In the wooded hillside of Hainberg, near Gottingen, Germany, stands an old seismological station.
Wiechert built several seismographs there to record tremors.
These instruments have been recording data uninterruptedly since then, becoming the worlds oldest, still functioning seismograph.
Emil Wiechert was interested in learning about the structure of the earth.
He concluded, correctly, that the earth has a heavy iron core.
The Mintrop ball readying for a drop.
Emil Wiechert was joined by many brilliant researchers, among which was a young German geophysicist named Ludger Mintrop.
Ludger Mintrop was an able student of Wiechert, and one of the founders of modern geophysics.
Portable seismographs were used to register the resulting artificial seismic ground waves at various distances from the drop site.
The experiment was a resounding success.
Mintrop successfully created a three-dimension image of the immediate area below the surface of the earth.
Photo credit:USGC
The 4-ton steel ball in its steel scaffolding still stands at the earthquake station.
It has been modernized with an electric motor and a remote release mechanism.
It is still dropped today whenever visitors are around.
There are lots of other interesting stuff at the earthquake station.
Visitors can see Wiecherts famous inverted-pendulum seismograph, which he built in 1902.
The mass is held near the equilibrium position by the pressure of thin springs at the top.
Records of the movement are made on smoked paper on a rotating drum.
Wiechert seismographs are still used in some of the worlds observatories and continue to supply valuable information.
