Build a 3D object that can cast the correct 2D shadows.

What is the challenge about?

The students are tasked with constructing a single, connected 3D object that casts the same 2D shadow shapes as the specified original.

As the teacher, you project three different shadows of an unknown object onto a screen one after the other. To do this, you change the orientation of the object approximately every 10–20 seconds.

The teams' task: reconstruct the object so that it casts identical shadows.

The first team whose object produces the matching shadows wins.

The Take Off candidates had to master this challenge individually in the episode “Light” (in season 3).

Example from the show:

Depending on its position relative to the light source, the unknown object casts three different shadows.

The teams consider: What must a 3D object look like to produce exactly these three silhouettes?

(Note: Shadows from thin threads or hangers can be ignored.)

Rules

Task: Build an object that casts the same shadows as the original.

• A replica object is considered correct if the shadows it casts match those of the original in shape and proportions.
• It must consist of a single, contiguous piece (monolithic).
• Size is not important—shape and proportions are.
• If a team believes it has found the correct solution, it steps forward for verification.
• If the object is correct, the team has solved the challenge. The other teams may continue working.
• If it is not correct, the team must return to its place and receives a 2-minute penalty (during this time, they may continue building, but may not come forward for verification).

Materials and preparation

Materials per team:

• Cardboard box
• Adhesive tape / hot glue
• Optional: CD, funnel, coffee filter, wooden sticks, party hat...
• Scissors and/or craft knife (with cutting mat)

Materials for the teacher:

• Any (homemade) 3D object
• A3 picture frame and A3 paper
• Flashlight / other light source

Procedure:

1. Divide students into teams of 2-3.
2. Hand out materials to each team.
3. Explain the challenge and rules.
4. Answer students' questions.
5. The challenge begins: the challenge master shows 3 different shadows cast by the object for approx. 10-20 seconds each. While the object is being rotated to show the next shadow, the light source must be turned off! The students should not see the shadow while the challenge master is turning the object.
6. There is one winning team and, if applicable, a 2nd and 3rd place.
7. Discussion: What was difficult about this challenge? What was the easiest solution and why? How good was the teamwork?

Our tips:

Make sure that the object is not visible when turning it – otherwise the brain will quickly recognize the 3D shape. It is best to stand in front of the light source so that the object remains hidden.

The light source should be stable, as should the object. Any movement distorts the shadow.

For a clear shadow image: place the light source as far away as possible and the object as close to the screen as possible.

Try out in advance how best to hold and rotate the object. A quick test run will make it easier to perform.

If teams get stuck, you can help them – for example, by briefly turning on the light while they are rotating or by giving them a hint: a simple solution can often be achieved with just a cardboard box and tape.

Afterwards, take a look together at how the Take Off candidates mastered this challenge:

Author: Lucie Zeches (FNR)