Forces of Nature Read online

  Copyright

  William Collins

  An imprint of HarperCollinsPublishers

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  London SE1 9GF

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  This eBook edition published by William Collins in 2016

  Text © Brian Cox and Andrew Cohen 2016

  Photographs © individual copyright holders

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  BBC logo © BBC 2014

  The authors assert their moral right to be identified as the authors of this work.

  Cover photographs © BBC 2016 (Brian Cox); other images © Shutterstock.

  A catalogue record for this book is available from the British Library.

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  Source ISBN: 9780007488827

  Ebook Edition © June 2016 ISBN: 9780007488834

  Version: 2016-06-27

  For my dad, David.

  — Brian Cox

  For Benjamin, Martha, Theo, Dan, Jake, Lyla, Ellie, Toby, Phoebe, Max, Zak, Josh, Isaac and Tabitha because curious young minds always ask the smartest of questions.

  — Andrew Cohen

  Contents

  Cover

  Title Page

  Copyright

  Dedication

  Chapter 1

  SYMMETRY

  The Universe in a Snowflake

  Why do bees build hexagons?

  Knocking on the doors of chemistry

  The fundamental building blocks and the forces of Nature

  Why is the Earth a sphere?

  Why does life come in so many shapes and sizes?

  Symmetry and symmetry breaking in biology

  The Universe in a snowflake

  Chapter 2

  MOTION

  Somewhere in Spacetime

  Life on an orbiting planet

  The formation of the Earth and Moon

  Life on an orbiting planet

  Life on an orbiting, spinning planet

  Einstein’s Theory of Special Relativity

  Somewhere in spacetime

  Spacetime calculations

  Chapter 3

  ELEMENTS

  The Moth and the Flame

  Chemistry is all about the movement of electrons

  Frankenstein’s Monsters

  On the Origin of Species

  The oldest life on Earth

  A warm little pond?

  Life, Thermodynamics and Entropy

  The Moth and the Flame

  A Very Different Eden

  Life beyond Earth

  Chapter 4

  COLOUR

  Pale Blue Dot

  The rainbow connection

  Why does the Sun shine?

  The nuclear physics of the Sun

  Why do hot things shine?

  Why do hot things shine?

  A serendipitous aside; the solar neutrino problem

  Pale blue green planet

  Pale blue green planet

  Pale blue green planet

  Pale coloured dots

  Index

  Picture Credits

  Acknowledgements

  About This Author

  About the Publisher

  SEARCHING FOR THE DEEPEST ANSWERS TO THE SIMPLEST QUESTIONS

  ‘What beauty. I saw clouds and their light shadows on the distant dear Earth.... The water looked like darkish, slightly gleaming spots.... When I watched the horizon, I saw the abrupt, contrasting transition from the Earth’s light-coloured surface to the absolutely black sky. I enjoyed the rich colour spectrum of the Earth. It is surrounded by a light blue aureole that gradually darkens, becoming turquoise, dark blue, violet, and finally coal black.’

  – Yuri Gagarin

  On 5 May 1961, Alan Shepard’s Freedom 7 launched into space from Cape Canaveral, Florida, for NASA’s first ever suborbital flight.

  Taking a different perspective

  ‘The first day or so we all pointed to our countries. The third or fourth day we were pointing to our continents. By the fifth day we were aware of only one Earth.’

  – Sultan bin Salman bin Abdulaziz Al-Saud, Space Shuttle STS-51-G

  This is a book about science. What is science? That’s a good question, and there may be as many answers as there are scientists. I would say that science is an attempt to understand the natural world. The explanations we discover can often seem abstract and separate from the familiar, but this is a false impression. Science is about explaining the everyday minutiae of human experience. Why is the sky blue? Why are stars and planets round? Why does the world keep on turning? Why are plants green? These are questions a child might ask, but they are certainly not childish; they generate a chain of answers that ultimately lead to the edge of our understanding.

  If you dig deep enough, most questions end with uncertainty. The sky is blue because of the way light interacts with matter, and the way light interacts with matter is determined by symmetries that constrain the laws of nature. We’ll encounter these concepts later in the book. But if one keeps on digging, and asks why those particular symmetries, or why there are laws of nature at all, then we are into the glorious hazy place in which scientists live and work; the space between the known and the unknown. This is the domain of the research scientist, and it is a place of curiosity and wonder.

  Grander questions lurk in the half-light. How did life on Earth begin? Is there life on other worlds? What happened in the first few moments after the Big Bang? These are questions that have a sense of depth and a feeling of complexity and intractability, but the techniques and processes by which we look for answers are no different to those deployed in discovering why the sky is blue. This is an important point. If a question sounds deep, it doesn’t mean that the way to answer it is to retire to the wilderness for a year, sit cross-legged and hope for something to occur to you. Rather, the answers are often constructed on foundations generated by the systematic and careful exploration of simpler questions. This idea is central to our book. In seeking to understand the everyday world – the colours, structure, behaviour and history of our home – we develop the knowledge and techniques necessary to step beyond the everyday and approach the Universe beyond.

