The main ingredient is a small amount of mercury, which is placed inside a strong yet light container made of a composite material such as Kevlar.

ECONOMIST: Mirror, mirror

One way to compute its value is to shine light through a gas-filled container.

ECONOMIST: Fundamental physics

The spectrum of light that emerges from such a container will show a series of dark lines interrupting what would be a continuous rainbow.

ECONOMIST: Fundamental physics

The container port recently received the green light.

CNN: BUSINESS