Skip to main content

Celestial Calculations - J. L. Lawrence ***

These days, amateur astronomers don’t need to do any calculations. If their telescope is of the ‘go-to’ kind, they just type in the name of the object they want to observe and the telescope does the rest. If they have an old-fashioned manual telescope, or if they want to see something that isn’t in the telescope’s database – such as the ISS or a satellite – they consult a mobile app or a website. With all these handy software aids, it’s easy to forget that what they’re doing – in a fraction of a second – is a long series of calculations of the sort astronomers used to have to do by hand.

 Those calculations are what this book is all about – but before you go running for the hills, there’s no advanced mathematics in it. You’ll scour it in vain for differential equations, complex numbers, logarithms or x-y graphs – for the simple reason that none of those things existed when astronomers started doing the calculations we’re talking about. It does use a few trigonometric functions like sines and cosines – originally developed by the ancient Greek astronomer Hipparchus, not as a sideline but because he needed them for his day job – and anyone can find those buttons on a calculator app even if they’re not sure what they mean.

 Some of the things the book shows you how to calculate, particularly in the first few chapters, won’t even look like astronomy to many people. There are calendar and time zone conversions, sunrise and sunset times, and the dates of equinoxes and solstices – but all of these are ultimately based on celestial motions. When the book moves on to the subject of orbits – whether of planets around the Sun or satellites around the Earth – there’s another surprise. The usual approach in popular science books is via Newton’s theory of gravity – but that’s not how J. L. Lawrence tackles it here. That’s because gravity is physics, and that’s not what this book is about. If all you need is a geometric description of orbits, you can find it in the work Kepler, dating from the very beginning of the 17th century – which is as ‘modern’ as the calculations in this book get.

 Having written several books myself, I was struck by just how much effort the author must have put into this one. It’s close to 400 pages long, but that’s just the tip of the iceberg. By the very nature of the subject matter, Lawrence didn’t simply have to write words, he had to do calculations – sometimes several on a page. On top of that, the book comes with a suite of downloadable computer programs, which do things like plotting star charts and working out rise and set times for the Moon and planets. Of course, it’s easy enough to find other free software which can do the same things – often in a slicker and more flexible way – but here you get a step-by-step explanation of the logic behind the number crunching.

 For the sort of person who is excited by the title Celestial Calculations, this book will be perfect; they can look forward to hours of enjoyment working through the examples. The catch is, I can’t imagine there are many people in that category. For a more general reader interested in popular science or amateur astronomy – and that includes me – the book still provides some fascinating insights, but it’s so long and detailed that reading it often verges on hard work rather than fun. Personally, I would have enjoyed it more if it had been a third of the length.
Paperback:  
Kindle:  
Using these links earns us commission at no cost to you
Review by Andrew May
Labels:

Comments

Post a Comment

Popular posts from this blog

Why Nobody Understands Quantum Physics - Frank Verstraete and Céline Broeckaert **

It's with a heavy heart that I have to say that I could not get on with this book. The structure is all over the place, while the content veers from childish remarks to unexplained jargon. Frank Versraete is a highly regarded physicist and knows what he’s talking about - but unfortunately, physics professors are not always the best people to explain physics to a general audience and, possibly contributed to by this being a translation, I thought this book simply doesn’t work. A small issue is that there are few historical inaccuracies, but that’s often the case when scientists write history of science, and that’s not the main part of the book so I would have overlooked it. As an example, we are told that Newton's apple story originated with Voltaire. Yet Newton himself mentioned the apple story to William Stukeley in 1726. He may have made it up - but he certainly originated it, not Voltaire. We are also told that ‘Galileo discovered the counterintuitive law behind a swinging o...
Post a Comment
Read more

How to Keep a Plane in the Sky - Alex Davies ****

If there's one big gap in the science writing sphere, it's popular engineering (you can quibble over whether engineering is science, but where else would you put popular engineering?). Alex Davies does the field a real service with this insightful introduction to the world of test engineering. The concept is simple. If we build something and sell it, we need to test it to make sure that it won't fail in a way that's dangerous to the consumer. The most obvious example is airliners, which feature at some length, but this applies to everything from cuddly toys to hair straighteners: someone needs to predict what could go wrong and to put the product through its paces to see if it will survive under any reasonable circumstances. When Davies is telling a story of test engineering in action, the book is a delight. He opens with the way that real bears are used to test if bears can get into coolers and trash cans - and the impressive ways these animals can  circumvent human in...
Post a Comment
Read more

On the Equality of All Things - Carlo Rovelli ****

There is a wide gulf between the worldviews of physicists and philosophers. Many physicists present a rather sweetly naive, child-like view of the world, where philosophers bring a distinctly more adult, cynical tone. This being the case, it can be a little worrying when a physicist dips a toe into the philosophical mire. Infamously, in The Grand Design , Stephen Hawking and co-author Leonard Mlodinow told us that philosophy was now dead because science could deal with anything it had previously been needed for. Thankfully, Carlo Rovelli is not trying to do away with philosophy, though it has to be said that when he veers into the topic that physicist's naivety can make it feel like the philosophising of an earnest eighteen-year-old. Take the opening paragraph, which tells us 'electrons and minds, stones and laws, judgements and galaxies do not essentially differ in nature from one another. They are notions that illuminate each other'. I almost expected a Pink Floyd soundtr...
Post a Comment
Read more