  Planet Earth is the easiest place in the Universe to study because we live on it, but it is also confusingly complicated. For one thing, it’s the only planet we know of that supports life. It is home to over seven billion humans and at least ten million species of animals and plants. Of its surface area, 29 per cent is land, and humans have divided that 148,326,000 square kilometres into 196 countries, although this number is disputed. Within these boundaries, reflecting the vagaries of 10,000 years of human history, there are over 4000 religions. Some want to increase the number of countries; others want to decrease the number of religions. For such a small world orbiting an ordinary star in such a run-of-the-mill galaxy, it’s not very well organised and difficult to understand through the parochial fog. Just over five hundred humans have travelled high enough to see our home in its entirety – a small world against the backdrop of the stars – and when they do, something interesting happens. They
see through the fog, and return with a description not of segregation and complexity, but of unity and simplicity.

  ‘When you’re finally up at the Moon looking back on Earth, all those differences and nationalistic traits are pretty well going to blend, and you’re going to get a concept that maybe this really is one world and why the hell can’t we learn to live together like decent people.’

  – Frank Borman, Gemini 7, Apollo 8

  Earthrise – possibly the most influential and best-known image in space history. Taken by astronaut William Anders in 1968 during the Apollo 8 mission.

  ‘If somebody had said before the flight, “Are you going to get carried away looking at the Earth from the Moon?” I would have said, “No, no way.” But yet when I first looked back at the Earth, standing on the Moon, I cried.’

  – Alan Shepard, Mercury 3, Apollo 14

  Alan Shepard became the first American in space but didn’t walk on the Moon until 15 February 1971, with Edgar Mitchell.

  Alan Shepard being hoisted into a US Marine helicopter after completing his 15-minute suborbital flight in Freedom 7, 5 May 1961.

  ‘ODDLY ENOUGH THE OVERRIDING SENSATION I GOT LOOKING AT THE EARTH WAS, MY GOD THAT LITTLE THING IS SO FRAGILE OUT THERE.’

  — MIKE COLLINS, GEMINI 10, APOLLO 11

  Harrison Schmitt, of the Apollo 17 lunar mission, January 1972, stands next to the US flag on the Moon, as it points to Earth in the distance.

  Scott Carpenter, who flew the second American manned orbital flight on 24 May 1962, getting suited up for his mission.

  ‘When you’re finally up at the Moon looking back on Earth, all those differences and nationalistic traits are pretty well going to blend, and you’re going to get a concept that maybe this really is one world and why the hell can’t we learn to live together like decent people.’

  Frank Borman, Gemini 7, Apollo 8

  ‘If somebody had said before the flight, “Are you going to get carried away looking at the Earth from the Moon?” I would have said, “No, no way.” But yet when I first looked back at the Earth, standing on the Moon, I cried.’

  Alan Shepard, Mercury 3, Apollo 14

  The astronauts were not making whimsical comments. These are statements from human beings whose experience has given them a different perspective. The astronauts see simplicity because they have been forced to look at the world in a different way. We are self-evidently one species, inhabiting one planet, and it follows that we have one chance not to mess it all up. We can’t all be astronauts, but we can all be scientists, and I think science provides a similar perspective to altitude. It lifts us up, mentally rather than physically, and allows us to survey the landscape below. We look for regularities and, once glimpsed, we try to understand their origin. I’ll put my cards on the table right away. I want you to draw the obvious analogy. On his return from space, Scott Carpenter, officer in the United States Navy and Korean War veteran, felt that our highest loyalty should not be to our own country, but to the family of man and the planet at large. Space travel is about a shift in perspective, and so is science. The more we understand about nature, the more beautiful it appears and the more we understand what a privilege it is to be able to spend our short time exploring it. Be a child. Pay attention to small things. Don’t be led by prejudice. Take nobody’s word for anything. Observe and think. Ask simple questions. Seek simple answers. That’s what we’ll do in this book, and hopefully, by the end, you’ll agree with Scott Carpenter.

  Scott Carpenter signed this photograph for my son, George, shortly before Carpenter died, aged 88, in October 2013.

  ‘This planet is not terra firma. It is a delicate flower and it must be cared for. It’s lonely. It’s small. It’s isolated, and there is no resupply. And we are mistreating it. Clearly, the highest loyalty we should have is not to our own country or our own religion or our home town or even to ourselves. It should be to, number two, the family of man, and number one, the planet at large. This is our home, and this is all we’ve got.’

  – Scott Carpenter, Mercury 7

  The Universe in a snowflake

  ‘Hast thou entered into the treasures of the snow?’

  – The Old Testament, Book of Job, 38:22.

  I love this photograph of Wilson ‘Snowflake’ Bentley; a tilt of the head, content, protected from the cold by curiosity, absorbed in Nature’s detail which he holds carefully in both hands, oblivious to the snow falling on his hat. No gloves. As a 15-year-old farm boy from Jericho, Vermont, Bentley spent the snow days from November to April with a battered microscope sketching snowflakes before they melted away. Frustrated by their transience, too short-lived to capture in detail, he began experimenting with a camera and, on 15 January 1885, he took the first ever photograph of a snowflake. Over the next 45 years he collected over 5000 images and dedicated his life to carefully observing and documenting the raindrops, snowfalls and mists that swept across his farm.

