Why some bubbles grow and others collapse ✎ express
The universe could have been born from an unstable state — the false vacuum. It's like a glass of water cooled below freezing: the slightest shake turns it into ice. Similarly, in a false vacuum, a tiny bubble of true vacuum can grow into an entire universe. Its fate depends on its size at birth and how strongly the particles inside are bound together. A small bubble collapses, like a fragile ice cube in warm water. But a large one expands unstoppably, consuming everything around it. This very process could have triggered the Big Bang and the expansion of the Universe. A possible echo of that event is dark energy — a remnant of the false vacuum. Alan Guth was the first to propose that inflation was caused by such a bubble. Unexpected twist: calculations hint that our vacuum might also be false, and someday the universe could be reborn.
If the false vacuum were a bit more stable, the universe might have remained forever in uncertainty, never coming into existence.
In Stephen Baxter's collection 'Vacuum Diagrams', bubbles of new vacuum give birth to universes with different laws of physics.