Human Universe

by Professor Brian Cox

  In Einstein’s equations, there are also these so-called derivatives hidden away in the compact mathematical notation. The known fundamental laws of physics all function in this way. Given knowledge of how some system or collection of natural objects is behaving now, we can compute what they will be doing at some time in the future. The system in question may be a solar system, a collection of atoms and molecules, or the weather. There are practical limitations, of course, and the weather forecast is a good example. Earth’s climate system is very complicated, with many hundreds of thousands of variables. Ocean currents in the Pacific might affect future rainfall in Oldham, and so long-term forecasting of local weather conditions comes with increased uncertainty.

  People do of course make statements, often based on human experience rather than science, which are more likely to be right than wrong. Red sky at night, Shepherd’s delight. Red sky in the morning, Shepherd’s warning. This is often true in countries like the UK whose weather is dominated by westerly winds, because a red sunset is usually a sign of high pressure to the west, which is associated with fine weather. But if you’re doing well in a statistically significant sense using ‘folklore’ or ‘ancient wisdom’, it’s because the patterns and regularities you are using to make your predictions emerge from underlying physical laws, which are described by differential equations. The laws of physics in essence reflect the underlying simplicity of nature and the regularity with which it behaves. They are not magic. We can describe the natural world using mathematics because it is regular and behaves consistently. It is my opinion that we must observe a universe that behaves in a regular and consistent way because such behaviour is necessary for complex structures like brains to evolve. A universe of anarchy, with subatomic particles interacting without some sort of framework or rules, would surely not support life, or indeed any structures at all. This is known as a selection effect. We observe a universe whose behaviour can be described by a limited set of differential equations because we wouldn’t exist if it were not so. This is my opinion, and there are scientists and philosophers who might disagree. It could be the case that there is no simple underlying framework to the universe, and our success to date has deceived us. Or perhaps the ultimate laws are and will forever remain beyond human understanding. We might simply not be smart enough to figure them out. There are also systems that cannot be described using differential equations. The patterns generated in Conway’s Game of Life are an example, where algorithmic rules are used to generate complex patterns and even computing devices such as Turing machines. But what can be said with certainty is that, as far as we can tell, the natural world does behave in a way that is amenable to a description based on the differential equations of physics, and these allow us to predict the future, given knowledge of the present. This is why our asteroid defence system will work if we make enough high-precision observations of the sky. Sort of.

  Ahhh, caveats. There are always caveats.

  SCIENCE VS. MAGIC

  We should be confident in science. It works. But it has limitations, some of which are fundamental. We’ve encountered Newton’s laws of motion and gravitation time and again in this book. They are very simple –the archetypal physical laws – and are used every day by engineers, navigators and asteroid watchers. One of the simplest imaginable real-life systems to which Newton’s law of gravitation can be applied is a single planet orbiting around a single star. For this case, Newton’s laws allow for a precise prediction of the future position of the planet. The orbit is predictable and periodic, which is to say the planet returns to precisely the same position around the star every orbit. It’s clockwork – the way the solar system is often pictured. If a third object – a moon, say – is introduced, it was proved in the late nineteenth century by Heinrich Burns and, later, Henri Poincaré that no general solution to Newton’s equations can be found. There are a handful of special cases, which are still being discovered, for which there are repeating solutions, but in general, the orbits of three bodies acting under gravity never repeat; their motion around each other traces out a tremendous ever-changing mess! This isn’t a failure of mathematics. Natural systems really do behave in this way. The solar system is a case in point. The planets orbit like clockwork on timescales of millions of years, but we are currently unable to predict the Earth’s orbit for more than 60 million years into the future. Beyond that, the sensitivity of the predictions to uncertainties in our current knowledge of the Earth’s orbit, and the gravitational influence of other bodies in the solar system, become too great. This isn’t only a reflection of our lack of knowledge. It also reflects an important fundamental point, which is that solar systems such as ours are unstable over long timescales. Their behaviour is chaotic; the apparent clockwork can break down into a whirling unpredictable swarm. Recent simulations suggest that Mercury could be wrenched out of its orbit and collide with the Sun, and that even the Earth may have a close encounter with Venus or Mars on time periods of 3–5 billion years. The words could and may are italicised for a reason. These predictions are statistical in nature – it is estimated that there is a 1 per cent chance that Mercury will be thrown into a much more elliptical orbit during the next 5 billion years. The uncertainty is down to the extreme sensitivity of the predictions to what physicists call the initial conditions – the current knowledge of precisely where everything in the solar system is at this instant, and how everything is moving at this instant. Other errors are caused by our precise knowledge of the mass and shape of all the objects in the solar system, not to mention the slight perturbations from incoming comets and the ever-shifting asteroids. The area of physics and mathematics concerned with such systems is called chaos theory, and as the pioneer of the field Edward Norton Lorenz put it, nature’s complexity usually leads to a situation in which approximate knowledge of the present, which is in practice all we ever have, does not approximately determine the future.

  Chaos: When the present

  determines the future, but

  the approximate present

  does not approximately determine

  the future.

