Rex wrote:

They say time is what the clock measures.
[snip]

If you don't like oscillators, go for radioactive decay.

How come physicists explore the possibility of
time travel.
[snip]

Grant funding. They'd go spelunking after canthariasis if it could be
modeled, funded, and published.

How can you go back to the past when it has already
happened.

Who says? The Earth is only 6000 years old. GOD said so. All the
overwhelming evidence for a 5 billion year old Earth was emplaced by
time travel. Is that made plain enough for you?

In newtonian argument, it may be as plain as this. But
in light of SR and GR. Time seems to be something more and
has an almost magical quality to it. Can you describe time in
such a way that it can make time travel makes sense (theoretically
speaking)?

The universe demands causality. No time travel except across
realities wherein it already happened. Niven diddled with the concept
some 35 years ago, "The Theory and Practice of Time Travel" in "All
the Myraid Ways", 1971. Catch up on your reading.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/lajos.htm#a2