Armed with a greater knowledge and understanding of our universe, and also with new technology and modern approaches to science, we can discover wonders of the Universe that would have remained hidden to us centuries ago. Galaxies such as the spiral-shaped Dwingeloo 1 have recently been found hidden behind the Milky Way. This discovery supports what we already know: that there are many more wonders out there in the Universe that we have yet to discover.
CHAPTER 1
MESSENGERS
THE STORY OF LIGHT
Throughout recorded history humans have looked up to the sky and searched for meaning in the heavens. The science of astronomy may now conjure thoughts of telescopes and planetary missions, but every modern moment of discovery has a heritage that stretches back thousands of years to the simplest of questions: what is out there? Light is the only connection we have with the Universe beyond our solar system, and the only connection our ancestors had with anything beyond Earth. Follow the light and we can journey from the confines of our planet to other worlds that orbit the Sun without ever dreaming of spacecraft. To look up is to look back in time, because the ancient beams of light are messengers from the Universe’s distant past. Now, in the twentieth century, we have learnt to read the story contained in this ancient light, and it tells of the origin of the Universe.
The spectacular remains and towering pillars of Karnak Temple are a testament to the Egyptian belief in the power and importance of the Amun-Re, the Sun God, in their daily life, and of the Sun itself.
Karnak Temple, home of Amun-Re, universal god, stands facing the Valley of the Kings across the Nile in the city of Luxor. In ancient times Luxor was known as Thebes and was the capital of Egypt during the opulent and powerful New Kingdom. At 3,500 years old, Karnak Temple is a wonder of engineering, with thousands of perfectly proportioned hieroglyphs, and an architectural masterpiece of ancient Egypt’s golden age; it is a place of profound power and beauty. Ten European cathedrals would fit within its walls; the Hypostyle Hall alone, an overwhelming valley of towering pillars that once held aloft a giant roof, could comfortably contain Notre Dame Cathedral.
Religious and ceremonial architecture has had many functions throughout human history. There is undoubtedly a political aspect – these monumental edifices serve to cement the power of those who control them – but to think of the great achievements of human civilisation in these terms alone would be to miss an important point. Karnak Temple is a reaction to something far more magnificent and ancient. The scale of the architecture forcibly wrenches the mind away from human concerns and towards a place beyond the merely terrestrial. Places like this can only be built by people who have an appropriate reverence for the Universe. Karnak is both a chronicle in stone and a bridge to the answer to the eternal question: what is out there? It is an observatory, a library and an expression carved out of the desert of cosmological curiosity and the desire to explore.
Egyptian religious mythology is rich and complex. With almost 1,500 known deities, countless temples and tombs and a detailed surviving literature, the mythology of the great civilisation of the Nile is considered the most sophisticated religious system ever devised. There is no such thing as a single story or tradition, partly because the dynastic period of Egyptian civilisation waxed and waned for over 3,000 years. However, central to both life and mythology are the waters of the Nile, the great provider for this desert civilisation. The annual floods created a fertile strip along the river that is strikingly visible when flying into Luxor from Cairo, although since 1970 the Aswan Dam has halted the ancient cycle of rising and falling waters and today the verdant banks are maintained by modern irrigation techniques. The rains still fall on the mountains south of Egypt during the summer, and before the dam they caused the waters of the Nile to rise and flood low-lying land until they cease in September and the waters recede, leaving life-giving fertile soils behind.
The dominance of the great river in Egyptian life, unsurprisingly, found its way into the heart of their religious tradition. The sky was seen as a vast ocean across which the gods journeyed in boats. Egyptian creation stories speak of an infinite primordial ocean out of which a single mound of earth arose. A lotus blossom emerged from this mound and gave birth to the Sun. In this tradition, each of the primordial elements is associated with a god. The original mound of earth is the god Tatenen, meaning ‘risen land’ (he also represented the fertile land that emerged from the Nile floods), while the lotus flower is the god Nefertem, the god of perfumes. Most important is the Sun God, born of the lotus blossom, who took on many forms but remained central to Egyptian religious thought for over 3,000 years. It was the Sun God who brought light to the cosmos, and with light came all of creation.
