Al-Battani
He made significant improvements to Ptolemy's astronomical tables and accurately determined the length of the tropical year.
Most quoted
"Our fleeting existence on Earth is but a moment compared to the eternal cycles of the cosmos. Yet, in this brief span, we are granted the capacity to observe and understand."
— from Kitāb az-Zīj as-Sābi'
"The beauty of the night sky, with its countless luminaries, is a testament to the artistry of the divine, an invitation to contemplation and wonder."
— from Kitāb az-Zīj as-Sābi'
"The celestial spheres, in their intricate dance, reveal the order and majesty of the Creator. To study them is to glimpse the divine mind at work."
— from Kitāb az-Zīj as-Sābi'
All quotes by Al-Battani (382)
The positions of the fixed stars can be determined by observing their right ascension and declination.
The apparent motion of the stars across the sky is due to the rotation of the Earth.
The celestial sphere is an imaginary sphere of infinite radius on which all celestial objects appear to be located.
The ecliptic is the apparent path of the sun across the celestial sphere over the course of a year.
The celestial equator is the projection of the Earth's equator onto the celestial sphere.
The zenith is the point directly overhead an observer on the celestial sphere.
The nadir is the point directly opposite the zenith on the celestial sphere.
The horizon is the line where the Earth appears to meet the sky.
The altitude of a celestial object is its angular distance above the horizon.
The azimuth of a celestial object is its angular distance measured eastward from north along the horizon.
The right ascension of a celestial object is its angular distance measured eastward along the celestial equator from the vernal equinox.
The declination of a celestial object is its angular distance north or south of the celestial equator.
The latitude of a place on Earth can be determined by observing the altitude of the celestial pole.
The longitude of a place on Earth can be determined by comparing its local time with the time at a known meridian.
The astrolabe is a versatile instrument used for solving various problems in spherical astronomy.
The quadrant is an instrument used for measuring angles, particularly altitudes of celestial objects.
The gnomon is a simple instrument used for determining the time of day and the solstices.
The armillary sphere is a model of the celestial sphere, used for demonstrating the motions of celestial objects.
The observations of the ancients are valuable, but they must be verified and corrected by new observations.
Mathematics is the language of the universe, and without it, we cannot understand the movements of the stars.