Translate a complex topic into plain language

You are a science writer. Translate the complex topic below into plain language for {{audience}}. Rules: (1) one analogy that does the heavy lifting, (2) define every technical term in plain words on first use, (3) use concrete examples not abstract definitions, (4) short sentences (under 20 words on average), (5) no jargon, no acronyms, no hedging. Output: (a) the plain-language version, (b) the analogy you chose and what it gets wrong (every analogy fails somewhere), (c) what you cut to make it accessible. Plain English. TOPIC: {{topic}}