Carl Zimmer’s Brief Guide to Writing Explainers

Carl ZimmerCourtesy of Carl Zimmer

Carl Zimmer

Imagine you’re a crime reporter writing a story about a shooting at a nightclub. Now imagine that none of your readers know what a gun is.

Suddenly, your story got a whole lot harder to write.

You can’t just jump into the shooter’s backstory, or the victim’s suffering, or the detective work that led to an arrest. Instead, you’ve got to explain the chemical properties of gunpowder, the physics involved in an explosion pushing a bullet down a gun barrel, the speed at which a bullet strikes a victim, and the effect that such a projectile has on the human body. And as you work on your explanation, you start wondering about other things you may need to explain. Maybe you need to explain how bullets are made, or why the materials in a bullet make it so deadly. Maybe you should explain the mechanism by which the shooter’s Beretta automatically loaded a new bullet in the chamber after each shot, so that your readers will understand why the victim ended up getting hit by so many bullets in so little time. The possibilities become paralyzing.

Welcome to the science writer’s dilemma. Science writers tell stories about things that many readers are unfamiliar with. Things like quasars, bosons, reversals of the Earth’s magnetic field, and the mating habits of bedbugs. Science writers can’t simply write stories about these things. They have to explain them along the way.

A good explanation achieves a happy medium between too little and too much. If you assume that your reader knows as much as you do, you will be prone to leaving out crucial information. It can be hard to notice what’s missing from an explanation, because every part of it exists in your mind, if not on the page. You read your drafts in the same way we look at optical illusions and fill in the blanks to create a complete shape.

There are only two ways to avoid this mistake: either have someone else read your story—someone who’s not an expert on the subject, of course—or develop the ability to override your own in-filling instincts. Paradoxically, the more expertise you have in a subject, the harder this journalistic brain training will become. If you learned about superstring theory 20 years ago in grad school, it will be challenging for you to imagine what it’s like to be someone for whom superstrings are not as simple to understand as parallel parking (or perhaps easier, depending on your driving skills).

But filling in the gaps is not the same as burying your reader alive. It’s a mistake to assume that in order to explain something, you have to deliver a semester-long introductory lecture course. It’s true that we can all learn a lot from a semester-long introductory lecture course, but we don’t expect to enroll in one whenever we open up a magazine or visit a news website.

What we expect, instead, are other experiences: a story, in some cases; an argument, in others. If you spend all your time explaining rather than telling a story or advancing an argument, the structure of your writing will collapse under that explanatory weight.

Thus, the most important step in explaining something well is to figure out what’s the minimum amount of explanation required for readers to understand your overall piece. How little explaining can you get away with? Once you’ve worked that out, then you have given yourself a clear set of goals to achieve. You can then try to make your explanation as delightful to read as the most unexpected plot twist.

There are many tricks and tools you can use to build up good explanations. Metaphors, of course, are essential. Rather than trying to break down an explanation into a buzzing swarm of details, think of an image that neatly wraps up those images into one concept and conveys the gist of what you want to say. If you’re interviewing scientists as part of your research for an explanation, ask them if there’s a metaphor that they like to use. You’ll be surprised how often people who deliver semester-long lecture courses can distill an idea into a few evocative words.

In some cases you deal with an explanation quickly and then move on. But sometimes you have to deal with some truly massive idea. In these cases, it’s often a good move to disperse pieces of the explanation throughout your story. The only reason you can explain global warming to your readers, for example, is that for a couple centuries, people have been struggling to piece that explanation together. Tell the story of the explanation, rather than giving the explanation itself. While few people are ready to sit down for a semester-long lecture course at the drop of a hat, we’re all up for a good story.


Guest contributor Carl Zimmer is a columnist for The New York Times, where his Matter column appears each Thursday. His books include Parasite Rex and Evolution: Making Sense of Life. His work has earned awards from the National Academies of Sciences and AAAS, and in 2015 he won the National Association of Biology Teachers Distinguished Service Award. Zimmer is a lecturer at Yale, where he teaches science writing. Follow him on Twitter @carlzimmer.


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  2. Great post, Carl! A reply to Dan Janzen: Every place I have seen Carl’s writings appear where it is pretty easy for him to know the knowledge level of his readers (e.g., Science Times section of NYT). The only difference is when his science news story is of such great popular interest that the page will be emailed by us NYT readers to a heck of a lot of our friends.

    So, Carl, post a blog on how you tweak your stories for those (albeit rare) incidents.

    P.S. to everybody: Know that I learned about this blog via Kirk Englehardt’s weekly list of most talked about science communication posts:

  3. “Instead, you’ve got to explain the chemical properties of gunpowder, the physics involved in an explosion pushing a bullet down a gun barrel, the speed at which a bullet strikes a victim, and the effect that such a projectile has on the human body.”

    Why? “The killer, armed with a small weapon which propels potentially lethal projectiles from a distance, approached his victim in an aggressive manner…” And off you go. Any further necessary explanation can be dropped into your narrative as it unfolds.

  4. Carl: you forgot to mention the other side of your quite correct coin (which applies to conversations as well as writing). There is no “reader”. There is a swirling collage of different readers with different desires as well as different knowledges, and you don’t have the luxury or energy to write 16 versions for 16 different guilds. The other side of your coin is asking yourself who are going to be the readers before you concoct the story. Writing for 4th graders is quite different from writing for graduate students in ecology, though the topic may be the same (e.g., “can two different species mate and have viable offspring?”). Smile. Dan Janzen

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  6. This is excellent guidance. And perfectly applicable as well for scientists (or anyone) giving public presentations on complicated topics. The perspective of the audience member, like the reader, is “I want you to explain something to me because I’m interested and curious about it, but I don’t want to take your semester-long course.”

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