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I have a sci-fi world that is very technologically advanced (at the stage of "sub-singularity" where they have already invented AIs posing danger to humans, but not achieving singularity, so it's not God-like and can be fought etc.). Both humans and the machines (so far the only inteligent "races") use technology. I want to specifically concentrate on the human technology regarding displays - are there any advantages, and could there be any advantages to use Cathode-Ray Tube displays, i.e. on a spaceship, despite the general inferiority of such display to LCD or plasma. Of course the old cathode screens "sucked" in their flickering, glitches, and image quality. But could there be some reasons, why their use would still be a good option to consider. Particularly in the military-utilitarian uses (similarly to how military planes and civilian planes differ) or industrial uses.

I was thinking about potential costs. Could it be that on some planet the cost of producing the liquid-crystal display is to high, because of material shortage? Could there be some other advantage to CRTs? Are they used anywhere right now in professional industries, for other reasons than "not yet replaced"?

I want to stick extremely true to physics as well as present a reasonable, believable future (meaning no "laser guns" shooting visible "laser bullets", no "telekinesis", at least without a good, scientifically correct explanation for it). But I also want to world to be consistent in terms of economy (at least to some point), people's choices etc. So if there are to be CRT displays, they need a reason to be there.

Finally: why do I want to include them? Cause I like the glitch effects, and generally their style. Already military ships will use terminal akin to the ones often used in linux systems - but this isn't "forced" retro, because I personally believe that the terminal is the best way to use a system ;) Anyways I can find justification for a military spaceship depending on an old-school terminal interface instead of some "touchscreen" stuff, but cannot find justification for using CRTs instead of LCDs.

EDIT: Thanks for the current answers, but I'd like to mention that the world I am describing is "our" world a number of years in the future. Interplanetary flight IS possible, common and even somewhat easy (the technical explanation for this exists, but I shall not go into details here). However we have to take into account the current human achievements, so LCD is or at least has been known. I guess it could be possible that some factory on planet XYZ which produces spaceships, got very very old design, and copied it. Or maybe the machines (which are quite a diverse, and active race) have been designing the spaceships for humans, but downloaded the easiest to find blueprints?

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  • $\begingroup$ Welcome to WorldBuilding,Niteraleph! If you have a moment please take the tour and visit the help center to learn more about the site. You may also find Worldbuilding Meta and The Sandbox (both of which require 5 rep to post on) useful. Have fun! $\endgroup$ – FoxElemental May 18 '18 at 14:00
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    $\begingroup$ "flickering, glitches, and image quality" There's no reason why CRTs have to "suck" with regards to those. A quality CRT monitor (including the tube and its support circuitry) driven at a proper refresh rate, at its dot pitch and with a high-quality input signal (analog or digital) can be every bit as clear as a TFT screen driven with a digital signal. If you want to see something that sucks, then drive a flat-screen monitor with a low-quality analog signal; even better, at a resolution other than an integer fraction of its native resolution. $\endgroup$ – a CVn May 18 '18 at 14:03
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    $\begingroup$ CRTs (until they get old) are sharper and have better contrast. They also easily go up to 85 and 120Hz refresh rates. $\endgroup$ – RonJohn May 18 '18 at 14:04
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    $\begingroup$ Under some circumstances, the signal radiated from the electron guns, scanning circuitry, and associated wiring of a CRT can be captured remotely and used to reconstruct what is shown on the CRT using a process called Van Eck phreaking. So they could use it for eavesdropping on other less advanced planets , without actually going down there. $\endgroup$ – The Integrator May 18 '18 at 14:05
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    $\begingroup$ @Niteraleph it seems unlikely to me that CRT would become cheaper than LCD at a point after LCDs became dominant. It's possible that there is some specific material that LCDs need that CRTs don't, but there's a significant hurdle to restarting mass production of an obsoleted technology so the advantage needs to be large and immediate. $\endgroup$ – Kamil Drakari May 18 '18 at 15:00

13 Answers 13

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Ease of manufacturing in the field.

