On Instapundit aka the Blogfather I see...
OKAY, the links didn't come through.
A PHYSICIST PROPOSES LAWS OF TIME TRAVEL.
He omits Niven’s Law of Time Travel, though: “If the universe of discourse permits the possibility of time travel and of changing the past, then no time machine will be invented in that universe.” The reason is that if it’s possible to change the past — and, thus the present — change will continue until it reaches the stable state in which no time machine is invented anywhere. Or as Hans Moravec glosses it:
There is a spookier possibility. Suppose it is easy to send messages to the past, but that forward causality also holds (i.e. past events determine the future). In one way of reasoning about it, a message sent to the past will “alter” the entire history following its receipt, including the event that sent it, and thus the message itself. Thus altered, the message will change the past in a different way, and so on, until some “equilibrium” is reached–the simplest being the situation where no message at all is sent. Time travel may thus act to erase itself
So maybe it already has.
Doesn't that seem like a convenient way of simply explaining away why there's no time travel in our universe? It's not really a 'theory' on time travel. Why should the 'simplest' state be one in which no message was sent? Wouldn't it be just as simple if no message were received? Or if the message were received and someone made a conscious choice to either 1: Not change anything based upon it, or 2: use the information in the message secretly (as in paragraph 6 )?
I wrote this, and lost the connection to Gaming Outpost. Let me try again.
Actually, it's really well considered; but I think there's a mistake in it.
The logic goes like this. If someone in the future believes that the past needs to be changed, he sends a message to the past and someone in the past makes the change; but then, the future will be corrected, and no message will be sent. Ultimately, the ability to send messages from the future results in correction of the past until there is no motivation to send any such messages, and the ability ceases to exist.
There is a similar outcome in Butterfly Effect, although someone different (and I am working from hearsay here). A counselor encourages young Evan Treborn to keep journals, and years later he uses those journals to travel into his own past and make changes. He manages to travel to a point before he met the counselor, and prevent that meeting, with the result that he never writes the journals and cannot travel to the past.
I think both make a critical mistake, however. If a message is sent to the past and the recipient acts upon it, the world changes. If, though, the message is never sent, it is never acted upon, and the world reverts.
Thanks for the posts. I think I need this for some comments made at The Examiner site.
--M. J. Young
Niven aka Larry Niven is the co-author along with Jerry Pournelled of the Ringworld books, Mote in God's Eye, and a book about a SF writer skeptic who landed in Dante's Hell (Inferno and ?? which are more recent).
Hans Moravec--I've heard his name in a number of places as a noted physicists.
I'd say both are 3@ in their fields. Which is good for you if you can carry the arguement against them.
Well, let me see if I can make it make sense to you.
I just used this argument over at The Examiner.
Suppose you (1) decide to prevent the Holocaust. You travel to 1920 and find and kill the unknown Hitler. You've changed history.
In the new history, Mussolini becomes the leading figure in Fascism, and develops his own anti-Jewish pogrom. Thus you (2) decides to prevent this pogram, and you travel to 1920 and find and kill the young Italian politician Mussolini.
Does that mean that you did not kill Hitler? Or does it mean that there are two of you in 1920, one killing Hitler and the other killing Mussolini?
If there are two of you, whence did the other originate? The you who killed Hitler must have had knowledge of a history that has never happened, because he prevented it sufficiently that the you who killed Mussolini had no knowledge about Hitler. There must be one of you, and that one is killing Mussolini; the other you never made the trip to the past, and Hitler thus must be alive.
But now, what if instead of traveling back to kill Mussolini, you (2) do nothing? Hitler is no one, and no one has any reason to want him dead. Yet if you were to travel to the past and not kill Hitler, we are agreed that Hitler would live. So if you do not travel to the past and so do not kill him, does that not also mean that Hitler would live?
The problem with the theory as espoused by Niven and Moravec is that it does not recognize the problem created by the failure of the time traveler to "keep his existence" in the past. Their theory works for divergent dimension theory (hey, isn't it cool that I can reference my articles like that?) but not for any other theory of time, really. And the thing about divergent dimension theory is that if anyone discovered a way to "change the past", they would also discover that it doesn't work, because the past is not changed in the universe of the people who sent the time traveler to the past, but in some other universe which branched off it at that point in the past.
--M. J. Young
I thought that they were supposing that George went back and changed things, and then Bob, and then Steven, and then Michael, and it finally had the effect of creating a stable state.
They are; but that only compounds the problem.
