This post describes “Mission to Mars: Concept and Implementation of a Design-Based (Hands-On) Smartphone Experiment Helping Students Understand the Effects Caused by Differences in Air Pressure”, published in The Physics Teacher (Vol. 59, 2021) together with Alexander Küpper and André Bresges.

The Problem With Air Pressure

Air pressure is one of those topics that students nominally know something about from everyday life while still using explanations that conflict with the physics. The education literature documents recurring ideas such as: air is “empty” (nothing in it), air is weightless, air only exerts pressure when it moves (like wind), a vacuum “sucks” rather than being a region where surrounding air pushes in, and pressure increases with height rather than decreasing.

Some of these misconceptions are stubborn precisely because everyday experience seems to support them. Air does not feel like it has weight. A vacuum cleaner does feel like it is pulling. The atmosphere, experienced from inside it, does not announce itself as a pressure source.

The standard approach to this material — explaining atmospheric pressure, defining $p = F/A$, working through barometric altitude formulae — addresses the conceptual gaps at the declarative level. Students can recite that air exerts pressure in all directions. Whether they have actually updated their mental model is a different question.

“Mission to Mars” is a design-based attempt to make those explanations testable through a physical encounter with pressure differences. The published paper describes the intervention; it is not a controlled study of conceptual change.

The Context: Why Mars?

The motivation for choosing the Mars context was empirical, not poetic. The international ROSE survey reported substantial interest in space and astronomy items, although the rankings vary by country, item, and gender. That is a reason to test an astronomical context, not evidence that it motivates every class or improves learning by itself.

“Mission to Mars” asks students: a crewed mission to Mars would travel through the vacuum of space, with the crew living in a pressurised compartment. The compartment has to maintain atmospheric pressure while surrounded by near-vacuum. What happens if it fails? And how would you design a spacecraft structure to prevent that failure?

The question is concrete. The physics behind it — the difference between the pressure inside the compartment and the near-zero pressure outside, and the forces this pressure difference exerts on any structure — is the content of the lesson.

The Experiment

The full version of the experiment, as we ran it at the astro-lab at the University of Cologne, uses a vacuum pump, a bell jar, and a smartphone running phyphox. A compatible smartphone’s built-in barometer records pressure inside the bell jar as the pump evacuates it. Not every phone exposes a pressure sensor to phyphox; the hardware must be checked before the lesson, or replaced by a rated external sensor.

Before building anything, students verify that the smartphone is a functional pressure gauge: they measure the current atmospheric pressure in the room and compare it with a provided reference value. This step matters pedagogically — it establishes that the phone is a real scientific instrument, not just a device for receiving worksheets.

Then comes the design-build-test cycle:

Design: Students are given PVC plumbing pipe sections, empty food containers, resealable bags, rubber bands, clamps, and other household materials. Their task is to build a prototype “spaceship” — a container that will maintain near-atmospheric pressure inside while the bell jar around it is evacuated to low pressure. The phone (or external sensor) goes inside the prototype to measure whether the prototype is holding.

Predict: Before testing, students are asked to state why they think their prototype will or won’t work. This surfaces their preconceptions in a low-stakes way and sets up the next stage.

Test: The prototype goes into the bell jar. The pump runs. The pressure sensor records. The light curve — sorry, the pressure curve — tells the story. In our implementation, traces included:

  • Nearly flat line: over the duration and resolution of the test, pressure inside stays near atmospheric. That is evidence of no detected leak, not proof of perfect airtightness.
  • “Bathtub” curve: a visible failure event — a cap pops off, the pressure inside drops sharply and then equalises. Students hear the pop. They did not expect the pop. This is the moment.
  • Gradual decay: the prototype leaks slowly, the pressure inside drops steadily. Invisible failure.
  • Noisy signal: a result requiring a sensor, seal, sampling, and setup check before interpretation.

The PVC pipe trap: in our apparatus, an impressive-looking push-fit PVC assembly could fail when the force from the pressure difference exceeded the lid’s retention. That outcome depends on the geometry, seal, pressure history, and fastening; PVC is not intrinsically the wrong material. Students rebuild.

The Misconceptions, Addressed

The design-test-rebuild cycle is intended to make the misconceptions listed above discussable against measurements:

Air is empty/weightless: approached in pre-activities with standard demonstrations (the dunked napkin, the deflated-vs-inflated balloon).

