The TOS episode Balance of Terror Indicates that this is the first time humans are aware of the Romulan Cloaking Device and the episode implies it is a new weapon the Romulans are using as well as their plasma bolt. However, in the ENT episode Minefeild, the romulans not only are able to cloak themselves but can cloak other objects such as mines. This contradicts information in the episode Balance of terror.
Furthermore, the TOS heroes themselves are familiar with the phenomenon of the enemy popping out of nowhere right next to their ship - the Thasians in "Charlie X", say. It also stretches credibility that invisibility would be a novel concept to them in the Trek universe where all sorts of players are shown to be capable of either cloaking themselves or then otherwise performing the functional equivalent of just plain appearing at a spot without bothering to fly there first. The dialogue in "Balance of Terror" clumsily stands out from the overall continuity of Trek, but also from the internal logic of TOS (as it was in those early days) or the general expectations of writing a scifi show. It might perhaps be salvaged by saying that our heroes only speak of this particular variant of invisibility device. Spock is often pedantic to a fault, and him speaking of "theoretical" could be misleading: perhaps he's thorougly familiar with the practical uses of invisibility in military history, but here speculates that the Romulans have opted to do it with "selective bending of light" as opposed to older techniques that Starfleet already can defeat. More damning is Kirk confessing that he doesn't understand why he cannot see the enemy. Makes him look stupid, now doesn't it? But perhaps the Romulans did not use invisibility a lot in the big war, despite having experimented with it right before the war? Perhaps they were more famous for having used that technology that made their ships look like the ships of other cultures? Timo Saloniemi
To be honest I think this is one of the most difficult circles to square in terms of continuity, precisely because the unknown nature of the cloak is so crucial to BoT. It isn't just a background bit of technology that can be overlooked in favour of the main thrust of the story, in many ways it is part of the main thrust. We can attempt to shoehorn explanations for the dialogue and make it almost work on a piecemeal basis, but overall the episode relies on the cloak and the plasma device being previously unseen technologies. The Romulans are show to have spent a prolonged period in comparative isolation and emerged stronger and more dangerous than ever, a kick in the federation's complacency so to speak. Without wanting to dwell too much on the Cold War and submarine/nuclear weapon allegories which have been done to death elsewhere, the episode simply doesn't work as well if these things aren't game changers, forcing Kirk to think on his feet before technological counters can be conceived of.
We do know that the Romulans employed holographic projection technology during the ENT timeframe - perhaps the cloaking device techniques used at the same time were an offshoot of that?
I realized a while back that 100 years of Romulan absence would more than account for that, especially if it turned out that nobody else was really using cloaking technology during that time. It would be considered a quirk of Romulan technology at the time, something they were able to do back then but nobody knew for sure if they kept it going. Imagine the captain of an ASW destroyer hunting a rogue Japanese submarine in the middle of the Pacific. He doesn't know anything about the Japanese Navy except what he's read about them from the second world war. Then all of a sudden this Japanese submarine pops to the surface, opens up a big hatch on the front of the tower and starts launching jet fighters to attack him. Would you fault this commander for not realizing that Japanese submarines also double as aircraft carriers? Because that's not something that people who aren't VERY familiar with Japanese naval history would have known, and it's certainly not something someone would have guessed would have become the cornerstone of their entire naval doctrine a hundred years later. It could be that cloaking technology just wasn't all that practical in the 22nd century, due to the power costs being so high that a cloaked ship could barely even move or defend itself even if it was detected (which, due to the limits of the technology, it frequently was). Starfleet might not consider invisibility to be something a modern starship would really employ just because there were lots of BETTER ways to defend yourself from attackers, such as deflector shields, warp drive, and the whole not-being-paralyzed-because-your-cloaking-device-is-using-all-your-power thing.
We can certainly make note of the Romulan invisibility device in "Minefield" being a poor one - the Romulan ships shimmer and decloak at inopportune moments, as if their devices were really struggling to maintain this tactical edge. However, that helps little in countering the issue of invisibility as such being perfectly routine and well-working in the Trek universe, even if only among the more mature cultures. The issue should never have been "Romulans have INVISIBILITY!", but "ROMULANS have invisibility?". And it's just too damned difficult to read Kirk's lines the latter way even if we can just barely squeeze Spocks lines to that mold. Timo Saloniemi
Actually it doesn't seem to be all that common of a technology in TOS. That it was common in the 22nd century doesn't seem supportable either considering only the Romulans and the Suliban had the gear and the Suliban technology immediately developed a countermeasure. Which is why I brought up the sumbersible aircraft carriers like the I-400 class, although the analogy is apt for submarines in general. That is, not everyone in the world actually uses submarines, and not every ship is capable of submerging. So the german U-boats of World War I and before would have come as a bit of a surprise to the first destroyer captains who encountered them despite the fact that CSS Hunley made its historic attack half a century earlier; Hunley, for that matter, came as a surprise to the Union Navy despite USS Turtle making a similar attack during the revolutionary war. Just because the technology EXISTS doesn't mean everyone has it or wants to use it. It's likely the Romulans specialize in cloaking systems more than any other defensive technology and simply build the best cloaking devices in the galaxy, where as all other cloak developers never quite manage to get them to a point where they would be useful on their ships. Kirk might not be expecting the Romulans to be using an invisibility screen on a ship that is actually under power and maneuvering. His other lines are also pretty interesting: SPOCK: Blip has changed its heading... And in a very leisurely maneuver. They may not be aware of us. KIRK: Their invisibility screen may work both ways. With that kind of power consumption, they may not be able to see us. This also tells us that previously-existing cloaking devices couldn't actually hide a ship that was in motion and scanning space around it. Probably something like a fixed pylon or a field generator that would hide everything in a fixed radius from it. In which case, the cloaked Romulan ships from "minefield" might not have "decloaked" at all, they may have just moved out of the range of the duck blind they were hiding in so that they could get a fix on the Enterprise.
