Interferometer arm vacuum tubes and gutenberg printing press: what they have in common

1. Step 1. Interferometer arm vacuum tubes — is part of — LIGO. Two 4 km vacuum tubes.
2. Step 2. LIGO — uses — Laser. A laser.
3. Step 3. Laser — includes — Laser diode. A semiconductor laser.
4. Step 4. Laser diode — is part of — Laser printer. A laser draws the image on the drum.
5. Step 5. Laser printer — is a kind of — Printer. A printer.
6. Step 6. Printer — works like — Gutenberg printing press. A printer is a personal printing press: it transfers an image onto paper.

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