Road roller and glasses: what they have in common

1. Step 1. Road roller — evolved from — Watt steam engine. The first rollers were steam-driven.
2. Step 2. Watt steam engine — has part — Flywheel. The flywheel evens out rotation.
3. Step 3. Flywheel — includes — Reaction wheel. A flywheel.
4. Step 4. Reaction wheel — is part of — Space telescope. Pointing Hubble.
5. Step 5. Space telescope — is a kind of — Telescope. A space telescope is a telescope above the atmosphere, so air does not blur the view.
6. Step 6. Telescope — evolved from — Glasses. The first telescopes were assembled by spectacle makers.

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