A
huge amount of
science fiction assumes that aliens will be very
similar to us. Sure, they may speak another language and look like giant bugs, but they are similar.
But why would they?
They could be the
size of
bacteria and live their entire species
lifetime under our
fingernails.
They could move through
time as easily as we move through
space, but they perhaps cannot move through
space.
They could
exist in only
two dimensions.
They could
consist mostly of
gas or of
liquid or even of
energy.
They could be the size of
galaxies. Perhaps the [galaxies are an
intelligent life form, but they try to communicate with us as much as we try to
communicate with the
molecules in our
cells.
We also
assume this in our search for life on other
worlds.
Venus can't have life because it is so
hot. (Maybe Earth is too
cold.
The Gas giants can't have
life because they are
gas. (Maybe they think life can't exist on Earth, as it is too
solid)
The
majority of alien
life if it exists will probably be
impossible to understand or
even interact with. But if the universe harbors
millions of
species, we may eventually find a
few that are
similar to us.