reply to post by Zagari
I have problems with several aspects of you propositions.
In case 1) you make assumptions that all is unlockable by the simple fact that someone came from the future, in fact you are observing the event in
the present, and from that perspective you would only get to know up to the state of the traveler. Any technological advances may even be excluded by
the simple fact of lack of knowledge from the traveler or limits in the information he may carry, technology is not only restricted to information, to
be practical it need to be applicable and technology tends to be incremental (that is knowledge depends on previous knowledge and as knowledge is
extended so is complexity). This disrupts your assertion about the end of time and linear time, since there must be a cost for time traveling if not
only of energy. We are all linear time travelers to the future and to alter that fact the nature of the universe would need to be changed.
In case 2) you advance the idea that they could chose not to be seen, in fact in such setup they could not be seen by the simple fact that being
observed would have an impact on the present. For instance if we consider that some UFOs are time-travelers, they can be said to have impacted our
culture. This construct also does not exclude the multi-verse theory, it only defines a way of traveling.
In case 3) the only one that is fully workable, you state that "We would discover the secret behind death." in fact only some versions of "we"
would discover the secret.
Case 4) is the version that does not work at all, it would be full of paradoxes...
Case 5) is a self correcting version of 4) it will again be prone to some paradoxes even if it excludes other...
I do like the idea of time traveling but do not believe it would be possible to anything more than information to be transfered, that would require
the two time ends having the technology, working to form something similar to quantum teleportation across time.