Most common answers to the question which follows the answers:

1. "Nothing"

2. "10,000 pounds"

Now the question:

**What is the mass of one cubic mile of air at sea level?**

Assume STP, of course, and a perfect cube. In other words, imagine a strong steel box 1 mile by 1 mile by 1 mile.

If it were evacuated, sealed, and weighed at sea level, and then unsealed and air allowed to fill it, what is the increase over the tare weight?

The answer will astound you.