Answer 1:
An observer moving close to the speed of light
would see the rest of the universe having time
moving slower, but the distances of everything
would be contracted so that their "history" would
proceed at a rapid rate anyway. The formulas are
as follows: Let Y = (1 
v^{2}/c^{2})^{(1/2)}This expression
shows up a lot in relativity, so just substitute
it. v = velocity of the object being
observed relative to the observer, and
c is the speed of light. Note that as v
approaches c, Y goes to zero  this is the reason
behind most of the counterintuitive things in
relativity. L = lY, where L is the
length of an object in its own reference frame,
and l is the length it has that the observer
measures. T = tY, where T is the
time between two events in their own reference
frame, and t is what the moving observer
measures. M = m/Y, where m is the
rest mass of the object, and M is the mass
measured by the relativistic observer. p
= Mv, where p is the momentum of an object
(use M from the previous equation). Now,
tachyons: If v > c, then Y above will be
imaginary (you're taking the square root of a
negative number). This means that a tachyon would
have to have an imaginary rest mass, imaginary
dimensions, and even an imaginary position in
space and time. An imaginary particle would
conversely see the "real" universe as imaginary. I
find it difficult to imagine how adding an
imaginary set of dimensions to the universe would
be observable, so a being composed of tachyons
would have similar problems observing us as we
would then. Of course, there are no data
that indicate that tachyons exist at all, so
anything we can say about them is pure
speculation.
