Taximeter and multistage rocket: what they have in common

1. Step 1. Taximeter — has part — Mechanical clock. It measures the time of the ride.
2. Step 2. Mechanical clock — evolved into — Quartz clock. Quartz clocks replaced mechanical ones: a vibrating quartz crystal took the place of the pendulum and balance.
3. Step 3. Quartz clock — evolved into — Atomic clock. The quartz oscillator is tuned to an atomic standard.
4. Step 4. Atomic clock — is used in — GPS (satellite navigation). The satellites carry atomic clocks; the position is calculated from signal arrival times.
5. Step 5. GPS (satellite navigation) — is part of — Reusable rocket. Navigation during landing.
6. Step 6. Reusable rocket — evolved from — Multistage rocket. The first stage returns.

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