Girard-Perregaux COSMOS User Manual

USER MANUAL

COSMOS

INSTRUCTION FOR USE

ASTRONOMY AS A TIME MEASUREMENT INSTRUMENT

The measurement of time finds its origins in the observation of astronomical phenomena such as
the motions of celestial bodies in the sky. Most of the calendars have been developed according to
the movements of the Sun as Man observed a regular alternation of diurnal and nocturnal periods
of time. Thus, it is customary to measure a day according to the position of the Sun with respect
to the Earth.

A sidereal day and a solar day must be differentiated in terms of duration. A sidereal day lasts 23
hours, 56 minutes and 4 seconds, which corresponds to a 360 degrees full rotation of the Earth
on itself, independently of its revolution around the Sun. Meanwhile, a solar day has an average
duration of 24 hours corresponding with the time interval passing between two culminations of
the Sun on a given meridian. This positive difference of 3 minutes and 56 seconds is due to the
revolution of the Earth around the Sun, leading to a rotation of more than 360 degrees of the
former.

A CELESTIAL GLOBE INDICATING THE CONSTELLATIONS OF THE ZODIAC

The celestial globe of Cosmos, whose mechanism is based on the duration of a sidereal day, is an
astronomical globe indicating the constellations of the Zodiac. It is composed of 12 constellations
which showcase their very own combination of stars. Their arrangement recalls the astrological
signs known today and divided into 12 periods of time throughout the year.

The Zodiac differs between astronomy and astrology due to the phenomenon called “precession
of the equinoxes”. It corresponds to the gradual change of direction of the Earth rotation axis,
resulting in a change of the stars position in the sky over the years. The astronomical calendar
of the zodiac thus refers to the stars that are actually visible in the sky at a given time, unlike the
astrological one that is invariant over time.

The current zodiacal constellation is the one that is placed behind the sun when it is 12 o’clock
solar time, referred to as “the sun passage through the constellation”. Invisible to the naked eye
because of the solar light diffusion in the atmosphere, the constellation is revealed by the celestial
globe of Cosmos.

Gemini

Cancer

Taurus

Leo

Aries

Pisces

Aquarius

Capricorn

Sagittarius

Scorpio

LibraVirgo

ZODIAC CONSTELLATIONS SETTING TABLE

June 21

August 10

October 30

October 31

November 20

TaurusAries PiscesAquariusCapricornSagittariusScorpioLibraVirgoLeoCancerGemini

April 19

-

May 13

May 14

-

June 22

-

July 20

July 21

-

August 11

-

September 16

September 17

-