Someone pointed me at the John Titor site. For those who don't know, John Titor
claimed to be a time traveller from from the year 2036. He hung around for a while and then, having announced his departure back to 2036, he disappeared from the Internet. He claims that the events in this time frame are subtly different from the timeframe that he originated from. In other words, his memory of events (coming from 2036) is different from the events that actually happened in this time frame. He attributes this at least in part to his anomalous presence in this era.Superficially this appears feasible. But we Martians have been investigating time travel since before Earth had a civilisation, and the view that we have come to is substantially different from that espoused by Titor. Our science indicates that there is only one 'time frame'. If an event happens it happens, whether or not a time traveller was present or not. You cannot return to kill your grandfather before you were born, because if you did, then you would not be born to return to kill your grandfather. There is no paradox there, just physics. Our Martian science indicates that the Universe is strictly deterministic - if an event happens, there is a cause, and time travel has to obey that law. A time traveller is caused (born!) because of events which he/she can't negate. At first glance this seems asymmetrical but it isn't because the existence of a time traveller can't negate an event which happens earlier because that would negate his existence at the time that he goes back. Er... Well, the words don't work too well, but the maths does, believe me!Martian time travel theory doesn't disallow the existence of time travel. It just put logical limits on it. While Martians have built time machines, it's pointless to travel back just to do something that (from your future point of view) has already happened.Oh, some people (Martians) have tried to go back and change things, but whatever they do, they always end up causing what they try to prevent! However, there is a school of thought that say that some of them did manage to change things and that, ever after, up to the point that they came back from and beyond, that is they way that it always was.Most Martians however think, as do most Earthians, that the universe is 100% deterministic, and that what happens is determined and cannot be changed. From the metaphysical point of view that means that the time traveller is observed in 2001 because he disappeared from 2036 and events from then on caused him to disappear in 2036.Some Martian philosophers think of time as a ribbon and time travel as if two points of the ribbon (2001 and 2036) are brought together so that the time traveller can slip from one era to the other. Martian philosophy is unclear about what dimensions the 'ribbon' could be curved and bent in.Where does that leave a Martian philosopher with regards to Titor? Titor claims that things are different because of his presence. This does not accord with Martian philosophy. However Titor may be claiming this because he is trying cover up for the inadequacies of his knowledge of the past. No time traveller is going to know everything about his/her past.He may be hiding unpalatable events from the future, to protect himself from disbelievers in the present. However he does mention things like a civil war in the US that happens in 2005, which has apparently not happened. He could have remembered incorrectly but one would have thought that he would have remembered such significant events. Unless we don't remember such events as civil war, or the events are reported as less significant events that are later identified as 'civil war'.But overall, we Martians, and I think I speak for a significant number on Earth, would assess Titor as either a clever construction or a deluded individual. A deluded individual would not have 'disappeared' so abruptly, I feel, so on balance, I'd think that Titor was a clever construction, abandoned by his creator when things became boring.A real time traveller? No, I don't think so.