Why do pirates always cover one eye?

When it comes to "single label", we often associate piracy. Many people believe that pirates cover an eye to protect the eyes. Or injured, blind, so I have to cover it.

Cover one eye to help pirates quickly adapt to the murky conditions inside the ship's cabin.

However, the answer is to increase visibility in the dark.

Because from morning to night, pirates need to go back and forth on the deck and in the cabin. The deck is always bright because of the sun, but the cabin is dark. Covering one eye helps pirates quickly adapt to the murky conditions inside the ship's cabin.

Discovery Channel's MythBusters program used to do a validation experiment.

They let a person be stimulated by the light outside, then enter a dark room. As a result, it takes 5 minutes for the person to adapt.

But if you let other people wear one eye cover for 30 minutes, it is also stimulated and then enter, the adaptive time will be only 2 minutes.