What the astro-lab Was

Before the pandemic, the astro-lab at the University of Cologne was a student laboratory focused on extrasolar planets. School groups — mostly secondary school students — came in and worked through a set of analogy experiments: how do you detect a planet you cannot see? How do you infer its size, its orbit, whether it might be habitable?

The pedagogical bet was that exoplanet research, precisely because it is headline-generating and genuinely open-ended, could counteract the motivational slump in physics that tends to set in around middle school. The context — life in the universe, habitable worlds, the possibility of something out there — did a lot of the work that no abstract force diagram could do.

The experiments themselves were analogy experiments: a lamp standing in for a star, a sphere on a track standing in for a planet. The key measurement was the transit: when the “planet” passed in front of the “star”, the light sensor registered a dip. Students measured the dip, estimated the ratio of areas, connected it to radius, and got a number that meant something. The number was not precise. It did not need to be. It was real.

Spring 2020

In March 2020, schools shut down, and the University of Cologne followed. Visits to the astro-lab were cancelled. The question the team faced — Alexander Küpper, André Bresges, and I — was not whether to do something but what was actually feasible.

German distance learning at the time was characterised by worksheet packages delivered to students with minimal interactive contact. Only 16% of German students reported being in video conferences with their teachers; 30% reported no contact at all since the initial shutdown. The infrastructure was not there, the habits were not there, and the expectation that students had the materials and equipment for a physics lab at home was not warranted.

What students did have, almost universally, was a smartphone.

Modern smartphones contain a remarkable array of sensors: ambient light sensors, accelerometers, gyroscopes, barometers, magnetometers. The app phyphox, developed at RWTH Aachen, makes those sensors accessible with a clean interface designed for use in education. If the sensor hardware was already in students’ pockets, the lab setup problem became: what household materials can stand in for the rest of the apparatus?

astro-lab@home: Bringing Science to the Sofa

The astro-lab@home project adapted the original lab experiments for home use with smartphones and everyday materials. The core transit experiment — measuring the dip in light caused by an opaque object passing in front of a lamp — turned out to be reproducible without any specialist equipment. A table lamp, a ball on a string, and a smartphone positioned beneath the lamp gave you the raw data. phyphox recorded the light curve in real time.

We designed the setup to be flexible enough to work with what students actually had. The default used the ambient light sensor in Android devices, which is directly accessible through phyphox. iPhones do not expose their light sensor through software interfaces, so for Apple devices we recommended an external Bluetooth sensor — an inexpensive workaround that also had the advantage of producing more consistent data across device types.

The resulting package was not just an equipment list. We developed accompanying materials that explained the physics (why does a transit produce a specific shape of dip rather than a sharp cutoff?), connected the analogy experiment to the real science (how does this scale up to the actual transit photometry done by TESS and Kepler?), and offered scaffolding at different levels of independence.

The project was published in the IAU’s CAPjournal in 2022 — a journal aimed at communicators and educators in astronomy. The audience was intentionally broad: teachers looking for accessible classroom activities, outreach organisations trying to reach students at home, curious individuals who wanted to do something real with their phone. “Bringing science to the sofa” was the headline, and that was genuine. The experiments worked in a living room.

What Came Next: astro-lab@school

When schools reopened and in-person teaching became possible again, the question was not simply “back to normal” but what the COVID period had actually taught us about the format.

The astro-lab@school, published in Astronomie+Raumfahrt in 2022, addressed that question directly. Some things from the home version had worked better than expected. The smartphone-based setup was cheaper, more portable, and more directly in students’ hands than the original benchtop apparatus. There was something pedagogically valuable about students using their own devices rather than lab equipment provided by someone else.

The astro-lab@school retained the smartphone-centred approach and adapted it for a school context: class sizes, time constraints, the reality of mixed equipment across a room of thirty students. The experiments from the home version were modified for group work and parallel execution. The scaffolding materials were reworked for the paced structure of a school lesson rather than the self-directed format of home use.

The result was not a reversion to the pre-pandemic lab. It was a hybrid: in-person group work, but with tools and methods developed for distributed individual use. The pandemic had, inadvertently, pushed the format toward something more robust.

A Note on What Made This Work

The core technical contribution — smartphones as measurement instruments for analogy experiments in astronomy education — is described in more detail in a later publication in The Physics Teacher, which covers the experimental setups, sensor comparison, and pedagogical progression in a form aimed at an international teaching audience. If you want the how-to, start there.

What I want to note here is something slightly different: the role of context.

The astro-lab bet on exoplanets as a motivational context, and the evidence supports that bet. Exoplanet research remains one of the few areas of physics that generates genuine public enthusiasm, and students' interest in the topic is empirically documented. What the COVID period showed is that the context is robust enough to survive the removal of the lab infrastructure. Students working on transit photometry with a lamp and a smartphone in their kitchen were doing the same thing, conceptually, as students at a benchtop sensor station at the university. The physical setup was different. The question was the same.

That is, I think, a more general lesson. Context-driven education is not dependent on a specific material configuration. The question carries.

For the curriculum unit that places these experiments in the context of the NRW Sekundarstufe I physics syllabus, see Fremde Welten. For the air pressure / Mars experiment that grew from the same lab, see Mission to Mars.

References

Spicker, S. J., Küpper, A., & Bresges, A. (2022). astro-lab@home — bringing science to the sofa. CAPjournal, 31, 12–17.

Küpper, A., & Spicker, S. J. (2022). astro-lab@school. Astronomie+Raumfahrt im Unterricht, 59(6).

Küpper, A., & Schulz, A. (2017). Das Schülerlabor astro-lab an der Universität zu Köln. Astronomie+Raumfahrt im Unterricht, 54(1).

Stampfer, C., & Staacks, S. (2020). phyphox — using smartphones as experimental tools. Physics Education, 55(5), 055007. https://doi.org/10.1088/1361-6552/ab8a2e