Chapter 2

Eternal inflation keeps making bubbles

Once inflation starts, many models don’t politely stop everywhere at once. Inflation ends locally — in bubbles — while the background keeps expanding and birthing more.

Bubble universes

Each “bubble” can be a whole Big-Bang-like region. Ours would be one pocket. Others might settle into different vacuum states — different effective laws, constants, particle menus.

That’s the leap from “inflation happened” to “our bang was one of many.”

Watch bubbles nucleate

Click the field to force a nucleation. Or let it run.

bubbles: 0 nucleation: med

Why “probably”?

Not because we’ve photographed another cosmos. Because the same inflationary framework that solves flatness/uniformity often has no natural off-switch that leaves only one bubble. Eternal inflation is a default in large classes of models — not a cartoon add-on.

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