A new generation of telescopes will probe the ‘unknown unknowns’ that could transform our knowledge of the universe

Illustration of the Extremely Large Telescope, currently under construction in Chile's Atacama desert. ESO, CC BY

In recent decades, we’ve learnt huge amounts about the universe and its history. The rapidly developing technology of telescopes – both on Earth and in space – has been a key part of this process, and those that are due to start operating over the next two decades should push the boundaries of our understanding of cosmology much further.

All observatories have a list of science objectives before they switch on, but it is their unexpected discoveries that can have the biggest impact. Many surprise advances in cosmology were driven by new technology, and the next telescopes have powerful capabilities.