Compass

Can you imagine a ship without a compass? This is our magnetic compass. It looks quite antique but beware; it is still an accurate and valuable aid to navigation. Although we are steering on gyro compasses with automatic pilots connected, the magnetic is still the "Mother Compass". Never crashes, no Ctrl-Alt-Del, no batteries needed, just a sensitive instrument which tells us where the magnetic North Pole is. In earlier days the wooden ships were of no influence to the compass, but nowadays with steel ships, a large error would occur if this still was not compensated. And that's exactly what the red ball is doing. Neutralizing the influence of all that surrounding steel.