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From Earth to the Galaxies

  • Planétarium
Planet Earth and a star, as seen from space
Photo: Stocktrek
Planet Earth and star seen from space

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Description of the activity

Your students will discover how the Universe is organized into different hierarchical structures (Earth-Moon system, solar system, Milky Way, galaxy cluster) and calculate the dimensions of these structures and the objects they contain. Students will become familiar with the concepts of light year, scale factor and unit conversion.

Equipment needed by the student

Each student (or student pair) requires:

  • A copy of the student handout From Earth to the Galaxies.
  • A ruler graduated in millimetres.
  • A calculator (optional).


Prepare enough copies of the student handout From Earth to the Galaxies.


Distribute the handout and explain what students must do. Tell them how long they’ll have to complete the questions. Remind them that they must measure the distances between the objects from centre to centre, except in the case of the diameter of the Milky Way and the diameter of the observable Universe, where arrows specify the distance to be measured. In this case, students must measure the distance between the tips of the arrows.

Category of activity

  • Preparatory activity

Sub-category of activity

  • Class activity

Grade level

  • Secondary cycle one
  • Secondary cycle two

Number of students per group

Individual exercise or in pairs


One 60-minute period

Activity Sheets

From Earth to the Galaxies[PDF - 310.41 KB - 8 pages]

Schedules for teachers

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