4 ms·

>"Because time travel is limited to these special particles, it is not possible for a man to travel back in time and murder one of his parents before he himself

>"Because time travel is limited to these special particles, it is not possible for a man to travel back in time and murder one of his parents before he himself is born, for example. However, if scientists could control the production of Higgs singlets, they might be able to send messages to the past or future," This is absurd. If you can send messages back in time, then someone can build a robot that can accept messages from the future, and kill your parents that way^. Sending information back in time is a paradox. Period.^^ ^An option available to everyone after the robot is built. Maybe this is actually enough to resolve the issues they're concerned with. I'm somewhat suspicious. ^^To be clear, I am not saying that the work is wrong or impossible, merely that their example is less than explanatory about why their theory does not have the problems of other theories.

lux 16y ago
This made me laugh out loud. Thanks :)
gte910h 16y ago
>This is absurd. If you can send messages back in time, then someone can build a robot that can accept messages from the future, and kill your parents that way^. Sending information back in time is a paradox. That's only true if "free will" exists, i.e. if its really "changing" the past instead of fulfilling it.
sophacles 16y ago
Well, to be fair, the ability to send messages to the past really only becomes useful once such messages are receivable. For the messages to be receivable, we must know the properties of the medium that the messages are to be sent on. Basically, this limits the very earliest that such backwards going messages can be received to around now-ish.[1] As a consequence it may not be a paradox anymore, since there will be no point at which we can operate without a suspicion of future interference, thereby reducing the paradox effect, and in fact encouraging it by divining the outcomes of our actions. Of course this divining rapidly loses power anyway, as multiple messages are sent conflicting with one another - it gets messy quick. It gets messier quicker if you choose to go with a "many worlds" interpretation of the universe. Further, there are questions regarding observation: does observing a message from the future cement that future into being, possibly incurring an absurd chain of events but not causing any paradox (the 12 monkeys thing)? What I am really driving at here is this: Your paradox claims are amusingly simplistic, the real deal here is that we just don't know enough to say. [1] I am ignoring two big possibilities: 1. that this has been known for some time by, say, evil wall street bankers with secret labs (and their ilk -- governments, supervillians and such). 2. That there aren't aliens at some point in the very distant past whom we get messages to, and convince to do our bidding, who show up at various key stages of history an change everything. This may or may not have happened, depending on what you believe from the history channel (ancient aliens) and Stargate.
bermanoid 16y ago
If you can send messages back in time, then someone can build a robot that can accept messages from the future, and kill your parents that way^. Sending information back in time is a paradox. Period Not quite. You're neglecting quantum mechanics. Very roughly speaking, in quantum field theory, the probability of an event happening is a weighted sum over all the possible ways that it could happen (a path integral), and (again, speaking roughly) the options that seriously violate the various conservation laws tend to have negligible contributions. Presumably the path integral formulation would still hold up even with closed timelike curves (time travel curves). An inconsistent state, like one where you kill off your own parents, would probably exhibit all sorts of self interference that would make its contribution to the path integral very small, whereas the consistent states would be much better represented, and much more likely to happen. Weird "violations" of physics could quite easily present themselves as the most probable outcomes, especially if the alternative was an inconsistent outcome. A good way to think about this is in terms of waves on a string, or the "wave" of an electron in orbit around a nucleus - the only vibration frequencies that "survive" are the ones that reinforce themselves, and the rest get cancelled out by interference (in the electron case, because they don't "match up" when they meet themselves after an orbit). If you think of the state of the universe as the electron, and the orbit as a loop through the closed timelike curve, then it's easy enough to imagine quantum mechanics doing all the hard work for us, and making sure that only consistent outcomes are reinforced, while all the other ones are destroyed by interference.
- bermanoid 16y ago
  I should point out, though, the fact that it's theoretically conceivable that the universe could support time travel doesn't necessarily mean that it does, and I suspect most physicists think it's highly unlikely.

lux 16y ago

This made me laugh out loud. Thanks :)

gte910h 16y ago

>This is absurd. If you can send messages back in time, then someone can build a robot that can accept messages from the future, and kill your parents that way^. Sending information back in time is a paradox. That's only true if "free will" exists, i.e. if its really "changing" the past instead of fulfilling it.

sophacles 16y ago

Well, to be fair, the ability to send messages to the past really only becomes useful once such messages are receivable. For the messages to be receivable, we must know the properties of the medium that the messages are to be sent on. Basically, this limits the very earliest that such backwards going messages can be received to around now-ish.[1] As a consequence it may not be a paradox anymore, since there will be no point at which we can operate without a suspicion of future interference, thereby reducing the paradox effect, and in fact encouraging it by divining the outcomes of our actions. Of course this divining rapidly loses power anyway, as multiple messages are sent conflicting with one another - it gets messy quick. It gets messier quicker if you choose to go with a "many worlds" interpretation of the universe. Further, there are questions regarding observation: does observing a message from the future cement that future into being, possibly incurring an absurd chain of events but not causing any paradox (the 12 monkeys thing)? What I am really driving at here is this: Your paradox claims are amusingly simplistic, the real deal here is that we just don't know enough to say. [1] I am ignoring two big possibilities: 1. that this has been known for some time by, say, evil wall street bankers with secret labs (and their ilk -- governments, supervillians and such). 2. That there aren't aliens at some point in the very distant past whom we get messages to, and convince to do our bidding, who show up at various key stages of history an change everything. This may or may not have happened, depending on what you believe from the history channel (ancient aliens) and Stargate.

bermanoid 16y ago

If you can send messages back in time, then someone can build a robot that can accept messages from the future, and kill your parents that way^. Sending information back in time is a paradox. Period Not quite. You're neglecting quantum mechanics. Very roughly speaking, in quantum field theory, the probability of an event happening is a weighted sum over all the possible ways that it could happen (a path integral), and (again, speaking roughly) the options that seriously violate the various conservation laws tend to have negligible contributions. Presumably the path integral formulation would still hold up even with closed timelike curves (time travel curves). An inconsistent state, like one where you kill off your own parents, would probably exhibit all sorts of self interference that would make its contribution to the path integral very small, whereas the consistent states would be much better represented, and much more likely to happen. Weird "violations" of physics could quite easily present themselves as the most probable outcomes, especially if the alternative was an inconsistent outcome. A good way to think about this is in terms of waves on a string, or the "wave" of an electron in orbit around a nucleus - the only vibration frequencies that "survive" are the ones that reinforce themselves, and the rest get cancelled out by interference (in the electron case, because they don't "match up" when they meet themselves after an orbit). If you think of the state of the universe as the electron, and the orbit as a loop through the closed timelike curve, then it's easy enough to imagine quantum mechanics doing all the hard work for us, and making sure that only consistent outcomes are reinforced, while all the other ones are destroyed by interference.

bermanoid 16y ago
I should point out, though, the fact that it's theoretically conceivable that the universe could support time travel doesn't necessarily mean that it does, and I suspect most physicists think it's highly unlikely.