Hollow quill barrel and LIGO: what they have in common

1. Step 1. Hollow quill barrel — is part of — Quill pen. A hollow shaft holds the ink.
2. Step 2. Quill pen — uses — Ink. It writes with ink.
3. Step 3. Ink — is used in — Ballpoint pen. Thick oil-based ink.
4. Step 4. Ballpoint pen — has part — Ball bearing. A ball in a socket — essentially a ball bearing.
5. Step 5. Ball bearing — is part of — Base isolation. Friction pendulum bearings.
6. Step 6. Base isolation — is part of — LIGO. The suspension damps ground vibrations.

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