The Lighthouse at the end of the world

My world is dead and mostly unexplored. And at the end of the known world, there is a beacon which serves that singular purpose: warning anyone approaching that beyond this point, there is nothing else.

This is no ordinary lighthouse

It is unconventionally designed. Because, instead of a rotating fresnel lens, it uses a vapor lamp which is switched on and off in patterns to form its navigation signal. This means the light turns on, and off, all day. All night. Forever. But WHY would it be built this way? Logically?

The keeper of this light goes insane, for several reasons. But the light itself ultimately breaks him. Instead of a quietly sweeping beacon scanning across the horizon peacefully like most lighthouses, the light has been designed as I have stated. It completes a pulsing pattern of three repeating flashes. The mechanism uses old electrical “valves” to connect the high powered arc lamps to their circuit, then disconnect it. The sound of the valves is the what is needed in my story. It is incessant, and inescapable. With help from many other factors, this tik-ah sound finally drives my character mad.

I had written the story and the effect really worked. But only after did I think about it; lighthouses with a rotating lens are almost silent. I know lighthouses don’t normally use this switching mechanism. But the story is done, and it’s awesome. I only need to justify this unconventional mechanism somehow, possibly by geography or topography (hence the title). Energy considerations? I don’t know. My thoughts lean toward some unique requirement in the light that it must shine only in certain areas, and not in others, or maybe it has to reach some points simultaneously which a sweeping light can’t do.

Q: Why would a lighthouse choose a flashing beacon instead of a rotating beacon?

Most lighthouses use rotating fresnel lenses, gapped to form the pattern as it sweeps the horizon. Lightships, I believe, may have used flashing beacons. But what factor might lead to the decision of a valve instead of a rotating fresnel lens?

For what practical reason did a lighthouse use noisy tech that is drives my keeper mad?


Story snippet

Here is part of this chapter, showing the effect the light has:

“OSCAR OSCAR, We have ze supplies. Nitre, one thousand two hundred gallons. Water, two thousand five hundred gallons. Do you hear?”


A pause on the radio. “Fire bucket, ten. Lamps, twenty-four. Wrenches, forty. Standard sizes. Cable, eight hundred feet. Gyros, eleven.” Another pause. “Do you hear?”


Another pause. “Books, thirty seven. Clothes, …”

“Which books.”


“You ‘ave Dostoevsky?”

Pause. “Que?”

“You ‘ave the book, ‘bout the brothers?”

“Attendez une minute” pause. “Oui, ze book is here.”

“I be ready.”

“Bon.” Radio noise from the room continued as the pilot and copilot spoke. The man listened, curiously. They were not speaking to him, they were speaking French. They forgot to shut off the radio. “Quel travail misérable.” More French came across which he did not understand, but it was apparently funny. He pulled a large lever to turn off his radio. Electric filaments began to fade from its tubes.

The man walked to a door. A crucifix hangs above it. He pulls back a long lever along its side. Locks along the edge are linked together, and turn in unison to release the door. Opening the door, a Steam engine pumping sound grows louder. He walks into the room, the light blinks in threes with the sound: Tic-ah tic-ah tic-ah. Tic-ah tic-ah tic-ah.

He takes down a large pair of trousers in a heavy fabric. He puts his legs into them. He sits on a bronze bench and puts on heavy shoes with large, wide soles. The pulsing lights continue in threes. He picks up a large jacket, and takes two metal bottles. He clips them into the inside of the jacket, they let out a fading hiss.

