The ELT will tackle the biggest scientific challenges of our time, and will aim for a number of notable firsts, including tracking down Earth-like planets around other stars in the habitable zones where life could exist — one of the Holy Grails of modern observational astronomy. It will also make fundamental contributions to cosmology by probing the nature of dark matter and dark energy. Other key science areas include the study of stars in our Galaxy and beyond, black holes, evolution of distant galaxies, up to the very first galaxies in the so-called "Dark Ages", the earliest epoch of the Universe, only 380 000 years after the Big Bang. On top of this astronomers are also planning for the unexpected — new and unforeseeable questions will surely arise, given the capabilities of the ELT.
The ELT is motivated by a wide range of scientific challenges in modern astronomy. Its discoveries will span a huge number of astronomical topics, to provide dramatic advances in our understanding of the Universe.
The Science Case for the ELT started being prepared in 2009 with the help of: