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Wonders of the Universe Professor Brian Cox & Andrew Cohen Contents Introduction The Universe Chapter 1 Messengers The Story of Light Our place in the. In the first programme, Professor Brian Cox explained the theory that the Universe has a finite 'life-span' – that it is inevitably going to cease to exist, although the. Many of you, no doubt, will have seen Professor Brian Cox's recent television series The The concept of wonder, indeed, lies at the heart of Cox's cosmology, .
Where did it come from? Why does it end? In this beautiful and definitive new book, Professor Brian Cox takes us on an incredible journey to discover how a few fundamental laws gave birth to the most complex, diverse and unique force in the Universe? There are thought to be as many as million different species on Earth? Everything in the Universe, from the smallest microbe to the largest cluster of galaxies, is constructed from the same fundamental building blocks and is subject to the same laws of nature. What is true for a bacterium is true for a blue whale. This is the story of the amazing diversity and adaptability of life told through the fundamental laws that govern it.
And because every animal and plant today shares the same basic building block — the same type of cell structure — we are very confident that this only happened once, somewhere in the oceans of the primordial Earth.
Brian explains how an energy source called a proton gradient may have helped life form at hot underwater vents. That remains one of the greatest mysteries about the origins of human existence. We still don't know how life arose, but it may well have happened at hydrothermal vents - underwater hot springs dotted across the ocean floor. They churned out a potent mix of chemicals and energy, that may have combined to create the first life.
The biggest, the giants, have been estimated to contain in the region of 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. 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.
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. 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.
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: 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.
Taken in December , 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. This image of the galaxy M51 clearly shows how it got its other name: The spiral shape of the galaxy is immediately obvious, with curving arms of pinky-red, star-forming regions and blue star clusters. Zwicky 18 was once thought to be the youngest galaxy, as its bright stars suggested it was only 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. 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.
The majority of stars lie in a disc around , light years in diameter and, on average, around 1, light years thick. These vast distances are very difficult to visualise. A distance of , light years means that light itself, travelling at , kilometres , miles per second, would take , years to make a journey across our galaxy.
You would have to lay around 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. The only known way of cramming 4. Beyond the S-stars, the galactic centre is a melting pot of celestial activity, filled with all sorts of different systems that interact and influence each other.
The Arches Cluster is the densest known star cluster in the galaxy. Formed from about young, intensely hot stars that dwarf our sun in size, these stars burn brightly and are consequently very short-lived, exhausting their supply of hydrogen in just a couple of million years. The Quintuplet Cluster contains one of the most luminous stars in our galaxy, the Pistol Star, which is thought to be near the end of its life and on the verge of becoming a supernova see Chapter 2.
It is in central clusters like the Arches and the Quintuplet that the greatest density of stars in our galaxy can be found.
As we move out from the crowded galactic centre, the number of stars drops with distance, until we reach the sparse cloud of gas in the outer reaches of the Milky Way known as the Galactic Halo. HE is a star in the last stages of its life; known as a red giant, it is a vast structure far bigger than our sun, but much cooler at its surface.
HE is interesting because astronomers have been able to measure the precise quantities of five radioactive elements — uranium, thorium, europium, osmium and iridium — in the star. Using a technique very similar to carbon dating a method archaeologists use to measure the age of organic material on Earth , astronomers have been able to get a precise age for this ancient star. This is why the detection of five radioactive elements in the light from HE was so important.
This dying star turns out to be Known as a barred spiral galaxy, it consists of a bar-shaped core surrounded by a disc of gas, dust and stars that creates individual spiral arms twisting out from the centre. Until very recently, it was thought that our galaxy contained only four spiral arms — Perseus, Norma, Scutum—Centaurus and Carina—Sagittarius, with our sun in an off shoot of the latter called the Orion spur — but there is now thought to be an additional arm, called the Outer arm, an extension to the Norma arm.
Close to the inner rim of the Orion spur is the most familiar star in our galaxy. The Sun was once thought to be an average star, but we now know that it shines brighter than 95 per cent of all other stars in the Milky Way.
Every second, the Sun burns million tonnes of hydrogen in its core, producing million tonnes of helium in the fusion reaction. Located 5, light years away, the Lagoon Nebula is one of a handful of active star-forming regions in our galaxy that are visible from Earth with the naked eye.
Roughly once a year a new light appears in our galaxy, as somewhere in the Milky Way a new star is born. The Lagoon Nebula is one such star nursery; within this giant interstellar cloud of gas and dust, new stars are created.
Discovered by French astronomer Guillaume Le Gentil in , this is one of a handful of active star-forming regions in our galaxy that are visible with the naked eye. This huge cloud is slowly collapsing under its own gravity, but slightly denser regions gradually accrete more and more matter, and over time these clumps grow massive enough to turn into stars.
