Invisible Questions

To cook an egg at altitude, does it have to be boiled longer than at sea level?

The world is full of standards. Why do we have the ones that we have, and do we deserve them?

The ancient Romans constructed aqueducts to overcome valleys. Why didn’t they just use pipes instead?

The electrical grid is made up of masts of different shapes that carry a variable number of power lines. What is the logic behind this variety?

Mountains are generally considered terrain elevations. But what distinguishes a mountain from a hill? And if an elevation is very close to the one next to it, when do they still belong to the same mountain, and when do they become mountains in their own right?

Some hard cheeses are full of holes, commonly known as eyes. Where do these eyes come from, and why did they start to disappear in what has come to be known as the Great Eye Crisis?

Most fish are vertical, but some are horizontal. How come?

On most sundials, the meridian — the mark indicating the sun’s highest point in the sky — points to 12 o’clock. But sometimes, it points to a much later hour, between 4 and 8 p.m. How come?