The problem is that George goes back to kill Hitler, which eliminates Hitler but puts Mussolini in power, so George does not go back to kill Hitler, and Hitler is not killed. But even so, Bob goes back to kill Stalin, so Stalin never comes to power, and Bob does not make that trip, and Stalin is not killed; Steven goes back to kill John Wilkes Booth, and having succeeded erases Booth from history, and so does not go back to kill him, so he is not killed.
The problem is that these theorists recognize that you could change the past by sending information to the past, and that by causing history B and so undoing history A, you eliminate the need/desire to make the change; but then they fail to recognize that in undoing the need to make the change, they also undo the change itself. That means the past reverts to its original unaltered form, providing the impetus to make the change.
The fixed time theorists are right in this: in the end there is only one history of the universe, and all causes and effects must be contained within it. Niven would allow that someone in the future could cause a change in the past which would then undo his act in the future, with the result that there is an uncaused event in the past--a message received which was never sent. (Poul's Time Patrol suffers from the same problem in some spots.) If you erase the sending, you must erase the receiving; if you erase the receiving, you erase all the choices which flow from the receiving, and restore the original version of history.
Having hundreds of time travelers do this--well, they couldn't, because once one of them does it, there is no history of the world after that moment, and the history that has been altered keeps oscillating between versions.
--M. J. Young
Pohl pretty clearly accepted chaos as the background of reality at least in his books. Universal order is something defended by the humans inside it because we like it, but our liking for order is something thrown up by random chaos.
In other words, the arguement for God's existence that without a Source of Reason there is no reason holds no sway with Pohl.
This is fundamentally illogical and unreasonable as it can be seen as a clear rejection of reason and logic if one follows the logic out which Pohl didn't. Also, if we are random noise, then how do we know that my random noise is better than yours?
Still, he's a very good historian even if not so great a philosopher.
Also, if we are random noise, then how do we know that my random noise is better than yours?
If there's no logic or reason, why would we need to know?
(Note: I do not hold this position. I'm just defending it, essentially on a whim.)
Its a good question. If we are random noise then reason is insanity, a delusion mankind is afflicted with. Except there is no delusion nor truth.
The only answers from the random noise crowd I've heard is A)belief in certain falsehoods has a beneficial evolutionary effect as it increases survival. Thus our 'need to know' is an evolutionary imperative. B)They ignore the problem, and live by reason even though they don't have a foundation for it.
We would not need to know. But obviously we do need, and so therefore we can rule out random noise.
It reminds me of something...
Imagine a world with a religious order of crusading monks dedicated to overthrowing the established order. Ultimately, they want to banish the Demon Reason which has afflicted Humanity for millenia.
I'd make them the bad guys, but it would be an interesting group. Ruthless, evangelistic, magic-wielding...probably the ultimate masters are chaotic things that spew magic out at random....as you rise in the order, you get more powerful and less orderly until finally you're a flaming crazy who shoots out tank-destroying fireballs when you burp.
How do we know time isn't already changing?
I mean, how do we know a time-traveller didn't, for instance, go back in time and become Hitler?
How would we know the difference? If someone were erased from time, or the past changed, isn't the fact that none of us who weren't the time-traveller himself would not know about it part of the whole effect?
Read MJ's and Larry Niven's ideas again. Logic argues against it. Of course, MJ also has his 'Oscillating Causality Theory' aka the Sawtooth Snap which could support your idea.
That said, one of J.P. Hogan's short stories was about the very long line of time travellers from varying eras who went back to kill Hitler. Hitler is perplexed, comes out apologizes..."I don't understand, but if people from different centuries and millenia all want to kill me because I'm evil, well..." At this point one of the time travellers snaps and shoots him. And then one of Hitler's security doubles (most leaders have them) steps up, and orders all the time travellers shot, and get those boxcars moving as well...
Or to be clearer, O7, we don't know from direct experience or observation, but we know from logic.
Niven's Assumption: If time travel is possible, it will be used at some point.
MJ Young's Assumption: Such time travel is automatically self-cancelling.
Suppose you had a dozen time travellers. Each making minor changes, minor enough that most of them would still be time travellers after the Cancellation Effect took place.
Unfortunately, you can't tippy-toe up to the edge and slide off because of CE. Scratches head.
There goes one theory.
Another theory is that TT is a possible one-step away from writing itself out of history, but again the CE.
The only way time travel is going to work that well is if the traveller is cut off from the present as a free-floating entity without causality in his past. IOWs', if you jump into the past at age twenty, it doesn't matter if someone jumps into your past at age nineteen and kills you. You're still alive in the past.
