Heinrich Gustav Magnus and the Magnus Effect

Heinrich Gustav Magnus

Heinrich Gustav Magnus (1802-1870)

On May 2, 1802, German physicist Heinrich Gustav Magnus was born. He is best known for the Magnus effect (the lift force produced by a rotating cylinder, which for example, gives the curve to a curve ball). In chemical research, he discovered the first of the platino-ammonium compounds compounds.

Heinrich Gustav Magnus was born in Berlin and received a very decent education in math and natural science. He enrolled at the University of Berlin studying chemistry and physics and earned his doctorate degree in 1827. Afterwards, Magnus traveled to Stockholm, working together with Jöns Jakob Berzelius [4] and later in Paris with Joseph Louis Gay-Lussac [5] and Louis Jacques Thénard. Heinrich Gustav Magnus was appointed first lecturer, later professor of physics and technology at the University of Berlin.

It is believed that Heinrich Gustav Magnus was a great teacher, able to stimulate and motivate his students which caused his rapid success. He was able to demonstrate the importance of applied science and held colloquies on physical questions at his own house. Magnus owned his laboratory privately (however, it was later integrated into the University of Berlin) and it became known as one of the best equipped in  Europe. Beneficiaries of his lab include Hermann Helmholtz and Gustav Wiedemann.[6]

As listed by the Royal Society of LondonMagnus published 84 papers in research journals. In the 1820s and early 1830sMagnus mainly devoted his time to chemical research questions, which resulted in the discovery of the first of the platino-ammonium class of compounds. Also, Magnus was able to identify the three sulfonic acids sulphovinic acid, ethanoic acid, and isethionic acid and their salts. Further research interests of Heinrich Gustav Magnus include the absorption of gases in blood as well as the expansion of gases by heat and the vapour pressures of water and various solutions in later years.

Named after the physicist is also the famous ‘Magnus effect‘ or sometimes called the Magnus force. He experimentally investigated the effect, it is responsible for the “curve” of a served tennis ball or a driven golf ball and affects the trajectory of a spinning artillery shell.

Magnus effect. In sum, the air flow around the side of the clockwise rotating cylinder, which rotates with the flow, is greater than on the other side causing a slight pressure difference. In the image that is on the underside of the cilinder, so that it experiences a downward force. The ball should have a horizontal speed -V toward RIGHT.

Magnus effect. In sum, the air flow around the side of the clockwise rotating cylinder, which rotates with the flow, is greater than on the other side causing a slight pressure difference. In the image that is on the underside of the cilinder, so that it experiences a downward force. The ball should have a horizontal speed -V toward RIGHT.

A spinning object moving through a fluid departs from its straight path because of pressure differences that develop in the fluid as a result of velocity changes induced by the spinning body. The Magnus effect is a particular manifestation of Bernoulli’s theorem: fluid pressure decreases at points where the speed of the fluid increases. In the case of a ball spinning through the air, the turning ball drags some of the air around with it. Viewed from the position of the ball, the air is rushing by on all sides. The drag of the side of the ball turning into the air retards the airflow, whereas on the other side the drag speeds up the airflow. Greater pressure on the side where the airflow is slowed down forces the ball in the direction of the low-pressure region on the opposite side, where a relative increase in airflow occurs.

However, it is also believed that already Isaac Newton had described it 1672 and correctly inferred the cause after observing tennis players at Cambridge college. It is further assumed that also Benjamin Robins, a British mathematician, ballistics researcher, and military engineer, explained deviations in the trajectories of musket balls in terms of the Magnus effect in 1742.

The German RoLo cargo ship E-Ship 1 in the harbour of Emden with four Flettner rotors

The German RoLo cargo ship E-Ship 1 in the harbour of Emden with four Flettner rotors

Next to these studies, Heinrich Gustav Magnus was also active in the introduction of a uniform metric system of weights and measures into Germany. Heinrich Gustav Magnus passed away on April 4, 1870, at age 67.

At yovisto academic video search, you can learn more about physics in Walter Lewin’s lecture on Newton’s Laws.

References and Further Reading:

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