According to The Making of Star Trek (Whitfield and Roddenberry, 1968), phasers emit beams of light like lasers, but the energy is “phased” to interfere with the molecular structure of matter.
Don’t ask me what this means; I don’t make this stuff up, I just parrot it. 
I wasn’t talking about “believing” the claims, just suspending disbelief.
Star wars = turn off brain regarding actual physics
Star trek = Imagine that some of the wilder speculative hypotheses published in legitimate journals actually turn out to be true. (OK, and also turn off brain sometimes regarding things like humans and aliens mating)
I don’t follow this.
The metamaterial that was described as being invisible WRT microwaves was not really invisible?
But if you know you’re only being looked at from direction +V, can you not vent everything in direction -V?
I wasn’t just a fake message, though. Spock wanted Kirk to get accurate info while Khan was misled. In practical terms, I’d expect all the communication devices assigned to a given starship to be using some futursticky offshoot of RSA encryption, involving 5000-digit prime numbers or whatnot, such that Spock and Kirk could have as detailed a chat as they wanted, and then maybe talking “in plain text” with all kinds of fake info.
I don’t really understand your question, but if your vehicle is ejecting a hot gas either in the form of a rocket plume or a coolant, that gas will be visible against the microwave background, as well infrared radiation from the vessel itself even if you contrive some way to conceal it in the visible spectrum.
Stranger
In the videogame Elite 4, which features Space Dogfighting, if you want to disappear from your enemy’s scanners for a while, you can activate some sort of A/C system which cools your ship and dumps all the heat into heat-sink blocks which are periodically ejected; the hot blocks show up on scanners but you yourself don’t. I’ll leave it as an exercise to the reader to calculate how feasible this is 
In Blish’s adaptation of “Balance of Terror,” Scotty (I think it is) says they can track the cloaked Romulan vessel from its de Broglie waves in space. In the aired version, it’s made clear they can aim using sensor readings, but the targeting won’t be accurate. So even if the Romulans are invisible to the eye, they of course can be detected as long as they’re moving.
The puzzle to me is why the Romulans couldn’t target the Enterprise while they were playing “the silent waiting game.” A starship isn’t large or massive enough to be detected when its systems are shut down?
It was shown in ST: TNG that humanoids throughout the Galaxy share fair amounts of DNA through interstellar seeding; this is evidently enough to allow crossbreeding.
In Spock’s case, we’re told in TMoST that he’s a product of “the highly advanced Vulcan school of medicine”; i.e., he’s something of a test-tube baby.
The point is, I’m aware that objects radiate EM based on their temperature, but it’s also the case that EM radiation can be trivially reflected / refracted etc, so I don’t see why it necessarily follows that it’s impossible for an object to be concealed from a particular detector.
And in fact, saying “even if you contrive some way to conceal it in the visible spectrum” is somewhat conceding the point, no? Because there’s a big difference between <impossible according to the laws of physics> and <it seems to be too hard an engineering task to me, to block all the frequencies a detector might be scanning at the same time>
Sure, but that was a post-hoc addition partly because people had pointed out how absurd it was.
It’s essentially “a wizard did it”, with the sci fi version of “wizard” being a super advanced ancient alien race.
ETA: Actually I’m being too kind. An explanation like that might, streching credulity, explain why most of the aliens are humanoid.
But actual interbreeding means we are the same species. That’s not going to happen across different planets for millions of year. Separations of a few thousand years will usually result in speciation.
What would the problem be in masking heat from a cloaked ship? Isn’t infrared just another form of electromagnetic radiation, which the cloaking device is selectively refracting anyway?
A spacecraft that is generating power will produce waste heat, and if it is using momentum exchange (e.g. rocket thrust) for propulsion, will emit a high temperature plume which will be visible even if the waste heat internal to the vehicle is somehow contained, e.g. dumped into a cold sink (low temperature reservoir). This isn’t just engineering; it is basic thermodynamics that all objects which produce net power or are hotter than the microwave background will radiate from thermal energy.
Since the entire principle behind the cloaking device is never explained except as technogibberish it is hard to make any qualified statements about what frequencies it can and can’t shield or reflect or whatever it is doing, but the fact remains that it has to be able to radiate away heat in some way, else the temperature will progressively increase until it becomes uninhabitable and even eventually reaches structural failure as the hull and other components reach melting temperature.