The centre of this vast stellar nursery, known as the Hourglass, is illuminated by an intriguing object known as Herschel Recent measurements suggest that Herschel 36 may actually be three large young stars orbiting around each other, with the entire system having a combined mass of over fifty times that of our sun. This makes Herschel 36 a true system of giants. Eventually Herschel 36 and all the stars in the Milky Way will die, and when they do, many will go out in a blaze of glory.
Eta Carinae is a pair of billowing gas and dust clouds that are the remnants of a stellar explosion from an unstable star system. The system consists of at least two giant stars, and shines with a brightness four million times that of our sun. One of these stars is thought to be a Wolf-Rayet star.
These stars are immense, over twenty times the mass of our sun, and are engaged in a constant struggle to hang onto their outer layers, losing vast amounts of mass every second in a powerful solar wind. In , Eta Carinae became one of the brightest stars in the Universe when it exploded. The blast spat matter out at nearly 2. Eta Carinae survived intact and remains buried deep inside these clouds, but its days are numbered. Because of its immense mass, the Wolf-Rayet star is using up its hydrogen fuel at a ferocious rate.
Within a few hundred thousand years, it is expected that the star will explode in a supernova or even a hypernova the biggest explosion in the known Universe , although its fate may be sealed a lot sooner. In , an explosion thought to be similar to the Eta Carinae event was seen in a galaxy over seventy million light years from the Milky Way.
Just two years later, the star exploded as a supernova. Eta Carinae is very much closer — at a distance of only 7, light years — so as a supernova it may shine so brightly that it will be visible from Earth even in daylight.
Out in the Milky Way we can see the whole cycle of stellar life playing out. Roughly once a year a new light appears, as somewhere in the Milky Way a new star is born.
Eta Carinae is one of the most massive and visible stars in the night sky, but because of its mass it is also the most volatile and most likely to explode in the near future. NASA Seeing the light from these distant worlds and watching the life cycle of the Universe unfold is a breathtaking reminder that light is the ultimate messenger; carrying information about the wonders of the Universe to us across interstellar and intergalactic distances.
But light does much more than just allow us to see these distant worlds; it allows us to journey back through time, providing a direct and real connection with our past. This seemingly impossible state of affairs is made possible not only because of the information carried by the light, but by the properties of light itself Eventually all the stars in the Milky Way will die, many in spectacular explosions.
Herschel 36 was formed from just such a stellar explosion, which occurred within the Eta Carinae system. If we aspire to understand the world around us, one of the most basic questions we must ask is about the nature of light. It is the primary way in which we observe our own planet, and the only way we will ever be able to explore the Universe beyond our galaxy.
For now, even the stars are far beyond our reach, and we rely on their light alone for information about them. By the seventeenth century, many renowned scientists were studying the properties of light in detail, and parallel advances in engineering and science both provided deep insights and catalysed each other.
The studies of Kepler, Galileo and Descartes, and some of the later true greats of physics — Huygens, Hooke and Newton — were all fuelled by the desire to build better lenses for microscopes and telescopes to enable them to explore the Universe on every scale, and to make great scientific discoveries and advances in the basic science itself. There were some notable exceptions, including the great mathematician Leonhard Euler, who felt that the phenomena of diffraction could only be explained by a wave theory.
In , the English doctor Thomas Young appeared to settle the matter once and for all when he reported the results from his famous double-slit experiment, which clearly showed that light diffracted, and therefore must travel in the form of a wave.
Diffraction is a fascinating and beautiful phenomena that is very difficult to explain without waves. Imagine two waves on top of each other with exactly the same wavelength and wave height technically known as the amplitude , but aligned precisely so that the peak of one wave lies directly on the trough of the other in more technical language, we say that the waves are degrees out of phase , and so the waves cancel each other out.
If these waves were light waves you would get darkness! This is exactly what is seen in diffraction experiments through small slits. The slits act like lots of little sources of light, all slightly displaced from one another.
This means that there will be places beyond the slits where the waves cancel each other out, and places where they will add up, leading to the light and dark areas seen by experimenters like Young. This was taken as clear evidence that light was some kind of wave — but waves of what? The experiment demonstrates the inseparability of the wave and particle natures of light and other quantum particles. In the mid-nineteenth century, the study of electricity and magnetism engaged many great scientific minds.
At the Royal Institution in London, Michael Faraday was busy doing what scientists do best — playing around with wire and magnets. He discovered that if you push a magnet through a coil of wire, an electric current flows through the wire while the magnet is moving.
This is a generator; the thing that sits in all power stations around the world today, providing us with electricity. A single amp is defined as the current that must flow along two parallel wires of infinite length and negligible diameter to produce an attractive force of 0. By , a great deal was known about electricity and magnetism.
