't touch style time machine. The other way would be a more useless version in which you could send particles back in time but had no control over where they ended up and what they did. Sort of like the reason you can't use quantum entanglement to send information. The third possibility would be to totally eliminate free will. While it may already be the case that free will doesn't exist and what we think of as free will is an illusion, the existence of such a time machine would instantly dispel that illusion as the first thing any experimenter would try would be to go back 5 minutes and say hello to ones self.
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Old 02-18-2020, 04:19 PM
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In order to really understand the hypothetical, we would need to know how the Novikov self-consistency principle is enforced. Either there are going to have to be severe restrictions on the application of the time machine, or else there are going to be severe restrictions on free will.
It's neither. It is simply that there is only one universe and time runs in one direction.

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Also if you do succeed in going back but try to act ahistorically what happens.
You didn't act ahistorically.
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Old 02-18-2020, 05:49 PM
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It's neither. It is simply that there is only one universe and time runs in one direction.


You didn't act ahistorically.
That is certainly what I intended in writing the OP, but it occurs to me that there is another possibility. Perhaps Quercus's machine creates a new reality each time backwards travel is used, but she also knows how to lock on to the original reality in each return trip. in other words, before her initial time travel trip (assuming she was the first time traveler ever), there were exactly 6^6^6 universes, but the action of her machine added one more, so that the new total was 6^6^6 +1. Each universe has a slightly different technobabble signature, and her technology permits her to home in on her original universe for each trip. thus it is not so much that no changes are allowed as it is that neither the time traveler nor the inhabitants of the "original" universe experience them. Thus no paradoxes.

This also would explain why Quercus works neither for Apple, Microsoft, nor Freedom Scientific .She is too competent to be an engineer for either company.
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Old 02-18-2020, 06:11 PM
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That is certainly what I intended in writing the OP, but it occurs to me that there is another possibility. Perhaps Quercus's machine creates a new reality each time backwards travel is used, but she also knows how to lock on to the original reality in each return trip. in other words, before her initial time travel trip (assuming she was the first time traveler ever), there were exactly 6^6^6 universes, but the action of her machine added one more, so that the new total was 6^6^6 +1. Each universe has a slightly different technobabble signature, and her technology permits her to home in on her original universe for each trip. thus it is not so much that no changes are allowed as it is that neither the time traveler nor the inhabitants of the "original" universe experience them. Thus no paradoxes.

This also would explain why Quercus works neither for Apple, Microsoft, nor Freedom Scientific .She is too competent to be an engineer for either company.
Well in that case the fact that everybody is going to grab a bunch of weapons and just murder the crap out of everybody in the past is no problem at all; the minute the person returns to the present the alternate timeline effectively ceases to exist as far as the original reality is concerned. Okay, sure, there's a certain moral factor to the fact that all the damage you did continues on existing in its own isolated dimension, all the injured and dead and infected and irradiated people keep suffering despite your absence. But would anybody in the original reality even know this is happening? For all they know this might as well be a video game that resets each time you play - albeit one that you can die in and/or never return from.
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Old 02-18-2020, 06:34 PM
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Your mere presence in the past profoundly affects it regardless of what you do or don't do (the butterfly effect), 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.

If such a device existed and was widely available, we'd certainly have a far more accurate knowledge of history, but culturally, the major impact I think it would have is the demise of all religions.
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Old 02-14-2020, 12:31 PM
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If the premise is that outcomes are fixed, then I see no reason why it shouldn't be shared. I don't think there are ethical problems about learning "the real truth" about past events.
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Old 02-14-2020, 12:54 PM
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Ah, the "Bill and Ted" time model. The one where you can go back and do anything you want, but everything you do already happened before you left, so you can't change history - or more precisely, you can't change any history that you or anybody else knows. If I know that I had a grandparent who survived puberty, no time traveler can possibly go back and change that fact, whether or not I know that they're up to.

If this time machine involves people physically going back in their phone booths and being physically present in the timeline, then there is no possible harm in going back or letting anybody else go back - or rather, any harm they might do has already happened and they quite literally can't make things worse. So there are only two possible negative consequences to this sort of time travel:

1) People can go into the past and not come back, either staying until their natural deaths or until their abrupt unnatural deaths. This can be bad if you wanted to arrest them and bring them to trial, or if you just want to spend time in their company.

2) People might be able to learn things they otherwise wouldn't. This might enable them to get ahead in life, which is always a bad thing.

Other than those things though, there's literally no risk (and no benefit) to letting people go back in the past.

