Would you like to discuss the temporal dynamics of the following? If man achieves time travel, would they have travelled back to our recent past or the present to make absolutely sure that we do what we need to do now, for them to have sufficient resources in the future? Or will they not have sufficient resources to "construct" a time-travelling vehicle? Perhaps someone has already travelled "back" to the present, and they were ignored or misunderstood? Or did they travel back to the present, but then realise that they had to go further back in time, or further into the future? Would we know if we have been visited by people from the future, or would they keep us in ignorance, so that we did not alter the course of events? It occured to me to add this to the "Aliens" thread, but decided it needed a thread of its own.