MESM and rock drill: what they have in common

1. Step 1. MESM — has part — Vacuum tube. About 6,000 vacuum tubes.
2. Step 2. Vacuum tube — evolved into — Diode. The first diode was a vacuum tube (Fleming); later diodes became semiconductor devices.
3. Step 3. Diode — includes — LED. A light-emitting diode.
4. Step 4. LED — is part of — Street light. LEDs.
5. Step 5. Street light — is part of — Tunnel. Lighting.
6. Step 6. Tunnel — uses — Rock drill. Driving the Mont Cenis tunnel.

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