Star tracker and vacuum pump: what they have in common

1. Step 1. Star tracker — works like — Sextant. Navigating by the stars — as sailors did.
2. Step 2. Sextant — has part — Lens. The sextant’s telescope.
3. Step 3. Lens — is part of — Microscope. An objective and an eyepiece.
4. Step 4. Microscope — evolved into — Electron microscope. Overcoming the limit of optics.
5. Step 5. Electron microscope — has part — Vacuum pump. A vacuum in the column.

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