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    $\begingroup$ This is unanswerable; the only criteria for being correct is that you like an idea more than others, rather than it being correct according to provided information. $\endgroup$
    – rek
    Commented Aug 23, 2023 at 5:03
  • $\begingroup$ You probably mean relays not valves - or if its high voltage, its called a contactor. I find the clicking of relays kinda lovely myself :D $\endgroup$ Commented Aug 23, 2023 at 10:57
  • $\begingroup$ In the United Kingdom, they still refer to electronic vacuum tubes as valves. $\endgroup$
    – Vogon Poet
    Commented Aug 23, 2023 at 12:35
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    $\begingroup$ @rek That implies that the decision to use rotating fresnel lenses was also arbitrary rather than a design consideration. I think the choice between technology A and B is usually not an arbitrary choice. Here I ask what world-based characteristic would drive the choice of tech B over tech A. My liking the answer doesn’t matter at all; the engineering answer is the engineering answer. What further information is needed in your opinion? $\endgroup$
    – Vogon Poet
    Commented Aug 23, 2023 at 14:47
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    $\begingroup$ Real lighthouse keepers could suffer problems just because you could not sleep for more than 2 hours at a time. $\endgroup$
    – John
    Commented Aug 23, 2023 at 20:41

8 Answers 8


The beacon is directional.

Rotating lenses are great if it's safe to send the beam in all directions equally. It's also fine if part of the arc can be blocked to cut the pattern in that direction. They're less good if you need "3 short pulses from 0 to 45 degrees, 2 medium pulses from 45 to 90 degrees, and on constantly from 90 to 180 degrees" (there are some combinations that could be achieved through clever use of a rotating lens assembly and some blocking material, but plenty that either couldn't be or where the gearing would be highly complex).

Thus, you don't have a single beacon, but you have several, each pointing in different directions. Each light is controlled by its own set of "valves", which click incessantly.

Originally, that was a design feature: the lighthouse was designed with the idea that an automatic monitoring system would listen to the clicks and watch the lights, making sure that everything was in working order. That system broke down. While awaiting repair, the soundproofing was removed so that the keeper would be able to hear them and note any deviation. Since then, the funds to repair the monitoring mechanism have never quite materialized, so the keepers are slowly driven mad. On the plus side, they're really good at listening for deviations to the click pattern.

Why not have multiple lights with their own rotating lenses? The monitoring system: either its "eyes" would need to be too far away from the lights to ensure that they didn't "see" other light sources or they would interfere with the rotation system of the lenses.

The lighthouse is a lure.

The lighthouse wasn't actually created by the denizens of the Something, but by the Nothing. Much like an anglerfish, it was intended to draw those of the Something to the border of the Nothing so that the Nothing could draw sustenance from the Something.

The organization that operates the lighthouse for the Something are well aware of this fact. They choose to sacrifice one or two minds to the Nothing every couple of years; doing so keeps the light active (thus keeping others of the Something away) and keeps the Nothing sated (at least, for now).

Why not both?

The former is the official reason, the latter is the real reason.

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    $\begingroup$ I like the idea of three pulses being three independent lamps. If cycle durations are coprime numbers and "clicks" are indistinguisahble from each other, then it would be hard to see a pattern between clicks and that seemingly aperiodic sound would be really annoying. $\endgroup$ Commented Aug 23, 2023 at 18:19
  • $\begingroup$ This fits the Q best. Thanks to others for many ideas beyond the ask; I’ll write as best I can (how do you narrate a Shepherd tone?) My question was: Why a lighthouse chose flashing light over rotating one. The post said the final cause of madness was the noise - it was the straw that broke the camel’s back among other psychological hazards inherent to such a remote outpost. Honorable mention: Nosajimiki, jpa (luminosity/recharging time), Nam2000 (spark gap), Falco (vertical slit, wear), TheDemonLord (disruptive Biorhythm), Revolver_Ocelot (reliability). The mechanism is surely maddening. $\endgroup$
    – Vogon Poet
    Commented Aug 24, 2023 at 16:51
  • $\begingroup$ @Revolver_Ocelot thanks for noticing the need for vertical beam width! I never considered that, and how it increases the power requirement for the lamp. $\endgroup$
    – Vogon Poet
    Commented Aug 24, 2023 at 16:54

You are behind the times

Before modern day rotating beacons were used because there either were no way to turn light on and off relatively quickly and repeadetly (for light produced by burning fuel) or it would greatly shorten light source lifetime (for filament bulbs), so periodically blocking the light by a rotating structure was the best solution at the time (light itself doesn't rotate, blackout structure and focusing lenses are).

