4 BC – The Compass – China

Chinese South Pointing Device

In the Chinese book “Book of the Devil Valley Master” (鬼谷子) is mentioned a “south pointing device” or compass. It was used at the time for fortune telling1.

Magnetized needle compass

The first reference to using a magnetized need a magnetized needle happens around around 1088, in the Dream Pool Essays by Shen Kuo. It isn’t until 1119 that the use of a magnetized needle compass was used for navigational purposes in Zhu Yu‘s book Pingzhou Table Talks (萍洲可談).

A magnetized needle compass was first mentioned in western literature written about 1180 by Alexander Neckam in De Utensilibus (On Instruments).

Experiment – make a compass

Items needed:

    • magnet or loadstone

    • thread

The experiment:

    1. Tie the thread at the mid point between the north between and south pole of the magnet.

    2. Suspend the magnet by the thread.

    3. Write down your observations

 

Experiment – magnetized needle compass

Items needed:

  • bowl

  • water

  • small piece of wood or cork

  • magnet or loadstone

  • pin or needle

  •  

The experiment:

  1. Partially fill the bowl with water

  2. Place the piece of wood or cork in the in the bowl

  3. take the needle and stroke it on the across magnet.

  4. Place the needle on the piece of wood

  5. Write down your observations

 

 

Experiment – magnetized needle compass II

Items needed:

  • bowl

  • water

  • magnet or loadstone

  • pin or needle

  • Single piece of toilet paper

The experiment:

  1. Partially fill the bowl with water.

  2. Take the needle and stroke it on the across magnet..

  3. Fold the toilet paper in half and in half the other way.

  4. Place the needle in the middle of the toilet paper.

  5. Hold the toilet paper by the edges and gently place the paper in bowl.

  6. Write down your observations.

 

Explanation:

The earth acts as really big magnet with a magnetic field. The magnet aligns itself with the magnetic field of the earth.

By stoking the needle on the magnet, the atoms in the needle align themselves and becomes a temporary magnet. Then the needle aligns itself with the magnet fields of the earth.

 

With the toilet paper the needle float on top of the water. This is due to the surface tension, due the cohesion property of water molecules.

 

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