To a human, living on Earth feels just right. Of course, many of the human race face challenges, such as poverty and sickness, on a daily basis, but it can feel like our planet was made for us.
We find ourselves in a neatly placed orbit around a stable, middle-aged star, with the strength of our bones nicely matched by the Earth’s gravitational pull, allowing us to ramble freely over the planet. There is oxygen to breathe, and we can power ourselves through the digestion of many tasty plants and animals that inhabit the surface. We would last but a few seconds if we were dropped onto our neighbouring planets. We would be crushed and roasted on the surface of Venus, or left gasping and freezing in Mars’s tenuous atmosphere. For humans, the Earth is a special place, a relative cosmic paradise where the conditions are just right for life, including our human life.
But over the past few centuries, we’ve come to discover how we came to be so nicely suited to conditions on Earth. Our physical properties, our bone structure, our organs, our senses, result from life continually changing and evolving over the last 3.5 billion years, adapting to the conditions that surround us.
The realization that the Earth is not unique changes our view of our place in the Universe. Driven by the continual advancement of science, we have found that humans are part of the web of life, that the Earth is just one of a myriad of planets, and the Sun is but a boringly typical star. Our place in the Universe is just like many, many others, and in no way unique.
Peering more deeply into these same scientific advances, examining the basic make-up of the Universe, reveals that we are not as mediocre as it seems. The fundamental particles from which everything is constructed, and the fundamental forces that dictate interactions, appear to be fine-tuned for life. Minor tinkering with either would leave the Universe dead and sterile.
With every step forward in science, these fine-tuning issues have become more significant. We find ourselves questioning the nature of many of the things we take for granted, from the fabric of space and time, to the mathematical underpinnings of the Universe. At every level, we find that our Universe’s ability to create and sustain life forms is rare and remarkable.
The discussion of this cosmological fine-tuning for life has found a very broad audience, from philosophers and physicists in the halls of academia, to religious believers who see the mysterious hand of the divine. It has captured the attention of the popular media, and generated random frothings in various recesses of the internet. All too frequently, the science, and what it is actually telling us about the fine-tuning of the Universe for life, is lost in the noise.
The goal of this book is to present the scientific viewpoint of the fine-tuning of the laws of science, and delve into its implications for the inner workings of the Universe. We will call upon the latest academic and philosophical musings to clarify what fine-tuning actually means and to set the scene for what we can conclude from our existence as life forms.
This book has been a long time in gestation, with the original idea coming from many rambling conversations between the authors and others, the kind of discussions and arguments that lie at the heart of science. Sitting around the table, we wondered about the expansion of the Universe, the nature of electrons, and how many different kinds of universes there could be. We scratched our heads over the make-up of dark matter and dark energy, and wondered deeply about how things could have been different. This quickly leads to the realization that life would be very difficult, if not impossible, in the vast sea of possible universes.
Our hope is that this book crystallizes these discussions, reflecting the rollercoaster of the scientific journey. We hope it gets you thinking about the question that drove us, the question that has dogged humans from the earliest times, the question that we hope we are on the road to answering: why are we here?