The cloaking device, as much as anything in Star Trek, is basically magic. It was conceived in order to create a story that was the space equivalent of a sub hunt, again without any real conception or effort to rationalize the mechanics behind it.
Stranger
I keenly await the day when I can sit in a room where all the walls can project any image and sound comes from speakers that make sound come from any direction. Add a bit of clever air conditioning and appropriate scents to entertain the nose. A souped up home cinema experience is feasible with current technology. Though largely a passive experience, we could look to gaming to add interactive elements.
Is this not a crude holodeck?
Let me be clear where I am coming from on this.
I am certainly not one to say “What the bleep do we know?” and believe in whatever woo. I actually don’t like that many science educators readily admit that any theory could be completely falsified tomorrow. How can a model which makes millions of predictions accurate to the 20th decimal place be outright wrong? It’s not realistically going to happen.
It may be amended or built on, but it’s not going to be falsified.
However, on the other hand, I see plenty of instances where people declare something to be “against the laws of physics” when it’s nothing of the kind; it just looks impossible because they are imagining one single engineering approach. They are the equivalent of declaring that flying is impossible because “human pectoral muscles aren’t strong enough to flap with the required speed”.
Now, I know from past threads that your scientific knowledge trumps mine, and I often enjoy reading your explanations.
But, respectfully, this doesn’t seem an appropriate instance to invoke “against the laws of physics”.
e.g. I didn’t mention momentum exchange or rockets or even that the ship is accelerating. And even in the case that its accelerating, doesn’t that imply a cloak could work when accelerating towards the detector?
Neither do the replicators in Star Trek. They’re explained on the show (and in associated media, such as the Technical Manual) as glorified transporters that rematerialize stuff from a store of pre-existing matter. In this respect they’re very much like today’s 3D printers.
You write as if translating between languages is simply looking up words one at a time in a bilingual dictionary. If you’ve ever tried to do this, you’ll know that it’s impossible. For one thing, words are ambiguous—most of them have several different meanings. Deciding which meaning corresponds to a certain usage of a word is an enormous problem for computers (and even for humans, in many cases). For another thing, words aren’t the only way that language encodes meaning. There’s also morphology and syntax. “Man bites dog” does not mean the same thing as “Dog bites man”, even though they’re the same three words. Different languages can use different word orders, and/or inflect words in different ways, to arrive at the same meaning, so any translator (human or computer) needs to have detailed knowledge of those rule sets and how they differ.
Star Trek’s universal translator is an enormous handwave. It always has been and always will be. Episodes that attempt to provide further details on the (mal)functioning of the translator (such as TNG’s “Darmok” or DS9’s “Little Green Men”) only raise more questions than they answer, particularly for those of us who work in machine or manual translation.
The third law of thermodynamics, as I’m sure you are aware, posits that any nonreversible (e.g. real world) process in which work is done increases entropy and therefore produces energy that is not available to do useful work, i.e. “waste heat”. That heat energy cannot stay within a closed system so it has to be removed (or absorbed into some heat sink within the system, which is naturally a finite resource and of which no mention is ever made), and in space the only way to eliminate that heat is via radiation.
Now, it is certainly possible you could have a kind of shield on the observer-facing aspect which is cooled to a surface temperature approximately that of the background environment, and an away-facing radiator to which that thermal energy is transferred and radiated away, and that would mask any heat signature. But that does not seem to be the way that the Romulan/Klingon “cloaking device” works; it instead creates a wraparound simulacra to make the vessel appear completely transparent from all aspects with no radiation (at least visible light) is seen at all, and is otherwise not detectable with “normal” sensors, which would presumably include infrared bands because every active body is going to radiate in the infrared band.
The films are actually pretty inconsistent about its use; sometimes it is possible to see a distortion, in others it is a perfect camouflage but a radiation surge can be detected at close range, and in Star Trek IV it is so good it can literally sit in Golden Gate Park and nobody recognizes it or somehow runs into it. In Star Trek IV the ship is actually tracked by “gaseous emissions” using a jury-rigged torpedo equipped with some kind of sensors the Enterprise was carrying for that purpose, which presumably means it uses some kind of plasma thruster or other momentum transfer system which emits a hot gas that should be observable by sensors. I can’t speak to the way it is used in the shows because detectability is so inconsistent that they never use the same method twice even though they come up with several ways to passively or actively detect a cloaked ship on the fly that are never used again after that episode.
