Mystery Tube

Have you ever wondered how scientists figure out how things work when they do not have a direct way of measuring the phenomena? For example, how do we know that the structure of an atom consists of electrons revolving around a positively charged nucleus, like the planets around the sun? In this activity, we will learn how to build scientific models based on observations, realize that different models can explain the same observations, and refine our models based on new data.

BEFORE the activity students should know:

  • The steps for the scientific method.
  • The difference between the scientific method vs. scientific model

AFTER the activity students should know:

  • Several models can be created from a set of observables.
  • Each model is equally acceptable if it predicts the observed results
  • In light of new data, we always new to revise our models

Key Question

  • What is a scientific model and how do we create one?

The Science Behind

The job of a scientist is to build models. Models are a way to create a mental picture of how something works. They are representations of real-life events, objects, or systems. Models can be used to gain an understanding of phenomena or processes which are difficult to observe directly. If an event occurs too slow or fast of a speed to detect directly or on a difficult scale to measure, creating a model to understand how it works makes things a lot easier. Sometimes the observable is impossible to see directly, or doing so would be too dangerous. Therefore, we use models to try to replicate those systems or events. In order to remain as accurate as possible, one must constantly refine and adjust a model when new information or data is received. For example, scientists initially believed that the Earth was the center of the solar system, with the Sun and all other objects rotating around. Astronomy knows this as the geocentric model. Scientists believed this because what they could observe was that the Sun appeared once a day everywhere around the Earth. The stars also rotated every day in a similar form. They also observed that standing on Earth, Earth did not seem to move, which then led them to believe that the Earth was stationary. Therefore, their geocentric model well predicted what they could observe at the time. However, in 1543 Nicolaus Copernicus presented a new model in which the Earth rotated around the Sun. Copernicus used the fact that observations of other planets in the solar system seen from Earth would require very complicated trajectories. Using his knowledge of mathematics and orbits, he proposed a new model to predict the same day, night, moon, planet, and star observations but with simpler trajectories.

Quantum mechanics is a field of physics that is very hard to study, especially before advancing technology, as it studies things that are on a very, very small scale, like the atom and smaller. Physicists have used models to study the phenomena of quantum physics. Another challenge of quantum physics is that, because we do not live or experience life at that tiny scale, it is not directly intuitive to predict what will happen in a quantum system. Often our observations of quantum phenomena challenge what we observe on the bigger scales. Therefore, it is challenging to create models that replicate the quantum observations and make sense in the non-quantum scale. In many quantum phenomena, there are no direct comparisons to the classical world. In the classical world, we measure things and observe behaviors to create models. However, in the quantum world, every attempt to observe what is happening alters the data, limiting the ability to refine models. One of the first examples of scientists using models to understand quantum mechanics in our classical world was with the atom model. Another example critical to the quantum mechanics field is the conundrum of an electron and how it can behave like both a wave and a particle. We will learn more about wave-particle duality in our next activity.



mystery tube tube

  • 1 drinking straw - cut up to tie to the ends of the string for the Mystery Tube to use as washer
  • 1 Tube 1.5" x 9” x 0.04”
  • 1 Push pin to pierce the side of the tube before the skewer is used to create the hole
  • 1 Skewer 4.5 x 11/64” to create the appropriate size hole in the tube
  • 1 thin pull wire to make threading the string through the holes easier
  • Yoyo string
  • Paper/whiteboard + pen/marker to write your observations down

If you are working at home and do not have the exact materials, you can always build your own mystery tube. You will need:

Cardboard tube

  • ex: Paper towel roll/toilet paper roll


  • ex: Nylon is the best for less friction ~ 60 inches of length

1 ring

  • ex: Metal washer or key ring of ~ 1/2 inch in diameter

2 end caps for the tube

  • ex: ~ 2 inches in diameter or aluminium foil secured with rubber bands, duck tape, juice, milk or pill bottle tops.


To construct your mystery tube:

  1. Make two holes an inch and a half from the end of each side of the tube. Ensure the holes are directly across from one another. You can use a pen to push through the cardboard tube to make the holes.
  2. Repeat for the two bottom holes, so you have 4 holes in total.
  3. Cut the string into two
  4. Thread one length of string through one of the top holes and then out through the hole below. Tie the made washers from each end of the string.
  5. Repeat the same for the other two holes with the other piece of string. Thread the string through the other string - as seen in the figure below
  6. Cover the ends of the tube. You can also have different variations of the mystery tube to prompt discussion, for example, one with a ring instead of threatening the strings, or doing top/lower holes instead of left/right holes.

Encourage students to build their own mystery tube without revealing how you built the original tube. Alternative ways to build your tube can be found here.

tube drawing

Setting Up

In the student’s guide, we have asked the students to develop a model that explains the behavior of the tube and then design their own tube to test their model. The idea is to encourage them to be creative, to understand how to design experiments, and think like scientists and engineers. Once they have drawn their model, ask them what materials they will need to build their own mystery tube. As the teacher, you can ask prompting questions to get them to think about the different aspects of the experiments. Below are the full instructions for one possible design.

The idea of the experiments is that they understand that different models can predict the same phenomena. They need to figure out which variables they should control for, for example, the number of pieces of strings and/or rings, that could affect the observed behavior, and consistency of the repeated experiments.

  1. Provide a mystery tube per group (groups of 5 max). Tell students that they need to draw a design of how the tube works without opening the tube. Ask students to follow the scientific method, to formulate hypotheses/predictions of what will happen when they pull the different string ends, does it make a sound when you shake it, does the diameter of the tube, strings, rings matter, or the length?
  2. Allow students enough time to try their combinations, noting the motion and tension of the strings or anything else that might help them decipher how the tube looks inside.
  3. Once the students in the group have reached a conclusion, ask them to draw their designs and share them with the class. Provide some time for a peer-review process in which students get to ask questions about their peers’ designs. Ask the groups if they want to revise their model after the peer-review session is completed.
  4. Once students have revised their models and adjusted their designs then provide the materials they request and ask them to build their own model.
  5. With the class, define a way to systematically test the accuracy of each group’s model, maybe by analyzing the diagram to see if it could predict the behavior that is actually witnessed when the strings are pulled., how the physical model compares to the diagram and if it actually behaves as it was expected.
  6. Once all the models are built, use the accuracy-test to judge the models. The models must be judged primarily on their ability to explain and predict the observations.
  7. Discuss how different models can arrive at the same observations and reflect what areas of science use models in similar ways - such as the model of the atom or the electron (particle and wave).
  8. Do not reveal the inside of the original tube.

Key Terms

  • Scientific Model - A physical,conceptual, or mathematical representation which can be used to explain and predict the behaviour of real objects or systems seen in natural phenomenons that are difficult to observe directly.
  • Phenomenon - an observable fact or event of scientific interest
  • Approximation - a mathematical quantity that is close in value to but not the same as a desired quantity; being close or near
  • System - a group of interacting items forming a unified whole
  • Peer Reviewed - a process by which something proposed (as for research or publication) is evaluated by a group of experts in the appropriate field
  • Quantum Mechanics - a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles

Extension Activities & Other Suggested Resources