The International Space Station is full of holes. Here's why.

Astronaut Don Pettit, the unofficial Don of space photography, explains some of the space oddities of the International Space Station's design in this episode of the YouTube video series 'Smarter Every Day.'

It's all about about the cupola, and features a demo from Italian astronaut Samantha Cristoforetti.

"7 HOLES in the Space Station – Smarter Every Day 135" [youtube.com, HT: Mitch Youts]

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