Pinwheel with sliding teeth and gas lamp: what they have in common

1. Step 1. Pinwheel with sliding teeth — is part of — Arithmometer. A wheel with retractable teeth sets a digit.
2. Step 2. Arithmometer — evolved into — Electronic calculator. Electronics replaced mechanics.
3. Step 3. Electronic calculator — has part — Liquid-crystal display. An LCD display.
4. Step 4. Liquid-crystal display — has part — LED. LED backlighting.
5. Step 5. LED — is part of — Street light. LEDs.
6. Step 6. Street light — evolved from — Gas lamp. Gas lamps.

Open Evothings