Spirit level and LIGO: what they have in common

1. Step 1. Spirit level — uses — Universal gravitation. The bubble rises to the highest point.
2. Step 2. Universal gravitation — is used in — Anchor escapement. The pace is set by a pendulum under gravity.
3. Step 3. Anchor escapement — is part of — Pendulum clock. An anchor escapement.
4. Step 4. Pendulum clock — evolved into — Quartz clock. Quartz replaced the pendulum as the frequency standard.
5. Step 5. Quartz clock — is made of — Silica (sand). The resonator is a quartz crystal.
6. Step 6. Silica (sand) — is material for — LIGO. The mirrors are fused silica.

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