Why the apparent flatness of space is an enduring cosmological mystery

Empty space isn’t ‘nothing’. Since Albert Einstein, scientists have known that space has distinct physical properties, giving it the ability to bend, ripple and expand. One of its most mysterious characteristics, however, is its apparent flatness, allowing objects travelling on parallel paths to continue on parallel paths unless acted upon by the gravitational force of another object – a feature of the Universe that appears to be ‘a gigantic, cosmic-level coincidence’. This brief animation probes our evolving understanding of space, brushing up against the edges of current human understanding.