February 3, 2021

The meaning of numbers –
Interview with Prof. Christian Hesse

Prof. Christian Hesse (born 1960) celebrates 30 years of teaching at the Institute for Stochastics and Applications at the University of Stuttgart in 2021. His contributions to corona figures, electoral reform and on general statistics-related issues have made him one of the best-known mathematicians in Germany. In the interview he speaks about the role of mathematics in advising politicians, fake news, and his personal experiences of intellectual beauty.
[Photo: Ivo Kljuce]

Mr Hesse, in the corona crisis people sometimes get the impression that virologists have the last word in politics. What’s it like with your profession, do you think mathematicians could make better politicians?

Christian Hesse (CH): No, most mathematicians I know wouldn’t make good politicians, even less so than the other way round. Mathematicians who analyze data for a living usually do make good political advisors though. This is due to the fact that mathematicians are generalists, and can apply their methods to practically any field of activity. Data which has been collected sensibly and analyzed properly is a key resource for politicians to know what action to take, but also for responsible members of the public. The famous science fiction author H.G. Wells predicted a hundred years ago that statistical thinking would one day become as important in life as the ability to read and write. Today this is no longer science fiction, but reality.

Before I used to think that mathematics didn’t have much to do with people, but now I’ve changed my mind.

Prof. Christian Hesse
Christian Hesse together with TV presenter Karsten Schwanke
Christian Hesse together with TV presenter Karsten Schwanke

You once spent two semesters studying medicine. Now you write books about how mathematics can help people in everyday life. Is it right to say that you have incorporated this wish to help people into mathematics?

CH: Basically, my attitude is to try and somehow make myself useful in whatever I do. That was also one of my motivating forces when I switched from medicine to mathematics. This has increasingly brought me to thinking about how to apply myself over the years. Especially now during the corona pandemic. Before I used to think that mathematics didn’t have much to do with people, but now I’ve changed my mind.

One focus of your work is on popularizing math-related issues. The fact that your ideas have become so popular with the media and with the general public is proof that you have been successful. Have you also had any feedback from business, politics or industry about your calculations as well?

CH: At the moment there is almost more feedback than I can deal with, especially from people in politics. The proportional representation system used for elections to the Bundestag is also mathematically very complex, particularly with regard to the effects of individual changes. During the debate about reforming the electoral system, I suddenly ended up acting as a political advisor in legal matters in my capacity as a mathematician.


2020 – The Year of Numbers

While numbers have long been seen in more abstract terms and a lot of people don’t have fond memories of math class at school, numbers have been in demand over the past year. Society looks at numbers, analyses numbers and is guided based on numbers. Can this affinity for numbers have a long-term impact on people’s enthusiasm for mathematics?

CH: Yes, I think so. I can see this for myself in the increase in interest in my type of mathematics. 2020 was the year of the coronavirus. But corona also made it the year of numbers. For many people, tracking the number of cases became part of their everyday life. A lot of people also looked into the numbers in more detail, such as R-values, moving averages, exponential growth and the like. People think it’s important to decode the information hidden within the data. It’s also important to be able to use hard data to objectively counter emotionally charged myths which distort reality.

Big data analytics also played a key role in the development of the vaccine when researching the structure of the so-called spike protein. I’m convinced that data literacy is the game changer in overcoming the pandemic.


Could you tell us more about how exactly you work? Where do you get the numbers from, how do they serve you as a tool and ultimately what goal guides you, for example, when you make calculations about stocks or mortality?

Image showing stock prices on a screen
Christian Hesse analyzes patterns and structures in the data flow of stock prices

CH: Let’s take stock prices for example. Huge financial flows can be seen on the world’s stock exchanges, which means huge flows of data. These flows of data are accessible to the public. I find it fascinating to try and find patterns, structures and correlations in this data. The aim is to investigate the effect that these ebbs and flows of data have on stock prices. Or also to answer the question of whether stocks behave differently in a particular way before a major stock market crash compared to during a bull market.

Also, how do they compare with other data flows before extreme events, such as for example seismograph measurements before earthquakes? It turns out that there are structural similarities.

When I have a new idea, I sometimes implant it in the mind of interested students for them to use as inspiration to write their thesis on. For example, modeling the dynamics of stock prices with processes including random structures. This doesn’t mean that stock prices fluctuate at random and that stock exchanges are governed by sheer chance, but rather that prices behave as if this were the case, and therefore that instruments of probability theory can be applied to it.


Using math to combat fake news

The titles of your books include words like “luck” and “life” alongside terms like “probability theory” and “stochastic”. Is math a philosophical way of perceiving the world?

CH: Yes. You could even say that mathematics is “ideology”. The teaching of ideas. Mathematicians perceive the world in a way which is based around ideas and problems. Being surrounded by problems is familiar territory for them. Quantitative problems, mind you. When they have solved a problem, they look for another one straight away. Of course, this also means not being able to solve problems straight away, or in some cases not being able to solve them at all. Mathematicians often need multiple attempts to solve a problem, and sometimes they reach a dead-end after a lot of painstaking work and have to start over. In this respect, having a strong tolerance for frustration is a typical trait of mathematicians. The life of a mathematician can be frustrating. Math is just difficult.

Another important aspect to consider too is that mathematics is an oasis of rationality, especially at the moment when irrationality is so widespread and when fake news has been presented as alternative facts. Mathematics provides actual facts. I find this to be very beneficial.


Fibonacci spiral, drawn with chalk on a blackboard
Leonardo Fibonacci (around 1200) already knew how much mathematics has to do with aesthetics. The Fibonacci numbers named after him, a sequence of natural numbers (1, 1, 2, 3, 5, 8 ...), describe a growth that is often found in nature, for example in a snail shell.

The feeling of intellectual beauty is a strong motivation to carry out mathematics.

Prof. Christian Hesse

You speak about the beauty of mathematics and the beauty that you can see in certain chess moves. Can you describe the beauty of numbers the way that you see it?

Picture of cabbage Romanesco. Just like matryoshka dolls, the individual parts have the same shape as the larger ones, so they are fractal.
Not a computer simulation: The Romanesco is the classic example of fractal structures with Fibonacci spiral in nature.

CH: Ultimately, it’s nothing more than the feeling that young children also have towards math. Most elementary school children have a positive attitude towards math. If you ask them why, the answer is often something like “Because it all comes together so well”. In a somewhat more intense form, a lot of professional mathematicians can also become encaptivated by how individual strands fit together perfectly to form a delicate construction in which everything merges to perfection. The feeling of intellectual beauty is a strong motivation to carry out mathematics. People wouldn't pursue a math career from a sense of obligation alone.


Mathematics as a refuge

To what extent can math help you to live your life more happily – even in times of crisis?

CH: I can speak about my own experience better than anything else. Math has helped me to find a proper outlet for my abilities, and particularly to find the limits of my abilities. And that’s a big thing. As far as the current crisis is concerned, it’s perhaps a little easier for mathematicians to deal with the restrictions. It’s not unusual for them to spend long periods of time by themselves. In some ways it is a type of self-imposed quarantine, or to put it in more positive terms, a refuge. This is because they spend their time thinking about problems that are close to their hearts.

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