Did the ancient Egyptians build their impressive monuments with the help of the world's first protractors? A paper published last week on the physics preprint server suggests that the mysterious object in this picture, found in the tomb of an ancient Egyptian architect, could have been used as one.

The architect was called Kha, and he lived during Egypt's 18th Dynasty, around 1400 BC (shortly before the reign of Tutankhamun). His intact tomb was discovered by the Italian archaeologist Ernesto Schiaparelli in 1906, located in Deir el-Medina, which was a village for the workmen who constructed the royal tombs of that time.

Kha was buried with his surveying instruments, including cubit measuring rods (one of them foldable) and an instrument that looks like a modern set square. It would have been stood up like an A frame, with a plumb line hanging down from the point of the A, to show whether a surface was level.

Then there's the strange wooden item pictured, with a circular section bulging out of a straight bar. It is hollow inside and has a hinged lid, so it seems to be a case for something, although it was found empty. Schiaparelli thought it held a levelling instrument. The Egyptian museum in Turin, where the objects are now on display, identifies it as the case for a balance scale.

But Amelia Sparavigna, a physicist at the Politecnico di Torino in Turin, Italy, now suggests that whatever the case originally held, it could also have functioned as the world's earliest known protractor. Sparavigna has applied her physics expertise to archaeology before. For example, she has used an imaging processing method developed for studying liquid crystals to identify archaeological features in satellite images, and has investigated the symmetry in ancient seals.

I've written a short story for New Scientist on Sparavigna's latest paper, but here's the story in a bit more detail. She has analysed the decoration on the circular section of Kha's mysterious case. It includes a rose pattern with 16 evenly spaced leaves, and a circular zigzag with 36 corners. Both numbers, 16 and 36, were significant to the ancient Egyptians. The fraction one-sixteenth features in a calculus system the Egyptians used, says Sparavigna, and they identified 36 star groups called the decans, which later formed the basis of a star clock. She suggests the object was "a protractor instrument with two scales, one based on Egyptian fractions, the other based on decans".

She thinks Kha could have used it for measuring the angle of a slope or wall, or even to orient temples of tombs to specific astronomical directions. If you placed the straight portion of the instrument on the slope and then you could read off the appropriate angle from vertical using a hanging plumb line - she was kind enough to send me this graphic of how she sees it working.

I asked Kate Spence, an archaeologist at the University of Cambridge who specialises in ancient Egyptian architecture, what she makes of the idea. She describes the idea was "intriguing" but is very sceptical. She says that ancient Egyptian measuring instruments tend to be carefully made and precise with neat labels. "They look like measuring instruments," she says. In contrast, the design on Kha's case isn't particularly even and looks decorative. What's more, to use the instrument as Sparavigna suggests would involve resting it on its hinged lid, which is slightly rounded. "If it was to be a surveying insturment, the solider and squarer the faces of the flat bit the better," she says.

There's no doubt that Egyptian architects and engineers were capable of very precise work, however. Spence says that if they wanted to, architects could orient a building to within a few sixtieths of a degree. But they wouldn't necessarily have needed a protractor. Instead, the Egyptians expressed slopes and angles in terms of proportional ratios - for example you might create a 45-degree angle by measuring along two cubits and up two cubits, rather than specifying the angle itself.

The Egyptians knew how to divide up a circle too. On the ceiling of the tomb of another 18th Dynasty architect called Senmut, there is a series of circles (pictured). These have been divided into 24 equal sections by drawing squares around the circles, and seem to be associated with the hours in the day. "They look mathematical, the case doesn't," says Spence.

Sparavigna stands by her suggestion, and I think it's a fascinating idea, although I do find Spence's arguments quite convincing. So, Kha's case aside, when did protractors first appear? I asked Tracey Rihll, an expert in Greek and Roman technology at Swansea University and she said that there's a Roman example of a surveying instrument similar to a protractor in the Aquincum museum in Budapest.

