[NullPrefix]

>twelve football stadiums stacked together

I understand that football stadium play area is standard, but how do you measure height? Is it a foul to kick the ball too high in the air? The play area, I assume isn't limited vertically.

[wlesieutre]

It says "volume of twelve stadiums" so maybe by treating an entire stadium as a giant bowl up to the top of the seating? But who knows what stadium is the reference stadium - that's not a consistent thing like the size of a football field.

[Narkov]

Excellent point. I just wish they'd use the correct SI unit for this kind of thing - "libraries of congress".