8 January 2011 | NewScientist | 23

researchers have a responsibility to so engage. Discussions of scientific responsibility often centre on questions of scientific integrity. But researchers are also under an obligation to the public who have placed their trust in them – by their implicit contract with the state, which by funding them makes the product of their labour a public good.

For as long as the scientific knowledge they produce remains under their control, they are its custodians, responsible for its safe delivery into public hands. They have an obligation to convey the results of their expertise to those likely to be affected by the implications of those results.

They need to redouble their efforts to make their arguments, their doubts, and the reasons for both their confidence and their concerns intelligible to the non-specialist citizen. They need to combat, piece by piece, the misrepresentations brought in support of attacks on their scientific integrity, and to show readers why the popular accounts and even the naming of “Climategate” are so misleading. And they need to explain why the expectations of science on which these accounts are based are similarly misleading. Doing so is rarely as difficult as they assume: disagreement, uncertainty and distortion are familiar territory to most readers who, even without specialist technical expertise, are capable of the discrimination needed to establish trust.

What I am proposing is far from a solution. But if it encourages climate scientists to take the lead in breaking the current impasse, both because they are best equipped to take on the task, and because their responsibility as scientists obliges them to do so, it is at least a start. n

Evelyn Fox Keller is emeritus professor of the history and philosophy of science at the Massachusetts Institute of Technology

Comment on these stories at www.NewScientist.com/opinion

What’s wrong with pi? Of course, pi is not “wrong” in the sense of being incorrect, it’s just a confusing and unnatural choice for the circle constant. Pi is the circumference of a circle divided by its diameter, and this definition leads to annoying factors of 2. Try explaining to a 12-year-old why the angle for an eighth of a pizza – one slice – is pi/4 instead of pi/8.

So what should replace pi?In The Tau Manifesto, which I published last year (see tauday.com), I suggest using the Greek letter tau which is equal to 2 pi, or 6.28318… instead. Tau is the ratio of a circle’s circumference to its radius, and this number occurs with astonishing frequency throughout mathematics.

If this idea is so fundamental, why haven’t we made the change before?The paper that got the ball rolling on this, “Pi is Wrong!” by mathematician Robert Palais, traces the history of pi. It’s only in the last 300 years that this convention was adopted, and I think it’s just a mistake. It’s one of those times in history when we chose the wrong convention.

And you are here to correct that mistake?Yes. The aim of The Tau Manifesto was first and foremost to be fun, but it’s true that I would like pi to be replaced by something more sensible.

Have you had much success?It’s definitely getting some traction among geeks. Eventually I think there is going to be a groundswell of support for it.

You are up against a formidable enemy, because pi is a popular constant…It is: there are books written about it, and people care enough to memorise tens of thousands of its digits. Google even changed its logo to honour pi on 14 March 2010 – Pi Day.

Doesn’t using tau ruin equations like the formula for circular area and Euler’s identity?Quite the opposite. As I show in The Tau

One minute with...

Michael Hartl

Manifesto, using tau reveals underlying mathematical relationships that are obscured by using pi. In particular, the famous formula for circular area is the manifesto’s coup de grâce.

Could tau exist alongside pi? Yes. There is no need to rewrite the textbooks.

Has anyone successfully changed notation like this in the past?In physics, there is an important quantity known as Planck’s constant, h. As quantum mechanics developed, it became clear that h-bar was more important, which is equal to h/2 pi – that’s the factor of 2 that pops up everywhere! h-bar is now the standard notation, though both are used.

People celebrate pi by eating pies on Pi Day. How can people celebrate tau?I’m planning a Tau Day party for 28 June, and if you think that the circular baked goods on Pi Day are tasty, just wait –Tau Day has twice as much pie!Interview by Jacob Aron

It’s time to kill off pi, says the physicist who believes that an alternative mathematical constant will do its job better

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ProfileMichael Hartl has a PhD in physics from the california Institute of Technology, and is the author of the web development book Ruby on Rails Tutorial. Having memorised 50 digits of pi, he is now memorising 52 digits of tau

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