You’ve all seen this in the movies. The good guys are flying through space and find a hostile ship. Disregard the extremely low chances of this actually happening. What’s the first thing the show’s heroes do?
If you said “Red Alert”, you’re right.
One thing that movies always seem to do is change the operating lights to red. Anyone who has sailed in a real warship will tell you that this is wrong. Please note that this all applies to Canadian warships. If anyone can correct me on other countries’ procedures, I will add the information here.
I like how the ship's emergency lighting in #TheExpanse is bright blue. It always makes me laugh in Star Trek when they go to Battlestations and immediately dim all the lighting so that nobody can see what the hell they are doing lol.— Spacedock (@SpacedockHQ) January 14, 2018
White lights during the day
Like every other human, we like to see what we’re doing. In general, this requires white lights. During the day, a warship has white lights running almost everywhere. There are a few exceptions, of course:
- The bridge is dark. The reason for this should be obvious. If it isn’t, try driving with your interior lights on. You’ll notice that it’s much harder to see what’s going on outside. Additionally, (and more important to a warship than to a car), you’re much more visible.
- The Operations Room uses red lights. Rumour has it that this relieves eyestrain in a room full of old CRT terminals. I don’t know if this is true.
Messdecks are dark. This is where people sleep. In a “1-in-2” schedule, you will almost always have people sleeping. These people appreciate their sleeping area being dark.
Apart from this, we have white lights during the day.
Red lights at night
At night, we like to preserve our night vision in case we have reason to go outside. Red lights keep human eyes closer to “dark” conditions than “light” conditions. About half an hour before sunset, we will “darken ship”. This entails the Petty Officer of the Watch switching common area lights to red. Additionally, office spaces will have half of their lights turned off. This allows a compromise where we can see what we’re doing, yet still be ready for action.
Just because the ship is darkened doesn’t mean that we can’t turn lights on. For example, cleaning tends to happen in the evening. Cleaning works better with lights. And, since we’re military, the cleaning needs to be inspected. This means that the inspecting officer will also require white lights (although this is sometimes done with a flashlight instead).
White lights for emergencies
All this brings us to emergencies. Remember, in the movies, warships like to turn on red lights when things are going wrong. In actuality, this is the time that you want to see what you are doing.
If the ship is in Action Stations (we’re expecting an attack), we may keep red lights on near the exits from the ship. This reduces blindness as people to transition from a brightly-lit station to an outdoor location. However, we will still have white lights in the areas that we intend to work or muster in. If a team needs to send someone out to a smoky room with breathing apparatus, the team leader needs to inspect. This requires white lights.
If the ship is in Emergency Stations, something bad has already happened. This means that we want to see everything we can. It also means that we probably don’t care about someone else seeing us. Either they caused the damage and know we’re there, or we want them to find us and render assistance.
Edit: Other militaries
Immediately after posting this I was corrected. Apparently, at least some US Navy ships use blue for action stations.
Low wavelength light to avoid being spotted makes a lot of sense in a surface navy. It's a non factor in a space navy. And the lighting shifting to blue in battle mode is directly from a tour of an Aegis class destroyer's CIC.— James S.A. Corey (@JamesSACorey) January 16, 2018