Magnets could be used to make electric currents flow, and flowing electric currents could deflect compass needles in the same way that magnets could. There was clearly a link between these two phenomena, but nobody had come up with a unified description. Electricity and magnetism can be unified by introducing two new concepts: The idea of a field is central to modern physics; a simple example of something that can be represented by a field is the temperature in a room.
If you could measure the temperature at each point in the room and note it down, eventually you would have a vast array of numbers that described how the temperature changes from the door to the windows and from the floor to the ceiling. This array of numbers is called the temperature field. In a similar way, you could introduce the concept of a magnetic field by holding a compass at places around a wire carrying an electric current and noting down how much the needle deflects, and in what direction.
The numbers and directions are the magnetic field. This might seem rather abstract and not much of a simplification, but Maxwell found that by introducing the electric and magnetic fields and placing them centre stage, he was able to write down a single set of equations that described all the known electrical and magnetic phenomena. These picture strips illustrate maps of the Milky Way Galaxy as they appear in different wavelength regions.
Where c is the speed of light and the quantities 0 and 0 are related to the strengths of electric and magnetic fields. The fact that the velocity of light can be measured experimentally on a bench top with wires and magnets was the key piece of evidence that light is an electromagnetic wave.
At this point you may be wondering what all this has to do with the story of light. Well, here is something profound that provides a glimpse into the true power and beauty of modern physics. In writing down his laws of electricity and magnetism using fields, Maxwell noticed that by using a bit of simple mathematics, he could rearrange his equations into a more compact and magically revealing form. His new equations took the form of what are known as wave equations.
In other words, they had exactly the same form as the equations that describe how soundwaves move through air or how water waves move through the ocean. But waves of what? The waves Maxwell discovered were waves in the electric and magnetic fields themselves. His equations showed that as an electric field changes, it creates a changing magnetic field.
But in turn as the magnetic field changes, it creates a changing electric field, which creates a changing magnetic field, and so on. And this will continue to happen forever, as long as you do nothing to them.
This is profound in itself, but there is an extra, more profound conclusion. When Maxwell did the sums, he must have fallen off his chair. He found that his equations predicted that the waves in the electric and magnetic fields travelled at the speed of light!
In other words, Maxwell had discovered that light is nothing more than oscillating electric and magnetic fields, sloshing back and forth and propelling each other through space as they do so. In modern language, we would say that light is an electromagnetic wave. In order to have his epiphany, Maxwell needed to know exactly what the speed of light was. Remarkably, the fact that light travels very fast, but not infinitely so, had already been known for almost two hundred years.
However, as the Greek philosophers gave more thought to the nature of light, a debate about its speed of travel ensued that continued for thousands of years. In one corner sat eminent names such as Euclid, Kepler and Descartes, who all sided with Aristotle in believing that light travelled infinitely fast.
In the other, Empedocles and Galileo, separated by almost two millennia, felt that light must travel at a finite, if extremely high, velocity. He considered light travelling across the vast distance from the Sun to Earth, and noted that everything that travels must move from one point to another.
In other words, the light must be somewhere in the space between the Sun and the Earth after it leaves the Sun and before it reaches the Earth. This means it must travel with a finite velocity. Aristotle dismissed this argument by invoking his idea that light is simply a presence, not something that moves between things. Without experimental evidence, it is impossible to decide between these positions simply by thinking about it! Galileo set out to measure the speed of light using two lamps.
He held one and sent an assistant a large distance away with another. When they were in position, Galileo opened a shutter on his lamp, letting the light out. His conclusion was that light must travel extremely rapidly, because he was unable to determine its speed. He was able to do this because if it had been slower, he should have been able to measure a time delay. The question, how fast is the speed of light, has plagued scientists for thousands of years.
Part of the answer came from observing how light travels between points: The first experimental determination that the speed of light was not infinite was made by the seventeenth-century Danish astronomer, Ole Romer. In , Romer was attempting to solve one of the great scientific and engineering challenges of the age; telling the time at sea. Finding an accurate clock was essential to enable sailors to navigate safely across the oceans, but mechanical clocks based on pendulums or springs were not good at being bounced around on the ocean waves and soon drifted out of sync.
In order to pinpoint your position on Earth you need the latitude and longitude. Latitude is easy; in the Northern Hemisphere, the angle of the North Star Polaris above the horizon is your latitude.
In the Southern Hemisphere, things are more complicated because there is no star directly over the South Pole, but it is still possible with a little astronomical know-how and trigonometry to determine your latitude with sufficient accuracy for safe navigation. Astronomers call this arc the Meridian. The point at which the Sun crosses the Meridian is also the point at which it reaches its highest position in the sky on any given day as it journeys from sunrise in the east to sunset in the west.