Any vessel operating far from home needs a way to deal with repairing damage and replacing broken or worn-out parts. Sailing ships carried saws and axes so they could cut down trees to repair the ship. Modern military ships have machine shops and welding shops to manufacture parts in the field.

A spaceship operating for extended periods away from home and help is going to need a way to replace anything which is essential to running the ship--either by carrying spare parts or by having the means to manufacture parts when needed. This would naturally include the computer hardware used to run the ship.

Manufacturing LCD or LED panels is a ridiculously high tech process. The process involves large amounts of water, exotic chemicals, micro-scale wiring and glass etching, and bonding together multiple layers of materials. This page about LCDs discusses how they're made, and it apparently took the industry until 2007 to produce LCD panels with better image quality than CRTs.

Cathode ray tubes on the other hand are much simpler and easier to manufacture. The first tube capable of displaying an image was produced in 1925, and televisions using CRTs were on the market in 1934. Color CRTs and color television was available by 1954.

A spaceship which needs to operate without resupply for long periods of time may find it easier to carry the equipment to manufacture CRTs than more advanced types of displays.

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  • $\begingroup$ All of the answers are valuable and provided good input, but if I decided to actually risk going with the CRTs, then this seems the most viable reason. I shall research deeper the issue of manufacture - both CRTs and LCDs, as this may be even incorporated in my world. While the tech in my world is pretty advanced, the ship(s?) where I want the CRTs to be are exactly the type which would benefit from ease of repair in the field and which are much more about practical utility than comfort. $\endgroup$ – Niteraleph May 21 '18 at 7:15
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CRT's are analog.

If humans start seriously worrying about the loyalty of the digital world analog might be valued. And there are a lot of rants about potential analog advantages available.

CRT's are human serviceable.

You can trace wires, manually inspect the parts and hand solder fixes. If people are worried about long term supply issues that might be important.

CRT's can be repurposed as boat anchors, space heaters, rayguns, tape-blankers, and magnetic field detectors with minimal work. If you are expecting to scrounge post-AI CRT's give you good options.

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    $\begingroup$ VGA (and its derivatives) is analog. Just looking at IBM's own lineup for the IBM 5150 PC and successors, which is what evolved into what most people today will call a personal computer (including, to a lesser extent, modern Macintosh computers), all of MDA, CGA and EGA used digital signalling from the graphics card to the monitor, but were all used with CRT monitors. There's no reason why you can't drive a CRT with a digital on-wire signal, nor is there any reason why you can't drive a flatscreen monitor with an analog on-wire signal. $\endgroup$ – a CVn May 18 '18 at 20:36
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    $\begingroup$ @MichaelKjörling LCDs that accept analog signal do so by converting it to digital first. You can't trust an AI to not put a backdoor in there. VGA to CRT is just a bunch of wires and two sawtooth generators. $\endgroup$ – John Dvorak May 19 '18 at 5:27
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    $\begingroup$ @JohnDvorak: Theoretically a fully analogue LCD is possible, but I’d hate to have to draw the wiring diagrams, let alone build the thing. $\endgroup$ – Joe Bloggs May 19 '18 at 15:37
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    $\begingroup$ @JoeBloggs hmm... I'd love to see you draw a fully analogue wire sweep circuit. My preferred choice would be a counter and a row of demultiplexers (are 74xx chips trustworthy?) or better yet a series of good ole serial to parallel converters. It almost seems the best choice to grab a cathode ray tube with an array of photodiodes instead of a phosphor, or a delay line with 1000 wires attached to it. The latter is solid-state but impossible to tune (good luck switching between SECAM and NTSC), the former involves a whole lot of vacuum and probably makes the whole thing count as a Rube Golberg. $\endgroup$ – John Dvorak May 19 '18 at 19:08
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    $\begingroup$ @JohnDvorak: Tube Goldberg, surely? $\endgroup$ – Joe Bloggs May 19 '18 at 22:01
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Racism.

