Opening our eyes to the Cosmos

For millennia, we homo sapiens have looked out into the night sky, wondering about what those twinkly shiny dots in the sky were. Some used their imaginations and made up shapes and constellations, others pitched their Gods and Goddesses high up in the cosmos.

But with the passage of time, we started using logic and science to explain the unknown. We noticed patterns in the movement of the Sun, Moon and stars across the sky; we saw that a bright star, today known as Polaris, always showed the way North; in 240 B.C Eratosthenes even used shadows to accurately calculate the Earth’s circumference!

But our unsatiated quest for knowledge continued, so we made new tools and instruments to aid us in our search. Ancient astronomers from Mesopotamia, Egypt, India, Greece and Rome used a variety of ancient astronomical tools, such as sundials, astrolabes, or quadrants and sextants, to identify and calculate astronomical phenomena and objects, such as predicting eclipses.

Ofcourse, we made mistakes according to our limited knowledge; in 230 B.C Ancient Greek astronomer Aristarchus of Samos first theorised the helio-centric model of the universe in which the sun, not the earth, was at the center. Although his theory was noted by other thinkers of his time, it was rejected as implausible, and the geocentric model was retained for 1,700 years afterward.  

In 127 B.C, Greek mathematician and astronomer Hipparchus discovered the precessional movement of the equinoxes. His work has earned him the title of the “father of scientific astronomy”, and his work greatly influenced Ptolemy of Alexandria, who around 150 C.E published the astronomical manual Almagest, in which his geo-centric model would be the one accepted for the next 1500 years.

In early 6th century India, Aryabhata correctly insisted that the earth rotates about its axis daily, and that the apparent movement of the stars is a relative motion caused by the rotation of the earth. Solar and lunar eclipses were scientifically explained by Aryabhata. Aryabhata calculated the sidereal rotation (the rotation of the earth referencing the fixed stars)

Whilst Europe was in the Dark Ages from around 800 till 1500 A.D, Islamic astronomers such as Al Biruni, Ibn al Haytham, Tusi and many others preserved and built upon the ancient works of Greek, Roman, Mesopotamian, Indian, Egyptian and Chinese astronomers. 

Then, in the year of his death in 1543, Renaissance polymath Nicolaus Copernicus's major work on his heliocentric theory Dē revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres) was published. He had formulated his theory by 1510, however it has remained a secret due to the expected opposition from the Church, as the understanding from the Bible was that the Earth was at the center of the Universe. Indeed, Copernicus’ model would incur suffering from the Church on many astronomers such as Galilieo, but it a major event in the history of science, triggering the Copernican Revolution and making a pioneering contribution to the Scientific Revolution.

In the late 16th century, not too far from Copenhagen, Tycho Brahe built the largest observatory in Christian Europe called Uraniborg, after Urania the Greek muse of astronomy. Built on the island of Hven located between the provinces of Zealand (Sjælland) and Scania (Skåne), and supported by King Frederick II of Denmark and even the church, Uraniborg was one of the most advanced observatories of its time, equipped with several astronomical instruments, including quadrant instruments, sextants, and astronomical clocks. Tycho Brahe's observations and calculations at Uraniborg allowed him to develop more accurate solar system models. He also compiled the most extensive and accurate catalog of stellar positions up to that time. Tycho Brahe's observations and calculations at Uraniborg allowed him to lay the groundwork for astronomers in the future. 

Around the same times, German astronomer Johannes Kepler published his 3 laws of planetary motion on 1609 and 1619, along with the Rudolphine Tables in 1927, which was a star catalog he had worked ypon together with Tycho.

Then in 1608, Dutch optician Hans Lippershey patented the telescope. Astronomers now had a new toy to play with, and Galileo Galilei used this to the utmost extent.

Making his own modified refracting telescope, the father of observational astronomy saw in late 1609 that the surface of the Moon is not smooth, instead full of craters. Early the next year, he observed the four largest moons of Jupiter. Later in 1610, he observed the phases of Venus—a proof of Copernicus’ heliocentrism—as well as Saturn, though he thought the planet's rings were two other planets. In 1612, he observed Neptune and noted its motion, but did not identify it as a planet. Galileo made studies of sunspots, the Milky Way, and made various observations about stars, including how to measure their apparent size without a telescope. 

Galileo's 1610 The Starry Messenger (Sidereus Nuncius) was the first scientific treatise to be published based on observations made through a telescope. It reported his discoveries of:

• the 4 Galilean moons of Jupiter(Io, Europa, Ganymede, Callisto)

• the roughness of the Moon's surface

• the existence of a large number of stars invisible to the naked eye, particularly those responsible for the appearance of the Milky Way

• differences between the appearances of the planets and those of the fixed stars—the former appearing as small discs, while the latter appeared as unmagnified points of light

Galileo published a description of sunspots in 1613 entitled Letters on Sunspots suggesting the Sun and heavens are corruptible. The Letters on Sunspots also reported his 1610 telescopic observations of the full set of phases of Venus, and his discovery of the puzzling "appendages" of Saturn and their even more puzzling subsequent disappearance. 

Astronomy had now entered the modern era.