What creates gravity inside the earth

GeoFlow: A look inside the earth

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What has so far been impossible on earth - the exploration of its internal structure - is paradoxically possible on the space station. A modeled mini-earth "GeoFlow" serves researchers on the ISS as a medium to better understand the currents and movements in the deepest interior of the earth. The Geoflow experiment in the European fluid laboratory FSL is expected to be completed in September 2012.

That is the central question of the international project "Geophysical Flow Simulation" - Geoflow for short. Even though the record for deep boreholes is an impressive 12,262 meters: They are nothing more than scratches on the planet's crust. The only way to understand processes and map depth areas that are directly are not accessible, represent explorations with the help of seismic waves as well as laboratory experiments. This is also the approach for the novel experiment. Geoflow is to check simulations in order to determine how exactly the previous numerical models reflect reality.

Jules Verne in a double pack

So far, only Jules Verne has managed to get to the center of the earth at a depth of 6371 kilometers - in the science fiction novel. Now a modern “Jules Verne” actually wants to realize it in a different way: Prof. Christoph Egbers, professor of aerodynamics and fluid dynamics at the Brandenburg University of Technology Cottbus (BTU), undertakes a journey with his team that takes us to the center of the earth , but takes place at a height of 360 kilometers above the earth's surface.
With GeoFlow, Egbers has developed a model that is supposed to provide information about the convection currents leading from the earth's core to the earth's mantle and the resulting continental drift. However, his mini-earth only works if no real gravitational field distorts the artificial central force field. Therefore, the experiment can only be carried out in weightlessness, that is, in space.

The mini earth in space

The biggest challenge was to realize the not a few boundary conditions in a mini earth model the size of a soccer ball. In February 2008, Geoflow reached the space station on the US space shuttle Atlantis (STS 122). It was used as the first German experiment in the Fluid Science Laboratory of the European Columbus module.
The interior of the earth is simulated by a spherical model: a special liquid is located between an inner, massive sphere, which represents the earth's core, and an outer hollow sphere. According to the temperature conditions in the interior of the earth, the inner sphere is heated and the outer one is cooled. An undistorted, centrally symmetrical force field is then generated in the spherical gap by applying an electrical voltage, which simulates the force of gravity on earth. In addition, the spheres are rotated to represent the rotation of the earth. Under the influence of rotation, temperature gradient and a simulated gravitational field, the fluid begins to circulate between the spherical shells. It behaves analogously to the liquid mass that flows around the solid core of the earth. The resulting flow images are recorded by a camera. The data is then transmitted to earth.

In the focus of GeoFlow I: The outer core of the earth

The course of the experiment is monitored by the "User Home Base" control center set up specifically at the BTU in Cottbus as the last link in the operational chain. If the employees come across something interesting, they can intervene directly. A total of ten research teams from Germany, France and Great Britain are involved in the experiment. Geoflow is significantly supported by ESA and DLR.
The first series of experiments from August 2008 to January 2009 (Geoflow I) aimed exclusively at the internal structure of our home planet and the simulation of the convective currents in the liquid outer core of the earth. After the return of the experiment container with the US space shuttle Discovery (STS 119) in March 2009, the equipment at Astrium in Friedrichshafen was revised.

In the focus of GeoFlow II: The Earth's mantle

The modified facility made its way back to the ISS in February 2011 with the European transport spaceship ATV-2. The focus of the Geoflow II experiment is now on the convection currents in the earth's mantle. The test series has been running extremely successfully since March 2011, so that the experiment has been extended by a few months until September 2012 after the nominal program was completed. This in turn is made possible by an additional scientific program Geoflow IIB.
One of the central questions in GeoFlow II is: How do the - often mushroom-shaped - magma flows move in the Earth's mantle? They not only lead to the drift of the continental plates. Natural events such as volcanic eruptions, earthquakes and tsunamis also have their origin here, as does the formation of raw material deposits.
The team around Christoph Egbers also hopes to find causes for the reversal of the earth's magnetic field. The last was about 780,000 years ago. Statistically, the next pole shift is already overdue. It could have serious consequences for life on earth.

Geoflow as a successful model

Geoflow is basic research. The findings contribute significantly to making the processes taking place in the earth's interior more transparent. Although the new knowledge does not prevent natural events, it can help predict and thus minimize damage.

Additional Information:

Prof. Dr.-Ing. Christoph Egbers
Chair of Aerodynamics and Fluid Mechanics
Brandenburg University of Technology Cottbus
Siemens-Halske-Ring 14
D - 03046 Cottbus
Phone: +49 (0) 355 / 69-4485 or 69-5011
Fax: +49 (0) 355 / 69-4891
egbers @ tu-cottbus.de

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