Machine gun and nuclear reactor: what they have in common

1. Step 1. Machine gun — is part of — Tank. The Mark I’s machine guns.
2. Step 2. Tank — has part — Periscope. Observation devices.
3. Step 3. Periscope — is part of — Submarine. A periscope.
4. Step 4. Submarine — evolved into — Nuclear submarine. Nuclear power let submarines stay submerged for months.
5. Step 5. Nuclear submarine — has part — Nuclear reactor. A reactor.

Open Evothings