We call this time noon, or midday. Earth rotates once on its axis every twenty-four hours — fifteen degrees every hour. If it reads 2pm when the Sun reaches its highest point in the sky where you are, you are thirty degrees to the west of Greenwich.
Easy, except that you need a very accurate clock that keeps time for weeks or months on end These spectacular star trails are produced in the sky as a result of diurnal motion. This is the motion created as Earth spins on its axis at fifteen degrees per hour, rotating once over twenty-four hours. The technological challenge of building sufficiently accurate clocks was too great, so scientists began to look for high-precision natural clocks, and it seemed sensible to look to the heavens.
Galileo, having discovered the moons of Jupiter, was convinced he could use the orbits of these moons as a clock, as they regularly passed in and out of the shadow of the giant planet. The principle is beautifully simple; Jupiter has four bright moons that can be seen relatively easily from Earth, and the innermost moon, Io, goes around the planet every 1. Thus by using the Jovian system as a cosmic clock, Galileo devised an accurate system for keeping time.
Despite this, it was clear this technique could be used to measure longitude accurately on land, where stable conditions and high-quality telescopes were available. In the process of further refining his longitude tables, he sent one of his astronomers, Jean Picard, to the Uraniborg Observatory near Copenhagen, where Picard employed the help of a young Danish astronomer, Ole Romer. Over the course of several months, the prediction for when Io would emerge from behind Jupiter drifted.
At some times of the year there was a significant discrepancy of over twenty-two minutes between the predicted and the actual observed timings of the eclipses. This appeared to ruin the use of Io as a clock and end the idea of using it to calculate longitude. However, Romer came up with an ingenious and correct explanation of what was happening. These sketches published in Istoria e Dimonstrazione in show the changing position of the moons of Jupiter over 12 days.
Jupiter is represented by the large circle, with the four moons as dots on either side. The three black spots are the shadows of the moons Ganymede top left , Io left and Callisto. The white spot above centre is Io, while the blue spot upper right is Ganymede. Callisto is out of the image to the right. NASA Romer noticed that the observed time of the eclipses drifted later relative to the predicted time as the distance between Jupiter and Earth increased as the planets orbited the Sun, then drifted back again when the distance between Jupiter and Earth began to decrease.
His explanation, which is correct, was simple. Imagine that light takes time to travel from Jupiter to Earth; as the distance between the two planets increases, so the light from Jupiter will take longer to travel between them. Conversely, as the distance between Jupiter and Earth decreases, it takes the light less time to reach you and so you see Io emerge sooner than predicted. Factor in the time it takes light to travel between Jupiter and Earth and the theory works.
Romer did this by trial and error, and was able to correctly account for the shifting times of the observed eclipses. The first published number for the speed of light was that obtained by the Dutch astronomer Christiaan Huygens, who had corresponded with Romer. Since a toise is two metres seven feet , this gives a speed of ,, metres per second, which is not far off the modern value of ,, metres ,, feet per second. His measurement of the speed of light was the first determination of the value of what scientists call a constant of nature.
In the s and s the sound barrier took on an almost mythical status as engineers worldwide tried to build aircraft that could exceed the kilometres per hour miles per hour at which sound travels in air at twenty degrees Celsius. But what is the meaning of this speed limit? What is the underlying physics, and how does it affect our engineering attempts to break it?
Sound in a gas such as air is a moving disturbance of the air molecules. Imagine dropping a saucepan lid onto the floor. As it lands, it rapidly compresses the air beneath it, pushing the molecules closer together. This increases the density of the air beneath the lid, which corresponds to an increase in air pressure.
In a gas, molecules will fly around to try to equalise the pressure, which is why winds develop between high and low pressure areas in our atmosphere. With a falling lid, some of the molecules in the high-pressure area beneath it will rush out to the surrounding lower-pressure areas; these increase in pressure, causing molecules to rush into the neighbouring areas, and so on.
So the disturbance in the air caused by the falling lid moves outwards as a wave of pressure. Once we reached 12, metres, the pilot put the Hawker Hunter into the roll and we dived down through the clouds, upside down.
Almost immediately, we broke through the sound barrier. The speed of this pressure wave is set by the properties of the air. To a reasonable approximation, the speed of the sound wave depends mainly on the average speed of the air molecules at a particular temperature. This was known long before aircraft were invented, but it did not satisfy those who wanted to propel a human faster than sound. Many attempts were made during World War II to produce a supersonic aircraft, but the sound barrier was not breached until 14 October , when Chuck Yeager became the first human to pilot a supersonic flight.
Flying in the Bell—XS1, Yeager was dropped out of the bomb bay of a modified B29 bomber, through the sound barrier and into the history books. Today, aircraft routinely break the sound barrier, but the routine element hides the fascinating aerodynamic and engineering challenges that had to be overcome so that humans could travel faster than sound.
