In my story there is a device that can open a portal leading from a person's current position to a set of coordinates on another planet light-years away. Do I need to figure out an explanation of why the portal opens on the other side (I.E. due to equipment already placed there) or can I just leave that to the readers imagination?
Well, you could base the way that device works on current theories, but I don't think it's "necessary". I've read a lot of stories about futuristic gadgets that can do amazing things, like time travel, without any logical explanation, and I don't think that makes them less believable. It's your universe after all and you create everything in it so, if you really feel you need an explanation for it, you could create one that could only be plausible within the "rules" of that same universe you made. It's up to you, basically
It's like magic in a fantasy universe really, there is no NEED for an explanation less so for a logical one (in the real world). You just need to be consistant and make sure a reader won't have an opportunity to say "Well, why don't they just use the teleporter now?" because they fail to see any real reason why they couldn't or your reason wasn't good enough, like "Sarah is too ill to be teleported."... why does it matter how sick she is? It';s an instant boom-bada-bing thing...
It all really depends on how you have established other elements in the story. If you have background explanations for other things, or, if there is a reason for the detail, then you should at least detail the basics of the device, insomuch as it works within the universe. But, it also goes back to the overall level of detail. In a story, things just work, or not, as the story works. A teleport is just like a door. Same as a spacraft with FTL is just like a car. It is a means. You don't need to explain how it requires a ring of unobtanium spinning at 50 cycles a second around a condensed blob of neutronium to generate the wavicle based field, for it to work as a means, unless that level of detail is required for other elements within the story.
Not only is it unnecessary, it's usually a bad idea to try to explain your technology. If what you are explaining is well-established science, you can explain enough to get some of your less savvy readers up to speed, but only to make the behavior clear for the purpose of the story. And that's the key. The reader needs to understand the behavior of science or technology that affects the story. He or she does not need to know why it works, and unless you have a very strong technical background, you're likely to blow it. Even if you do have such a background, you may end up embarrassed as science or technology advances.
I don't think that you need to explain the science, but very high-level things like "We can go anywhere for which we have coordinates" versus "We can only go to places where we've set up equipment" seem potentially relevant. But only potentially. If people travel to this place every day and twice on Saturday, we probably don't care how. If they're setting foot on a completely new planet, as explorers, we probably care a little bit--a couple of sentences' worth.
Just make sure the way it works is consistent, define what it can do and don't deviate from that (no last minute deus ex machinas,) maybe have an idea of how it works for yourself, but it's not necessary to explain it to others.
In 'Contact' by Carl Sagan, at least in the film , the travel portal had been created by a now departed/vanished race. So, even the aliens using it don't appear to know how it works. Or at least they don't explain it.
I figure one way to go around that is to just point out in the story that the character or characters don't know how the device in question actually works. I'd be fine with that Either way it's all about continuity, after everything is said and done. If that fails it's a big and very annoying problem for a reader.
Even if the character "knows" all about the science/tech, it's not necessary for him or her to prove it to the reader. And even if the character is an egotistical bore, you can convey that without trying to snow the reader with a big steaming pile of technobabble.
A full on technical explanation can be saved for a collector's guide book, much like the USS Enterprise folders for Star Trek fans. For a novel you should be able to drop hints about the advanced technology - what it does, what it looks like, how it moves and possibly what powers it. You could occasionally have an explanation to a non-technical character faced with repairing the technology when it gets damaged, but keep it concise - the reader needs only to know what the non-technical character needs to know. Swamping your story with explanations will slow down the pace and kill the story for the reader, so only include the details which you need to convey the use/function of the device, with further details added where it suits the progression of the story.
There was a great quote in an interview with the authors of Leviathan Wakes concerning the Epstein drive: Q. So how does the Epstein drive work? A. Very well. Efficient Depending on the context of the tech and the characters seeing and using it, as long as they know it works, that can be enough. In much the same way as I plug my MP3 player into my car but cannot grasp how the sounds travel through the cable and out of the speakers.
If it can open portals using only the equipment at the transmitting end, you may have to invent reasons why it cannot be used to open portals to certain places, such as specially shielded places. Otherwise they could simply use a portal to reach the location of the antagonist and end the story short, assuming they have the coordinates. On the other hand, it should be quite simple to describe the device once, then say there's an identical or similar device required at the other end, such as: <character name> stepped out of the portal. He looked around the unfamiliar room, the silence broken only by the hum of the portal. Then he turned around; the portal was being sustained by a machine similar to the one on Earth, only with more dust and corrosion.