No mechanism is ever given for how the cloaking device actually works, so maybe it creates some kind of a pocket universe, or converts she ship to Inviso-Matter and the waste heat into Contra-Energy or whatever technobabble is necessary to justify the fact that it is actually an Invisibility Spell cast by a space orc thaumaturge on his star chariot. Douglas Adams’ parody of the trope was the Sombody Else’s Problem field, which is actually more plausible because people ignore and block out things they don’t want to know about or acknowledge all the time.
Star Trek has never been about science or presented any degree of scientific plausibility beyond occasionally using the names of real or theorized particles in generally completely incorrect ways. Which should not stop you from enjoying it any more than you wouldn’t watch a Bond movie because no real spy would behave like that, or Harry Potter because magic isn’t real. But the attempts to rationalize the various technologies of Star Trek are mostly pointless exercises because those concepts are not based on actual science. To be fair, they did predict the flip phone, although they apparently predicted we’d still be using them in the twenty-third century, and while I suppose there might be some luddite still using a Motorola Razr two centuries from now, I hope it isn’t humanities supposed-elite space exploration agency.
Stranger
Sure, and that was my objection.
If we’re just talking a given mechanism (or lack of) in Star Trek, I’m fine with the conclusion that it’s impossible.
But some of the comments seemed to be slipping into implying cloaks are inherently impossible, no matter the mechanism, and I don’t think that’s been shown.
Yep. I liked the one where the cloak actually “de-phased” the ship with the rest of the universe, so could also be used to pass through solid rock 
(Note: even if de-phasing was a thing, why can’t they already do this trick via subspace)?
The specific capabilities seen of the Star Trek cloaking devices are on nigh impossible without a significant retooling of physics, but an active camouflage system like the “retroreflector panels” on Stark’s plane in Spiderman: Homecoming are plausible (and they way they realized them in the film was really well done, especially the entire plane turning into Spiderman while he is crawling on the bottom side of it). However, masking a heat signature is a really difficult problem because heat is so low frequency it defies the normal optical means of manipulation, and if you insulate to keep the heat energy from escaping your vessel just keeps getting hotter. It’s even tough in terrestrial applications, and heat sensors are used on the battlefield to track everything from tanks and infantry to aircraft and satellites, because everything radiates.
Actually, the thermodynamics of rejecting heat are problematic in space travel in general. It is a problem that is rarely addressed in any science fiction literature where it is assumed that fusion or antimatter systems can generate virtually unlimited amounts of power without producing any waste heat, even though there is no medium to convect away heat energy the way we do with cooling towers and lakes for terrestrial applications. There is a Frederick Pohl short story that as a crew which is lost in space burning up because they can’t find a planet to land on and take on air to use as a coolant to evaporate heat into space, and of course the story that in Stanley Kubrick removed the radiator fins from Discovery One in 2001: A Space Odyssey because he was afraid people would think he intended them to be wings and mock the film for inaccuracy. (I think Kubrick just wanted the ship to look like as much as possible like a spermatozoon because for him everything was about sex, but whatever.)
Stranger
Especially when they never turned off their running lights. It would be trivially easy to target between the red and green flashing lights.
My complaint about plausibility goes to the never-explained “sensors”. Sensors, especially in tricorders, seem to be able to detect things that are not detectable, such as the age of rocks and metals (impossible in any science), or detect “life forms” (whatever that means).
Kirk famously said in Man Trap that the ship sensors could detect a match on the planet. I must assume he was just trying to shut up Crater, because assuming the resolution was such that the sensors could detect a match, it would take forever to scan the entire planet at match resolution. Plus weeding out everything that was “almost a match” (no pun intended).
But yet, the sensor didn’t seem t0o be able to find the salt vampire or the dead red shirt lying in the open behind a rock, so maybe they’re not all that useful after all.
And these “sensors” don’t seem to cause any ill effects, damage the object being sensed, are rarely affected by anything. Magic. Even the sick bay body scanner measures things that shouldn’t be remotely measurable.
That depends; how far away are the two ships, and how much light and matter is there between them might interfere with the detection? Keep in mind that in the present day, our satellites have tremendous difficulty detecting even planet-sized objects in our own solar system. (The discovery of another dwarf planet in our solar system was announced only a few days ago.)