Smoking and LIGO: what they have in common

1. Step 1. Smoking — uses — Combustion. The smoke of smouldering wood.
2. Step 2. Combustion — is used in — Oil lamp. Burning oil gives the light.
3. Step 3. Oil lamp — evolved into — Incandescent light bulb. The electric lamp replaced oil and gas lamps.
4. Step 4. Incandescent light bulb — uses — Vacuum. The bulb was evacuated so the filament would not burn out.
5. Step 5. Vacuum — is used in — LIGO. 4 km vacuum tubes.

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