Galileo Thermometer

This ancient weather instrument was invented by Galileo Galilei (1564-1642).

Galileo was an Italian mathematician, physicist, astronomer and inventor.  He is best known for his works involving gravity and astronomy.

He is often credited with inventing the microscope and the early development of the telescope.

His career was not without controversy, as he was twice summoned before the Inquisition at Rome, and made to renounce his beliefs and writings supporting Copernican theory (the Earth revolves around the sun) which contradicted the doctrine of the church at the time.

How it works

The Galileo Thermometer is based on his discovery that the density of liquids change as temperature varies.  Each of the glass balls is exactly weighted by partially filling the spheres with liquid.  When the temperature rises the liquid in the glass cylinder becomes less dense and the balls sink slowly to the bottom.

How to read it

The lowest temperature ball within the group at the top of the thermometer tells the correct temperature.