Test pilot Dave Southwood demonstrated these to me in the making of the programme in a beautiful aircraft that was not designed to break the sound barrier in level flight — the Hawker Hunter. Designed in the s, the Hawker Hunter is a legendary British jet fighter of the post-war era. Designed to fly at Mach 0. We climbed to 12, metres 42, feet , flipped the Hunter into an inverted dive, then plunged full-throttle towards the Bristol Channel.
In just seconds the jet smashed through the sound barrier and the air flow surrounding the jet changed, which is heard on the ground as an explosion, or a sonic boom. So the sound barrier is not a barrier at all; it is a speed limit only for sound itself, determined by the physics of the movement of air molecules. Is the light barrier the same? It would seem from our description of light as an electromagnetic wave that is so.
The reason for this is that light speed plays a much deeper role in the Universe than just being the speed at which light travels. A true understanding of the role of this speed, ,, metres ,, feet per second, was achieved in by Albert Einstein in his special theory of relativity. Hence spacetime is referred to as four-dimensional, with time being the fourth dimension.
Einstein abandoned the Newtonian ideas of space and time as separate entities and merged them. This special speed is a universal constant of nature that will always be measured as precisely ,, metres ,, feet per second, at all times and all places in the Universe, no matter what they are doing.
Why can we only travel into the future, not the past? In this sense, the special speed is built into the fabric of space and time itself and plays a deep role in the structure of our universe.
What does it have to do with the speed of light? Nothing much! There is a reason why light goes at this speed, and it seems to be a complete coincidence. Conversely, anything that has mass is compelled to travel slower than this speed.
Particles of light, photons, have no mass, so they travel at the speed of light. There is no deep reason we know of why photons have to be massless particles, so no deep reason why light travels at the speed of light!
The key point is that the speed of light is a fundamental property of the Universe because it is built into the fabric of space and time itself. Travelling faster than this speed is impossible, and even travelling at it is impossible if you have mass.
The consequence of light travelling fast, but not infinitely fast, is that you see everything as it was in the past.
In everyday life the consequences of this strange fact are intriguing but irrelevant. It may be strictly true that you are seeing your reflection in the mirror in the past, but since it takes light only one thousand millionths of a second to travel thirty centimetres twelve inches , the delay is all but invisible. However, the further away we get from an object, the greater the delay becomes. Although over tiny distances the effect is always utterly negligible, it should be obvious that once we lift our eyes upwards to the skies and become astronomers, profound consequences await us.
As light takes longer to reach Earth from other planets and moons, depending on how far away they are, we see further into their respective pasts. However, take a look at the Sun and you really are beginning to bathe in the past. The Sun is million kilometres away 93 million miles — this is very close by cosmic standards, but at these distances the speed of light starts to feel rather pedestrian. We are seeing the Sun as it was eight minutes in the past.
This has the strange consequence that if we were to magically remove the Sun, we would still feel its heat on our faces and still see its image shining brightly in the sky for eight minutes.
And because the speed of light is actually the maximum speed at which any influence in the Universe can travel, this delay applies to gravity as well. So if the Sun magically disappeared, we would not only continue to see it for eight minutes, we would continue to orbit around it too.
We are genuinely looking back in time every time we look at the Sun. However, this is just the beginning of our time travelling. As we look up at the planets and moons in our solar system, we move further and further into the past. The light from Mars takes between four and twenty minutes to reach Earth, depending on the relative positions of Earth and Mars in their orbits around the Sun.
This has a significant impact on the way we design and operate vehicles intended for driving on the surface of Mars. When Mars is at its furthest point from Earth it would take at least forty minutes to be told that a Mars Rover was driving over a cliff and then be able to tell it to stop, so Mars Rovers need to be able to make up their own minds in such situations or must do things very slowly.
Jupiter, at its closest point to Earth, is around thirty-two minutes away, and by the time we journey to the outer reaches of our solar system, the light from the most distant planet, Neptune, takes around four hours to make the journey. At the very edge of the Solar System, the round-trip travel time for radio signals sent and received by Voyager 1 on its journey into interstellar space is currently thirty-one hours, fifty-two minutes and twenty-two seconds, as of September But look beyond our solar system and the time it takes for light to travel from our nearest neighbouring stars is no longer measured in hours or days, but years.
We see Alpha Centauri, the nearest star visible with the naked eye, as it was four years in the past, and as the cosmic distances mount, so the journey into the past becomes ever deeper TO THE DAWN OF TIME When filming a series like Wonders of the Universe, the locations are chosen to be visually spectacular, but they must also have a narrative that enhances the explanation of the scientific ideas we want to convey.
