**Sir William Rowan Hamilton** (August 3/4 1805 – September 2, 1865) was an Irish physician, astronomer and mathematician that brought important contributions to classical mechanics, to the development of optical systems and of algebra. William Rowan Hamilton is known for his studies of mathematical physics and of Newtonian mechanics formulation renamed **Hamiltonian Mechanics**. His work proved to be essential for the study of electromagnetism and for the development of quantum mechanics.

William Rowan Hamilton was the son of a lawyer, but he lived with his uncle, an Anglican priest who also educated him.

Besides his aptitude of learning Latin, Greek, Hebrew before 5 years old, until he turned 12 he already knew Arabic, Sanskrit, Persian, Syriac, French, Italian and German. However, Hamilton started to be more interested in mathematics after he read **Analytical Geometry** by Bartholomew Lloyd, at the age of 16.

In his first published book, **Theory of Systems of Rays**, is presented the innovation of associating to a system of rays, a constant characteristic function on each of the surfaces on which the rays are orthogonal.

Since 1833, William Hamilton adapted his optical methods to the study of dynamics problems. From his paper works appeared the theory according to which associating a function of a system of attraction and rejection, the solutions of the equation of motion of the system can be easily obtained.

In 1835, Hamilton was ennobled by the Irish lord lieutenant in a meeting in Dublin British Association for the Advancement of Science and between 1837- 1846 he was the president of the Royal Irish Academy.

In 1856, Hamilton analyzed the closed paths along the edges of a dodecahedron that pass once through each node. In graph theory, such paths are known today as Hamiltonian circuits. On the basis of these theories, WR Hamilton and the British mathematician Thomas Kirkman mathematically formulated the travelling salesman problem that ask for an answer to the question: “*Given a list of cities and the distances between each pair of cities, what is the shortest possible route that visits each city exactly once and returns to the origin city?* ” Hamilton gave a mathematical explanation for the apparent difficulty of calculating to find the best routes. This problem is considered to be the most important one of the computer science history because it represents the key to solving other mathematical problems.

In the last six years of life, he dedicated himself to the paper works **Elements of Quaternion** that have been finished a few days before he has died, on September 2, 1865, because of a severe attack of gout.

Shortly before, he had received the news that he was chosen as the first foreign member of the National Academy of Sciences of USA.

The travelling salesman problem was directed in the guise of a movie entitled Travelling Salesman, in 2012, by Timothy Lazone. After screenings in 8 countries , inclusively screenings of Pennsylvania and at the University of Cambridge, the movie was globally launched on September 10, 2013.

*Daniela Anei (**translated by Elena Golăi**)*