But it may have been the Greeks who invented them. The first-century astronomer Ptolemy described how to make a 360-degree ring, and a 90-degree quadrant, so it was apparently routine by then to make instruments to measure angles. And of course the Antikythera mechanism, which dates from the 2nd century BC, has a 360-degree dial on it too.

Thanks to Sparavigna for sending me the picture of Kha's case (copyright Jane Maria Hamilton).

Yesterday I posted my talk from the literary storytelling session at the recent World Conference of Science Journalists in Doha, Qatar. Here's a follow-up post, with some brief comments on the other talks, as well as some tips and recommendations from all the panellists that we didn't have time for in the session itself.

I was lucky enough to be on a panel with David Dobbs and George Zarkadakis. David writes features and essays on brain and behaviour for publications including the Atlantic, New York Times and National Geographic (including this great piece on the genetics of temperament) and is now working on his fourth book. George has experience in writing both fiction and non-fiction. He has a PhD in artificial intelligence and is a novelist, playwright and science journalist, as well as having worked as a magazine editor and book publisher.

The focus of the session was the challenges of writing longer articles, over four or five thousand words. David talked about the importance of getting the right structure. For long pieces, he pointed out, the conventional feature template of lede, back story, narrative and close doesn't work - each individual section is too long, and the reader will get impatient. He suggested cycling through those elements, having mini-features within a feature, to keep the reader interested. When you change the scene, he said, you can vary things like the voice you use and how zoomed in you are, like changing the focal length of a lens. He also talked about learning from the structures used in music or drama, for example the idea of introducing a new character towards the end of the second act.

I loved George's talk too, he spoke about the importance in fiction or narrative non-fiction of making connections - your chapters can't be separate blocks of information. He explained the use of mind maps for getting all of the elements of your story down on one page, so you can see them all at once and chart the links between them. These could be between different people, ideas, fields or time periods, for example. These are your added value - links that perhaps the researchers themselves haven't even made. Both George and David said that they keep diaries when they're writing a book to record what they've done each day and keep track of these connections.

Another thing we talked about was the importance of knowing what to cut. When I started writing my first book I got excited about finally having space to put in all of the fascinating (to me) details and anecdotes that I unearthed in my research. I soon realised that you have to be just as disciplined - perhaps even more so - than in a shorter piece in knowing what to cut.

That's because you're expecting people to invest a lot of time in your piece, it's quite an endurance test and the reader can get distracted easily. Sometimes I think it's like clinging to a t-bar ski lift as it pulls you up a mountain. If there are too many lumps and bumps the reader's concentration will waver - they'll fall off and they won't get on again. As a writer, everything you leave in has to play a role in supporting or moving on your narrative (something that I think applies to blogs too - having unlimited space doesn't necessarily mean you should use it...)

The famous "kill your darlings" quote came up of course. I'm not sure who said it first, some people say Hemingway, some say William Faulkner, but this blog post says that it comes originally from the British author Arthur Quiller-Couch (pictured), describing "style" in his 1916 publication On the Art of Writing:

"Whenever you feel an impulse to perpetrate a piece of exceptionally fine writing, obey it -- whole-heartedly -- and delete it before sending your manuscript to press. Murder your darlings."

George quoted a great line from the French writer and aviator Antoine de Saint-Exupéry: "A designer knows he has achieved perfection not when there is nothing more to add, but when there is nothing left to take away." And David mentioned a lovely passage written by Janet Malcolm, in which she describes the biographer's struggle of knowing what to throw out, and likens it to clearing the clutter from a crowded house (see his blog post).