Cathode-ray displays flicker. Humans see them correctly because they are kept at a refresh rate that is good for humans. Other species may have lots of problems. Different species have different flicker thresholds. What looks like animation for us may look like a strobe to other races. Also robots and cyborgs may run at a specific frequency. To them the image could just be a dot.

So it could become a class system. People with expensive high speed visual implants can see CRT's but anyone running at around 60 hz can't. So the rich get crts to show off.

So why do it? So you could watch tv yourself. Put on some headphones and watch that screen. You are rich. And now your servants won't be distracted by an image they can't see or is unpleasant to look at. Also they can't sneak of from work and watch TV if it all looks bad. Maybe when in a way the enemy can't see your instrumentation either.

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  • $\begingroup$ Well this would be an answer to my question, but I specifically mentioned that there are only Humans and Robots. And that I specifically care about humans. Still, not a bad idea to think about. $\endgroup$ – Niteraleph May 18 '18 at 14:38
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    $\begingroup$ This does seem like a good counter to robotic surveillance or manipulation of controls by robotic individuals. Maybe a union of human crewmen mandated that Cathode-ray be the standard to all space ships to prevent robot crews from replacing them on old ships? $\endgroup$ – Pinion Minion May 18 '18 at 16:14
  • $\begingroup$ Jack the refresh rate up to ~1k, and have 1 out of 1k frames be the desired image. Humans see the flicker - that one useful frame. Those with less developed eyesight see a useless solid image. But I don't see why that wouldn't work, and be far easier, with LEDs or LCDs... or just be defeated using a motion picture camera. $\endgroup$ – Mazura May 19 '18 at 15:38
  • $\begingroup$ Unless you're trying to defeat them with epilepsy I don't see how it strobing matters. The lower the refresh rate, the easier it is to differentiate the images. $\endgroup$ – Mazura May 19 '18 at 15:58
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Vector vs raster

CRTs can implement one of two display technologies:

  • A raster display, which is scanned left-to-right, top-to-bottom, to produce a fixed grid of pixels set by the sweep timings.
  • Or a vector display, where the image data is fed in as a set of instructions that both govern the sweep of the electron gun(s) and their intensity.

LCD and OLED displays, though, are inherently raster in nature by virtue of being assembled from discrete pixels. This means that a technological society that embraced native vector display wholesale would have a much tougher time migrating away from CRTs than we did, where most of our mass-market CRT usecases could be readily migrated to LCDs because the display model used was no different.

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  • $\begingroup$ There were a number of old vector systems, particularly aerospace systems that were converted to raster. You just digitize the input lines and write it into a frame buffer. It's not particularly difficult. Same thing with the last vector systems, oscilloscopes. $\endgroup$ – user71659 May 22 '18 at 5:33
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The only real pros of CRTs against LCD or LED, are

CRT do not have a native resolution, they will display in pretty high quality up to their maximum resolutions without requiring any form of scaling and therefore the GPU of the computer can maintain a fairly high FPS, this is why when LCD first came out a lot of gamers still used CRTs, (that and we tended to spend our money on better GPUs rather than screen) however as price was a factor in this and that has since come down so significantly and GPUs are far better these days that this pro has been effectively neutered.

CRTs are capable of true Black, a total absence of light, LCD and LED have black lights so the contrast between darkness and light on screen has to be set as a standard, wheres CRT simply do not emit light in the dark areas so provide basically perfect contrast, however OLED technology has now eliminated this benefit.

Dead pixels, CRTs don't get dead pixels, they can lose an entire tube but this is immediately obvious, whereas an LCD or LED screen can suffer from a dead pixel that will simply not show anything...

Basically, there's only those three reasons to use CRTS over and LED or LCD and about 20 reasons to use LCD or LED over CRT... its gonna be a tough cookie to sell

Maybe... they didn't have Hollywood? maybe Films and TV never progressed well on this alien world, without these driving factors, colour screens would not have been so readily required, so black and white screens were the main thing, if all the people wanted was Black and White at high quality then CRTs would be perfect for it, not point in an LED screen if all they need to do is light up white every time...

in terms of price... CRTs use glass and electrodes, not much else, LEDs use the same elements but also use gallium arsenide (GaAs) and gallium phosphide, so if Gallium was very rare, that might affect its use, however Gallium is used in semi-conductors all over the place, and is a very useful element, so that might affect the world in other ways.

