Dear friends of
ancient coins!
"
We are dwarfs on the shoulders of giants". This parable is first attested around AD 1120 by
Bernard of Chartres, quoted by John of Salisbury in
his Metalogicon published around 1159, and used by Isaac Newton, among others. And with Hipparch, one of these giants stands before us!
The coin:Bithynia, Nikaia,
Gallienus, AD 253-268.
AE 25, 5.38g, 25.62mm, 30°
Obv.: Γ ΠOVB ΛIK EΓN ΓAΛΛHNOC AVΓ
Bust, draped and
cuirassed, seen from behind, wearing
radiate crown, r.
in neck c/m (H in circular
incus, (
Howgego 821e).
Rev.: NIK - A - IEΩN
in ex. IΠΠ
APX (ΠAP ligated)
The astronomer Hipparchos in
himation seated on a sella l., pointing with
his right hand to a globe on a slender
column.
Ref.:
cf. Waddington, Asie Mineure, no. 843 (other dies), pl. 87, fig. 36 (
reverse);
cf. Imhoof-Blumer (1908) no. 6 (other dies)
Very
rare (2 ex. Coin
Collection University of
Cologne).
The counterstamp probably conceals a declining
weight standard. The majority of
von Aulock's coins come from a large find at
Nicomedia (
Howgego).
Hipparchos was born around 190 BC in Nikaia and died around 120 BC on Rhodes. He was the most important Greek astronomer of
antiquity and is considered the founder of scientific
astronomy based on observations.
Which discoveries and inventions can be traced back to Hipparchos?
(1) He compiled the first
star catalogue with 1 028 stars, which was later processed by C.
Ptolemy in
his Almagest. The
catalogue itself has not survived, but in 2012 a palimpsest, the Codex Climaci Rescriptus, was found in the Monastery of St. Catherine on the Sinai Peninsula, which turned out to be
part of Hipparch's
star catalogue. This enabled Gysemberghh and
his working group to reconstruct parts that turned out to be more accurate than those of
Ptolemy. Unlike
Ptolemy, he used the celestial equator rather than the ecliptic. These lists were
still used by Copernicus. The asterisks show that he made
his observations from Rhodes. He was also the first to create a
scale of
star brightnesses.
(2) He could only achieve this accuracy by using new invented devices and methods. Since he
had no telescope, according to Gysembergh, he must have used a sighting
tube, a so-called dioptre, or already an
armillary sphere or a wall quadrant.
(3) Hipparchos introduced the graduation of the
circle and used chord tables for
his calculations, on which the relationships between angles and lengths were recorded. He thus introduced trigonomy ("chordal calculation") into
astronomy and thus became the founder of spherical trigonometry.
(4) With these methods he became the originator of stereographic and
orthographic map projection.
(5) When the moon occulted the stars, he was able to determine
star positions in the
zodiac more precisely. When he compared the
star positions he
had measured with older data, e.g. those determined by Timarchos and Aristyll about 150 years earlier, he found that they
had shifted by 2° in the meantime. This makes him the discoverer of precession. Precession is a property of the earth's movement, whereby the earth's
axis shifts in relation to the constellations. Today we know that it is caused by a circular movement of the Earth's rotation. However, this explanation was not accepted at that time. Its exact value is 25850 years. With
his observation of 2° in 150 years, he arrived at 27000 years. Not bad!
(6) He calculated the distance and size of the moon and the sun from eclipse observations and determined the first solar and lunar ephemerides. These are tables with the daily positions of the celestial bodies, which could be used by seafarers for navigation.
(7) He found the midpoint equation or Great Inequality, which refers to an irregularity in the moon's motion. It occurs because the moon does not revolve around the earth, but because the earth and moon move around a common centre of gravity, which is located inside the earth due to the mass ratios.
(8) Through astronomical observations he determined the length of the solar year to within 6.5 minutes and established the exact different lengths of the
seasons, which he attributed to an eccentric orbit of the sun around the earth.
(9) Hipparchos rejected the heliocentric system of Aristarchos and adhered to the geocentric system. In order to be able to mathematically explain the deviations of the planetary orbits with their retrograde movements, he worked out the eccentric theory of apparent planetary motion, which later led to the epicycle theory.
(10) It was probably under
his supervision that the mechanism of Antikythera, a marvel of
antiquity, an astronomical computer, was built on Rhodes and found in 1900 in a wreck near the Greek island of Antikythera.
Hipparch's main works are lost.
Ptolemy, who knew them, calls him "
the greatest lover of truth" and celebrates him as
his most important pioneer. He is considered the "
Einstein of antiquity". Pliny the Elder, however, called the measuring of the stars a
work contrary to God. In particular, he was annoyed that Hipparchos
had described a new
star, probably a supernova, which violated the eternal symmetry of the
celestial sphere. This shows that Hipparchos
had taken the
side of science in the dispute between religion and science. It was only after the exit from the dark centuries of Christianity that this scientific height could be reached again in the Renaissance.
Pauly writes: Without the retarding scepticism of Hipparchos, the heliocentric system might have been accepted some 1700 years earlier, admittedly to the detriment of science, to which a flash of
genius is beneficial, but the strict method based on pedantic data processing and mathematical deduction is indispensable.
Notes:(1) The
armillary sphere (
armilla = bangle,
sphaera = sphere) is a further development of the astrolabe. It consists of several metal
rings that can be rotated together, forming the shape of a sphere. The imaginary observer is located in the centre of the sphere. If the device depicts the geocentric view of the world, a specific location on Earth is found there.
It remained in use throughout the Middle Ages, mainly in
Islamic regions. In Central Europe it only became known again in the 15th century through Regiomontanus and reached its perfection in the 16th century with the Danish astronomer Tycho Brahe.
(2) The
wall quadrant is an instrument that can be used to measure exact elevation angles and positions of stars. It consists of a quarter
circle with an exact
circle division and an associated reading device, a sighting device and a plumb bob. It is firmly mounted on a wall running north-south and exactly perpendicular. This has made it possible that the accuracy could be increased considerably. The most accurate angular quadrant stood on Tycho Brahe's island of Uranienborg and
had a radius of 2m.
I have attached:
(1) The pic of a model of Hipparch's celestial globe
The constellations marked, horizontal planes and meridian
circle are used to read coordinates or times (Wikiwand).
(2) Renaissance
armillary sphere (
Wikipedia)
(3) Model of a wall quadrant, Johann Wolfgang Goethe University
Frankfurt a. M.
Literature:(1) Der Kleine
Pauly(2) American Scientific
(4)
Cologne Coin Portal
(5)
WikipediaBest regards
Jochen
