Five Photons: Remarkable Journeys of Light Across Space and Time

by James Geach

Have you ever wondered what is the most distant source of light we can see, or how a star shines? Did you know that black holes can blaze like cosmic beacons across intergalactic space, and that ancient radio waves might herald the ignition of the very first stars? Have you ever thought about what light really is? Five Photons explains what we know about the universe through five different journeys of light across space and time. They are tales of quantum physics and general relativity, stars and black holes, dark matter and dark energy. Let yourself be swept away on a journey of discovery towards a deeper understanding of the cosmos.

Genres: Science, Nonfiction, Physics, Stem

192 pages, Hardcover

Published November 15, 2018

Reviews

[Brian Clegg · Rating 4 out of 5]

It is generally acknowledged that Stephen Hawking's A Brief History of Time is one of the most common books to be bought but not read beyond the first few pages. If you are the kind of popular science reader who found Hawking hard going, you can stop now - Five Photons is not for you. If, on the other hand, you found A Brief History of Time a piece of cake and wished you could get into more depth without resorting to heavy mathematics or a tedious textbook style, Five Photons could be just up your street.

Astrophysicist James Geach starts of fairly gently with a chapter on the nature of light that mostly sets aside quantum physics, leading up to the observation that light is our vehicle for for stripping back the history of the universe to its earliest times (or, at least, the point where the universe became transparent). From here on, the five photons of the title take us on different journeys, from the oldest surviving light of the cosmic microwave background radiation to that from around black holes.

All that makes this book sound like a fairly straightforward cosmological title, even if it does have the rather nice 'five photons' hook. What makes it different (and definitely not for everyone) 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. Each chapter opens fairly gently, but soon we're plunged into the detail.

A good example is the opening of the fourth chapter, Dark Energy's Imprint. Geach starts by telling us a cosmology joke from a seminar: 'I once sat in a cosmology seminar that opened with the line "What is the integrated Sachs-Wolfe effect?" This prompted a few moments of awkward silence from the audience until the speaker continued, "It's like the Sachs-Wolfe effect... only integrated!"' As Geach says, maybe you had to have been there. But Geach goes onto describe what the Sachs-Wolfe effect is - a variation in gravitational redshift of photons emerging from the early universe as the cosmic background, depending on the density of the region they emerge from - and, indeed also explains the integrated effect, which brings in similar variations on the photon's journey due to dark energy.

I need to stress again that Five Photons is only for the advanced cosmology buff. Think of it as a sequel to A Brief History 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 and you won't go far wrong. And if you are in the audience for that, it's great.

[Fabrizio · Rating 5 out of 5]

It's important to note that this book is not for someone who knows absolutely no physics. I'm not saying that you need to be a cosmologist, but it's better if you have some experience reading this type of text so that you can understand the deeper concepts that require some fundamental knowledge of physics jargon and ideas, as the author often jumps from one basic thought to the next without an in depth explanation. I must say, however, that this is completely fine, since the author's focus is to get straight into the kind of details about astronomy that you wouldn't find in most pop science books.

I think that this book's value also lies on the precise explanations that the author offers of concepts I'd previously been introduced to without fully comprehending because they were presented in a rather shallow manner. Reading the enthusiastic words of someone who truly loves what he's talking about sparked a fascination for the universe I didn't know I could have. Exceptional, brief, to the point, recommended for anyone who's looking to resuscitate old fondness for the subject or be enthralled by the specifics of our exciting and intriguing universe for the first time.

[Timothy Rooney · Rating 4 out of 5]

The book begins with an introduction to what light is. Since this is also so closely related to electromagnetism, that topic is also introduced very early. The exploration of frequency and amplitude are covered as expected. We examine all the different varieties of electromagnetic radiation, microwaves, infrared, x_rays, etc.

Next, the quantum mechanic nature of physics is introduced. The double slit experiment is examined.

Next, the "age" of light is examined. This is done through the standard red and blue shift descriptions. Next, the early stages of the formation of the universe are detailed, touching on the Epoch of Recombination. We also learn about the cosmic microwave background radiation. We are also reminded of the necessity of dark matter in models of the universe.

Next, we explore extra-galactic astronomy courtesy of Edwin Hubble and his research. We also touch on why the sky is blue and red and those physical phenomenon. We also explore the origin of starlight--accompanied by a very informative illustration! We also explore the consumption of gas in stars.

We then get to learn about the charge coupled device, CCD. This was a good, brief introduction too how this instrument is used in astronomy.

Next, we explore the evidence of dark energy. This also includes a nice summary of the effects of gravity and relativity. This includes the Sachs-Wolfe effect. We also learn about standard candles here.

As the book wraps up, we learnm more about black holes. We also learn about quasars and the supermassive black holes. The last chapter is about trying to detect signals from the very early universe. This is an excellent exploration of the difficulties we face and what we're looking for to reveal answers to questions touched on earlier in the book. Here we are also reminded of our attempts to send spacecraft into the greater universe. We touch on the pioneer spacecrafts. We also learned about the Crab nebula supernova of 1054.

Overall, this is a pleasant read. It is certainly more specific and in-depth than A Brief History of Time. It certainly is a good follow-up to that book, though! Also, it is a relatively quick read with easy to follow presentation of material and very good flow. My hesitation in only four stars is that such material is necessarily dry and nearly impossible to present at a five-star level!

[Mills College Library]

523.01 G292 2018