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    $\begingroup$ LEDs don't have black lights, and are capable of "true black". You might be confusing the term with LED lit LCDs which are often marketed as "LED TVs". Also OLEDs are LEDs. $\endgroup$ – Gene May 18 '18 at 15:34
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    $\begingroup$ Note that color CRTs do have native resolution - It's a function of the shadow-mask/aperture-grille. Also, they do get a dead-pixel equivalent: burn-in. Basically, if an image is displayed for a long time, the active phosphor degrades, and becomes less bright. Eventually phosphor areas could become completely degraded and not illuminate at all (though that would take quite a while). $\endgroup$ – Fake Name May 19 '18 at 0:10
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    $\begingroup$ @FakeName - The shadow-mask is there to prevent the wrong color being activated by the electron beam. This may result in a tiny ring of black for each dot on a screen (depends if phosphor lighting "leaks" outwards a bit), but a beam can start or stop within a dot boundary, and the top or bottom of the beam can sweep across within a dot boundary, so that only a portion of a phosphor dot is lit, and it's this sub-dot lighting, that effectively makes the grains of the phosphors the native resolution, so that CRTs do not have a fixed native resolution in the same sense as digital monitors. $\endgroup$ – rcgldr May 19 '18 at 8:57
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    $\begingroup$ Also, CRTs have the stroboscope effect that reduces motion blur: When you watch something move on CRT, you see it at a certain location when it's refreshed, after that, it's mostly your brain that caches the sharp image. When you watch something move across an LCD, the stationary image on the screen does not go away until the next image overwrites it. So, when your eyes are moving across the screen, the object will get blurred by the movement of your eyes. $\endgroup$ – cmaster May 19 '18 at 9:07
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    $\begingroup$ For a monochrome monitor, no shadow mask is needed, and if scrolling is not needed, the phosphor persistence can be quite long, allowing for a very thin beam and very sharp and smooth characters, such as the old IBM 3270 monitors. Rear projection CRT TV's used 3 CRT's, red, green, blue, with no shadow mask. They had to be aligned on a regular basis, but there was no native resolution and they could handle 480p or 1080i without issue. $\endgroup$ – rcgldr May 19 '18 at 9:08
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CRT is essentially a vacuum tube on steroids.

While it took us a long time to develop LCD technology, at its core are liquid crystals. The modern LCD use LED for backlight, a solid-state semiconductor technology.

Do you see already, where I am going? Let's heal a headache with decapitation!

No silicon-based electronics

And also no germanium or gallium arsenide.

Transistors were never invented. Diodes are still regarded an esoteric technology part from early radio days: detector radios are just as primitive as camera obscura and just that far from the real modern tech.

While LCD is strictly not a transistor-based tech, it became practical in the integrated circuit era. The major benefit of LCD (even with non-OLED backlight) is its size. You don't really need to spare on size, if your devices are not portable anyway.

So, just follow the tube-based electronics ad absordum. People still built TVs and computers with it in real history. So, things like "let's simulate an earthquake or an A-bomb explosion" are still feasible. Things like "let's give almost everyone a portable device with computation speed of a decade-old supercomputer to look at pictures of cats" are rather not.

Already in our history people got quite creative with tubes. Tubes in metal hulls. Mini-tubes. Tubes almost as efficient as easy as early transistors. You microwave is most certainly still tube-based deep inside.

Unsure, if PCBs exist, by the way. While early tube design surely did not have this, in the later years people indeed used some circuit boards. This could habe been the transistor influence or indeed a genuine development. People generally get very creative with a technology piece, especially in absence of alternatives. So, expect a lot of creative usage and miniaturisation of the tubes, but not "transistor revolution" and also no "digital revolution".