Alok Jha, who chaired the session expertly, had asked us all beforehand to come up with some tips and recommendations for the audience. We got so carried away with the discussion that we didn't have time for them in the session itself, but George and David have kindly emailed their notes to me, so here they are below:

AN ARTICLE OR BOOK THAT BUDDING WRITERS SHOULD READ TO GIVE A SENSE OF GOOD WRITING

David recommends Beware of Greeks Bearing Bonds, a Vanity Fair piece by Michael Lewis. He says:

"It's about finance, not science, and that's part of the point. Lewis, one of our very best longform writers, faces a task similar to that of writing about science: Explain the workings and consequences of a seemingly arcane, jargonophilic discipline (finance) in a way that engages the reader. He doesn't just engage you: He provides wild, raucous, riveting entertainment - theater, really - in a way that gets all the essentials right and sets up a magnificent close. A huge percentage of what you need to know to write well and beautifully is in this piece."
(For another perspective on the financial situation in Greece, see George's recent blog post)

David's second recommendation is Song of the Dodo, by David Quammen:

"One of the best books, period, written in the last two decades, and easily one of the best science books written in the 20th century. If I could have only one grocery bag full of books to read for the rest of my life, this would be in it. As with Lewis, this is not an explanation but a story, a tour of a new and important idea about evolution told through visits with smart, driven, startlingly original and articulate scientists. Quammen is one of our very best; I don't know a science writer I'd rank above him. He's also grievously underrecognized, and I'm shocked far too often to discover that many science writers have never heard of him. He's magnificent, and this book is a tour de force. It also has one of my favorite sentences of all time (ranking close behind 'Shut up,' he explained.'): 'Cor! You don't see that every day, do you.' When you hit it you'll know why."

My choice was Gilgamesh, in particular an English version published in 2004 by Stephen Mitchell. The Epic of Gilgamesh is the oldest known work of world literature - written down on clay tablets in ancient Mesopotamia in the second millennium BC. I love the writing because it is simple, clean and direct, there are no wasted words. Yet the prose has an energy and a beauty, it feels alive. It switches effortlessly from the broad and sweeping to the personal and intimate. Much of this is Mitchell's work, but I wonder if it also owes something to the oral tradition which would have been like a continual editing process every time the story was told out loud - it would have been instantly clear to the narrator from the audience's reaction which bits worked and which bits didn't.

The prologue describes how the hero, the king of Uruk, has been on an epic adventure - experienced all emotions from exultation to despair, journeyed to the edge of the world and back - and carved his trials onto stone tablets. The narrator invites the reader to admire his gleaming city, the mighty walls, gardens, orchards, palaces and temples. Then it tells you to climb the ancient stone staircase:

"Find the cornerstone and under it the copper box
that is marked with his name. Unlock it. Open the lid.
Take out the tablet of lapis lazuli. Read
how Gilgamesh suffered all and accomplished all."

I love this because it sucks you right in, straight away you imagine opening the box, taking out those tablets and starting the story...

TIPS FOR SOMEONE LOOKING TO IMPROVE THEIR WRITING TOOLKIT

Here are David's:

1. Read lots of good writing --- and read hard. Read the great things things two or three times. And by all means, read a mix of science and of things NOT science. And learn to read to take it apart and see how it works and how they solve problems. Mark the good points and go back later to see how they work. Read to steal. Which is to say, not to take a tactic or strategy and imitate it, but absorb it and fully understand it and make it an integral part of how you write. (Knowing how to throw a curve ball isn't enough; you have to know when and where to throw it.)

But you can't steal unless you learn how to read first. How does John McPhee move so smoothly between places in time? (Answer: He finds the right structure first.) How does Janet Malcolm move herself and her own observations in and out of scenes? Why does Michael Lewis put himself in some stories as "I" and leave himself completely out of others? How does David Quammen get away with opening a book with 80 pages of backstory? What makes Vladimir Nabokov's sentence (in Lolita), These burst. so incredibly effectlve? How does Deborah Blum manage to generate sympathy for Harry Harlow's work even while conveying the horror of some of his experiments? What decisions does Rebecca Skloot seem to have made about handling her first-person presence in The Immortal of Henrietta Lacks?

Answering some of these questions will take you only minutes or hours. Others may take days or weeks. But every time you answer one, you'll add an invaluable arrow to your quiver.

2. When you get to your later drafts. READ THEM OUT LOUD. The sour junk will rise to the top, and you can throw it out.

George seconds those tips and adds two more:

1. Respect for the economy of language. In every language there are many ways of expressing the same thing but only one that is the simplest. Chose this one and make sure is from the heart.

