Early indigenous knowledge

Astronomy is one of the oldest sciences. Ancient civilisations around the world watched the night skies, noting the patterns they saw in the sky. These patterns are called the constellations. A constellation is any group of stars, as seen from Earth, that seems to form a pattern or picture in the sky. Different nations, cultures and people have given different names for the different star patterns and how they interpreted the patterns.

A well known example is the Southern Cross. Have a look at the photos which show the stars in the night's sky and how to view the pattern making up the cross.

The Southern Cross, Crux, and the two bright Pointer stars were used by farmers to mark the beginning of the planting season. According to Sotho, Tswana and Venda traditions, these stars were called Dithutlwa, meaning "The Giraffes". The bright stars of Crux are male giraffes, and the two Pointers are female giraffes.

Another example is the constellation Orion. It is named after Orion, a supernaturally, strong hunter in Greek mythology. This is one of the most recognised constellations around the world and many cultures have identified with it, each forming their own myths, many around a strong man or hunter.

People also watched the movement of the stars and planets across the sky marking the passage of time. Early cultures tended to identify the stars and planets they saw in the night sky with gods, spirits or animals. Ancient astronomers could tell the difference between stars and planets as the relative positions of the stars remain fixed in the sky whereas planets appear to move across the sky relative to the background stars. Not all the planets were known to the ancient people, rather only Mercury, Venus, Mars, Jupiter and Saturn. Uranus and Neptune were only discovered after telescopes were invented.

Ancient civilisations like the Sumerians, Babylonians and Egyptians were responsible for introducing many of the constellations that astronomers use in the West today.

Knowledge of these constellations were later passed on and added to by later civilisations like the ancient Greeks, Romans and Arabs. Native Americans, Aboriginal Australians, Mayans, Aztecs, Polynesians and ancient Chinese and Japanese peoples took a keen interest in the stars and had their own constellations and stories about the stars.

Astronomy played an important role in religion at the time, and the dates of festivals and holy days were fixed by the alignment of the stars or the phase of the Moon. In fact, the ancient Egyptian and Mayan pyramids and temples were designed in such a way that the Sun, Moon, stars and planets would be visible from the top or through certain windows at important times of the year, such as solstices or equinoxes.

Here in South Africa, early cultures also had their own constellations and stories which were passed down from generation to generation.

Early cultures used the stars for navigation. When travelling to new areas or over water they would have been unable to use familiar landmarks. When viewed from a particular location, a star always rises and sets in the same direction and follows the same path across the sky. We are familiar with this idea as the Sun is a star and we see it rise and set in the same direction every day. Early navigators learnt to use the directions of rising and setting stars to find their way.

Early cultures also used the observed changes in the sky for timekeeping. A day was marked by the time between one sunrise and the next, just as it is today. The Moon's regular phases made it a very convenient "clock", and the time period between one New Moon and the next formed the basis of many of the oldest calendars.

The lunar cycle was useful because it was predictable in the same way as day and night, however, each Moon cycle was also connected to a slightly different season with its own name and activities.Tally sticks made of bones with notches etched into them have been found dating as far back as 20-30 000 years ago and are believed to mark the phases of the Moon. Today we use a solar calendar, a calendar in which a year is defined by the complete revolution of the Earth around the Sun, but some religious calendars still use a lunar calendar. Accurate timekeeping was particularly important for farming communities because people needed to know when to plant their seeds and when to harvest their crops.

The Pleiades, also called the Seven Sisters, is a bright cluster of stars. Traditional farming communities in South Africa used the Pleiades to help them plan their planting. Once the constellation was visible in the early morning in June they knew it was time to start planting their crops. The Khoikhoi call the Pleiades Khuseti or Khunuseh meaning "rain stars". They are called Selemela in Sotho and Tswana, Shirimela in Tsonga, Tshilimela in Venda, and isiLimela in Xhosa and Zulu. In Xhosa the stars are called the "digging stars". In East Africa and Zanzibar the Pleiades are called Kilimia, which also means "ploughing stars" or " digging stars". Not only were the Pleiades used in Africa to mark planting season, they were also used by the ancient Mayans in Mexico and Central America to mark the start of their rainy season too.

As well as their practical uses in timekeeping, stories surrounding the Sun, Moon and constellations have been passed down from generation to generation. These mythical stories are called star lore. For example some believed that after sunset the Sun travelled back to the east over the top of the sky and that the stars are small holes which let the light through. Others said that the Sun is eaten each night by a crocodile and that it emerges from the crocodile each morning.

