On This Day #2

If we look back on this day in history, it marks the birth anniversary of Wilhelm Eduard Weber. He was a German physicist born on 24th October 1804 who together with Carl Friedrich Gauss studied terrestrial magnetism and invented the first electromagnetic telegraph.

A portrait of Wilhelm Eduard Weber. Source: Wikipedia

He developed a number of magnetic maps with his colleagues. Thanks to this, there are now magnetic observatories all over the globe that measure the magnetic field on the surface. These observations are used by scientists to make models of the Earth's magnetic field originating from different sources. They are also important in estimating magnetic indices that provide an indication of the solar disturbances.

The first usage of the letter c was done in Kohlrausch and Weber (1856) to denote a number very close to the speed of light. In his honour, Weber (Wb) is the unit of magnetic flux in the SI units (International System of Units).

On This Day #1

If we look back on this day in history, it marks the birth anniversary of Hans Christian Ørsted. He was a Danish physicist and chemist born on 14th August 1977 who formed the foundation of electromagnetism.

A portrait of Hans Christian Ørsted by Christian Albrecht Jensen (1842). Source: Wikipedia

The presence of an electric current deflects a compass needle was the starting point of this discovery. Now, we apply it to objects as big and far away as the planets and space. Much of what the IAGA community does is based on the interaction of electric and magnetic fields.

In his honour, Ørsted (Oe) is the unit of magnetic field strength in the CGS (centimeter-gram-second) system of units. The first Danish satellite was also named after him. The Ørsted satellite launched in 1999 provided magnetic field data around Earth. Many geomagnetic field models make use of this data even today.