The power of the supreme god Amun-Re is felt everywhere at Karnak. Representations of him cover the walls; the carvings mostly depict him as human with a double-plumed crown of feathers alongside the Pharoah, but also in animal form as a ram.
The location and alignment of this impressive building, like everything else about it, has meaning. Egyptologists have evidence to support their belief that it was constructed as a sort of calendar; two columns frame the light of the sun as it rises on the winter solstice.
At Karnak, the Sun God reigns supreme as Amun-Re, a merger between the god Amun, the local deity of Thebes, and the ancient Sun God, Re. This tendency to merge gods is widespread in Egyptian mythology, and with the mergers comes increasing theological complexity. Amun can be seen as the hidden aspect of the Sun, sometimes associated with his voyage through the Underworld during the night. In the Egyptian Book of the Dead, Amun is referred to as the ‘eldest of the gods of the eastern sky’, symbolising his emergence as the solar deity at sunrise. As Amun-Re, he became the King of the Gods, and as Zeus-Ammon he survived into Greek and Roman times. Worship of Amun-Re as the supreme god became so widespread that the Egyptian religion became almost monotheistic during the New Kingdom. Amun-Re was said to exist in all things, and it was believed that he transcended the boundaries of space and time to be all-seeing and eternal. In this sense, he could be seen as a precursor to the gods of the Judeo-Christian and Islamic traditions.
The walls of Karnak Temple are literally covered with representations of Amun-Re, usually depicted in human form with a double-plumed crown of feathers – the precise meaning of which is unknown. He is most often seen with the Pharaoh, but he also appears at Karnak in animal form, as a ram.
The most spectacular tribute of all to Amun-Re, though, lies in Karnak’s orientation to the wider Universe. The Great Hypostyle Hall, the dominant feature of the temple, is aligned such that on 21 December, the winter solstice and shortest day in the Northern Hemisphere, the disc of the Sun rises between the great pillars and floods the space with light, which comes from a position directly over a small building inside which Amun-Re himself was thought to reside. Standing beside the towering stone columns watching the solstice sunrise is a powerful experience. It connects you directly with the names of the great pharaohs of ancient Egypt, because Amenophis III, Tutankhamen and Rameses II would have stood there to greet the rising December sun over three millennia ago.
The Sun rises at a different place on the horizon each morning because the Earth’s axis is tilted at 23.5 degrees to the plane of its orbit. This means that in winter in the Northern Hemisphere the Earth’s North Pole is tilted away from the Sun and the Sun stays low in the sky. As Earth moves around the Sun, the North Pole gradually tilts towards the Sun and the Sun takes a higher daily arc across the sky until midsummer, when it reaches its highest point. This gradual tilting back and forth throughout the year means that the point at which the Sun rises on the eastern horizon also moves each day. If you stand facing east, the most southerly rising point occurs at the winter solstice. The sunrise then gradually drifts northwards until it reaches its most northerly point at the summer solstice. The ancients wouldn’t have known the reason for this, of course, but they would have observed that at the solstices the sunrise poin
t stops along the horizon for a few days, then reverses its path and drifts in the other direction. The solstices would have been unique times of year and important for a civilisation that revered the Sun as a god.
Standing in Karnak Temple watching the sunrise on this special midwinter day the alignment is obvious, but proving that ancient sites are aligned with events in the sky is difficult and controversial. This is because a temple the size of Karnak will always be aligned with something in the sky, simply because it has buildings that point in all directions! However, a key piece of evidence that convinced most Egyptologists that Karnak’s solstice alignment was intentional concerns the two columns on either side of the building in which Amun-Re resides – one to the left and one to the right when facing the rising Sun. These columns are delicately carved, and it is the inscriptions that suggest the sunrise alignment is deliberate. The left-hand column has an image of the Pharaoh embracing Amun-Re, and on one face are three carved papyrus stems – a plant that only grows along the northern reaches of the Nile. The right-hand column is similar in design, except the Pharaoh embraces Amun-Re wearing the crown of upper Egypt, which is south of Karnak. The three carved stems on this column are lotus blossoms, which only grow to the south.