I think my position has been overstated here. What I maintain is that someone who travels to the past intending to change it in specific ways will undo his reason for making the trip, and so undo the trip. That does not mean that time travel never will or never can happen.
For example, Marty McFly traveled to the past and very nearly undid his own birth; but he managed to "undo the undoing" while still in the past, with the result that someone very like him was in the same parking lot using the same time machine to flee from the same terrorists. McFly did nothing to prevent himself from making that trip, and thus he made the trip. He did change history in several ways, including that his father was an affluent sci fi/fantasy author instead of an office flunky, and that the Twin Pines Mall became the Lone Pine Mall when he ran over the other pine tree. So you can change the past; you just can't change it in specific intended ways unless you have some means of ensuring that your temporal duplicate will make the same trip for the same purpose (which is extremely difficult to do).
--M. J. Young
Carrying with you a message to leave in the past, to be delivered to your future self, is an effective means of doing that. Or at least, it worked for David Xanatos. :)
It's a little trickier than that. The problem is that you have to be much the same person, so that you will act much the same way. You can explain it to yourself, but he didn't live through it, so it doesn't mean the same thing to him.
I've done a modification of the show 7 Days that works. It requires four separate teams, the communications team being the only one that has any contact with any of the others. It goes something like this:
- Disaster happens; investigation team is put into actions, finding out what happened and what could have been done within the last three or four days that would have prevented it. All of this is delivered to the communication team, which organizes this information into a format that is a relatively durable data medium--e.g., compact disk or blue ray disk. The disk is delivered, without any other contact, to
- the time travel team, which has been in isolation constantly, all information coming to them on a seven-day delay so that this is the first they have heard about the disaster. Any member of this team who leaves the complex for any reason is put in quarantine upon return, having no contact with either the outside world or the time travel team for seven days, so that he cannot bring current information to contaminate the team's knowledge base. The time travel team sends the data disk back in time seven days in the care of their chrononaut, who delivers the disk back to
- the communication team, who now make an exact copy of this disk, which they deliver to the time travel team at the specifically designated moment (the same moment it was delivered in the previous timeline, which is recorded in the data), and give the original to
- the response team, who uses the data to prevent the disaster.
That would make it possible to change the past and confirm the changes, because the people responsible for changing the past do not know whether or not they have succeeded until after they have made the attempt.
--M. J. Young
Is there not a risk that, every time a disaster happens that would fall under the purview of this organization, the response team (at least) would then know that the current time line is not what will become the true time line (by virtue of the fact that a disaster occurred for which they have not received instructions) - and, secure in this knowledge, begin rationally behaving as though the world were coming to an end?
I really like this set-up, by the way.
Scott--last things first, thanks, it would make an interesting game world if you could figure out how to incorporate the player.
Concerning the response team acting as if it were going to be the end of the world because they had not received instructions on how to prevent it, well, I'm not certain what you mean. There is the chance that this particular disaster could not have been averted, and thus that no data was sent back on how to prevent it; or that someone in power decided not to prevent this disaster (after all, those backsteps cost a lot of money, and is the death of the President in a terrorist attack really all that bad a thing, given that the Vice President who now succeeds him has to make that call? O.K., so a panel must have been involved in the original decision--that part is not covered in my model). It may be that this is the first bit of the disaster, and that the information is coming back later today for how to prevent the next part.
But maybe what you mean is, if I'm part of the response team (or even the communications team) and a disaster happens for which I received no advance intel, it must mean that I'm in the "original" "AB" history, and that in a few days anything that happens will be erased and no one will ever know what would have occurred. Based on that, maybe I go a bit crazy--spend all my money on riotous living, kill the guy I've always hated just for the moment of pleasure I get, take that skydiving lesson I've always feared since my death will never have happened. I can see that as a possibility.
One way to avoid it is to have several response teams, or a response team that is formed to meet the need. In the old Mission Impossible TV series (and in the revised series, too, I think), it always began with the head of the IMF going through a folder and selecting the people he would need for the job. That would mean that just because I am part of "the response team" does not mean that I would necessarily know whether a response was attempted.
And it might be that "the White House was hit by a terrorist bomb, killing a hundred staffers" was the resolved outcome--the President was removed before the strike, which was the best they could do. That recalls my theory of bad things happening: we can say "how could God allow X", but we don't know what (if anything) God has forbidden. If hangnails were the worst thing we ever experienced, someone would be asking how a loving God could allow hangnails. In something of the same way, just because a disaster happened does not mean a far worse disaster was not averted.
So I see the danger, but I think it's not really all that severe.
And from a macro perspective, if whatever those people do will be undone, how much does it matter?
--M. J. Young