The moiré effect lights that guide ships home

I'd never heard of moiré effect beacons until I got an email asking me about them. It seemed like a really clever idea - but it was really hard to research. Or at least it was, until I stumbled upon one magic phrase that revealed its history.

It turns out this thing's called an "Inogon leading mark" or "Inogon light" -- Inogon, not Inogen -- and it's a Swedish invention from the 1980s. But there's still a question: why is being used to mark an undersea cable, instead of guiding people home?

(Full disclosure: there were some weird strobing effects from the light that only showed up when I got the footage into the edit, so the image you see here has been digitally stabilised so it appears the same way on screen as it does in person!)

Thanks to Andrew Stine for suggesting this!

References:

(you can find contact details and social links there too)

[TomScottGo]

I'm getting emails from people who've misunderstood what I'm asking at the end of this video. Don't waste your time copying what I've already done! To be clear: I'm looking for solid evidence of why this particular light was chosen for a use that doesn't seem to make sense: flagging something to avoid. I don't need more information about where it is (Southampton) or what it's pointing at (a pipeline)!

[TomScottGo]

I tried for ages to fit the ♫ If new lines hit your eyes when two patterns combine, that's a moiré ♫ joke into my script, but couldn't figure out how. I put it here instead.

[reynaldneron]

Hi Tom, in maritime navigation, navigation aids always shows where the danger is. Since people have been going to sea, they have placed fires on dangerous peninsula, that are now light houses. Nowadays, there is a navigation aid called "isolated danger" (red and white marker - to simplify). That marker indicates where the danger is, and leave it to the seafarer to decide what is the best way to avoid it. Based on that principle, the arrow shows where the underwater cable is, and not where the boat should be going, that is a decision left for the responsibility of the seafarer. Hope that helps. (If they - the organisation in charge of managing those navigation aids- tell you where to go, then their responsibility is engaged, that is why they never do it).

[OfficialMGMusic]

The cool thing about this community is that within minutes after the video went online somebody updated the wikipedia article and noted that they're called Inogon lights.

[shawniscoolerthanyou]

Imagine being the person that typed "inogen" instead of "inogon" and wasted precious hours of Tom Scott's life.

[aantonop]

Have you looked at PAPI lights at airports? Not Moire effect, but using narrow beams of light to change color depending on whether you are observing them from above or below the 3deg glideslope on approach. Similar concept, observer-angle-based variation in picture.

[hignaki]

The back of our old humvees in the Army had something similar (but different) to these using fresnel lenses. When driving with blackout lights, it is normally difficult to maintain a convoy, because you can't really tell how close the vehicle in front of you was. The humvees had special blackout taillights that showed two dots when you were the proper distance away, three dots when you were too close, and one dot when you were too far away. In addition, if you were off to either side too far, you'd see only one dot "streaked" towards the direction you were supposed to go, like a comet with a tail.

[OrigamiMarie]

I call this issue with researching things the Rumpelstiltskin problem. Once you have the name, you have the power to understand it. Until then, it has power over you.

[LuizAlexPhoenix]

That is named an Anomalous State of Knowledge (ASK), when you are aware of a need for knowledge but cannot find it because knowledge is cumulative so to find specialized knowledge you require previous knowledge, such as terminology. It's a very important part of Information Science that we make knowledge available to the most people possible and not only specific demographics, because often times people seeking information and explicit knowledge are those without the tacit knowledge of how to search for it.

[Styrola]

This was fun to see. When I was in high school Inogon had their "innovation factory" in our village. They made other moire pattern things like a spirit level with a circular moire "window" that also produced arrows if it wasn't aligned.
They also experimented with a silicone graphite pressure switch. And even fluorescent light to see if it could be useful to make traffic safer.
The innovator Bergkvist also was a uncle to one of my classmates.

[rahulkayastha]

You are perhaps one of the best content creators on youtube. Thanks for everything you do.

[lettersnstuff]

I absolutely love that you would take the time to go out and find one of these lights, and make a video on it, just to say “I think this is really neat, if people know more about it, I’d like to learn” because it really does feel more like a 2-way relationship with viewers, as opposed to just a presentation to us.

[SciManDan]

I know that when I ran past it the other day I thought it was going to burn me to a crisp!

[marinepilotchris]

Well, I’ve got to admit that after 20 years at sea, with 7 of those years as ships Captain followed by 5 years and counting as a Marine Pilot, I have never heard of these things ever!
I know about the more modern sector leading lights that change colour to indicate position in a channel, and also the simple transit leads but before today I’d never heard of Moiré or Inogon. Every day is a school day it seems!

[antonymitchell]

When the light, changes signs, when you're on the right line, that's a Moiré..

[RandomGeko]

Looking forward to see a spin off series of "Things You Might Not Know" called "I Don't Know..."

[JonTheGeek]

I love that someone has finally told the world how hard it is to search for obscure things when you have no idea what it's called. I've had that feeling too many times before.

[liamcrabbe]

“When a grid misaligns with another behind, that’s a moire!”
(Credit to xkcd)

[caioac-nqkc]

PLEASE!!! I LOVE THIS! We need more videos for mysterious inventions that can be so simple or so complex and yet all unique, but haven't been recognized by the world.

[juandenzer]

"And normally I try to discourage messages like that. I am not Google or a reference Librarian"
Thank you. You sir are awesome.
A Librarian