It seems clear therefore that the columns are positioned and decorated to mark the compass directions around the temple, which is persuasive evidence that the heart of this building is aligned to capture the light from an important celestial event – the rising of the Sun in midwinter. It is a colossal representation of the details of our planet’s orientation and orbit around our nearby star.
The temple represents the fascination of the ancient Egyptians with the movement of the lights they saw in the sky. Their instinct to venerate them was pre-scientific, but the building also appears to enshrine a deepening awareness of the geometry of the cosmos. By observing the varying position of sunrise, an understanding of the Earth’s cycles and seasons developed, which provided essential information for planting and harvesting crops at optimum times. The development of more advanced agricultural techniques made civilisations more prosperous, ultimately giving them more time for thought, philosophy, mathematics and science. So astronomy began a virtuous cycle through which the quest to understand the heavens and their meaning lead to practical and intellectual riches beyond the imagination of the ancients.
The step from observing the regularity in the movement of the heavenly lights to modern science took much of recorded human history. The ancient Greeks began the work, but the correct description of the motion of the Sun, Moon and planets across the sky was discovered in the seventeenth century by Johannes Kepler. Removing the veil of the divine to reveal the true beauty of the cosmos was a difficult process, but the rewards that stem from that innate human fascination with the lights in the sky have proved to be incalculable
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By following the light we have mapped our place among the hundreds of billions of stars that make up the Milky Way Galaxy. We have visited our nearest star, Proxima Centauri, and measured its chemical compositions, and those of thousands of other stars in the sky. We have even journeyed deep into the Milky Way and stared into the black hole that lies at the centre of our galactic home. But this is just the beginning…
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The Universe is an awe-inspiring place, full of wonder and demanding the answers to so many questions. We have so much to learn and so many places to explore.
OUR PLACE IN THE UNIVERSE
The scale of the Universe is almost impossible to comprehend and yet that’s exactly what we’ve been able to do from the vantage point of the small rock we call Earth. As we have discovered the grand cycles that play out above our heads we have come to realise that we are part of a structure that extends way beyond our solar system and the 200 billion stars that make up our galaxy.
Nathalie Lees © HarperCollins
OUR GALACTIC NEIGHBOURHOOD
From our small rock, we have a grandstand seat to explore our local galactic neighbourhood. Our nearest star, the Sun, is 150 million kilometres (93 million miles) away, but each night when this star disappears from view, thousands more fill the night sky. In the most privileged places on Earth, up to 10,000 stars can be seen with the naked eye, and all of them are part of the galaxy we call home.
A galaxy is a massive collection of stars, gas and dust bound together by gravity. It is a place where stars live and die, where the life cycles of our universe are played out on a gargantuan scale. We think there are around 100 billion galaxies in the observable universe, each containing many millions of stars. The smallest galaxies, known as dwarf galaxies, have as few as ten million stars. The biggest, the giants, have been estimated to contain in the region of 100 trillion. It is now widely accepted that galaxies also contain much more than just the matter we can see using our telescopes. They are thought to have giant halos of dark matter, a new form of matter unlike anything we have discovered on Earth and which interacts only weakly with normal matter. Despite this, its gravitational effect dominates the behaviour of galaxies today and most likely dominated the formation of the galaxies in the early Universe. This is because we now think that around 95 per cent of the mass of galaxies such as our own Milky Way is made up of dark matter. In some sense this makes the luminous stars, planets, gas and dust an after-thought, although because it is highly unlikely that dark matter can form into complex and beautiful structures like stars, planets and people, one might legitimately claim that it’s rather less interesting. The search for the nature of dark matter is one of the great challenges for twenty-first-century physics. We shall return to the fascinating subject of dark matter later in the book.