2. Connect with the reader. A writer is a reader who mutated. Often this mutation causes selective amnesia: the writer forgets that she was once a reader. Reconnect with your previous self and talk to her about what moved you in the subject you chose to write a book about. Do not presume that being smart is enough. A book full of smart ideas but no emotion will vanish swiftly in the all-devouring quicksand of indifference.

I couldn't agree more with the above. My tips are just a couple of things that I do sometimes to get over that feeling of staring at a blank page.

1. Brainstorm then edit
If I want to convey an elusive feeling or thought and I'm not sure where to start, I write down individual words and phrases that seem to capture any part of it. I try to switch off any inhibition, I don't worry about sentences, or whether what I'm writing makes sense logically. It's just a cloud of words that pop into my head and feel as though they might be at least partly right. Then, once I have those raw ingredients on the page, I become more analytical/critical and try to make a piece of sensible writing out of them.

2. Stream of consciousness then edit:
If I want to get a story to flow, then I read through my notes and sources to get the events straight in my head. Then I put all those notes to one side and just write the story down. I don't stop to check dates, facts etc -- if necessary I'll just put in xxs where I can't remember exact details, I just try to write the story all in one go, as I'd tell it to a friend. I do it longhand because it stops the temptation of editing as I go along. I just write it all down in one go, with no stopping or thinking about it too much. Then, only once I've got the story down, I'll go back and edit - clean up sentences, check quotes, facts, figures, cut unnecessary bits. The aim is to end up with a narrative that hopefully has some pace and energy to it.

If anyone has any more tips or reading recommendations, or writing experiences to share, please do comment below.

When the Guardian's Alok Jha asked me to speak on a panel at this year's World Conference of Science Journalists on the importance of narrative in science journalism, I agreed straight away. After a decade writing and editing for Nature and New Scientist I felt well qualified to discuss the topic.

Subsequently, the title of the panel changed to "literary storytelling" - a small tweak but one that filled me with fear. Writing clear, engaging science news is one thing but when it comes to "literary" writing, well, that's a different world in which I feel a complete beginner.

The other speakers on the panel - David Dobbs and George Zarkadakis - are experienced authors, with many beautifully written long-form articles and books to their names. I have written just one book.

So I decided to talk about what it was like making that first step in the transition from "science reporter" to "author". What was the biggest mistake I made, and how did I have to change the way that I write?

A lot of the points I'm about to make may seem obvious to anyone trained as a "proper" writer, but for me, coming from a science background and used to writing for outlets like New Scientist and Nature, it required quite a paradigm shift. In fact, I think there are certain things about some kinds of science journalism that actively inhibit the parts of the brain and ways of thinking that you need for creative writing.

I was used to writing in a very logical, left-brain way - news journalism is pretty much about finding out facts, and putting them in the right order. Space is at a premium, so you have to convey information in a very economical way, with a fact in every sentence. What was done, who by, how, what did they find?

You have to explain complex technical concepts clearly and unambiguously. You talk about what things mean in a very analytical way. You don't generally put in anything of yourself - your thoughts or emotional reactions (or if you do, your editor will take them out). Constructing a story is a bit like constructing an argument.

Then I came to write my book, which is about a mysterious astronomical computer found on an ancient shipwreck. The first chapter should have been a dream of a tale. In 1900, sponge divers crossing the Mediterranean were blown off course by a storm, and took shelter by a rocky islet. The next day they dived into the water and discovered a wreck, filled with treasures from ancient Greece. They spent the next 10 months salvaging the artefacts in a treacherous mission during which one of them died of the bends, and two were paralysed.

I did painstaking research, raiding historical archives and translating old Greek documents to find out as many details as I could about the episode. When I wrote the chapter, it was clear, well-structured and packed with facts. But I discovered that what works for a New Scientist news story doesn't necessarily work for an 8,000-word book chapter. I gave my draft to a journalist friend to read and he came back to say that it was dense, flat and unmoving - a barrage of facts that was exhausting to read.