Occasionally, the locations deliver more. There is a resonance, a symbiosis between science and place that serves to amplify the facts and generates something deeper and more profound on screen. For me, the Great Rift Valley was such a place. We arrived in Tanzania on 10 May for the first day of filming.
After a brief overnight stay close to the airport at Kilimanjaro, we were driven out into the Serengeti in vintage dark green Toyota Land Cruisers, complete with exaggerated front cattle bars and shovels tied to the rear doors. The landscape is unmistakably African; the warm, damp light still wet from the rains illumines plains seemingly too vast to fit on our planet. The horizon, darkened by scattered thunderclouds stark against the early summer skies, is simply more distant than it should be.
The rains have brought with them journeys, and as you drive you experience first-hand the thousand-mile migration of the Serengeti wildebeest. The relentless advance of these herds creates ruts in the drying savannah along the precise and ancient roads that always seem to run at right angles to your direction of travel, shaking the Land Cruisers to the edge of their design tolerance.
The Great Rift Valley is not just an extraordinary geological feature…there is more to this place because the echoes of the history of humanity ring louder across these plains than anywhere else on the planet.
The summer skies were darkened by rainclouds, but these soon departed to reveal dusty, unmistakably African landscapes and breathtaking vistas. Our camp is idyllic by the strictest definition of the word. Khaki tents nestle beneath acacia trees in the shadow of a giant copper-striped rock populated by a tribe of itinerant baboons intent on stealing our tape stock.
So much for the visuals; the reason for the resonance of this place lies in the deep past of this dramatic landscape of life. The Great Rift Valley is not just an extraordinary geological feature that stretches 6, kilometres 3, miles from Syria to Mozambique; there is more to this place because the echoes of the history of humanity ring louder across these plains than anywhere else on the planet. To walk this earth is to walk in the footsteps of the true ancients. Ancestors like Lucy, one of the most important fossils ever discovered, a skeleton uncovered in the Ethiopian section of the valley in by Donald Johanson.
Lucy is 3. Further down the rift, in Tanzania, more closely related human ancestors have been discovered. In the early s, Mary and Louis Leakey unearthed the remains of the earliest known species of our genus, Homo.
Homo habilis is thought to have been a direct descendant of Australopithecus, and may be the first of our ancestors to have made tools. With no cities to pollute the darkness, the plains of the African night are bathed in the light of a billion suns. The glowing arc of the Milky Way Galaxy dominates the sky, a silver mist of stars so numerous, they are impossible to count. Every single point of light and every patch of magnificent mist visible to the unaided human eye have as their origin a star in our own galaxy, or the misty clouds known as the Magellanic clouds — two small dwarf galaxies in orbit around the Milky Way.
Cassiopeia, being so close to Polaris, is a constant feature in the northern skies — it simply rotates around the pole once every twenty-four hours and never sets below the horizon at high latitudes. It is comparable in brightness to most of the stars surrounding it, although dimmer than the bright stars of Cassiopeia. This unremarkable little patch is, in my view, the most intellectually stunning object you can see with the naked eye, because it is an entire galaxy beyond the Milky Way. It is called Andromeda, and is our nearest galactic neighbour.
It is home to a trillion suns, over twice as many stars as our galaxy. It is roughly twenty-five million million million kilometres fifteen million million million miles away, and here is the connection.
This Homo habilis skull was found in the Olduvai Gorge in Tanzania and is believed to be around 1. As that light beam raced across space at the speed of light, generations of prehumans and humans lived and died; whole species evolved and became extinct, until one member of that unbroken lineage, me, happened to gaze up into the sky below the constellation we call Cassiopeia and focus that beam of light onto his retina.
NASA Observing the night skies with the naked eye can only take us so far on our journey to discover and understand the wonders of our universe. Advances in technology have brought us crafts that can take humans on expeditions beyond our planet, but also sophisticated equipment that has changed our view of the Universe entirely. The Hubble Space Telescope being repaired by an astronaut from Endeavour.
This eleven-tonne telescope has allowed astronomers and scientists to see further into our universe than ever before. Until recently, Andromeda was the furthest we could look back unaided, but modern, more powerful telescopes now enable us to peer deeper and deeper into space, so that we can travel way beyond Andromeda, capturing a bounty of messengers laden with information from the far distant past.
The Hubble Space Telescope was conceived in the s and given the go-ahead by Congress during the tenure of President Jimmy Carter, with a launch date originally set for Named after Edwin Hubble, the man who discovered that the Universe is expanding, this complex project was plagued with problems from the start.
By , the telescope was ready for lift off, three years later than planned, and the new launch date was set for October of that year. But when the Challenger Space Shuttle broke apart seventy-three seconds into its launch in January , the shutters came down not only on Hubble, but on the whole US space programme. With the restart of the shuttle programme, the new launch date was set for 24 April and, seven years behind schedule, shuttle mission STS31 launched Hubble into its planned orbit kilometres miles above Earth.
