Readme Phyphox™ (properly spelled phyphox, short for “physical phone experiments”) is an app developed and used at RWTH Aachen University for physics education (Lahme et al., 2025 [1]; Staacks et al., 2018 [2]). The app enables easy acquisition and analysis of data using the sensors of students’ own smartphones and thereby promotes low-barrier, authentic experimentation both inside and outside traditional laboratory settings. A central feature of phyphox is the live visualization of incoming sensor data on the smartphone display, including, for example, real-time plots, derived quantities, and automated analysis routines. Students can therefore directly observe how physical processes translate into measurement signals while performing the experiment itself. This real-time monitoring of sensor data supports exploratory and self-directed experimentation because measurements remain interpretable and controllable immediately during acquisition, even before they are uploaded to a shared repository or formally embedded into a theoretical framework. Building on these possibilities, phyphox advocates a measurement-before-theory approach in its teaching materials, suggesting that students may first conduct experiments “blind,” i.e., without prior theoretical explanation, and only later derive and discuss the corresponding physics concepts from the jointly collected data (see phyphox modular online worksheets [3]). This approach is intended to strengthen exploratory learning, student agency, and the connection between empirical observation and theoretical understanding. The same educational idea has also been taken up beyond the official phyphox project itself, for example on the German higher-education platform e-teaching.org, where phyphox-based experiments are described as opportunities for students to conduct experiments before deriving the associated theory. By explicitly comparing this situation to scientific research itself (“ähnlich der Forschung”), e-teaching.org reframes incomplete theoretical understanding as a productive and motivating feature of scientific inquiry and research [4]. Here we put these ideas of exploratory—impromptu—measurement to the test by analysing data from a repetitive “swish swish” hand-wave gesture performed near the smartphone’s light sensor. The data was acquired spontaneously during a Zoom™ call on 13 February 2026 and subsequently uploaded to the sciebo repository of RWTH Aachen University [5]. We provide (i) the original phyphox dataset (“Licht 2026-02-13 13-34-38.xls”), (ii) an upsampled and annotated version thereof (“preview_resampled_annotated.xlsx”), and (iii) the lecture slides used for presentation (“Module_phyphoxSNR.pptx”). Acknowledgement: The author would like to thank the Federal Government and the Heads of Government of the Länder, as well as the Joint Science Conference (GWK), for their funding and support within the framework of the NFDI4ING consortium. Funded by the German Research Foundation (DFG) - project number 442146713. References [1] DOI: 10.1103/bwpv-z3xh [2] DOI: 10.1088/1361-6552/aac05e [3] URL: phyphox.org/de/module/ [4] URL: e-teaching.org/community/digital-learning-map/phyphox-physical-phone-experiments [5] URL: rwth-aachen.sciebo.de/login All links were accessed on the day of publication.