## Development in Astronomy

 10.1 Development in Astronomy

The solar system model:

• The Solar System is the system in which the Earth is located and the other planets orbiting the Sun in their own orbits

• In addition, asteroids, meteoroids, comets also orbit the Sun

Ptolemy's model:

• Claudius Ptolemy, a geographer, astronomer from Alexandria formulated Ptolemy's model which was a mathematical model of the universe around AD 150

• Ptolemy's geocentric model is that the Earth is the center of the universe and is surrounded by the Sun, Moon, planets, and stars

• The orbit is perfectly circular

• Objects that orbit the Earth move in a circular path (epicycle) and the epicycle moves in a larger circular path around the Earth (deferent)

• The equant is the point at which the center of the epicycle is observed to move through the same angle over the same period of time

Copernicus's model:

• In the 16th century, an astronomer named Nicolai Copernicus (1473 - 1543) suggested that the Sun was at the center of the Solar System instead of the Earth

• Copernicus heliocentric model where the Sun is the center of the universe and is surrounded by the Earth and other planets, the stars are far from this center

• The orbit is a perfect circle

Kepler's model:

• In 1609 and 1619, Johannes Kepler, a German scientist published a model that is still in use today

• Kepler's Law of Planetary Motion there are three laws

• Kepler's First Law is the Law of Orbit - all planets move in an elliptical orbital path (two focal points)

• Kepler's Second Law is the Law of Extent - a planet moves faster in its orbit and close to the Sun while moving slower if away from the Sun

• Kepler's Law Three is the Law of Period - the relationship between the distance of a planet and the duration of a planet to complete an orbit around the Sun

## Development in Astronomy

 10.1 Development in Astronomy

The solar system model:

• The Solar System is the system in which the Earth is located and the other planets orbiting the Sun in their own orbits

• In addition, asteroids, meteoroids, comets also orbit the Sun

Ptolemy's model:

• Claudius Ptolemy, a geographer, astronomer from Alexandria formulated Ptolemy's model which was a mathematical model of the universe around AD 150

• Ptolemy's geocentric model is that the Earth is the center of the universe and is surrounded by the Sun, Moon, planets, and stars

• The orbit is perfectly circular

• Objects that orbit the Earth move in a circular path (epicycle) and the epicycle moves in a larger circular path around the Earth (deferent)

• The equant is the point at which the center of the epicycle is observed to move through the same angle over the same period of time

Copernicus's model:

• In the 16th century, an astronomer named Nicolai Copernicus (1473 - 1543) suggested that the Sun was at the center of the Solar System instead of the Earth

• Copernicus heliocentric model where the Sun is the center of the universe and is surrounded by the Earth and other planets, the stars are far from this center

• The orbit is a perfect circle

Kepler's model:

• In 1609 and 1619, Johannes Kepler, a German scientist published a model that is still in use today

• Kepler's Law of Planetary Motion there are three laws

• Kepler's First Law is the Law of Orbit - all planets move in an elliptical orbital path (two focal points)

• Kepler's Second Law is the Law of Extent - a planet moves faster in its orbit and close to the Sun while moving slower if away from the Sun

• Kepler's Law Three is the Law of Period - the relationship between the distance of a planet and the duration of a planet to complete an orbit around the Sun