No way out?

You can see why so many physicists do not accept that time travel
to the past will ever be possible. There is yet another paradox that
I have not mentioned which is to do with using a time machine
to create multiple copies of yourself, thus violating sacred laws
of nature like conservation of mass and energy. For instance, you
could travel back to five minutes ago and meet yourself. Are you
then able to both enter the time machine and go back five minutes
earlier to meet a third you and so on? This is really just another
form of the no choice paradox. As there is only one version of
the past and you know before you first set off that no copy of you
arrived five minutes ago from the future, you cannot be free to join
yourself. You cannot go back to meet yourself because you have
no memory of meeting yourself.
It seems that I have provided more than enough nails in the
time travel coffin and you may be wondering whether it is worth sticking with the rest of the book in which I explain how a time
machine may be built. But don’t despair just yet. It is clear that
there have to be certain ground rules about which times we are
allowed to go to and what we are allowed to do in order that
paradoxes cannot arise. Many die-hard time travel fans are not
too worried about the no choice paradox. They agree that we
must sacrifice free will if time travel to the past is to be possible.
For them, we do not have free will anyway, we just think we do.
Since we live in a deterministic universe where everything is preordained
anyway, we do not need to appeal to anything new. As
long as everything is logically consistent there is noproblem. Thus,
you can go back one hour to meet your (slightly) younger self if
you remember meeting your (slightly) older time travelling self
an hour ago. If you don’t remember it then you will not be able
to travel back. Not even the something-from-nothing paradox
deters such ardent supporters. “So what,” they say, “the Mona
Lot painting being caught in a time loop does not give rise to any
logical inconsistency.”
For me though, this is a much more serious abandonment of
free will. At least in a deterministic universe we are under the
illusion that we are making our own free choices and decisions. In
time travel, we are not allowed the luxury of this feeling. Our free
will is wrenched from us in a way that is far from clear.
If you are determined to allow for the possibility of time travel
into the past then there is another price you must pay. You have
to take the block universe description of spacetime seriously. Past
present and future must all coexist. The reason for this is simple: If
you go back into the past (which we reluctantly admit might exist
since at least we know it did exist) then for those people you meet
when you travel back in time (even a younger version of you) that
time is their ‘now’, their present moment. You have arrived from
their future. They would have to admit that the future is just as
real as the present. We cannot even claim that our present is the
true ‘now’ and that they just think they live in the present, since we
can similarly imagine time travellers from our future visiting us in
our present. If they do, then our future, and indeed all times, must
exist together. This is precisely what the block universe model tells
us.