Five Photons

'The Universe is something to behold, and with his elegant, supremely clear writing, Geach has succeeded at creating both a state-of-the-art cosmic overview and a rather wonderful meditation on the nature of our reality. The vital components that let us experience and study the world have quite a story to tell.'
Caleb Scharf author of The Zoomable Universe

'From the oldest light in the universe to the photons streaming from our sun right now, Geach's beautiful cosmic biography takes readers on a sweeping tour of all that was, is, and ever will be. Five Photons is as elegant as it is enlightening'
Lee Billings author of Five Billion Years of Solitude

'This deft primer by astrophysicist James Geach captures the elusive electromagnetic wave in five processes. His meditation on 'old' light takes us back to the singularity: the 'cosmic seed' that expanded into the Big Bang. A study of starlight plunges us into the seething stellar surface. We peruse dark energy, radio waves and quasars - beacon-like galaxies in which supermassive black holes feed off interstellar gas and release vast amounts of energy. A masterclass in elucidating hard science with elegance and brevity.'
Nature

'What makes Five Photons different . . . is the depth that Geach goes to - not in a mathematical sense, but in describing subtleties of the work of astrophysicists and cosmologists that popular science titles usually gloss over . . . Think of it as a sequel to A Brief History of Time that explains some of the real detail of what has been discovered and brings in factors cosmologists have to consider that you won't see anywhere else in a popular science title.'
Popular Science

'Light permeates almost everything around us. It is the primary way in which we communicate and with which we try to understand the Universe. Light is the central theme of James Geach's book. After an introductory chapter on what light is, the book identifies five different sources of light that are key probes of the cosmos. This framework allows Geach to cover everything from the cosmic microwave background, to stars, dark energy, black holes and the epoch of reionization. No equations are to be seen and the style is conversational, making this book a perfect entryway to anyone interested in learning a bit more about the inner workings of the Universe.'
Nature Astronomy