Letter: We need a replacement for a standard light

From Danny Colyer, Bristol, UK

Leah Crane tells us that batteries on the New Horizons spacecraft can power the equivalent of three standard light bulbs (5 January, p 7). What is a “standard light bulb”? Once upon a time, I might have imagined a 60-watt filament bulb, but they are obsolete. It would make more sense to say how many watts they can supply.

The editor writes:

• The batteries deliver 190 watts, and we were indeed thinking of 60-watt bulbs.