Being the most prominent object in the night sky, the Moon also has many stories and legends associated with it. If you look closely at the Moon you can see that it has lighter and darker patches. The pattern formed by the light and dark patches had been interpreted differently by different cultures: some see a rabbit, others a buffalo, others a "Man in the Moon". One urban legend that some people still incorrectly believe is that the the Full Moon is linked to insanity. There is no evidence to support the claims of increased birth rates, admissions to psychiatric hospitals, traffic accidents, homicides or suicides during a Full Moon.

The Khoikhoi called the Moon kham, or khab meaning "the Returner". The Khoikhoi also considered the Moon to be "the Lord of Light and Life" and would sing and dance at times of New and Full Moon. In /Xam San star lore, there is the following story:

The Moon is a man who has made the Sun angry. The Sun's sharp light cuts off pieces of the Moon until almost the whole of the Moon is gone, leaving only one small piece. The Moon then pleads for mercy and the Sun lets him go. From this small piece, the Moon gradually grows again until it becomes a Full Moon.

What do you think the San were observing which they explained with this story?

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The Xhosa considered the time of New Moon to be a time of inaction. When it reappeared as a crescent in the evening sky, it was cause for celebration. Important events were scheduled to take place around the time of Full Moon.

The Milky Way is also a prominent feature of the South African nighttime sky visible away from cities. Ancient peoples in South Africa described the Milky Way as as a footpath across the sky, along which the ancestor spirits walked. In San starlore, the Milky Way was created by a girl who scooped up a handful of ashes from a fire and flung them into the sky. This made a glowing path along which people could see the route to return home at night.

Meteors (also called shooting stars) and comets also feature heavily in starlore around the world. In most cultures meteors and comets were regarded as signs of important events. In Tswana starlore, a very bright meteor is an indication of a good season ahead. However, the .Xu San saw a meteor as an evil spirit racing across the sky to cause mischief among people. The /Xam San, thought that a meteor announced the death of one of them. In Xhosa starlore, a comet, Uzatshoba, is associated with bad luck, wars and death. There was also a strong belief that comets predicted the death of a chief. The Sothos called comets naledi tsha mesela, and the Zulus called them inkanyezi enomsile, which means "stars with tails".

Modern developments

The earliest astronomers had no sophisticated observatories. They studied the stars and planets using just their eyes. This is called naked eye observing. The South American Mayans, ancient Egyptians and ancient Chinese built some of the first observatories. These are special buildings used for studying the stars. These ancient observatories had no telescopes inside.

Nowadays modern observatories contain large telescopes with extremely sensitive cameras and instruments mounted on the telescopes. Astronomers use computers to move the telescopes and operate the instruments. As technology has progressed, we have been able to see a lot more and have learnt a lot more about the Universe.

South Africa currently has the largest optical telescope in the Southern Hemisphere, the Southern African Large Telescope (SALT). SALT is located just outside Sutherland in the Karoo where the skies are clear and very dark. SALT's main mirror is a hexagon shape measuring 11 x 9 metres across and is made up of 91 individual smaller mirrors which are slotted together. Its mirror is so large so it can collect a lot of light from very faint and distant objects. SALT is used to study a variety of objects including asteroids, stars and galaxies.

South Africa will also be hosting part of the Square Kilometre Array (SKA), the world's largest radio telescope, scheduled to be completed in 2024. The SKA will be located in the Karoo near the town of Carnarvon, far away from big towns and cities where there is little radio interference. When complete the telescope array will be 50 times more sensitive than any other radio telescope to date. The array will contain 3000 radio dishes as well as other types of radio detectors.

Two thirds of the SKA will be built in Africa (mostly in South Africa), while the remaining third will be built in Australia.

An array means a large number of the same items. For example, when the desks in your classroom are all lined up neatly, we can call that an array of desks.

Astronomers plan to use the giant telescope to test the laws of gravity using black holes. They will also peer at some of the most distant clouds of gas in the Universe which formed before the first stars. Astronomers will also study how galaxies form, and change over time, and perhaps also detect life elsewhere in the Universe.

We still have so much to learn about our Universe, we only understand about 5% of the content of our Universe presently. SALT and SKA will help us understand far more about our Universe, so much is still to be discovered.

Let's look at some of the highlights in our journey of scientific discovery so far.

Summary

Concept map

Throughout this year we have been looking at how to produce concept maps after each chapter. This is now your chance to make your own concept map. The concepts in this chapter about the development of astronomy can easily be divided into two main themes. Firstly, about "early indigenous knowledge" and then about the "modern developments" that people have made and are still making. The concept map has been started for you. Copy this into your notebook to first practice drawing your concept map. Once you have your final version, with the help of your teacher, draw it into the space below to act as the summary for this chapter.