Ask people what sparked their interest in science, and you will hear of encounters with someone who was passionate about nature, about the stars, about the inner workings of a machine, or of the encouragement of a teacher. They will also tell of the role played by encyclopaedias, scientific books or children’s TV shows. Others may recount their fascination of a trip to, for example, a natural history museum. But not all young science enthusiasts go on to pursue a career as a professionally trained scientist, even though most of them retain their interest in the subject.

Credit: ESA / M. COWAN / SCIENCE PHOTO LIBRARY

Commonly, scientists are associated with the extraordinary amount of time spent on education and training in which they gain highly specialized knowledge. But science was not a profession one could easily choose until the twentieth century. Pursuing science was restricted to a few people, typically from a wealthy background to finance their endeavours, or to people with a day job that paid their bills but allowed them to study science on the side. Friedrich Wilhelm Herschel belonged to this second group when he discovered the planet now known as Uranus in 1781. He was a musician and composer by training and was gainfully employed as the director of the Bath orchestra. Today we might consider him an amateur scientist — or a citizen scientist.

Citizen science refers to the participation of non-professionals in the scientific process, ranging from the provision of resources to the collection or analysis of data. In recent years, more and more ways have emerged for almost anyone with an interest in science to get involved in different projects ranging from the life to the physical sciences. One of the main drivers of this development is the tremendous increase in available data, and the fact that their collection, generation and analysis can be facilitated using modern technology, such as smartphone apps.

For example, the AstroPlant project (pictured) aims to collect data on plant growth and development under different environmental conditions, which will inform the design of artificial ecosystems suitable for operation in space1. Apart from automatic measurements from sensors implemented in the kit, citizen scientists are asked to take weekly measurements. Without their help, the data collection alone would take hundreds of years2.

In 2016, the BIG Bell Test Collaboration brought together more than 100,000 people for 13 experiments across the world, performing Bell tests with photons, single atoms, atomic ensembles and superconducting devices3. Through a web platform, the participants chose zeros and ones, generating a flow of over 1,000 bits per second. The bits were then used to control the settings of the measurement devices. Not all citizen science requires this much active involvement. Participants of the LHC@HOME project, for example, provide computing power for simulations of the Large Hadron Collider (LHC) and some of its main experiments4.

Another popular way to engage citizen scientists are apps. Whether they are linked to a specific project, such as Loss of the Night5, which aims to measure light pollution by determining the number of stars visible at a certain location, or bundle many different projects from climate to art and physics, such as Zooniverse6, apps allow anyone to get involved anywhere at any time.

As much as these apps rely on gamification, citizen scientists of all ages make serious contributions. The human randomness created by amateur scientists for the BIG Bell Test produced results that strongly contradict local realism7, advancing our fundamental understanding of quantum mechanics. And this is not the only publication driven by amateur scientists. The classification of telescope images of galaxies according to their shape within the Galaxy Zoo project on Zooniverse led to the discovery of so-called green pea galaxies8. And in certain cases, these contributions are so significant that the citizen scientists have even been included as authors of published papers9.

Beyond assisting in research projects, citizen science can also help to counteract the increasingly popular scepticism towards experts, including scientists, by providing the general public with a behind-the-scenes perspective.

However, despite its positive impact, citizen science comes with certain pitfalls10. There are ethical questions surrounding the potential exploitation of citizen scientists by governments or non-governmental groups. Another issue is accessibility for marginalized groups and for citizens of lower- and middle-income countries. Although citizen science may appear to be open to all, participation is still often restricted to those with both the time and the means to spend their days with scientific projects — much like the Victorian gentleman scientists.

Efforts to overcome access barriers and to engage a more diverse group of amateur scientists are underway. Sonification — a technique to translate visual into acoustic signals — can make projects more inclusive, in particular for visually impaired people11. It will be part of the four citizen science projects under development by the REINFORCE project12. Furthermore, to improve accessibility in rural areas, the project aims to establish virtual training workshops as well as information and communications technology training workshops for citizens not familiar with the required technology.

Citizen science isn’t a perfect system, but it has proven its value to scientific discovery and has the potential to change the perception of science in society by including as many people as possible in the scientific endeavour.