I think the Romulans of ENT use the same cloaking radiation as the Suliban. When the Romulans are encountered by Archer, Good Future Guy's cloak scanner modification works against the Romulan cloak just as it did the Suliban cloak, which it was originally intended to defeat. This foiling of the cloak technique is perfect, so it is reasonable to think the Romulans completely drop cloaking tech sometime during the Earth-Romulan war, until TOS. Later in ENT the Romulans have a holographic cloak for imitating ships, but not disappearing. I do not recall how that system was defeated, only that it was. The TOS cloak has supposed limitations which sound completely different from that of the ENT cloak and later TNG cloak, indicating it is completely new.
Now we have seen metamaterials... https://phys.org/news/2021-06-safer-invisibility-cloaks.html ---but what we all think of is field effect devices. That may have been given a start--at the small scale https://phys.org/news/2021-06-hydrodynamic-cloaking-shielding-microscale.html The new technique and paradigm introduced by this team of researchers could also have implications for other areas of physics. For instance, it could allow physicists to cloak objects in electromagnetic or acoustic fields. https://phys.org/news/2021-06-scientists-ultra-fast-optical-orbiting-nanoparticles.html As a result, the spin angular momentum of light is converted into the orbital angular momentum of particles with super high efficiency. Sensor tech: https://phys.org/news/2021-06-scientists-signatures-life-remotely.html It could be a milestone on the path to detecting life on other planets: Scientists under the leadership of the University of Bern and of the National Center of Competence in Research (NCCR) PlanetS detect a key molecular property of all living organisms from a helicopter flying several kilometers above ground. The measurement technology could also open up opportunities for remote sensing of the Earth. https://techxplore.com/news/2021-06-smartphone-camera-illuminate-bacteria-acne.html https://phys.org/news/2021-06-daily-use-deep-uv-source-sterilization.html https://phys.org/news/2021-06-ufos-odds-alien-spaceship.html Crystals and lasers https://phys.org/news/2021-06-tailored-laser-fields-reveal-properties.html https://phys.org/news/2021-06-2d-material-symmetry.html https://phys.org/news/2021-06-chirped-pulses-defy-conventional-wisdom.html However, the chirped pulses live in 'normal' dispersion cavities in which red light travels faster. The dispersion is called "normal" because it is the much more common case, which will greatly increase the number of cavities that can generate pulses. https://phys.org/news/2021-06-giant-quantum-tornados-hybrid-light-matter.html What we show here is a system that shares a lot of characteristics with a black hole, which still emitting, a white hole if you wish." Professor Lagoudakis adds. Glasses https://sciencex.com/news/2021-06-invisible-tiny-crystal-night-vision.html Measure electrons with a ruler https://phys.org/news/2021-06-absorption-individual-electrons-captured-video.html Turn photo to video https://techxplore.com/news/2021-06-photo-video.html A real cloak https://phys.org/news/2022-05-transparency-demand-artificial-materials-transparent.html "Our research provides the recipe for structuring a material in such a way that light beams pass as if neither the material, nor the very region of space it occupies, existed. Not even the fictitious cloaking devices of the Romulans can do that," says co-author Dr. Matthias Heinrich, circling back to the final frontier of Star Trek. Non-Hermitian quantum mechanics https://phys.org/news/2022-06-duality-physics-mystery.html In conventional wisdom, producing a curved space requires distortions, such as bending or stretching a flat space. A team of researchers at Purdue University have discovered a new method to create curved spaces that also solves a mystery in physics. Without any physical distortions of physical systems, the team has designed a scheme using non-Hermiticity, which exists in any systems coupled to environments, to create a hyperbolic surface and a variety of other prototypical curved spaces. Controlling sound https://phys.org/news/2022-05-discovery-mechanisms.html To their surprise, they discovered new mechanisms, so-called "geometric phases," with which they can manipulate and transmit sound in systems where that was thought to be impossible.