Those elsewise poor folks also happen to have a much better and nicer sound, if you ask audiophiles, but I digress.


Byline: The whole solid-state electronics was missed by this version of humanity. Or even the physics in that world does not work this way: tubes work, transistors don't. (Doubt.)

Anyway, they don't have LCD display, because CRT is enough. Because it's impossible to pack a single computer in less than two racks.

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  • $\begingroup$ you can have digital electronics without transistors $\endgroup$ – dn3s May 19 '18 at 3:01
  • $\begingroup$ @dn3s I don't get your point. This whole answer says that you can have digital electronics without transistors, so I don't understand why you wrote that comment. Is there something missing or wrong? $\endgroup$ – pipe May 19 '18 at 8:26
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    $\begingroup$ You can build digital computers with tubes, and people indeed did. That's not my point. You can't build compact digital computers with tubes, as we know them. So, the digital devices are still there, but the growth is much slower, they are not so compact, and they are used for more for the scientific computations, and less for viewing porn. $\endgroup$ – Oleg Lobachev May 19 '18 at 13:03
  • $\begingroup$ Yeah, I see where you're going. It's called, The Wasteland... and it's harsh. And war.... War Never Changes. $\endgroup$ – Mazura May 19 '18 at 15:45
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    $\begingroup$ In my opinion it is impossible to have a digital revolution, if the computers don't get smaller than two racks. $\endgroup$ – Oleg Lobachev May 19 '18 at 19:48
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Security (sort of)

Information leaking from CRT is different, and in several ways more jumbled, than that emitted from LCDs. There might be ways of tuning to the Van Eck emissions of a LED panel and reasons why it was easier than with CRTs.

Bringing the concept to its extremes, most if not all light-emitting diodes (being powered by quantum mechanical processes, which means they're magic) could turn out to also give out a distinctive, non-electromagnetic handwavium radiation that is almost impossible to shield, that allows detecting ships in space. LEDs are therefore used, but as communicators. For security purposes, all lights and screens on starships are lightbulb or CRT powered, giving them a distinct 1960 air.

Resistance to radiations

Semiconductor screens cannot be shielded, since they need to be seen. But this exposes them to radiations that will in time degrade their performance.

Both

If the enemy has advanced electronic warfare capability, then you want to have the dumbest electronics that will do the job. Whatever cannot be reliably shielded from outside hostile signals (and monitors can't) must be physically unhackable. In A Fire upon the Deep, the Blight - a super-advanced AI - is able to penetrate a ship through an overlooked laser sensor, and have it self-destruct. If you meddle with rogue AIs, you probably want pilots having mechanical watches and looking at dumb CRTs. You might actually need that.

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Hacking

In the first skirmish against a rogue AI, we learned that we can't trust our monitors. As you know spaceships don't have windows, we depend only in our screens and sensors. Just using a few small commands, they blinded a whole group of fighters.

For that reason we had to go back to our roots, they can mess with our touchscreens with ease, but an old CRT is inmune to those kind of attacks.

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    $\begingroup$ Why is it immune? A CRT screen receives instructions from a processing unit which tells it what to display, likewise the LCD display. If the processing unit is compromised in that way, you wouldn't change the screen and try again ... $\endgroup$ – B.fox May 18 '18 at 23:29
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In opera and musical theater all analog signal chains are used for a live "conductor cam". Any use of A2D or D2A converters along the chain will cause lag. Therefore big old CRT TVs are used for the monitors, otherwise the screen view of the conductor's baton will be considerably behind the actual beat. Analog security cameras must be used too on the other end.

Not sure how this could apply to your Sci-Fi world, but it is definitely an example of a current professional use for a reason other than "didn't replace it yet".

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I can imagine an answer that is similar to the question of why we're still using fossil fuels when better alternatives are available?

The answer is simply because their society is addicted to them. They have an industrial complex that benefits from maintaining the status quo (because it means continuing demand for the product without needing money to be spent on developing anything new) and has the political power to keep the world from moving to different technologies.

