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History of Astrology

Claudius Ptolemy – 87 – 150 CE Nicholas Copernicus – 1473 – 1543 Galileo Galilei – 1564 – 1642 Johannes Kepler – 1571 – 1630 Isaac Newton – 1643 - 1727

Claudius Ptolemy – 87 – 150 CE

Ptolemy did not have the ability to look deep into the sky, so with his un-aided eyes he developed a geocentric model of our solar system.

Ptolemy stated that the earth was at the centre of the solar system. Everything else revolved around Earth.

The order of planets was as follows: Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn and then the stars.

Nicholas Copernicus – 1473 – 1543

He was also very passionate about astronomy. In 1514, Pope Leo X hired Copernicus to

revise the Christian calendar. By the time he started working on it, the calendar was over 1500 years out of date and without revision Christmas would occur in the middle of the summer.

Nicholas Copernicus – 1473 – 1543

Copernicus noticed that Ptolemy’s model had many mathematical errors.

After reading ancient Greek philosophers books, he noticed that the Greek’s believed that the Sun was at the centre of our solar system – also known as heliocentric.

Copernicus made this switch, and not only was he able to correct for all the mathematical errors that Ptolemy’s model created, but it also agreed with the notion that the Sun warmed up all the planets.

Galileo Galilei – 1564 – 1642

Galileo was the first scientist to construct an accurate telescope.

His telescope was so powerful that he was able to discover the four moons orbiting Jupiter and he could see the rings of Saturn.

He calculated the distance between the stars and the planets. Through his calculations he was able to conclude that the stars were much farther away from Eath than the planets were.

Johannes Kepler – 1571 – 1630

Kepler wanted to prove to the world that Copernicus’ model of our solar system was right.

Kepler purchased a telescope from Galileo and worked with astronomer Tycho Brahe.

Upon Brahe’s death bed he gave Kepler all of his instruments, calculations and his work.

Johannes Kepler – 1571 – 1630

With Brahe’s calculations and Galileo’s telescope Kepler was able to create three profound conclusions about planetary motion The planets ravel in an elliptical orbit around an off-centre Sun The speed of a planet’s orbit depends on its distance from the

Sun. When a planet is near the Sun it moves fast, when it is further away from the Sun it moves slower.

The further the planet is from the Sun, the longer its orbit. Earth’s year is 365 ¼ days, Pluto takes 248 earth years to orbit the Sun and Sedna takes 10,000 Earth years to orbit the Sun

Isaac Newton – 1643 - 1727

Kepler was able to finalize the location of the Sun, Earth, all the planets and the stars without any mathematical errors.

One problem did exist though… why were we revolving around the Sun?

In comes our man Newton…..

Isaac Newton – 1643 - 1727

Newton agreed that our solar system was heliocentric. Newton noticed that the Moons orbit around Earth was

created by the force of gravity between itself and Earth.

Newton also discovered how gravity works. He created two important rules about gravity: The masses of the objects involved affect gravity; The distance between the objects affects gravity.

Isaac Newton – 1643 - 1727

Ultimately, Newton stated an object of greater mass exerts a greater amount of gravitational pull between the two objects. He also stated that the closer the two objects are to each other the greater the force of gravity is exerted between them.

This is why, Earth, being larger than the Moon, will attract the Moon to Earth yet because of the Moon’s gravitational force it pushes back against the Earth and thus the Moon will orbit the Earth.