Welcome to practical physicsPracticle physics - practical activities designed for use in the classroom with 11 to 19 year olds

Model of the early Greek scheme


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

flask bung and knitting needle model of early Greek universe

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 experiment Model of the celestial sphere) and represent the Sun with a sticky label.



a Rotate the flask around its axis, so that the 'heavens' can rotate about the Earth.
b 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-checked in April 2007


Related experiments

Model of the celestial sphere 

Thales model of the Universe