The longer this scenario continues, the harder it becomes for new technology to emerge, because the little competition that does exist between manufacturers means that the CRT technology does develop and becomes highly refined and extremely capable, to the point that even if someone did try to develop an alternative display tech, it would take a long time before they were able to develop it sufficiently to compete with the established players, and the cartel could very easily close them out of the market entirely.

In the real world, LCDs had the killer advantage of being flat, low energy and lightweight. Early LCDs certainly couldn't have competed with CRT TVs, but did make excellent watches, calculators and handheld game machines. This gave them an entry point to the market, from where they could continue to be developed.

You need to imagine a world where the CRT makers are powerful entities, and feel threatened by the emergence of LCDs, even when it's just being used for calculators, and are to cut off the development of the tech by whatever means they can.

Why would they feel threatened by it and try to kill it? In the real world, if they're that rich and powerful and they see it as a promising tech, they may want to buy it instead rather than bury it. So in your world, there needs to be a reason why they would react that way. I don't have an answer to that bit, so I'll leave you to ponder it.

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CRTs are heavy, draw a lot of currant, take up a lot of space and no it would be impractical to repair the glass tube that is under a vacuum and the display face is covered in phosphor. For the mass of all the equipment to attempt a repair of the tube you could carry many spare flat displays. We are talking about space craft that will need to break free of gravity. Saving mass and space in the craft is important.

Then there are the health and safety issues. The electrons from the gun do not magically stop at the display surface. They continue on to the operators eyes and cause cataracts. I worked with Air Force Radar and have had to have both my eyes operated on. Since you have this glass vessel under vacuum you have the implosion issue that will send out a shower of broken glass shards if there is an incident. Then there is the high voltage that is required to operate the gun and electron beam steering.

Lastly these displays are easy to shield from emitting signals since we are dealing with smaller voltages. There are conductive fabrics that are see through that will keep any signals from escaping the face of the display. Think of woman's stockings.

Just my thoughts, thanks

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It's hard to see why; there's the matter of weight and size and power, which would be a factor for spacecraft or aircraft (since you're keeping it realistic. I'm typing at a desk with two 27" monitors, massing a total of about 7 kilos (not counting the mounting arm): the equivalent screen size in CRTs would be about 63 kilos. The two flatscreen average a total of about 42 watts of power in operation combined; two equivalent CRTs would be 150-200 watts combined. The flatscreens are only a few centimeters deep allowing mounting pretty much anywhere, while the CRTs would need almost a half meter of space behind the screen. And it's easier to make arbitrarily sized displays (as long as you're willing to pay). You want a monitor 3000 pixels wide and 100 pixels high for some stupid reason? Flatscreen tech can do it, a CRT not so easily.

There are some applications (such as showing true black) where CRTs might have a slight advantage, but it's not going to be that significant a demand.

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    $\begingroup$ CRTs are massively heavy because they require a vacuum between the electron gun and the screen. Maintaining this vacuum in atmosphere requires a heavy case. That would not be as much of an issue in space. $\endgroup$ – Tacroy May 18 '18 at 20:46
  • $\begingroup$ @Tacroy, it will be an issue if you expect the CRTs to be in the same environment as humans, who respond rather poorly to vacuum. $\endgroup$ – Keith Morrison May 22 '18 at 5:08
  • $\begingroup$ You already have a spaceship, which is a device for keeping vacuum on one side and humans on the other. Mount a phosphorous-coated transparent window with an electron gun behind it at the interface between the two, and you've got a space CRT. $\endgroup$ – Tacroy May 22 '18 at 14:25
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Cathode ray tubes arranged as displays for seated humans will irradiate the testicles of the males with Bremsstrahlung X-rays, which radiate perpendicularly to the electron path as it impacts the glass at a speed in excess of the speed of light (in glass) causing genetic damage and reducing fertility. You can be sure that advocates of this solution are either AI instances or Russian subverts.

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