  Edward Lorenz

  * * *

  EQUINOXES AND SOLSTICES

  When the Sun is crossing the celestial equator, day and night are of nearly equal length at all latitudes, which is why these dates are called the equinoxes (‘equal nights’). In March, as the Sun is moving northwards along the ecliptic, this is called the vernal equinox, and in September as the Sun is moving southwards we refer to it as the autumnal equinox. The times when the Sun is at its furthest from the celestial equator are called the summer and winter solstices. The world ‘solstice’ comes from the Latin meaning ‘Sun stands still’ because the apparent movement of the Sun’s path north or south stops before changing direction.

  * * *

  For the asteroid hunters, this is an intensely problematic truth. It is not possible to observe an asteroid once, and then pop its position and velocity into a computer to work out whether it will ever hit us. Instead, a gravitational keyhole system is used. A keyhole is a small volume of space close to the asteroid’s current orbit. If an asteroid passes through the keyhole, perhaps because of a gravitational nudge from some other object in the solar system, then it is highly likely that it will impact the Earth on its next pass. 99942 Apophis was assigned such a keyhole in 2004 when it was classified at 4 on the Torino Scale. Fortunately, it didn’t pass through, and this is why it is currently classified as harmless. The keyhole system reflects the fundamental unpredictability of complex physical systems over long timescales. This is why we have to keep observing and retain a keen understanding of the fundamental limits of our calculational prowess. Science isn’t magic. This realisation is of course important in a practical sense if one is interested in saving the planet from asteroid impact. But it is also very important to embed caution and humility into our/my polemical celebration of the power of science. Scientific predictions are not perfect. Scientific theories are never correct
. Scientific results are always preliminary. Whole fields of study can be rendered obsolete by new discoveries. But, I insist, science is the best we can do because it is not simply another arbitrary system of thought based on dreamt-up human axioms. It is the systematic study of nature, based on observations of the natural world and our understanding of those observations. Scientific predictions are not matters of opinion. At any given time, science provides the best possible estimate of what the future might bring, given our current understanding. The predictions may be wrong, they may be inaccurate, the errors may be fundamental in origin, but there is simply no other rational choice than to act according to the best available science, imperfect though, by necessity, its predictions will always be.

  THE WONDER OF IT ALL

  As of September 2014, in a population of 7.24 billion, 545 people have been to space, 24 people have broken free of the Earth’s gravitational pull and 12 have landed on another world.

  In 2013 Charlie and Dorothy Duke, a retired, church-going couple from New Braunfels, Texas, reached their 50th wedding anniversary. With two grown sons and nine grandchildren, Charlie and Dottie must have celebrated a life well lived, captured in photographs adorning the walls and mantelpieces of the family home. There is one Duke family photograph, however, that holds a unique place in history. I myself have a copy of it on my wall at home, signed by Charlie, and it’s one of my favourite things. The photograph, taken in 1972, is an image of Charlie, Dottie and their two young sons Charles and Thomas when they were just six and four years old. The picture itself is of no particular note – a simple portrait of a family in 70s clothes, sitting on a bench in a garden. It’s not dissimilar to one of me and my grandad photographed at around the same time. I was in Oldham, the Dukes were in Florida.

  The reason I have a copy of the Dukes’ photograph is not what it is – we are not related – but where it is. Charlie and Dorothy Duke are the only grandparents on Earth who can point their grandchildren’s eyes towards the Moon and tell them there is a photo of Grandma, Grandpa, Dad and Uncle resting on the surface.

  Charlie Duke was the Pilot of Orion, the Apollo 16 Lunar Module. At the age of thirty-six he remains the youngest human ever to have walked on the Moon. Together with Commander John Young, my childhood hero, the two astronauts spent three days in late April 1972 exploring the Descartes Highlands, covering almost 27 kilometres in the Lunar Rover.

  The primary scientific aim of the mission was to explore the geology of the lunar highlands. It was thought that the unique rock formations around the landing site were formed by ancient lunar volcanism, but Young and Duke’s exploration demonstrated that this explanation was incorrect. Instead, the landscape had been forged by impact events, scattering material outwards from the craters and littering the surface with glass. After three days on the lunar surface and setting a lunar land-speed record of 17km/h, Charlie Duke removed his family portrait from his spacesuit pocket, placed it on the lunar surface and snapped it with his Hasselblad. Inscribed on the back are the words ‘This is the family of Astronaut Duke from Planet Earth. Landed on the Moon, April 1972.’

  I remember being four years old in Oldham when Apollo 16 was on the Moon. Forty-two years later I talked to Duke for hours in a diner in Texas, with absolutely no regard at all for the film crew trying to make Human Universe. ‘When I stepped onto the Moon it occurred to me that nobody had ever been here before. You looked out onto the most pristine desert – the most incredible beautiful place I’ve ever seen. No life, nothing like Earth, the rolling grey lunar surface with the blackness of space above.’

