The , one of the greatest enigmas of the universe, is not exactly dark, but invisible. Astronomers know that this component of the cosmos has to be there because of the force of gravity it exerts, but no one has ever been able to see it or catch it. Now, the European Space Agency has just approved a mission designed to study dark matter and understand if it is exactly what current theory predicts. There is a chance that things won’t fit together, which would upend our idea of how the universe works; a historic discovery.
