No, I am not referring to the famous hill in San Francisco, nor to the one in
London, also known as Plowed Garlic Hill but to Potsdam's
Telegrafenberg, a hill of 96 meters. Red Baron
has visited Potsdam several times, but I always missed one attraction and, for a physicist, a must: The
expressionist Einstein Tower (
Einsteinturm) in Potsdam's
Albert Einstein
Science Park. This astrophysical observatory was built by
Erich Mendelssohn
on
Telegrafenberg from 1919 to 1922.
During my last trip to Berlin, I took the S-Bahn to Potsdam
Hauptbahnhof, intending to take the uphill bus to
Telegrafenberg.
However, the line only operates in the morning and late afternoon, transporting
the science institutes' employees up and down the hill. Eventually, I took a
taxi taking me to the guarded entrance of the Science Park.
I told the man
behind the counter that I wanted to visit the monument dedicated to my famous
physics colleague. He smiled, stood up, and handed me a pound of paper
information. Well documented, I started my uphill walk passing various
information panels and institute buildings.
The
Telegrafenberg got its name from the mechanical telegraph that the
Prussian government implemented in the first half of the 19th century. Following
Napoleon's defeat and the Congress of Vienna in 1814/15, most of the old borders
in Europe were restored, with some noteworthy exceptions.
Austria cleverly gave up its possessions on the Upper Rhine - note that on
Napoleon's order, the Breisgau with its capital Freiburg had already become
"badisch" in 1806 - thus avoiding any future confrontation with France while
Prussia acquired territories on the Lower Rhine, including the coal-rich Ruhr
district as well as the cities of Cologne and Coblenz. Thus, the Prussians
assumed the
Wacht am Rhein (The watch over the Rhine river) concerning
France.
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Königlich-Preußische Optische Telegrafenlinie from Berlin to Koblenz
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Reconstructed Prussian optical-mechanical telegraph station in
Cologne-Flittard. The many signal arms enabled the
transmission
of information-rich messages (©Superbass/Wikipedia)
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With such a vast territory spanning from Königsberg in East Prussia to Aachen
at the Belgian border, fast transmission of information in the kingdom was a
challenge. It took messengers on horseback three to four days to cover the
distance between Berlin and Coblenz. Thus Prussia began the construction of an
optical-mechanical telegraph line in 1833, with 62 relay stations covering a
distance of 550 kilometers between Berlin and Coblenz. The line started
at
Dorotheenstraße in Berlin, joined the Saint Anna Church in Dahlem,
passed the miserable hill of the
Schäferberg (shepherd's mountain!),
went to the
Telegrafenberg at Potsdam, and continued to Magdeburg's
Saint-Jean Church. After going through many more relay stations, the line
crossed some regions belonging to the Duchy of Brunswick, regained Prussian
territory in Westphalia at Paderborn, and eventually reached Coblenz via the
Cologne-Flittard relay. With the new installation, the transmission of a
telegram took 1.5 hours.
On my way to the Einstein Tower, I passed the street sign
Schwarzschildweg honoring
Karl Schwarzschild, the German astronomer. He was director of Potsdam's Astro-Physical
Observatory
from 1906 to his early death in 1916. In 1897, while in Vienna, he derived a formula to calculate the optical density of a
photographic emulsion. The intensity of faint stellar light sources
could now be calculated with high precision from photographic
measurements.
Whereas Einstein only gave an approximate solution for his field equations of
general relativity around a single spherical non-rotating mass, Schwarzschild
calculated the exact solution while serving with the Prussian Army in Russia
in 1915. He wrote to Einstein:
As you see, the war treated me kindly enough, despite the heavy gunfire, to
allow me to get away from it all and take this walk in the land of your
ideas.
Needless to say, Einstein was impressed. Schwarzschild's calculations
resulted in the famous Schwarzschild Radius being the size of the event
horizon of a non-rotating black hole. Karl's son
Martin
became a distinguished professor of astronomy at Princeton University.
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The Michelsonhaus
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The first impressing landmark on my way to the Einstein Tower was the former
astrophysical observatory built in the late 1870ies. The building has three
observation towers with rotating domes initially equipped with telescopes.
Later the building became known as
Michelsonhaus, for in 1881, the
Nobel prize winner of 1907,
Albert A. Michelson, had performed his key experiments in its basement, proving that the
velocity of light is always constant. His discovery was the basis for
Einstein's theory of relativity. In 2000, the
Institute for Climate Impact Research (PIK) moved into the building
following important renovation work.
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Großer Refraktor
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Another impressive sight is the Big Refractor Building. The
Großer Refraktor features two telescopes in parallel, one for the
observer and one for the camera. The installation was built in 1899, used
until 1968, and completely refitted in 2006.
The Einsteinturm was built on the summit to house a solar telescope designed
by the astronomer
Erwin Finlay-Freundlich. The telescope supports experiments and observations to validate (or
disprove) Einstein's relativity theory.
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The Einstein Tower, as seen from the front.
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Here the building is seen from the back with the Big Refractor in
the background.
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On my way back to the gate, I passed a nostalgic monument. The GDR was proud
of having sent, with Russian help, the first German cosmonaut - the name
distinct from NASA's astronauts - into space.
Sigmund Werner Paul Jähn returned from space station Salyut 6 to earth together with Russian
Commander
Valery Fyodorovich Bykovsky
on the Soyuz 29 mission. They both became
Heros of the German Democratic Republic. In 1983 Jähn received a
doctorate from the
Zentralinstitut für Physik der Erde (Central
Institute for the Physics of the Earth), specializing in remote sensing of
the earth and located on Potsdam's
Telegrafenberg.
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Together on earth and in space
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