Steel well casing and atomic clock: what they have in common

1. Step 1. Steel well casing — is part of — Oil well. Steel pipes line the borehole.
2. Step 2. Oil well — is used in — Crude oil. Oil is extracted from wells.
3. Step 3. Crude oil — is material for — Kerosene. A fraction of crude oil.
4. Step 4. Kerosene — is material for — Reusable rocket. The fuel is kerosene or methane.
5. Step 5. Reusable rocket — has part — GPS (satellite navigation). Navigation during landing.
6. Step 6. GPS (satellite navigation) — uses — Atomic clock. The satellites carry atomic clocks; the position is calculated from signal arrival times.

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