Modern lighthouses use static LED arrays which are turned on and off periodically. In addition they are mostly unmanned and solar-powered, with batteries which are charged every day to allow function during the night with a diesel generator as a backup source.

Most lighthouses either already did the conversion to flashing electric lights or are in line for conversion. Ones that remain either have a historical importance or are a popular tourist destination.

For your needs, you need blinking design to be more robust than rotating one.

As design without moving parts is inherently more reliable that one that has them, your only problem is reliability of flashing lamp vs constantly burning. And there lies the problem: incandescent lamps hate on-off cycles. Your arc lamps (I assume that they are built like HID lamps) are not better, since the highes wear occures when they are reignited before completely cooling, blinking kills them fast.

You need to make lamp resilent to constant cycling somehow for static blinking design to be preferable to rotating one.

Or maybe rotating mechanism is for some reason less reliable, so it is better to replace lamps regularly than to constantly repair rotating system.

Or you have to maintain a specific light characteristic (sequence of specific length on-off pulses which makes a light identifiable, actually used in navigation) to aid navigation. Which is easy to do with blinking light, but hard to do with rotating system.


I've got two/three answers to why the Lighthouse keeper goes insane. Not going to comment on the design of the Lighthouse though.

The Mechanism of the Lighthouse is at a specific frequency that interrupts normal brain waves

This wasn't a conscious design choice, it was a freak chance that the combination of Valves and the frequency of the electricity creates an effect in the Lighthouse keeper. It disturbs the Brain waves, not enough to be fatal, but enough to interrupt sleep. Slowly, over time, these disturbances grow more and more (due to the longer exposure) and start to manifest symptoms of Madness, this causes a sort-of accelerating effect where the Brain is producing it's own hallucinations, that themselves are further distorted by the interference.

Starring into the Abyss, the Abyss stares into you

I think that's a Nietzsche quote, or at least, some paraphrase of it. You said the Lighthouse is at the end of nothingness. No matter what the Lighthouse keeper tries to do - they will gaze into Nothingness. Not like merely empty space - but actual nothingness. First it might be an accidental glance, then perhaps a fleeting look, then as time progresses and their self-control and resistance starts to fade, they will look longer and longer into the void, their sanity pouring out of them as the Human Brain cannot comprehend true nothingness.

It's not actual Nothingness... or at least not that we can comprehend

There are things... In the Dark... Ancient things... Malevolent things... Things from a time and place that has long since been forgotten.

They live beyond time and entropy, in the void in blackness and they can see us, in our world full of light, corporeal form, energy and emotion.

And they hate it. They would dearly love to invade our world and suck everything from us, but they cannot. See, the Lighthouse has a secondary purpose... It keeps them at Bay. It's the reason why it must be maintained, it's the reason why one unfortunate has to sacrifice their sanity to keep it running.

But although they cannot traverse past the Lighthouse... They can whisper to the Lighthouse keeper, in their dreams, calling them to look into the void, to see the manifestation of timeless hatred of life.

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    $\begingroup$ You’re a natural storyteller I can see. But your opening sentence basically says you’re not going to answer the question LOL! Thanks. $\endgroup$
    – Vogon Poet
    Commented Aug 23, 2023 at 2:53
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    $\begingroup$ @VogonPoet - I answered the question that most interested me - The idea of something at the edge of nothingness was interesting. $\endgroup$ Commented Aug 23, 2023 at 4:03
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    $\begingroup$ "It's not actual nothingness" ... explains the mechanism. It's a really bad idea to shine a bright light into the void, which a 360 degree rotary mechanism would inevitably do. So there are permanently fixed mirrors, lenses, and blocking plates, to make sure no light goes into the void. So if flashing was deemed desirable, it has to be done with electrical switches. $\endgroup$
    – nigel222
    Commented Aug 23, 2023 at 16:57
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    $\begingroup$ @nigel222 you can avoid flashing the void by replacing some of glass storm panes with non-transparent ones. I believe that was actually done to avoid flashing populated areas. $\endgroup$ Commented Aug 23, 2023 at 17:27

A rotating beacon with a lens has several benefits. The lens bundles the light into a bright beam, increasing brightness and reach. The rotation sweeps the beam in a wide arc over the horizon, covering a wide arc of sea.

