Hearing that someone you admire is about to die is, to put it simply, shocking. Hearing this after you have poked the said person with e-mails to ask where’s the foreword he promised is even more so.

This was how I, unfortunately, learned that David JC MacKay was about to leave us far too soon. Back in autumn 2015, me and Rauli had just finished our “COP21 Edition” of Climate Gamble, and in the hectic days when we were preparing to print and hand out 5000 books during the Paris climate negotiations, we got a “great” idea: what if David JC MacKay wrote a foreword to the COP21 edition?

We both admired prof. MacKay greatly. His 2008 book, “Sustainable Energy: Without Hot Air,” remains the best overview of the energy/environment problem, its scale, and the potential solutions. It is fair to say that this book, more than any other, was the inspiration for us to try to write a no-nonsense book about nuclear energy and its potential role in the climate fight. I cannot praise enough David’s skill in conveying sometimes quite difficult concepts with quick back of the envelope calculations and lucid phrase; nor can I heap enough praise for his adamant demand to make the book completely freely available over the Internet. These decisions ensured that a relatively unknown professor from Cambridge became probably one of the most influential voices in the global energy/climate/environment discussion. Fortunately, his skills were recognized by the British government, which recruited him as the Chief Scientific Advisor for Department of Energy and Climate Change in 2009 and eventually knighted him in 2016. Notably, he was not a professor of environmental sciences: his own research concerned machine learning and neural networks!

Perhaps the greatest strength of his approach in Without Hot Air was its neutral tone. Professor MacKay presented the facts as he saw them, often derived from fundamental physics. By now, some of the calculations and assumptions in the book are beginning to be a bit dated and one may always take issue with a turn of phrase here and there, but the gist of the message remains solid: while renewable energy and energy efficiency are often great options and should be promoted, relying solely on renewable energy and efficiency is a risky strategy that may leave the Earth’s citizens burning fossil fuels to slake their thirst for reliable energy. As he noted in one of the many talks he gave about the subject, he was not pro-nuclear, but pro-arithmetic. The plan was not important: what was important was that the numbers added up.

Independently, we had come to similar conclusions and began to write a book detailing the “nuclear option.” At the time, we thought that having an endorsement in form of foreword from such a colossus would be undeniably helpful to us – as it indeed was. Little we knew that he had been just diagnosed with stomach cancer, advanced enough so that surgery was no longer an option. I recall thinking he must be busy with other things and mailed him at least four times, each plea a bit more urgent as our printer’s deadline approached. Finally, we received the foreword to our inboxes; in the message, he apologized for the delay as he had just got out of chemotherapy.

Needless to say, we were mortified, and dashed off letters of apology and support. We really should have read his blog, where he discussed the disease and its progress with heartrending openness. Probably for the rest of my life, I will feel bad for not doing my homework and taking precious time from him and his family, even though I’m extremely glad he wrote the foreword – and a good one, too.

One of my great regrets is that I never had the chance to know him personally, particularly as we have some mutual acquaintances and everyone spoke so highly of him – not just as an intellectual, but as a great guy to be around. A particularly nice account of David MacKay and the birth of Without Hot Air has been written by its publisher; my brief e-mail encounters fully support the picture of a man painted there. Unfortunately, I’m no poet and my words cannot do justice to what I feel, so I’ll just say that I thought David to be a very smart, very kind man who cared deeply: and not just that, but a true scientist to heart, following the evidence wherever it may lead.

David JC MacKay, father of two, husband, knight, professor, Fellow of the Royal Society, passed away on 14th April 2016, at 48 years of age. Too soon by far, but one may find some consolation in the thought that life should not be measured in years, but in deeds. At least by this measure, he truly lived. Although David himself may now be beyond hearing, I want to tell to his family, friends and acquaintances that he will be missed by people who never even knew him; and even though we will have trouble living up to the standards he set in his work and in his approach, we’ll try our best.

You can donate in memory of David MacKay to Arthur Rank Hospice Charity, which supports people in Cambridgeshire who are living with a life-limiting illness. To celebrate his memory, I’d also encourage anyone who’s not done so already to read his book, and recommend it to anyone who hasn’t. Let’s form the greatest study circle in history, shall we? – and let’s make sure his ideas and his methods remain in circulation and serve as a basis for even more measured and reasonable discussion about the great problem of the 21st Century.