File teeth and solar panel: what they have in common

1. Step 1. File teeth — is part of — File. Rows of fine teeth.
2. Step 2. File — is made of — Bronze. Ancient files were bronze, then iron.
3. Step 3. Bronze — is material for — Reflecting telescope. Newton’s mirror was made of speculum metal.
4. Step 4. Reflecting telescope — includes — Space telescope. Hubble is a reflector.
5. Step 5. Space telescope — has part — Solar panel. Solar panels.

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