So, it seems like most of the existential risks from time travel are only if the Non-Cancel Principle you described is false? It also seems like the Non-Cancel Principle also prevents most time paradoxes, so that seems like strong evidence towards it being true?
It seems like the Non-Cancel Principle would lead to only two possible ways time travel could go about. Either everything “already happened” and so time travel can only cause events to happen as they did (i.e. Tenet), meaning no actual changes or new timelines are possible (no free will), or alternatively, time travel branches the timeline, creating new timelines in a multiverse of possible worlds (in which case, where did the energy for this timeline come from if Conservation of Energy holds?).
I find the latter option more interesting for science fiction, but I think the former probably makes more sense from a physics perspective. I would really like to be wrong on this though, because useful time travel would be really cool and possibly the most important and valuable technology that one could have (that or ASI).
Anyway, interesting write up! I’ve personally spent a lot of time thinking about time travel and its possible mechanics, as it’s a fascinating concept to me.
The law of conservation of energy is when thing “A” exists now and thing “A” exists in the future. The existence of the Universe in the future is not considered a violation of the law of conservation of energy if there is one future. Why then should the existence of the Universe be considered a violation of the law of conservation of energy if it exists in two futures? The idea that the “new” timeline did not exist before, and then it appeared, is a subjective illusion (like the word “new” used above). There is simply timelessness and a Universe with two futures. The traveler creates one of them subjectively, but objectively both have always existed. The same “paradox of free will” as in the case of the “vote of the average voter”. If you are inclined to interpret the Universe without branches as “there is no free will”, then you can interpret the Universe with branches in the same way.
Let’s assume that time travel becomes possible when an advance civilization reach a rotating black hole, as it follows from general relativity.
However, non-cancel principle is valid and can’t be fulfilled by new timeline creation. (That is, equal to Novikov’s principle).
In that case, the only way to prevent timeline collapse is to prevent civilizations to achieve blackholes!
In that case, the universe should be organized in the way which prevents large scale civilizations and space travel. This solves Fermi paradox and really terrifying to us.
However, if we precomit never come close to black holes, we can escape the “curse”!
Why would the only way to prevent timeline collapse be to prevent civilizations from achieving black hole-based time travel? Why not just have it so that whenever such time travel is attempted, any attempts to actually change the timeline simply fail mysteriously and events end up unfolding as they did regardless?
Like, you could still go back as a tourist and find out if Jesus was real, or scan people’s brains before they die and upload them into the future, but you’d be unable to make any changes to history, and anything you did would actually end up bringing about the events as they originally occurred.
I also don’t see how precommitting to anything will escape the “curse”. The universe isn’t an agent we can do acausal trade with. Applying the Anthropic Principle, we either are not the type of civilization that will ever develop time travel, or there is no “curse” that prevents civilizations like ours from developing time travel. Otherwise, we already shouldn’t exist as a civilization.
Universe will choose the simplest way to stop time travel. It doesn’t care is it the destruction of a civilization or some mysterious way to prevent changes in the past. Moreover, as civilizations naturally have a tendency to fall and this prevents all time machines, then civilization destruction is easier way to prevent time travel.
If a non-cancel principle is false, then causality should move along a timeline twice. First normally, and second time—when the time line is canceled. The interesting question arises: can the canceling wave reach the normal wave and if yes, when? (the answer must be “yes” because if it never reaches the now moment, the canceling never happens). For example, if cancel wave has finite but high speed, it will reach us just before we were going to start the time machine.
From anthropic considerations, we can say that we will take this precommitment and will follow it.
I should point out that the natural tendency for civilizations to fall appears to apply to subsets of the human civilization, rather than the entirety of humanity historically. While locally catastrophic, these events were not existential, as humanity survived and recovered.
I’d also argue that the collapse of a civilization requires far more probabilities to go to zero and has greater and more complex causal effects than all time machines just failing to work when tried.
And, the reality is that at this time we do not know if the Non-Cancel Principle is true or false, and whether or not the universe will prevent time travel. Given this, we face the dilemma that if we precommit to not developing time travel and time travel turns out to be possible, then we have just limited ourselves and will probably be outcompeted by a civilization that develops time travel instead of us.
Of course, I meant not Bronze age collapse, but known plethora of existential risks. But your argument that others will outcompete us is valid—unless the totality of x-risks is a universal Great Filter.
