Here's Why The 'Power' On-Off Button On Our Devices Has This Weird Alien Starship Symbol

You probably hit this button at least five times a day, knowing exactly what it does without necessarily knowing why its symbol is designed that way.

It’s an on/off switch, so why exactly is it represented by a stick and a half moon?

If you know the context of the symbol, it’s actually very easy to parse what it means. Those aren’t actually just symbols on the power switch, they’re representations of numbers. Specifically, ‘one’ and ‘zero’.

The symbol is a 1 in the centre, while the crescent below it represents a zero. It draws from binary, the language of computers made up of only zeros and ones. In binary, 1 represents the on state of a transistor in the computer’s processor, while zero represents the off state. Hence, the on/off switch.

But there’s more nuance to it as well. If the line interrupts the circle it means it won’t fully cut power to the device, merely switch it to a standby mode. If there’s instead, a line fully enclosed in the circle then it’ll fully shut down. Of course, the point of using a symbol in the first place is to make the button’s function intuitive.

It was the International Electrotechnical Commission that added the symbol to the “graphical symbols for use on equipment” collection in 1973. This list also contains the universal symbols for temperature (a mercury thermometer icon), you car’s headlights and windshield wiper controls, and even the fragile symbol found on shipping boxes

It’s just that the history of the symbol has gotten lost in the process.