Not that you have a choice. The side effect of the Bill and Ted time model is that the entire timeline, past and future, is fixed and unchanging. There cannot be multiple possible futures - if a bunch of creepy dudes appear in a tomb, steal a body, and pretend to be angels and the dead person's body double for a while, that means that two thousand and twenty-four years later a group of dudes will hatch a plan, get together costumes, makeup, and drones capable of lifting a person into the sky, and then take all that back with them via their walmart-issue time machine. The future that includes those events is already determined, which means that all future events are already determined. This is an unavoidably true in the Bill and Ted time model.
  #34  
Old 02-14-2020, 02:24 PM
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With the Novikov self-consistency principle operative, any journey back by a human would be fruitless, because 1) anything done there has already happened, and 2) there's no guarantee of return; the traveler dies back there. I'd like to see the return-rate tables - how many make it back from which years? Is 33 CE a sinkhole for temponauuts?
  #35  
Old 02-14-2020, 02:55 PM
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It is even worse in a 'multiple-timelines' version of time travel; the traveller might attempt to come back, but returns to the wrong future. You could wander through multiple versions of reality forever, never finding the place where you started.

Or using another model of time travel, sometimes called the 'radical rewrite' model, you can change history just by being in the past, and thus destroy the future that you came from. This is more-or-less the model used in Back To The Future and The Butterfly Effect.

Compared to these options, Self-Consistency is relatively benign.
  #36  
Old 02-16-2020, 01:35 AM
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Originally Posted by Skald the Rhymer View Post
Trying to avert anything known to have occurred ó weather as trivial as a failed geometry test or as monumental as 9/11 ó will always fail. Both the mathematics of Quercus's theory and experimental evidence (she has already made more than a hundred time travel trips) bear this out. She even takes you back several times so that you can see this for yourself.
I see no mention of temporal range limits - how far back can we travel and return? Nothing about spatial displacement either - can a target location be chosen or are we stuck in one spot X km from Earth's core? I wouldn't want to slip back a few centuries from suburban Fresno and emerge far under the surface of the lake then covering the San Joaquin Valley.

Quercus may have notched hundreds of trips and taken us on a few, but where to and how long? Consider Larry Niven's early displacement booths. Vertical jumps cause temperature differentials so with great leaps we emerge freezing or baking. Large temporal displacements should have similar effects. That fireball on the horizon? Just another early time traveler burning up.

What is the temporal displacement mechanism - a booth, body wrap, amulet, implant? How does a downtime voyageur trigger their return or is the duration preset, tightly scheduled? Have they an emergency Bug-Out! switch?

Assuming travelers have some (if unknown) chance of return, and they can't change things, the ethics / morality of revealing this technology IMHO depends on temporal range limits. Zip back a few hours or days to spy on family, friends, foes, celebs? Not good. Flash back to a dangerous time? There should be cheaper suicide methods.

Oh yes, what's the energy expenditure? Is power from a small fission reactor needed?
  #37  
Old 02-16-2020, 08:02 AM
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My answer depends on the history of this world. You see, if she goes public and everyone has the ability to use this, then there is no chance that there is not evidence of time travel in the past. Even if everyone tries to be secretive about it, there would be an extremely high number of people using it, and some will slip up enough for it to wind up in recorded history. Not even a secret organization could keep it secret.

So, if there is no such evidence in history, then my conclusion is one of the following: (a) she will decide to not take it public (2) something will happen to her to keep her from going public (III) something happen to humanity to prevent it from being used too much. Of those options, option A seems the least bad, so I would encourage that, while sharing my logic.

If, on the other hand, there is sufficient evidence of time travel in the past, then it seems humanity is destined to learn about it, so she might as well go public. Though I could throw in a little test where I, like Hawking in our universe, set up a party where I invite time travelers after the fact to show up. Assuming I get the word out sufficiently, someone will eventually decide to show up. And then I can just ask them how time travel became public.
  #38  
Old 02-16-2020, 10:00 AM
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If I understand the O.P. correctly:

We cannot change history a hundred years ago.
We cannot change history ten years ago.
We cannot change history ten minutes ago.
We cannot change history one microsecond ago.

Which raises uncomfortable questions about how much free will we have in the present.

"Should it be shared with the world?" Well, if the past is fixed, then the decision is probably predestined anyway.

I would say, go public. Let the history of every corrupt politician be revealed. There's some embarrassing stuff in my past, but nothing that would ruin me if it were exposed.
  #39  
Old 02-17-2020, 04:48 PM
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If I understand the O.P. correctly:

We cannot change history a hundred years ago.
We cannot change history ten years ago.
We cannot change history ten minutes ago.
We cannot change history one microsecond ago.

Which raises uncomfortable questions about how much free will we have in the present.
Questions nothing - an unchangeable timeline is an unchangeable timeline. If you believe in a free will that requires you to defy causality then your free will cannot exist.

If you're a compatiblist there's no problem of course, but most people it seems can't accept compatiblist free will.
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