For time time travel to be possible, we must find a resolution to the fundamental paradox of time travel. This can be stated in many ways, here is an example sent by a friend:
We build a 'back in time' communicator with a healthy delay of several minutes between two adjacent rooms A and B. I send you, in room A, a message from the future in room B. You then march swiftly into room B before I have sent the message and make sure that I send a different message. This paradox seems to imply that there is a missing ingredient to do with 'isolated systems' or even conscious interference....
Let us look at ways to solve the paradox. I have identified four general approaches.
1. The Multiverse Approach. Lets work through what happens in the above scenario. Assume I am the man in room A who will change the message sent from room B. Once I have changed the message, what can I say about my past. I have a record of receiving a different message to the one I know was sent, therefore I conclude that there is another world in which another version of reality occurs in which the original message was sent unchanged. The world splits and I cannot ever meet myself in that other world. But if I consider the situation at the moment I received the message, there were two versions of the future, one sending the original message and one sending the modified message. At the point where I receive the message, I cannot distinguish between those two possible future worlds, because there is no way of predicting in advance whether I change the message. I might not even have decided what I intend to do and take my action on impulse. Therefore I should receive messages from both versions of the future. The situation with the actual proposed form of signaling is that each individual bit of the message is constructed by averaging over several quantum events. Any message will require us to interpret a large number of quantum events and these are equally likely to be caused by either future. The message received will be a mixture of the two: a scrambled mess. The multiverse does not appear to resolve the paradox.
2. The Hermetic approach. Perhaps room B, where the sender equipment is located, has to be isolated to make it impossible for me to alter the message. This approach would require that we invent some foolproof setup that guarantees that nothing I do can change the message. Two criticisms at once spring to mind. One, how does the quantum system sending the message 'know' that it is in an isolated and protected environment. In technical jargon, how do we entangle the wave function of the quantum phenomena sending the signal with that of the protective environment? Two, how do we protect against the inevitable fallible nature of human efforts? Even if the sender system is setup light years away so there is no chance of my interfering, nothing humans do is ever perfect, how can we be sure this system performs faultlessly?
3. The Consciousness Approach. Perhaps it is something to do with human nature, perhaps if we have pure intentions or temporarily lose our free will or perhaps we do not have free will at all, then we will never interfere with the message sent. A criticism arises because we can recast the paradox removing me and replacing the process of making a decision as to whether to change the message with an automated mechanism that uses a random process to decide. A counter criticism would assert that the automated random process is not equivalent to a person being present and that it is sufficient to have pure intentions not to interfere with the message to resolve the paradox. Perhaps we need to look to Buddhism for deeper insight into the nature of being.
4. Reinventing rational knowledge. It can be argued that standard quantum mechanics without time travel, is inconsistent at a quantum level with either logic or reality existing. We have to abandon one of the two: logic or reality. Given this stark choice, Chris Isham has begun to wonder whether conventional logic is inappropriate in the quantum realm. The kind of logic used in the foundations of mathematics, based on the Boolean concept of truth or falsehood excludes any middle. We cannot say that something is a little bit true or that is fifty percent true and fifty percent false, etc. The alternative approach being explored under the general name of Topus Theory is a branch of pure mathematics that allows other logical possibilities to exist. Some of these 'topoi' can be applied to quantum mechanics. They are all very abstract and hard even for specialists to understand. No one knows at the moment if this approach will lead anywhere but it offers the hope that entirely new forms of mathematics are emerging that might give more insight.
Perhaps none of the four approaches alone can solve the problem but a mixture of them does. Lets try and see how it might work. If we receive a message from the future and possess free will, that message cannot be arriving from our future, it comes from a similar but not identical world. We can see that this must be true because the moment we receive a message, we have choice in how we react and the message would have little value if we did not not. For example if the message is warning that an earthquake is about to strike, we would want to take action to minimise our risk. It appears the multiverse must exist, it is a necessary requirement of any solution using standard logic and the expectation that we have free will. It is not clear to me that topos theory will alter that conclusion. It has a precedent amongst a group of mathematicians called intuitionists. They tried to find a way to incorporate the excluded middle and never succeeded. Perhaps Topos theory will now accomplish something where they failed, we shall have to wait and see.
Buddhism might help us be able to intuit a reality in which space and time are not fundamental and develop the pure intentions to operate this delicate process. While it may help, I do not believe it is necessary, but our intentions cannot be dismissed in considering the paradox. The automated random process is not equivalent to our being free to make a decision, free will exists but is always conditional. We cannot do absolutely anything we like. We have to choose between possible options, or have the imagination to think of something else that is also possible. Whilst it is true that if a purely random process chooses the message, the results will be scrambled in the multiverse, this does not prove that the paradox stands. That shows that messages might not be received under all possible conditions. We can choose what message is sent by having the intention not to interfere or through the hermetic approach, physically making it difficult to interfere. While our intentions or the hermetic precautions may never be perfect, they can be be sufficient to insure that the undisturbed message is received in the majority of universes. If we happen to find ourselves in one of the universes in which the message becomes scrambled, we will put that down to a perfectly normal equipment malfunction.
There still remains a further problem. Many Worlds denies the existence of non locality, but the specific method proposed to send signals back through time depends on non locality. A successful outcome to this experiment will precipitate a crisis in physics as no interpretation of quantum mechanics can explain the phenomenon. Physicists will be forced back to the drawing board.
This problem is profound. The evidence coming from the Dopfer experiment is provocative. The interpretation I have presented is based on standard quantum mechanics. An alternative resolution to the implications of the experiments is that standard quantum mechanics is wrong. If that is the case, further experiments might not reveal how to build a time machine for information, but will become an instrument to probe errors in standard quantum mechanics. We simply do not have enough evidence to say what is going to happen. We stand at a very interesting point. Either time travel is impossible but even so standard quantum mechanics will have to be modified, or time travel is possible and quantum mechanics will have to be modified. Any clear outcome to the proposed experiments will present a theoretical challenge. The moment we observe interference fringes whose visibility can be modified by a remote action to their entangled partners, the need to understand what is happening becomes intense.
As an artist I have always had the intuition that I am already in contact with the future. My suspicion is that receiving information from the future is one of the senses of the unconscious mind. Most people do not notice if it happens or do not have the gift, but precognition, in one form or another is widely recognised outside the world of hard science. For many people ideas come in dreams but it can happen just as easily when we are wide awake. I would not pretend to be able to will this sense or direct it in any way yet I feel convinced that it has been a channel for inspiration, and on at least one occasion for more direct information too. Today this would be considered a profoundly irrational and unscientific statement. It is my judgment that my personal intuition is correct and that one day we will have a scientific understanding of these mental phenomena that are presently considered beyond the pale. Perhaps this research on time will lead to new theoretical insight that resolves the mystery of precognition.
26 April 2007