Astronomers can see only so far out into space, corresponding to a time 400,000 years after the Big Bang. Why can't we see further back in time?
a) The universe is not old enough, and light travels at a finite speed.
b) The universe was opaque before that time, and photons were unable to travel freely.
c) There were no objects giving off light before then, so there is nothing to see.
d) We haven't developed the technology yet to see farther away in space (and therefore further back in time).