Several factors could offset these benefits:

  • a rotating beacon needs to run smoothly, maybe dust/sand in the atmosphere makes bearings hard to maintain and prone to failure.
  • a rotating beacon can only flash in simple periodic patterns. If you want a complex pattern, like a whole message in morse-code, you will need relays
  • If the light is for air-ships you cannot focus a beam on a single height like on the sea, you would need a special lens to focus a slit spanning from ground up in the sky. A relay might be easier.
  • depending on the energy and light-source you might be able to produce very bright short pulses with capacitors, while a traditional rotating beacon uses a permanent light source

If you include the capacitors, they can also emit a high-pitched whining noise while charging - static electricity building up in the air. You can almost taste it before each bright flash of the light (like flash in old cameras). And you could also use a complex pattern of light flashes (aperiodic, so off-world travelers will know it is not a natural phenomenon, but a deliverate signal)

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    $\begingroup$ Incidentally, the high-pitched whining noise might just at the edge of hearing perception, so that no one quite hears it, but over time it would certainly drive one mad... oh wait, the Lighthouse Keeper! $\endgroup$ Commented Aug 23, 2023 at 12:33
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    $\begingroup$ @MatthieuM. I do not know what exactly causes CRT TVs to emit high-pitched noise that most people cannot hear, but it makes me unable to focus or sleep in the same room as the TV. I cannot fathom what would happen to me if I heard it 24/7. What is worse many people wouldn't believe me when I tell them about it. "There is no noise, you just imagining things" $\endgroup$ Commented Aug 23, 2023 at 13:27
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    $\begingroup$ Technically I think this system would need a ballast (high frequency transformer) and some large capacitors (they were called condensers at that time). The first rectifiers were two-terminal vacuum tubes, and called valves rather than diodes. Now I have a writing challenge to artfully describe this new maddening noise that can’t be heard. $\endgroup$
    – Vogon Poet
    Commented Aug 23, 2023 at 14:57
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    $\begingroup$ @VogonPoet like an ivisible mosquito flying inside your head. Like a tinnitus you hear in an absolutely quitet room. Pretty annoying sound. $\endgroup$ Commented Aug 23, 2023 at 16:37

There's something about the bulb

It's built by a mad engineer, with a requirement that it run on as little power as possible. Some massively impractical abuse of physics later, and he has a flashing bulb, that works on completely contrary priciples.

It lights things by emitting photons, as normal, for a flash. Then by some unexplained process, reversing the flow of entropy, or time (left unexplained by the protagonist, who is not a physicist), it drags all those photons back, recapturing the energy.

It also has the benefit of stopping the Nothingness from engulfing the lighthouse, by undoing the damage each reversal, but has the downside that the keeper watches a consistent tearing away of a large chunk of reality, and then seeing it restored on each gap between flashes.

From a proper physics perspective, it doesn't make a lot of sense - but for a Lovecraftian horror, it might work. You'd see tendrils of nothingness strip away and decay bits of the tower on each flash, and then the gap between flashes drag the pieces back together.

The lighthouse keeper is completely insane, not just from watching this, but also from being partly or completely destroyed by the Nothingness, before reappearing again seconds later.

  • $\begingroup$ My vote. LEDs flicker, sometimes I feel like I can see it. They make high pitched noise, particularly when attached to something that causes dirty power like a dimmer. Or like those tube fluorescents. The color is "wrong", too blue, too yellow. $\endgroup$
    – DKATyler
    Commented Aug 24, 2023 at 18:11

Why the 3 blinking lights?

