Forces of Nature. Andrew Cohen

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?: Part 1: James Clerk Maxwell and the Golden Age of Wireless

       Why do Hot Things Shine?: Part 2: Max Planck and the Quantum Revolution

       A Serendipitous Aside; The Solar Neutrino Problem

       Pale Blue Green Planet: Part 1: The Oceans

       Pale Blue Green Planet: Part 2: The Sky

       Pale Blue Green Planet: Part 3: The Land

       Pale Coloured Dots

      Plate Section

      Picture Credits

      Index

       By the Same Author

       Acknowledgements

       About the Authors

       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

      Taking a different perspective

      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.

      ‘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

      ‘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

      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 from space – 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

      ‘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. 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