The promise of Hubble was simple: The returning images showed there was a significant optical flaw, and after preliminary investigations it slowly dawned on the Hubble team that after decades of planning and billions of dollars, the Hubble Space Telescope had been launched with a primary mirror that was minutely but disastrously misshapen.
Such was the value and promise of Hubble that an audacious mission was immediately conceived to fix it. This was possible because Hubble was designed to be the first, and to date only, telescope to be serviceable by astronauts in space. A new mirror could not be fitted, but by precisely calculating the disruptive effect of the faulty mirror, NASA engineers realised that they could correct the problem by fitting Hubble with spectacles.
The Hubble Space Telescope has had a greater impact on astronomy than any other telescope. This huge telescope orbits Earth, sending back images of parts of the Universe that would otherwise remain invisible to us. The telescope has been orbiting Earth since , and its revolutionary and revelatory journey continues to this day. In charge of the repairs, by far the most complex task ever undertaken by humans in Earth orbit, was astronaut Story Musgrave.
Already a veteran of four shuttle flights, a test pilot with 16, flying hours in aircraft types, ex-US Marine and trauma surgeon with seven graduate degrees, Musgrave is quite an extraordinary example of what people can do if they put their minds to it.
To work on something so beautiful, to give it life again, to restore it to its heritage, to its conceived power. The work was worth it — significant. The passion was in the work, the passion was in the potentiality of Hubble Space Telescope.
This shot of the spiral galaxy NGC is one of the largest images taken by the telescope. This image shows nearly 10, galaxies of various ages, sizes, shapes and colours. The nearest galaxies appear larger and brighter, but there are also around one hundred galaxies here that appear as small red objects. These are the most remarkable features in this image; these are among the most distant objects we have ever seen.
These are places forever beyond our reach. However, there is one Hubble image that has done more than any other to reveal the scale, depth and beauty of our universe. Known as the Hubble Ultra Deep Field, this shot was taken over a period of eleven days between 24 September and 16 January This area of sky is so tiny that Hubble would have needed fifty such images to photograph the surface of the Moon.
From the surface of Earth this tiny piece of sky is almost completely black; there are virtually no visible stars within it, which is why it was chosen. By using its million-second shutter speed, though, Hubble was able to capture images of unimaginably faint, distant objects in the darkness.
Almost every one of these points of light is a galaxy; each an island of hundreds of billions of stars, with over 10, galaxies visible. If you extend that over the entire sky, it means there are over billion galaxies in the observable Universe, each containing hundreds of billions of suns.
However, there is something more remarkable about this image than mere scale, due to the slovenly nature of the speed of light compared to the distances between the galaxies.
The thousands of galaxies captured by Hubble are all at different distances from Earth, making this image 3D in a very real sense. But the third dimension is not spatial, it is temporal. The photograph contains images of galaxies of various ages, sizes, shapes and colours; some are relatively close to us, some incredibly far away.
The nearest galaxies, which appear larger, brighter and have more well-defined spiral and elliptical shapes, are only a billion light years away. Since they would have formed soon after the Big Bang, they are around twelve billion years old. However, it is the small, red, irregular galaxies that are the main attraction here. There are about of these galaxies in the image, and they are among the most distant objects we have ever seen. Some of these faint red blobs are well over twelve billion light years away, which means that when their light reaches us it has been travelling for almost the entire The most distant galaxy in the Deep Field, identified in October , is over thirteen billion light years away — so we see it as it was , years after the beginning of the Universe itself.
It is hard to grasp these vast expanses of space and time. So, consider that the image of this ancient galaxy was created by a handful of photons of light; when they began their journey, released from hot, primordial stars, there was no Earth, no Sun, and only an embryonic and chaotic mass of young stars and dust that would one day evolve into the Milky Way. They were almost here when the first complex life on Earth arose and within a cosmic heartbeat of their final destination when the species that built the Hubble first appeared.
The story hidden within the Hubble Ultra Deep Field image is ancient and detailed, but how can we infer so much from a photograph? Fuelled by the mighty Zambezi River, the falls lie on the border between Zambia and Zimbabwe in southern Africa. The falls were named by David Livingstone in , the first European to see them. He later wrote: It had never been seen before by European eyes; but scenes so lovely must have been gazed upon by angels in their flight.
There are few better places on Earth from which you can experience the visceral power of flowing water, but there is an ethereal feature of the falls that is just as enchanting and far more instructive for our purposes, because it holds the key to interpreting the Hubble Deep Field Image. Hovering in the skies above the falls are magnificent rainbows, a permanent feature in the Zambian skies when the Sun shines through the mist.