You don't have to invent a reason. You only need to establish that the terminus will only form where conditions permit. You don't have to define those conditions precisely.
Don't forget that the reader is curious. Mystery is good but too much of it unsolved, too much questions unanswered and he will put down the book. I usually do that and think the writer was lazy and did not want to spend his precious time on setting up his world properly.
Perhaps "invent" was the wrong word. The reason why it wouldn't be able to open a portal in a place that would end the story prematurely could simply be "included".
I like to know how things work at least on some basic level. I don't require a long explanation. Reading about a portal would lead me to wonder if someone had been to that planet before and installed equipment to make this possible or if there's some other reason for it. Unless, of course, you want to intentionally keep it a secret.
You needn't give the reader everything he or she wants, as long as you give the readers all they need. Assume your reader is capable of coming up with theories to fit the described behavior. This is especially true in science fiction - readers prefer an intellectual puzzle over being spoon fed. If you doubt this, log on to any fan forum for a popular piece of science fiction. The technical discussions become quite heated! Always leave the reader a bit hungry.
This is so important. There needs to be a little bit of magic - I'd focus on the story more than the intricacies of the tech. I agree with @ToeKneeBlack , it needs some restrictions and they need to maintain continuity throughout the story. If they can literally teleport anywhere in the galaxy, that could act as the focal point for the story. The plot could even be about the protagonist trying to discover the the origins of the device or learning how to use it. It's all up to you, but as @Cogito said, it's gotta maintain the readers interest.
It dependent on your writing, how you picture it to readers. You can explain the matter indirectly. For example by similar words like this : " Samuel took the device out from chest. He had decided to go back to Castle planet because he had misplaced the reserve ruby there, that was necessary for resonance power in the transformer... He putted the device on the table and pushed the button of primer electromagnetic transmitting. Then he turned on the concentrator of high gamma ray power. When the red light changed into the green, He pushed down the lever of the final accelerator... Thus readers themselves will understand the task of the device and the matter of that transmitting.
As a reader of science fiction, I'd want at least an explanation or some set of rules for where they open. Even saying "The scientists can't figure it out" would at least give us something to latch onto.
I can agree with this in general. As I wrote mystery is good. The problem comes when it is used to cover holes in the story's inner logic which the writer was too lazy to close. Basically you are telling me that if I read that the protagonist of a book "has a device capable of jumping to a spot in space lightyears away but it can't jump to the villain's base" without any plausible explanation, it's giving me (the reader) the freedom of imagination. Sorry, but in this case my imagination says "Next time I buy an empty book and imagine a better story". It's lazy writing. As @maskedhero mentioned, at least a short sentence should be there as proof that the writer haven't simply forgotten the possibility to jump there directly.
That isn't t all what I am saying. What I am saying is that you establish from the start that your technology can cross great distances, but not every point can be reached by it. You don't have to explain why, you just need to make the behavior well-defined and consistent. Better to leave them wondering what might cause such a limitation than giving a justification that reeks of bovine excrement. It could be that the technology is still young, and further advances will remove or redue some of the limitations. It could even be that the limitation is understood but takes a dual PhD in advanced mathematics and quantum relativity to understand it. Many writers try to prove how smart they are, and end up proving the exact opposite. No, it's smart writing. Give the reader enough information, but know where to draw the line. Those who ignore this principle bear the Sigil of Technobabble, the modern Scarlet Letter that brands a writer as mediocre.
I echo everyone who said to leave the reader hungry. This is a skill very hard to master though, this ability to immerse the reader into the story and manage to convey the richness of the new world and technology, without writing in an explanatory manner. So very hard to find the right balance. It's ok to dribble on in the first draft, perhaps it's even desirable, so that you have more to work with later on. But the goal should be to get rid of everything that reeks of explanation to a reader who lives in a world where such things are impossible. At the very least, imagine the reader knows everything an average citizen of your futuristic world knows. You wouldn't be describing intricate details of mobile phone technology in a book set in the present, and the funny thing is, a lot of people who use them every day, have no idea how they work. But if you write about someone using a mobile phone to call home, text a girlfriend, FaceTime, send emails, record a voice, take pictures, even a reader who never saw or heard of a mobile phone will get the gist and fill out the blanks. This usually works best, imo.