I realised that I needed to relax, and slow the pace right down. I couldn't just relay information, I had to really tell a story. It was a harsh lesson that to sustain a reader's attention over a long span, you have to say what things mean as well as just what happens. You have to transport the reader into the story, to carry them along with you.

I'm sure there are much better names for this but as I went through the book I started thinking of it as "inside out writing". Instead of processing and conveying facts in quite a superficial way, you need to internalise all of the information that you're gathering, to think very honestly and deeply about what it means, have an emotional reaction to it, and then try to bring that out in your writing.

I would do all my research for a particular scene, then try and turn off my left brain. I'd shut my eyes and imagine being there; think about the sounds, sights, smells; what the characters would have been feeling; the greater significance of the events I was describing.

I think there are a couple of overlapping aspects to this. The first is to describe a scene in a lifelike way, put the reader right in the middle of things. Think about involving all five senses to capture the feeling of a particular moment. Maybe it's looking up to see shafts of sunlight shining down through the water, or hearing the sound of helicopters whirring overhead like ravenous giant mosquitoes (the mosquitoes are from Andrew Smith's book Moondust: In search of the men who fell to Earth, which I think does this really nicely).

 To do this you don't have to be writing a narrative-led or biographical book, it can be important even in the more traditional type of science book, that discusses a particular subject. For example, Being Wrong by Kathryn Schulz (which I absolutely love) is about how holding false beliefs is part of being human, and how good we are at convincing ourselves that we're right even in the face of overwhelming evidence that we're wrong. There's a chapter about how often witnesses make mistakes when identifying criminals, and how the strongest, most emotionally charged memories are the most likely to be false.

In this chapter, Schulz tells the story of a woman who is raped while running alone on a beach. Her description is powerful and immersive, she makes you feel that woman's fear, her pain, her strength of will, her determination to remember, how she made sure that every detail of her attacker's face was etched onto her memory. After reading it, you feel some of the same shock and disbelief when you later find out that she had emphatically identified the wrong man.

The other aspect to inside out writing is that you need to get beyond simply saying what happened, to say what things mean, and what they mean to you.

Saying what something means is of course the role of a writer. You're trying to capture the essence of something, to give it a meaning that's personal yet universal. Often when I was writing I'd have this elusive feeling about why something is important - about how events or ideas were connected or why I wanted to include a particular anecdote. But I'd struggle to put it into words. That's the important bit, that's what you have to try to drag out from inside, and to express on the page.

In her book Longitude, Dava Sobel opens one chapter with her musings on time: "Time is to clock as mind is to brain. The clock or watch somehow contains the time. And yet time refuses to be bottled up like a genie stuffed in a lamp. Whether it flows as sand or turns on wheels within wheels, time escapes irretrievably, while we watch."

This passage doesn't contain any facts, and it doesn't move on the story at all. But I think it was important for Sobel to stand back at that point and give a very human account of what the essence of her story is about.

It is possible to do this even in shorter news pieces too, but it's rare. One example is an 800-word news article written by James Meek, which ran in the Guardian in 2003 (thanks to Ian Sample for passing it on to me). The article was about Iraqi families and soldiers who tried desperately to get inside government buildings after the fall of Saddam Hussein, clinging to the belief that their loved ones who had gone missing during the regime might still be alive, kept in secret underground cells.

The first two paragraphs describe fairly conventionally what is happening, then the first sentence of the third paragraph hits you like a bullet: "Those who have lost what they loved the most are always the richest in hope." For me, this one line crystallises the human meaning of the story.

Of course this is what proper writers do all the time. But as a news journalist, and I think especially a science journalist, it can feel like a huge change. In trying to take this approach I felt that I was breaking a lot of ingrained rules. To tell a real story you have to be subjective, creative, emotional even, but to write about science you have to be accurate, clear, unambiguous, and not mess with the facts themselves. There is always going to be a tension between those conflicting principles.

Despite all my experience as a science journalist, the biggest thing that writing a book taught me was how much I have to learn about what it actually means to write well about science (or anything else, for that matter). If there are any other scientists or science journalists out there dealing with similar issues I'd love to hear about your experiences.