  How ambitious was Apollo, I asked? ‘They gave us eight and a half years to do it and we did it in eight years and two months. Nobody even knew how to do it,’ replied the test pilot, who was used to doing things that nobody can do. ‘Yeah sure. Fifteen minutes in space and we’re going to land on the Moon in eight and a half years? But the remarkable part is that we did it, and I had a part in it.’ Would it be possible now? ‘No. We don’t have the manpower to do it. Four hundred thousand people and unlimited budget and you can do a lot, and that’s what we had!’ What do you say to people who criticise manned exploration? There is surely more to human exploration than just science. ‘It’s the wonder of it all,’ replied the astronaut. ‘And that’s what we bring – what manned flight brings to the human spirit, the human being – the wonder of it all. The beauty of the universe, the orderliness of the universe, and you see it with your own eyes and it just captures your imagination. Let’s see it, let’s do it and let’s discover it – that’s been the human spirit all along.’

  I think Apollo is the greatest human achievement. People argue with me of course. Gil Scott-Heron wrote a song called ‘Whitey’s on the Moon’. ‘A rat done bit my sister Nell, with Whitey on the moon. Her face and arms began to swell, and Whitey’s on the moon. I can’t pay no doctor bill, but Whitey’s on the moon. Ten years from now I’ll be payin’ still, while Whitey’s on the moon.’ The economics of Apollo are interesting. As Charlie said, the budget was whatever it had to be to get to the Moon by 1970. At the peak of spending in 1966, NASA received 4.41 per cent of the federal budget, equivalent to around $40 billion today. That’s a lot of money – almost half of the United Kingdom’s annual debt interest bill. That’s meant to be sarcastic, of course. The total cost of Apollo was in the region of $200 billion at today’s prices, which is around a quarter of the cost of the UK’s bank bailout programme initiated in October 2008. That’s unfair, a City-type might splutter over a glass of Dom Ruinart, because that money was an investment in financial stability and has been repaid, give or take the odd £100 billion, which is neither here nor there. My reply would be yes, but Apollo was probably the most savvy investment in modern history. In 1989, the then US President George Bush said Apollo provided ‘the best return on investment since Leonardo da Vinci bought himself a sketchpad’. Many academic studies have been carried out, and the most commonly quoted figure is that for every $1 spent on Apollo, $7 was returned to the economy over the period of a decade. Why? Because Project Apollo was conceived and executed in a tremendously smart way, distributing high-technology jobs and R&D projects across the country. It was also unarguably inspirational, propelling thousands of kids into science and engineering. The average age in Mission Control, Houston, on 20 July 1969 when Neil Armstrong landed on the Moon was 26. The old man in charge, Gene Kranz, was 36, and the old man flying the lunar module was 35. What happened to all those brilliant engineers? They went out into the economy of course, took the technology and expertise developed for the Moon landings and invented the modern world. The kids they inspired became known as Apollo’s Children; the generation of optimists steeped in possibility who powered the United States economy through the last third of the twentieth century. The world loves this America, the one that flies to the Moon not because it’s easy but because it’s hard.

  I think America has lost its way, which might seem rich from a citizen of a small island that spends more on the wages of Premier League footballers annually than it does on research into the physical sciences and engineering, including its contributions to CERN, the European Space Agency and all UK-based scientific facilities. We’ve lost our way too, and so has the world. The World Bank defines R&D as ‘current and capital expenditures (both public and private) on creative work undertaken systematically to increase knowledge, including knowledge of humanity, culture, and society, and the use of knowledge for new applications’. The United States spent 2.79 per cent of its GDP on increasing knowledge in 2012 – the UK spent 1.72 per cent. It has been estimated that the return on R&D spending in today’s world economy is approximately 40:1. Imagine what we could do if we took these figures seriously.

  My grandad, sitting behind me in that 1972 family Christmas photograph, was born in 1900. He was three years old when, on 17 December 1903 at Kill Devil Hills in North Carolina, Orville Wright took the controls of the Wright Flyer and lifted off the ground for twelve seconds. He was 68
when he saw Neil Armstrong walk on the Moon. Orville Wright himself died in the year that Neil Armstrong began studying aeronautical engineering at Purdue University, Indiana. I still find it hard to believe that I have spoken to someone who was born before powered flight, and to someone who walked on the Moon. It is important to notice that this sentence can’t be followed. Someone who walked on the Moon, comma, and someone who … What? Where will the next generation of Apollo’s Children come from? Perhaps a new superpower will take America’s place as the great exploring nation. China and India, those re-emergent cradles of civilisation, have ambitions in space. As Jacob Bronowski wrote in The Ascent of Man, ‘Humanity has a right to change its colour.’ But I share his regret that the retreat of Western civilisation may leave Shakespeare and Newton as historical fossils, in the way that Homer and Euclid are. If that is the case, it will be our choice.

  Two more astronauts followed Duke and Young onto the lunar surface. They left at 10.55pm GMT on 14 December 1972. Commander Gene Cernan, as he prepared to step on to the ladder of the Lunar Module, quietly spoke the final words from the Moon.

  … I’m on the surface; and, as I take

  man’s last step from the surface,

  back home for some time to come – but

  we believe not too long into the future

  – I’d like to just say what I believe

  history will record. That America’s

  challenge of today has forged man’s

  destiny of tomorrow.