Model of the early Greek scheme

Demonstration

Using the flask model of the celestial sphere to demonstrate early Greek ideas about the structure of the Universe.

Apparatus and Materials

• Flask, large (e.g. 2 litre wide neck)
• Bung to fit flask
• Knitting needle, long
• Wooden washer (about 25 mm diameter)
• Retort stand, boss, and clamp or Tripod
• Sun label

Health & Safety and Technical Notes

Read our standard health & safety guidance

Slip the wooden washer over the knitting needle so that it rides freely. Push the needle through the bung so that the point of the needle almost reaches the bottom of the flask when the bung is inserted.

Half fill the flask with water and carefully insert the bung so that the wooden washer floats centrally on the water surface. Turn the whole upside down and place the flask in a ring on a tripod. Alternatively, attach it to a retort stand so that it is inclined at an angle.

Mark stars on the outside of the flask with an alcohol based marker pen. Mark the ecliptic on the outside at 23.5° to the celestial equator (see below experiment) and represent the Sun with a sticky label.

Model of the celestial sphere

Procedure

1. Rotate the flask around its axis, so that the heavens can rotate about the Earth.
2. Turning the neck will show the Sun's daily motion. The Sun can be moved to successive positions on the ecliptic, the daily motion being shown for each.

Teaching Notes

• See guidance note

  Early astronomical observations

• The globe represents the heavens, the flat wooden washer the flat Earth.

This experiment was safety-tested in April 2007.