This is a thing we do in real life. Modern communication towns have blinking lights on them at evenly spaced heights. The blinking means that the lights consume less power than if they stayed always on. When you need a light bright enough to be seen from many miles away, a blinking light can give you much more reach than a solid light of the same power usage, and blinking is also more likely to catch someone's attention than a solid light pattern which further increases your effective reach.

The spinning thing that older lighthouses did was to send out a directional light sweeping across the sea (again, for maximum reach), but when creating a beacon for aircraft, you don't want a directional beam of light because you don't know what elevation to aim at. So, an omni-directional light that blinks is the preferred beacon method for aircraft which is what this lighthouse is meant to serve.

The reason there are 3 lights is because of how tall the tower is. Communications towers that are tall enough to reach into low air space are supposed to place lights about every ~45 meters. This is because at night, you can't tell how far away a light is, but if they are a known distance apart, you can tell distance by thier spacing.

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Why is the lighthouse keeper driven mad?

The sound of the light creates a Shepard Tone

Shepard tones are a pattern of sounds that increase or decrease over time in such a pattern that they start and stop exactly one octave apart. So your lighthouse has 3 lamps. As one lamp starts up, the sound starts low and slowly increases in frequency until it fades off one octave later and shuts down. But each of the 3 lights are staged 1/3rd of a cycle apart. Because the brain has a hard time differentiating two sounds that are one octave apart, it makes the sound appear to continue to increase in frequency infinitely until your mind perceives the existence of a sound so high pitch that it actually exceeds the limits of your ears to hear. While a descending Sheppard tone can be calming, the kind that goes up in pitch like this has been reported to cause considerable anxiety and panic attacks after just a few minutes.

A person who had to live day-in and day-out listening to an ascending Shepard tone would very likely develop a severe anxiety disorder, and anxiety disorders are linked to certain schizotypal symptoms like hallucinations and paranoia.

And/or he is alone

Humans are not meant to be alone. Whether the sound of the lights themselves are a major issue, lighthouse keepers who live by themselves, cut off from the outside world, are at a severe risk of solitary confinement disorders. When placed in solitary confinement, humans often exhibit a wide range of mental health problems including: anxiety and stress, depression and hopelessness, anger, irritability, and hostility, panic attacks, worsened preexisting mental health issues, hypersensitivity to sounds and smells, problems with attention, concentration, and memory, and hallucinations that affect all of the senses, paranoia, poor impulse control, social withdrawal, outbursts of violence, psychosis, fear of death, self-harm or suicide

So, even if the sound of the lighthouse itself is nothing extraordinary, it could easily become a fixation for his isolation induced psychosis leading him to believe that it is the source of his growing madness.


The beacon does not only emit light

The mechanisms you describe for controlling the beacon could also (and with all likelihood without careful design would also) generate a great deal of broad spectrum electromagnetic radiation. If the light operates on some sort of spark-gap mechanism for switching on and off, perhaps this same spark gap is being used to generate a radio/x-ray/light/infrared/etc pulse as a warning for systems that can't sense the light as easily.

As a plot device this may be additionally useful:

  • The X-rays may cause all sorts of other problems within and near the tower (or motivate careful shielding for certain areas).
  • The radio signals could make communication near the tower very annoying (not only can the operator hear the click, he can hear the amplified click on the radio).
  • As people approach the tower the interference would get louder - perhaps a nice warning of their impending doom. Even if they can't see the tower they could be picking up a increasingly loud click on their radio.
  • A remote location could monitor the tower for correct operation even without direct line of sight by monitoring the ionosphere reflection of the radio pulse.

Strobe light

The brightest lamp they have technology to manufacture is a strobe light, such as xenon flash tube. Depending on the atmosphere, it might even not need a lamp but use an artificial lightning bolt.

Because the lamp can be illuminated only for a bright flash before a second or two of recharging, it necessarily has to blink and there is no point having a rotating lens.


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