Square bronze diviner board and monitor: what they have in common

1. Step 1. Square bronze diviner board — is part of — South-pointing spoon (Chinese compass). A smooth plate marked with the cardinal directions.
2. Step 2. South-pointing spoon (Chinese compass) — evolved into — Compass. A magnetic pointer.
3. Step 3. Compass — works like — Hall sensor. Both sense the Earth’s magnetic field.
4. Step 4. Hall sensor — uses — Electron. The magnetic field deflects the electrons.
5. Step 5. Electron — evolved from — Cathode-ray tube. Thomson discovered the electron in cathode rays.
6. Step 6. Cathode-ray tube — is part of — Monitor. The first monitors were CRTs.

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