So, it seems like most of the existential risks from time travel are only if the Non-Cancel Principle you described is false? It also seems like the Non-Cancel Principle also prevents most time paradoxes, so that seems like strong evidence towards it being true?
It seems like the Non-Cancel Principle would lead to only two possible ways time travel could go about. Either everything “already happened” and so time travel can only cause events to happen as they did (i.e. Tenet), meaning no actual changes or new timelines are possible (no free will), or alternatively, time travel branches the timeline, creating new timelines in a multiverse of possible worlds (in which case, where did the energy for this timeline come from if Conservation of Energy holds?).
I find the latter option more interesting for science fiction, but I think the former probably makes more sense from a physics perspective. I would really like to be wrong on this though, because useful time travel would be really cool and possibly the most important and valuable technology that one could have (that or ASI).
Anyway, interesting write up! I’ve personally spent a lot of time thinking about time travel and its possible mechanics, as it’s a fascinating concept to me.
P.S. This is Darklight from Less Wrong.
The law of conservation of energy is when thing “A” exists now and thing “A” exists in the future. The existence of the Universe in the future is not considered a violation of the law of conservation of energy if there is one future. Why then should the existence of the Universe be considered a violation of the law of conservation of energy if it exists in two futures? The idea that the “new” timeline did not exist before, and then it appeared, is a subjective illusion (like the word “new” used above). There is simply timelessness and a Universe with two futures. The traveler creates one of them subjectively, but objectively both have always existed. The same “paradox of free will” as in the case of the “vote of the average voter”. If you are inclined to interpret the Universe without branches as “there is no free will”, then you can interpret the Universe with branches in the same way.
Ah, that makes sense! Thanks for the clarification.
Let’s assume that time travel becomes possible when an advance civilization reach a rotating black hole, as it follows from general relativity.
However, non-cancel principle is valid and can’t be fulfilled by new timeline creation. (That is, equal to Novikov’s principle).
In that case, the only way to prevent timeline collapse is to prevent civilizations to achieve blackholes!
In that case, the universe should be organized in the way which prevents large scale civilizations and space travel. This solves Fermi paradox and really terrifying to us.
However, if we precomit never come close to black holes, we can escape the “curse”!
Why would the only way to prevent timeline collapse be to prevent civilizations from achieving black hole-based time travel? Why not just have it so that whenever such time travel is attempted, any attempts to actually change the timeline simply fail mysteriously and events end up unfolding as they did regardless?
Like, you could still go back as a tourist and find out if Jesus was real, or scan people’s brains before they die and upload them into the future, but you’d be unable to make any changes to history, and anything you did would actually end up bringing about the events as they originally occurred.
I also don’t see how precommitting to anything will escape the “curse”. The universe isn’t an agent we can do acausal trade with. Applying the Anthropic Principle, we either are not the type of civilization that will ever develop time travel, or there is no “curse” that prevents civilizations like ours from developing time travel. Otherwise, we already shouldn’t exist as a civilization.
Universe will choose the simplest way to stop time travel. It doesn’t care is it the destruction of a civilization or some mysterious way to prevent changes in the past. Moreover, as civilizations naturally have a tendency to fall and this prevents all time machines, then civilization destruction is easier way to prevent time travel.
If a non-cancel principle is false, then causality should move along a timeline twice. First normally, and second time—when the time line is canceled. The interesting question arises: can the canceling wave reach the normal wave and if yes, when? (the answer must be “yes” because if it never reaches the now moment, the canceling never happens). For example, if cancel wave has finite but high speed, it will reach us just before we were going to start the time machine.
From anthropic considerations, we can say that we will take this precommitment and will follow it.
I should point out that the natural tendency for civilizations to fall appears to apply to subsets of the human civilization, rather than the entirety of humanity historically. While locally catastrophic, these events were not existential, as humanity survived and recovered.
I’d also argue that the collapse of a civilization requires far more probabilities to go to zero and has greater and more complex causal effects than all time machines just failing to work when tried.
And, the reality is that at this time we do not know if the Non-Cancel Principle is true or false, and whether or not the universe will prevent time travel. Given this, we face the dilemma that if we precommit to not developing time travel and time travel turns out to be possible, then we have just limited ourselves and will probably be outcompeted by a civilization that develops time travel instead of us.
Of course, I meant not Bronze age collapse, but known plethora of existential risks. But your argument that others will outcompete us is valid—unless the totality of x-risks is a universal Great Filter.