In a vacuum inside a free-standing globe the vanes constantly revolve in sunlight. The simplest possible demonstration of solar power.

The radiometer is made by traditional Thuringian hand-blowing in Germany, of crystal-clear Lauschaer bottle glass. In the glass body is a 4-vane drive assembly, which turns under the influence of light. One side of each vane is black, the other is silver.

Height: ca. 15cm. Globe diameter: ca. 8cm.

The Crookes radiometer was invented by the chemist Sir William Crookes as the by- product of some chemical research. In the course of very accurate quantitative chemical work, he was weighing samples in a partially evacuated chamber to reduce the effect of air currents, and noticed the weighings were disturbed when sunlight shone on the balance. Investigating this effect, he devised the device named after him, still manufactured and sold to this day as a curiosity item.

This is claimed to be 'the original' in the sense that it is made in America, by the successors to the firm who first marketed it in 1917. It is entirely metal and smartly packaged with string and stand.

Produced since 1917, the gyroscope has been a classic educational toy for generations. It continues to fascinate young and old alike with its mysterious force that seems to defy gravity. Each gyroscope is packed in a clear styrene box with starting string, pedestal and instructions for several amazing tricks.

A gyroscope is a device which demonstrates the principle of conservation of angular momentum, in physics. The essence of the device is a spinning wheel on an axle. The device, once spinning, tends to resist changes to its orientation. The gyroscope was invented and named in 1852 by Léon Foucault for an experiment involving the rotation of the Earth.

This demonstrates Newton's principle that 'action and reaction are equal and opposite'. If one of the steel balls is lifted and allowed to fall back at one end, then one will swing out the same distance at the other end. This causes the beginning of perpetual motion which dies down only as a result of friction, an interesting process to watch.

    * Stands 18.5 cm (7.25") high

    * Classic desk-top executive toy

If you raise and release one ball, one ball is ejected the other side; if 2, then 2 balls are ejected. If you raise the single ball higher so it hits at a higher velocity, still only one ball is ejected. How does the system 'know' how many balls to eject?

Newton's cradle is a well known system made of about 5 pendula, each attached with 2 strings, that demonstrates the conservation of energy^ and conservation of momentum^. One can show, using the corresponding equations, that the ejected balls must have the same velocity and mass as the incoming balls. An interesting experiment is to place a credit card between or before the suspended balls.