These telescopes have two goals that could redraw our place within the universe, much as previous discoveries — like Edwin Hubble’s discovery with a previous world-record holding telescope that the Milky Way was just one galaxy among many — redefined the centrality of our own galaxy.
First, the telescopes will bring the study of Earth-sized planets around local stars within human reach. We will be able to determine how rare Earths are, and by extension, how likely Earth-like life is to exist elsewhere in the galaxy. Second, by gathering more light than ever before, astronomers will be able to detect fainter objects that are further back in our universe’s history. They hope that the new telescopes will see “first light,” when the first stars formed out of the primordial universe’s post-Big Bang mass.
neat article from wired science about telescope design