Foreword

One of the following is true...

· Every breath you take contains an atom breathed out by Marilyn Monroe

· There is a liquid which can run up hill

· You age faster at the top of a building than at the bottom

· An atom can be in many different places at once, the equivalent of you being in New York and London at the same time

· The entire human race would fit in the volume of a sugar cube

· 1 per cent of the static on a TV tuned between the stations is the relic of the Big Bang

· Time travel is not forbidden by the laws of physics

· A cup of coffee weighs more when it is hot than when it is cold

· The faster you travel, the slimmer you get

No, I'm joking - they're all true!

As a science writer, I am constantly amazed by how much stranger science is than science fiction, how much more incredible the Universe we find ourselves in is than anything we could possibly have invented. Despite this, however, very few of the extraordinary discoveries of the past century seem to have trickled through into the public consciousness.

The two towering achievements of the past 100 years are "quantum theory", our picture of atoms and their constituents, and Einstein's "general theory of relativity", our picture of space, time and gravity. Between them, the two explain virtually everything about the world about us. In fact, it can be argued that quantum theory has actually created the modern world, not only explaining why the ground beneath our feet is solid and why the sun shines but making possible computers and lasers and nuclear reactors. Relativity may not be as ubiquitous in the everyday world. Nevertheless, it has taught us that there are things called black holes from which nothing, not even light, can escape; that the Universe has not existed forever but was born in a titanic explosion called the Big Bang; and that time machines – remarkably - may be possible.

Although I have read many popular accounts of these topics, the explanations have often left me baffled. Since I have a background in science, I can only guess what it must be like for non-scientists.

Einstein said: "Most of the fundamental ideas of science are essentially simple and may, as a rule, be expressed in a language comprehensible to everyone." All my experience tells me he was right. My idea in writing this book was to try to help ordinary people to understand the principal ideas of 21st-century science. All I had to do was to identify the key ideas behind quantum theory and relativity – which turn out to be deceptively simple - and then show how absolutely everything else follows from them logically and unavoidably.

Easier said than done. Quantum theory in particular is a patchwork of fragments, accrued over the past 80 years, which nobody seems to have sewn together into a seamless garment. What’s more, crucial pieces of the theory such as "decoherence" – which explains why atoms but not people can be in two places at once - seem to be beyond the power of physicists to communicate in any intelligible way. After corresponding with many "experts", and beginning to think that decoherence should be renamed "incoherence" (!), it dawned on me that maybe the experts didn’t completely understand it themselves. In a way this was liberating. Since a coherent picture seemed not to exist, I realised that I had to piece together my own from insights gleaned from various different people.

Because of this, many of the explanations you will find here you will not find anywhere else. I hope that they help to lift some of the fog that surrounds the key ideas of modern science and that you can begin to appreciate what a breathtakingly amazing Universe we find ourselves in.