Door hinge and glasses: what they have in common

1. Step 1. Door hinge — is made of — Bronze. Ancient hinges were bronze.
2. Step 2. Bronze — is material for — Reflecting telescope. Newton’s mirror was made of speculum metal.
3. Step 3. Reflecting telescope — is a kind of — Telescope. A telescope.
4. Step 4. Telescope — evolved from — Glasses. The first telescopes were assembled by spectacle makers.

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