This is another version of The Fermi Paradox
. Basically, if time travel
backwards in time is ever to become possible
where are the travellers? Stephen Hawking
presented this question by wondering
why we aren't awash with thousands
of time travellers.
Possible replies are:
- Time travel back in time isn't possible.
- Time travelers are here.
- They haven't gotten this far back yet.
- They open a new dimension and don't appear in ours.
- They died before inventing time travel.
Time travellers may be here but have technology
that doesn't allow us to see
them. It is also possible that the mystical creatures
's some see are, in fact, time travellers from our future. Perhaps, because of the Grandfather Paradox
the universe conspires
to keep us from seeing them. For example
, when they walk by we look the other way and when we turn around they duck.
Maybe their time machine
doesn't allow them to come far enough back to see us. It could take too much power
or only go back to a critical
date. And it is always possible that the civilization
dies before it ever creates the time machine.