‘i2=j2=k2=ijk=−1’ was what a thrilled Hamilton carved into the stone of the Broom Bridge (then the Brougham Bridge) as Helen Maria Bayly, Hamilton's wife, watched from the sidelines on October 16, 1843. In introducing a fourth dimension, the 19th-century mathematician described the geometry of vectors in a 3D space through quaternions, which are quadruples of real numbers. His unconventional discovery that bent the laws of ordinary arithmetic and would go on to revolutionise quantum mechanics, robotics, navigation and animation was commemorated on the same bridge by the Royal Irish Academy in 1958.
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