A short history of astronomy

Astronomy is the oldest science by far. As long as mankind exists we have looked up to the skies and wondered what was out there. Almost every culture throughout history has studied the Sun, Moon and stars, and watched how celestial bodies move across the sky. For early civilisations, like the ancient Egyptians, astronomy was a way to keep track of the changing seasons. They used it to know when it was time to plant and harvest crops and it was used to make calendars and sundials to keep track of time. In 1000 BC, Indian and Babylonian astronomers had already calculated length of a year as 360 days (which resulted in a 360 degree circle, with each degree representing a solar day). Later the ancient Egyptians refined this calculation to 365.25 days. The most important discoveries
of ancient astronomers included how to find the north, south, east and west. This knowledge enabled the precise orientation of buildings like temples and burial monuments and helped to produce accurate terrestrial maps. Later on it was used for navigation at sea as well. The ancient Greek lay the base for scientific astronomy. After the decline of the Greek city-states, the most important advances in astronomy were achieved by Arabic scholars. This period lasted from about 620 AD until the 15^th century, when European astronomers took over again.
For centuries astronomers had placed the Earth at the centre of the Universe. In the 16^th century the Polish Nicolaus Copernicus published a ground-breaking treatise about a Sun-centred, or heliocentric, Universe. This explained many, previously puzzling, observations because there were now two types of planets; those inside the Earth’s orbit and those beyond. In 1608 a Flemish spectacle-maker invented the telescope and the news spread quickly. The Italian Galileo Galilei made his own telescope and became the founder of the telescopic astronomy. He provided the proof that Copernicus was right. In 1687 Isaac Newton published the first clear mathematical definition of gravity, it revolutionised astronomy and physics. In the 18^th and 19^th century there was great progress in science due to improved scientific methods. During the 19^th century a new field emerged in astronomy; astrophysics. Before, astronomy had been mainly about observing the movement of planets and stars, whereas astrophysics applied mathematics, physics and chemistry to examine radius, mass, temperature and composition of celestial objects.
In the beginning of the twentieth century astronomers realised that there were billions of galaxies, millions of light years apart, instead of just our own Milky Way galaxy. They also started to understand the sources of stellar energy. More and bigger telescopes were build and became available for a larger number of astronomers. In the 1950’s the era of spaceflight started and travel beyond Earth became a reality. The dawning of radio, infrared, ultraviolet, x-ray and gamma ray astronomy, together with space probes and telescopes in space offered a whole new perspective to the Universe. Although we have learned a lot since first men looked up to the sky, there is still much

more to be learned and the more we learn, the more we realise how much we still don’t understand.

Regards from the bush,
Miriam