The key is that there is a broad, continuous spectrum between gamers that buy used and gamers that buy new.

FORBES: Prediction: Neither Xbox 'Durango' nor PS4 Will Block Used Games

These give out a continuous spectrum of light, and thus affect a wide range of frequencies that are of interest to astronomers.

ECONOMIST: Going, going, nearly gone

Mr Ball next treats us to a brisk description of the human eye (remember rods and cones from school biology?), an explanation of why Newton was right and Goethe wrong about the composite character of white light, and an account of the 19th-century regimentation of the continuous colour spectrum by means of colour wheels and other classifying devices.

ECONOMIST: Science and history of colour

Wealthfront also found that more diverse portfolios, in the middle of their risk spectrum, had the most to gain from continuous tax-loss harvesting compared to year-end only.

FORBES: A Magical Tax-Loss Harvesting Machine?

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