*** The picture is a portrait of the Russian short story writer Vsevolod Garshin, just because he looks like he found writing tough too...

Here's a short video about the Antikythera mechanism posted last week by the Greek ministry of culture and tourism, the Swiss watchmakers Hublot, and the 3D video magazine NVP3D. It includes animations of the mechanism, shots of a wristwatch based on the device, and some lovely footage of the island of Antikythera. Definitely worth 7 minutes of your life. This video is in 2D, but there's a 3D version too (you need a stereoscope), or you can watch it in French.

I just got back from a really fun week in Doha, Qatar, at the World Conference of Science Journalists. I gave two talks there so I thought I'd put what I said into a series of blog posts, in case they're of interest to anyone who wasn't able to attend.

In the next couple of posts, I'll pass on what I had to say about "literary storytelling" in science journalism, and give some tips and recommendations from all the panelists that we didn't have time to talk about in the session itself.

But first, let's talk about the other panel session, on the role of history in science journalism. This panel was chaired by Tom Levenson of MIT, and the aim was to talk about how historians and reporters can use the past to write better science stories. The other panelists were the authors Deborah Blum, Reto Schneider and Holly Tucker.

Deborah spoke beautifully about how she explores the different paradigms or frameworks of thinking that enclose and define science at different points in history. For example, the assumption in the first half of the 20th century that "love doesn't exist" provided the context for the psychologist Harry Harlow's controversial experiments on mother-child bonding in monkeys, which she describes in her book Love at Goon Park.

Reto argued that science news is over-rated, and suggested that perhaps we should redefine it as interesting stories in science that people don't know. And he showed us how he is using Google Maps to plot the locations of different weird science experiments through history.

Holly described her book Blood Work, about the first blood transfusions, performed in the 1660s, and talked among other things about how looking at early science gives us context to discuss our own responses to technological innovation. It reminded me of a feature I wrote recently for New Scientist, about George Church's work on genome engineering. He predicts that his techniques could soon allow us to engineer virus-resistant humans. That might seem like ethically a really bad idea, but he argues that so did IVF and organ transplants when they were first introduced.

I also really liked a point Tom made about historical biographies. Although their subject is in the past, he said, biographies are actually about the present, reflecting the concerns and agenda of the writer's own time, rather than that of the subject.

My job was to talk from a more practical point of view as a science reporter. How can you use history to add depth and value to a piece of science journalism, whether it's a short news article or a whole book? For me, four approaches immediately came to mind:

1. Telling a story

A fairly obvious use of history is that including a chronological narrative - describing a series of events over time, for example following the trials and tribulations of the characters involved in a particular area of science - allows you to convey your subject as a compelling human story.

This can be a personal history - events as they happen to an individual or group of individuals, for example. The reader gets a feel for personal motivations, invests in the characters. He or she can root for particular people, or see them through challenges and setbacks. You can have feuds and battles, with winners and losers. Or it can be an intellectual history - in other words the history of the development of ideas. So the reader gets carried along by that intellectual journey as well. The ideal story would probably have both kinds of history.

A story like this can be set thousands of years ago, or last century, last year or last week. It can focus on a particular episode in time, or it can involve a grand sweeping narrative. I think this kind of approach is especially important for science writing, where you're often dealing with complex, technical subject matter. You can explain concepts bit by bit as the plot unfolds.

One successful example is Longitude by Dava Sobel. It's about a race to develop a clock that could keep time at sea - to enable sailors to calculate their position. Simply writing about the technology involved, the exact design of the springs and escapements, is unlikely to have excited people on its own. It would still have been history, but it's the way Sobel used that history, how she turned it into the story of a race between competing rivals, that made it such a fascinating book.

Another is Fermat's Last Theorem by Simon Singh, about the reclusive scholar Andrew Wiles' solution of Fermat's 350-year-old maths problem. Singh could have just described the maths involved in Fermat's theorem and Wiles' solution, but telling the history of both of these things is what really brought the subject to life. In both cases, the historical story gives you a human dimension and a plot.

