About the Book

Excerpts from Introduction

What does it mean to say that the sky is blue? Is it true? Why?

At one level, it is a question about physics, and there is a fascinating story to be told that can be explored down to the level of quantum mechanics. But many other levels of understanding are relevant even to this apparently simple question. For example, there are philosophical issues about what “the sky is blue” means: The sky is not blue all the time. Sometimes it looks black, red, white, or grey. How do I know that what I mean by “blue” is the same as what you mean by “blue,” and so forth? Cultural and poetic associations also give whole new layers of meaning: Suppose I say that the (blue) sky is the same color as my mood, or my blood. These statements are obviously false if taken literally.

The sky on Mars is not blue. Our blue sky depends on properties of our atmosphere, which in turn depend on some of the remarkable characteristics of Earth. Both Jupiter and the moon help shield us from frequent large-scale impacts. The composition of our atmosphere has been largely shaped by biological activity. The earth’s magnetic field shields us from high levels of cosmic radiation. The color of the sky also depends on the distance we are from the sun. Planets on which any intelligent life-form resembling humans would be likely to evolve would probably have a blue sky, so in an important sense the sky is blue because we are here to observe it. Hence for a Christian, a fuller account of why the sky is blue would connect with what we see as the loving purposes of God.

No one has asked us why the sky is blue, but over the years people from all over the world have e-mailed us questions relating to science and religion. To the ones that raised particularly significant issues, Nicholas has given a preliminary response and then faxed the question and his response to John, who has added his comments. The results have then been e-mailed to the questioner and posted on the Web. For this book we have taken fifty-one questions, based on those that we have been asked, and have provided revised and expanded responses. We hope that readers will follow their own paths through the book, dipping into the questions that interest them and looking at the additional material we provide where they are moved to do so. We’ve tried to give definitions of any technical terms that we use in the glossary at the end. We’re offering responses rather than giving answers, and we’d be surprised if anyone fully agreed with everything we have written. But even after decades of reflection on these topics, we’ve found the process of bringing these responses together instructive, and we suspect that however well-informed a reader is, there will be some new and interesting material….

We don’t attempt to develop everything from first principles. But we hope that this book will be a useful resource to readers from many different backgrounds and positions, and that if people want to explore topics further they will find the references and appendix material useful. Knowledge is in many ways more like a tree than a building, with roots that grow as the branches do. We hope that this tree in the forest of knowledge will provide some interesting paths to climb, and that from its branches readers will be able to glimpse some of the amazing diversity of love and wisdom that underpins the universe as a whole.


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“a refreshing contrast to the polemic and misinformation that have characterized much of the writing in this area” William Phillips

“Richly nuanced responses … simply a fantastic resource” Francis Collins

“Wonderfully accessible, informative and authoritative.” Alister McGrath

“an important contribution” Martin Nowak

“this matters to every man and every woman” Onora O’Neill

“of universal interest. Many readers will welcome this accessible format” Publishers Weekly

“antidote to Richard Dawkins … intriguing … a thought-provoking work” Library Journal

“deals eloquently with many of the issues…in the science-religion debate.” Times H. E.

“commendably clear…those who would most benefit from reading it are… atheists who believe that the religious are manifestly irrational” FT.

“remarkably even-handed …lucid explanations … a valuable lesson” Physics World

“rich…digestible..intriguing” Church Times

“evokes the shimmering beauty of a stained glass window … will repay rereading and rereading” Living Church.

One Erratum has been found in Appendix A – see here.

The new Polkinghorne Q&A website is now here.