One of the challenges our exhibitions and interpretation teams faced when putting together the Ships, Clocks & Stars exhibition was how to get across the sense of being truly lost at sea to an audience who, with the help of their the smart phones in their pockets and other modcons, have likely never truly felt what it means to be lost.

They rose to the challenge admirably and the introductory space of the exhibition (including what I refer to as the ‘storm wall’) projects a seascape with absolutely no landmarks as far as the eye can sea, and the atmospheric Van de Velde painting gets across the sense of danger of not having the technology available to help you find your longitude and therefore navigate your way out of stormy seas to safety.

Willem van de Velde, Two English Ships Wrecked in a Storm on a Rocky Coast, about 1700

These are contrasted with a small number of objects that represent why so many people were risking their lives not knowing where they were at sea: trade and the wealth that it brings.

Lewis Dartnell’s latest book, ‘The Knowledge’, uses a different kind of approach to get across this sense of ‘a time before’. The book is based on the thought experiment of, if the apocalypse has come, what is the most useful information you’d need to get civilisation back on track as quickly as possible. Lewis’ book covers topics ranging from agriculture to chemistry: everything you need to kickstart civilization-including how to work out where you are and what time it is. This is exactly the same problem faced by navigators at the beginning of the 18th century.

Lewis Dartnell will be discussing his new book on Thursday 27 November at National Maritime Museum Lewis Dartnell will be discussing his new book on Thursday 27 November at National Maritime Museum

One of my favourite things about the book is the role it posits for museums after the apocalypse. Spinning machines or steam engines can be reverse engineered from those in museum collections, and where else are we going to get the rudimentary ploughs we need to kickstart agriculture after the apocalypse? Similarly, if we want to work out where we are in the world, the National Maritime Museum has plenty of sextants to be pilfered*

Lewis Dartnell will explain how to make a rudimentary sextant on Thursday 27 Nov Lewis Dartnell will explain how to make a rudimentary sextant on Thursday 27 Nov

However, if Greenwich has been abandoned once the apocalypse comes, as Lewis says, once you’ve rebooted the basic capabilities for shaping metal, grinding lenses and silvering mirrors (all expertly covered in Chapter 6: Materials), you’ve got everything you need to make your own sextant. But what good are they to us if we don't know how to use them to work out where on earth we are? Luckily, next Thursday evening Dr Lewis Dartnell will be on hand to explain some simple observations you can make yourself, to work out where in the world you are.

Lewis Dartnell talks The Knowledge: How to rebuild our world from scratch next Thursday 27 November 2014

*Only in the case of the apocalypse