<a href="https://en.wikipedia.org/wiki/William_Rowan_Hamilton" id="mwdQ" rel="mw:WikiLink" title="William Rowan Hamilton">William Rowan Hamilton</a> invents <a href="https://en.wikipedia.org/wiki/Quaternion" id="mwdg" rel="mw:WikiLink" title="Quaternion">quaternions</a>, a three-dimensional system of complex numbers.