Space probe and gas lamp: what they have in common

1. Step 1. Space probe — has part — Ion thruster. Ion thrusters (Dawn).
2. Step 2. Ion thruster — is made of — Tungsten. The cathodes are tungsten.
3. Step 3. Tungsten — is material for — Incandescent light bulb. A tungsten filament (since 1904–1910).
4. Step 4. Incandescent light bulb — evolved from — Gas lamp. Electricity displaced gas lighting.

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