Why does a crumpled paper balloon inflate when batted around?

An unexpected way to inflate a balloon - Numberphile

An unexpected way to inflate a balloon - Numberphile Watch this video on YouTube. Numberpile looks at an interesting phenomenon using a common Japanese toy: a small paper balloon that…

Numberpile looks at an interesting phenomenon using a common Japanese toy: a small paper balloon that can be crushed and re-inflated. What's the science behind it?

The balloons are called kamifusen and are related to the sky lanterns that make such spectacular launches.

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An unexpected way to inflate a balloon (YouTube / Numberphile)