  These delicate snapshots of a world available to everyone but rarely seen captured the public imagination. How could they not? They are magical, even today in an age familiar with photography. I challenge anyone to look at these structures, endless and most beautiful – to paraphrase Darwin – and not be curious. How do they form? What natural mechanism could mimic the work of a crazed, impatient sculptor obsessed with similarity and yet incapable of chiselling the same thing twice?

  Wilson Bentley absorbed in capturing unique and delicate images of snowflakes on film in Vermont in 1885.

  These are questions that can be asked about any naturally occurring structure, and which Darwin famously answered for living things in On the Origin of Species. In May 1898 Bentley co-wrote an article for Appletons’ Popular Science with George Henry Perkins, Professor of Natural History at the University of Vermont, in which he argued that the evidence he’d collated frame by frame revealed that no two snowflakes are ever alike. ‘Every crystal was a masterpiece of design and no one design was ever repeated,’ he wrote. Their uniqueness is part of their fascination and romance, yet there is undoubtedly something similar about them; they share a ‘six-ness’. Which is more interesting? Perhaps it depends on the character of the observer.

  Johannes Kepler is best known for his laws of planetary motion. He pored over the high-precision astronomical observations of the Danish astronomer Tycho Brahe, just as Snowflake Bentley pored over his photographs, and he noticed patterns in the data. These patterns led him to propose that planets move in elliptical orbits around the Sun, sweeping out equal areas in equal times and with orbital periods related to their average distances from the Sun. Kepler’s empirical laws laid the foundations upon which Isaac Newton constructed his Law of Universal Gravitation, published in 1687; arguably (I would say unarguably, but one has to keep argumentative historians happy) the first modern scientific work.

  In December 1610, shortly after the publication of two of his three laws in Astronomia Nova, Kepler was walking across the Charles Bridge in Prague through the Christmas dark when a snowflake landed on his coat. The evident structure of the elegant, white near-nothing interested him, and he wrote a small book entitled On the Six-Cornered Snowflake. It is a piece of scientific writing that transcends time and provides an illuminating and entertaining insight into a great mind at play. The title page of the book is addressed ‘To the honorable Counselor at the Court of his Imperial Majesty, Lord Matthaus Wacker von Wackenfels, a Decorated Knight and Patron of Writers and Philosophers, my Lord and Benefactor’. Modern language lacks a certain flourish; I wish I had something equally magnificent with which to begin this book.

  These captivating images, taken by Wilson Bentley through a light microscope attached to his camera, reveal the uniqueness of each snowflake.

  As a modern research proposal, Kepler’s Six-Cornered Snowflake would fall at the first hurdle because it begins: ‘I am well aware how fond you are of Nothing, not so much on account of its inexpensive price as for the charming and subtle jeu d’esprit of playful Passerea
u.1 Thus, I can easily tell that a gift will be the more pleasing and welcome to you the closer it comes to nothing.’ Now there’s a statement of projected economic impact; the closer my research comes to nothing, the more valuable it is. Stick that on your spreadsheet… Kepler doesn’t succeed in explaining the structure of snowflakes – how could he? A full explanation requires atomic theory and a good fraction of the machinery of modern physics; we will get to that later on. What he does achieve is to make vivid the joy of science; the idea that the playful investigation of Nature has immense value, irrespective of the outcome. His book explodes with excited curiosity, fizzing with speculations on snowflakes and their similarities to other regular shapes in the natural world; five-petalled flowers, pomegranate seeds and honeycombs. He covers so much ground, bouncing thrillingly from subject to subject, that eventually, with magnificent perspicacity, he has to rein himself in: ‘But I am getting carried away foolishly, and in attempting to give a gift of almost Nothing, I almost make Nothing of it all. For from this almost Nothing, I have very nearly recreated the entire Universe, which contains everything!’

  Kepler does have a clear question, however, which surely occurs to anyone who studies Snowflake Bentley’s exquisite photographs: how do structures as ordered and regular as snowflakes form from apparently form-less origins? ‘Since it always happens, when it begins to snow, that the first particles of snow adopt the shape of small, six-cornered stars, there must be a particular cause; for if it happened by chance, why would they always fall with six corners and not with five, or seven, as long as they are still scattered and distinct, and before they are driven into a confused mass?’

  Kepler knew that snow forms from water vapour, which has no discernable structure. So how does the snowflake acquire structure? What is the ‘six-ness’ telling us about the building blocks of snowflakes and the forces that sculpt them? This is a modern way of looking at the world, one that any physicist would recognise. Kepler’s insight, and his delighted frustration at not possessing the knowledge to approach an answer, echoes loudly down the centuries. ‘I have knocked on the doors of chemistry,’ he writes, ‘and seeing how much remains to be said on this subject before we know the cause, I would rather hear what you think, my most ingenious man, than wear myself out with further discussion. Nothing follows. The End.’