In shorter articles, even news articles, using a historical sequence of events can still give you a plot line, an internal logic that drives the story forward. This can be just a small part of the article, it doesn't have to be the whole thing.

For example, I wrote a feature for Nature recently about an argument over Egyptian mummy DNA - some groups are publishing papers on this DNA, while other groups don't believe the results. In this article, I didn't want to just say "A thinks this, B thinks that". To show where the argument had come from, I went back to the origins of the ancient DNA field in the 1980s, explaining the excitement as researchers realised they could amplify DNA from ancient samples, and the harsh lessons they learned as it became clear how many studies had been ruined by contamination. The "sceptics" in the argument had lived through that experience, while many of the "believers" had come in later from other fields. This history doesn't tell you who is right, but it gives you a deeper perspective on the debate. And it gives you a story instead of a static argument.

Even when writing short articles I would always ask researchers how they got into a particular field and why they did a particular study, to get a sense of what is driving them and what has gone before. Even just a sentence or two on that can be enough to sweep the reader into a story.

2. Judging what's new, and what things mean

News is about the present, but an understanding of history is still vital because otherwise how do you know what's new? I think this is particularly important for science journalism because science is all about how our understanding progresses over time. You can't judge the significance of a step forward unless you know where you've come from. In science, it makes all the difference in the world whether something is being done for the first time or for the hundredth time.

Imagine you're writing a story about a cloned chimp embryo. Have scientists cloned a chimp embryo before? A primate embryo before? Has a cloned chimp been born before? You can't necessarily rely on press releases because they often have a vested interest in presenting a story as new. So if you're not already familiar with a field then you need to ask other experts how a new finding compares to what has gone before. This is important when choosing whether to cover a finding, but it is also important information to include in an article for the reader. It doesn't have to be written as a chronological sequence of events, but it does need to be in the story.

Having this perspective is what turns a vacuous account of events into a useful piece of analysis. I once spent some time doing work experience at The Economist, and I asked what was the secret of their success. One of the reporters said to me, it's the 3Cs: compare, contrast, context. To make meaning out of an event you have to set it in its place with what has gone before (as well as what else is going on at the time).

3. Transporting the reader

Writing about different historical periods in a long article or book is like travelling to different exotic places. It immerses you in another world where the landscape is different but so are beliefs, norms, the understanding of how the world works.

You can use the details of different historical periods to engage, surprise and transport the reader. You can also move between time periods to give variety and contrast. For example, my book Decoding the Heavens tells the story of a mysterious ancient Greek machine (called the Antikythera mechanism) that was found in a shipwreck, and the efforts of modern-day scientists to work out what it was. I wanted to combine stories from the astronomers and philosophers of ancient Greece, the archaeologists of the 1900s, and the high-tech scientists of today. That was all mixed in with other aspects of life in those time periods, from the Roman armies sweeping through the Mediterranean region in the first century BC to the sponge divers of the early 20th century with their clunky diving suits (pictured).

4. Gaining big picture perspective

Science is all about understanding, at deepest possible level, why things are the way they are. So I love looking at the big picture, being able to zoom out and see where a story fits in the grand scheme of things. Looking at things on a historical time line enables you to do that.

For example one aspect of understanding where the Antikythera mechanism comes from is to look right back in geological time to the forces that formed the copper and tin that went into the bronze that made it. Once you understand where the metal came from, you can understand why it was scarce, the trade routes that supplied the bronze, and the reasons why bronze objects were valuable and were almost always melted down and reused. This all feeds into why there are so few artefacts like this that survive from the ancient world.

Or, to understand how the survival of particular kinds of object colours our view of ancient societies, you can look far forward to imagine how our own society might look to the archaeologists of the future.

A nice example of this big picture historical perspective is Fermat's Last Theorem. Singh doesn't just go back to Fermat's work in the 17th century, but to the origins of mathematics in ancient Greece. Another lovely book, Life: an unauthorised biography by Richard Fortey, tells a 4-billion-year story. Time lines don't get much bigger than that.