Air only exerts pressure when moving: the bell jar demonstration makes this concrete — the sensor shows pressure even in a static, undisturbed volume. When the pump evacuates the jar, the “stillness” of the remaining air doesn’t change its pressure.

A vacuum sucks: this is the crucial one. A lid failure can make the force direction visible. The lid does not get sucked outward. The air inside the prototype at near-atmospheric pressure pushes the lid open against the external near-vacuum. When the lid fails and students hear the rush of air flowing back in after the valve is opened, the direction of the pressure force becomes clear: the net force follows the pressure difference across the lid.

The inquiry is scaffolded through worksheets and index cards. In the lab version, trained staff operate a rated chamber and pump, inspect the apparatus, keep people clear of the failure path, and set limits appropriate to the chamber, sensor, and device. A personal phone should not be put under reduced pressure unless its manufacturer permits it and a documented risk assessment covers the device, battery, chamber, and likely failure modes.

What Can Safely Be Varied

The published implementation explored apparatus at different cost levels, but cost is not a safety specification. Household food containers, improvised bell jars, and vacuum cleaners are not substitutes for pressure-rated equipment: containers may buckle or fragment, hoses and lids may become projectiles, and consumer pumps are not designed as laboratory vacuum systems.

For a school implementation, the vacuum side should therefore remain a supervised demonstration using a rated chamber, compatible pump, gauge, shield where required, and the institution’s risk assessment. Students can still own the intellectual work: predict the pressure curve, design and inspect a model, analyse supplied or remotely displayed data, explain a failure, and revise the design. A low-budget or remote version can use recorded datasets rather than an improvised pressure vessel at home.

A Note on Where This Fits

“Mission to Mars” grew out of the astro-lab at the University of Cologne, the same student laboratory context as the exoplanet transit experiments. The common thread is not the specific physics topic (air pressure here, photometry there) but the experimental approach: smartphones as real measurement instruments, everyday materials as apparatus, an astronomical context that sustains engagement, and a design-build-test cycle that forces students to encounter the physics physically rather than only propositionally.

The air pressure content connects naturally to the exoplanet unit at a curriculum level: habitability of exoplanets depends partly on atmospheric pressure. In the Fremde Welten article, atmospheric pressure is listed as one of the factors that determine whether a detected exoplanet could support life — an explicit cross-link between the two units.

The astro-lab@home post describes how the broader astro-lab programme — including this experiment — was adapted for home use during the pandemic. The air-pressure experiment is among the more challenging to replicate at home; the safe remote adaptation is to analyse a supervised live demonstration or a recorded trace, not to improvise a vacuum chamber.

The design-build-test structure of this experiment also ended up at the centre of a methodological argument during my thesis work. The short version: everyone told me to use grounded theory instead of design thinking as the research framework, and they were right to do so. That story is in a separate post.

References

Spicker, S. J., Küpper, A., & Bresges, A. (2022). Mission to Mars: Concept and implementation of a design-based (hands-on) smartphone experiment helping students understand the effects caused by differences in air pressure. The Physics Teacher, 60(1), 47–50. https://doi.org/10.1119/10.0009109

Küpper, A., & Schulz, A. (2017). Schülerinnen und Schüler auf der Suche nach der Erde 2.0 im Schülerlabor der Universität zu Köln. Astronomie+Raumfahrt im Unterricht, 54(157), 40–45.

Staacks, S., Hütz, S., Heinke, H., & Stampfer, C. (2018). Advanced tools for smartphone-based experiments: phyphox. Physics Education, 53(4), 045009. https://doi.org/10.1088/1361-6552/aac05e

Sjoberg, S., & Schreiner, C. (2010). The ROSE project: An overview and key findings. University of Oslo.

Changelog

  • 2025-10-03: Updated the self-citation to the correct year (2022), volume/issue (60(1)), pages (47–50), and DOI (10.1119/10.0009109).
  • 2026-07-11: Added the literature cutoff and clarified in the research note that device sensors, vacuum level and learning outcomes depend on the specific implementation.
  • 2026-07-11: Recast the classroom outcomes as implementation observations, corrected the pressure-force and sensor limits, and removed unsafe instructions for improvised home vacuum systems.

Experiment and literature record checked through 2026-07-11.