Rainbows are natural phenomena that have enchanted humans for thousands of years; to see one is to marvel at a simple but beautiful property of light and, as is often the case in nature, they are made more beautiful when you understand the science behind them.
Scientists have attempted to understand rainbows since the time of Aristotle, trying to explain how white light is apparently transformed into colour. Our old friend Ibn al-Haytham was one of the first to attempt to explain the physical basis of a rainbow in the tenth century.
The basis of our modern understanding was delivered by Isaac Newton, who observed that white light is split into its component colours when passed through a glass prism. He correctly surmised that white light is made up of light of all colours, mixed together. The physics behind the production of a rainbow is essentially the same as that of the prism. Light from the Sun is a mixture of all colours, and water droplets in the sky act like tiny prisms, splitting up the sunlight again.
But why the characteristic arc of the rainbow? Water droplets in the air are essentially little spheres of water, so Descartes considered what happens to a single ray of light from the Sun as it enters a single water droplet. As the diagram opposite illustrates, the light ray from the Sun S enters the face of the droplet and is bent slightly. This is known as refraction; light gets deflected when it crosses a boundary between two different substances point A , then when the light ray gets to the back surface of the raindrop, it is reflected back into the raindrop point B , finally emerging out of the front again, where it gets bent a little more point C.
The light ray then travels from the raindrop to your eye E. The key point is that there is a maximum angle D through which light that enters the raindrop gets bounced back. Descartes calculated this angle for red light and found it to be forty-two degrees. For blue light, the angle is forty degrees. Colours between blue and red in the spectrum have maximum angles of reflection of between forty-two and forty degrees.
No light gets bounced back with angles greater than this, and it turns out that most of the light gets reflected back at this special, maximum angle. So, here is the explanation for the rainbow.
When you look up at a rainbow, imagine drawing a line between the Sun, which must be behind you, through your head and onto the ground in front of you. There is some light reflected back to your eye through shallower angles, which is why the sky is brighter below the arc than above it.
On the picture on the previous page, you can see the sky brightening inside the rainbow over the Victoria Falls, and the relative darkness of the sky outside it. So raindrops separate the white sunlight into a rainbow because each of the consituent colours gets reflected back to your eye at a slightly different maximum angle.
But why the arc? In fact, rainbows are circular. Think of the imaginary line again between the Sun, your head and the ground. This is also why you tend to see rainbows in the early morning or late afternoon. As the Sun climbs in the sky, the line between the Sun and your head steepens and the rainbow, which is centred on this line, drops closer and closer to the horizon until at some point it will vanish below the horizon.
All the way back to Aristotle, scientists have been trying to understand rainbows and how white light is transformed to colour through this medium. The Victoria Falls are perhaps one of the most spectacular places on Earth to see rainbows; here, these features hover in the sky above the cascading waters whenever the Sun shines through the mist. Our eyes are sensitive to a limited range in the middle which we know as visible light. These colours hidden in white light are not only revealed in rainbows; wherever sunlight strikes an object the different colours are bounced around or absorbed in different ways.
The sky is blue because the blue components of sunlight are more likely to be scattered off air molecules than the other colours. As the Sun drops towards the horizon, and the sunlight has to pass through more of the atmosphere, the chance of scattering rays of yellow and red light increases, turning the evening skies redder.
Leaves and grass are green because they absorb blue and red light from the Sun, which they use in photosynthesis, but reflect back the green light. But what is the difference between the colours that makes them behave so differently? The answer goes back to our understanding of light as an electromagnetic wave. Waves have a wavelength — which is the distance between two peaks or troughs of the wave.
Blue light has a shorter wavelength than green light, which has a shorter wavelength than red light. Our eye has evolved to discern about ten million different colours, which is to say that it can differentiate between ten million subtle variations in the wavelength of electromagnetic waves.
The picture below shows some of the most distant galaxies we have observed. The most obvious thing about them is that they are all red. Why is this so? To answer this question correctly, we need our friend Edwin Hubble, the astronomer, again.
These Cepheid variables are stars whose brightness varies regularly over a period of days or months, and they are astonishingly useful to astronomers because the period of their brightening and dimming is directly related to their intrinsic brightness.
In other words, it is a simple matter to work out exactly how bright a Cepheid variable star actually is just by watching it brighten and dim for a few months. If you know how bright something really is, then measure how bright it looks to you, you can work out how far away it is.
During his observations, he discovered two remarkable things: For the first time, Hubble showed that there are other galaxies in the Universe, millions of light years away. This image shows some of the most distant galaxies that we have observed — and all appear in a bright, sharp, red colour. While he and others were also busy measuring the spectrum of the light from the stars in the spiral nebulae, which thanks to Hubble were now understood to be other galaxies beyond the Milky Way, they quickly observed that many of the galaxies appeared to be emitting light that was redder than it should be.