The word ‘galaxy’ comes from the Greek word galaxias, meaning milky circle. It was first used to describe the galaxy that dominates our night skies, even though the Greeks could have had no concept of its true scale. Watching the core of our galaxy rise in the night sky is one of nature’s greatest spectacles, although regrettably the light of our cities has robbed us of this majestic nightly display. For many people it looks like the rising of storm clouds on the horizon, but as the Earth turns nightly towards the centre of our galaxy, the hazy band of light reveals itself as clouds of stars – billions of them stretching thousands of light years inwards towards the galactic centre. In Greek mythology this ethereal light was described as the spilt milk from the breast of Zeus’s wife, Hera, creating a faint band across the night sky. This story is the origin of the modern name for our galaxy – the Milky Way. The name entered the English language not from a scientist, but from the pen of the Medieval poet, Geoffrey Chaucer: ‘See yonder, lo, the Galaxyë, Which men clepeth the Milky Wey, For hit is whyt.’
M87, also known as Virgo A and Messier 87, is a giant elliptical galaxy located 54 million light years away from Earth in the Virgo Cluster. In this image the central jet is visible, which is a powerful beam of hot gas produced by a massive black hole in the core of the galaxy.
NASA
ABOVE: Taken in December 2010, this is the most detailed picture of the Andromeda Galaxy, or M31, taken so far. It is our largest and closest spiral galaxy, and in this picture we can clearly see rings of new star formations developing.
TOP: This image of the galaxy M51 clearly shows how it got its other name: the Whirlpool Galaxy. The spiral shape of the galaxy is immediately obvious, with curving arms of pinky-red, star-forming regions and blue star clusters.
NASA
ABOVE: Zwicky 18 was once thought to be the youngest galaxy, as its bright stars suggested it was only 500 million years old. However, recent Hubble Space Telescope images have identified older stars within it, making the galaxy as old as others but with new star formations.
TOP: M33, also known as the Triangulum, or Pinwheel, Galaxy is the third-largest in the Local Group of galaxies after the Milky Way and Andromeda Galaxies, of which it is thought to be a satellite.
MAPPING THE MILKY WAY GALAXY
Our galaxy, the Milky Way, contains
somewhere between 200 and 400 billion stars, depending on the number of faint dwarf stars that are difficult for us to detect. The majority of stars lie in a disc around 100,000 light years in diameter and, on average, around 1,000 light years thick. These vast distances are very difficult to visualise. A distance of 100,000 light years means that light itself, travelling at 300,000 kilometres (186,000 miles) per second, would take 100,000 years to make a journey across our galaxy. Or, to put it another way, the distance between the Sun and the outermost planet of our solar system, Neptune, is around four light hours – that’s one-sixth of a light day. You would have to lay around 220 million solar systems end to end to cross our galaxy.
At the centre of our galaxy, and possibly every galaxy in the Universe, there is believed to be a super-massive black hole. Astronomers believe this because of precise measurements of the orbit of a star known as S2. This star orbits around the intense source of radio waves known as Sagittarius A* (pronounced ‘Sagittarius A-star’) that sits at the galactic centre. S2’s orbital period is just over fifteen years, which makes it the fastest-known orbiting object, reaching speeds of up to 2 per cent of the speed of light. If the precise orbital path of an object is known, the mass of the thing it is orbiting around can be calculated, and the mass of Sagittarius A* is enormous, at 4.1 million times the mass of our sun. Since the star S2 has a closest approach to the object of only seventeen light hours, it is known that Saggitarus A* must be smaller than this, otherwise S2 would literally bump into it. The only known way of cramming 4.1 million times the mass of the Sun into a space less than 17 light hours across is as a black hole, which is why astronomers are so confident that a giant black hole sits at the centre of the Milky Way. These observations have recently been confirmed and refined by studying a further twenty-seven stars, known as the S-stars, all with orbits taking them very close to Sagittarius A*.
Wonders of the Universe Page 2
