I don't think this was ever stated in canon (did DEs ever apparate onto the train when it was moving in DH?) but can you do this? You have to concentrate on your desired location to apparate to it right? But with a moving location, your desired location would not always occupy the same space so how would this work?

 

I presume as long as it feels like it's not moving, it shouldn't affect things. Like if you have a still image of a car, you should be able to jump inside it.

The entire planet is effectively moving through Space and it doesn't stop people apperating to places on it, so it's likely a case of if it feels like it's not moving, you can apparate to it, as magic works on concepts like that.

 

The fact that the transport isn't instantaneous makes me doubt this somewhat. I mean, yes, inertia is zeroed in the process, but I'd give some credence to the idea that it is difficult at best, and only for something moving in a predictable path. Apparating onto a fighter jet in combat would be nigh-impossible, but going onto a train would be very do-able.

 

I would disregard things like coservation of momentum and other physics considerations with the HP magic system. It's been repeatedly stated that magic overrides physical phenomena.

 

This.

Magic pretty much doesn't care on what the actual scientific reality is. It seems to work more based on what the caster perceives reality as on a macro level. If it doesn't feel like it's moving to the user, it's not moving. I wouldn't be surprised in cases where it's obvious an object is moving that it's not possible to apperate onto that object, like we've never seen wizards try to apperate onto the broomsticks of opponents in a aerial dual.

 

Yeah I was planning on writing a story with space as a big factor, and having Harry apparate onto his ship as someone was doing a fly-by was my idea.

 

You're thinking of location as a scientific thing rather than a conceptual thing. Is "the interior of a moving vehicle" a location? Yes. The altitude and longitude/latitude are not the important things here, but the concept of a location. As @ScottPress said above, momentum and such are not relevant distinctions in the HP magic system. Fire spells don't excite particles until combustion occurs, they just make fire. Teleportation spells don't take you to a coordinate, they take you to a place.

 

Of course you can. It's magic.

 

poor attempts to combine science and magic leads to apparation coordinates chliche.
It seems all HP wizards got internal GPS.

 

Must have been how fanon Voldemort found the chamber.

He wrote in his own diary, resulting in a Tom X Tom fic.

 

I had the thought that, yes it has to to with picturing the conceptual 'place' as your target destination. However, the 'place' must still be static in its relation to other 'places'. So, for example: the 'corner closest to the door' of a 'room' within a 'house' on a 'street' in a 'city' would qualify as a 'place' because it stays the same in relation to all those other static 'places' that define it. By that I do not mean that Wizards need to know the postal address to a place or a GPS, they need not know exactly what 'city' or 'street' or 'house' the 'room' is located in as long as they know that THAT 'corner' is located in some 'room' in some 'house' etc.

On the other hand, the 'seat' of a 'car' standing or rolling somewhere would not. The Wizard can't know where that 'seat' is because the chain of static relation is broken to soon.

Of course the relative 'distance' between the starting point and the target is still an issue and is treated separately.

Hypothetical example #1: A Wizard is knocked out in an 'alley' and awakens sometime later in a 'room' in a 'house' on a...etc. somewhere else. The Wizard can try to Apparate to that 'alley' and back again because those are both eligible 'places', possibly bringing some Aurors along to investigate the kidnappers. However, they might fail if the 'distance' is to great.

Hypothetical example #2: A Wizard is blindfolded in an 'alley', but not knocked out, and stuffed in the 'trunk' of a 'car' that drives somewhere for a couple of minutes. The Wizard can safely Apparate to the 'alley' because the 'distance' covered by a car in that time wouldn't exceed their range. However, they may not try to Apparate back to that 'trunk' later with Auror reinforcements because they have no idea of where it might be by then.

This is the best that I can do to explain my interpretation. I could be completely off, I could have missed something, I have most likely forgotten to take some conditions in consideration. Please, I would be grateful if people could poke holes in my hypothesis so I can see where I went wrong.

 

Why must it be static in relation to the others? Here's a question, do you think that a wizard could apparate onto the deck of Durmstrang's ship? The ship is constantly moving, either by virtue of sailing or simply due to the natural shifting of the water beneath. If a wizard is able to apparate onto a moving vehicle such as a ship, then at what point is it moving too quickly to be a valid destination? Those are the types of rules that define systems such as D&D and Dresden, but quickly fall apart in the HP universe.

How about this for an example? Harry is on a train during the seventh book, and says Voldemort's name. The Taboo gives the Snatchers his location, and they apparate to him. He is in motion, and quickly at that. Will they apparate into the same train car as him, or will they apparate onto the tracks where he was at the moment of triggering it? Will they simply appear offset to the side in the approximate vicinity of the tracks, watching the train continue on? The simplest and most likely answer is that they will appear within the train car. There is no qualitative difference between a ship's deck, a train car, or the back seat of a 1972 Gran Torino.

 

By apparating north and south around the world you are dramatically changing your spin velocity in relation to the Earth. Far more than any simple train or car. So yeah, you can change speeds while apparating.

 

HP magic works on the principle of most drama. There are no limitations to what magic can do except when unlimited magic would just makes the story dumb as fuck. That's why Dumbledore can't apparate in PS, that's why Barty didn't just tag Harry with a portkey after class instead of using the tournament as an elaborate trap, that's why James and Lily didn't use each other as the secret keepers, that's why Dumbledore didn't ask Fawkes to just go grab Voldemort when he was sleeping.

If preventing apparation makes the story better, then make it so. An important caveat is that long, technical explanations of why something is impossible always makes a story worse.

 

Now I wanna see a fic where exactly this happens damnit.

 

I agree with most of your points except that the simplest explanation for Dumbledore flying to the Ministry is that Rowling hadn't thought of the apparation system yet.

 

Harry apparates onto train in motion.

Hermione: Harry! How did you do that? You can't apparate onto a moving platform!

Harry: It's magic. I ain't gotta explain shit.

 

In real life there's no such thing as an absolute frame of reference - there is nothing in the universe which is static. You can say the car is moving across the static Earth. Equally you can say the Earth is moving under the static car. And of course both are in motion relative to some other frame of reference.

So even if you were inclined to impose limits on magic based on some kind of quasi-physics (which I am not), this is not a promising avenue.

Undoubtedly the case (especially when considered in combination with the fact that Hagrid says he flew to the hut on the rock) but a decent in-universe explanation is that McGonagall simply means he is flying to Hogwarts' boundary, at which point he will apparate.

The real problem isn't actually apparition, it's Floo.

 

This is a lot like the Roger Rabbit principle of most comedy.

Eddie Valiant: "You mean to tell me you could've taken your hand out of that cuff at any time?"

Roger: "No, not at any time; only when it was funny."

 

A wizard could probably try, but I would imagine that in most or all cases, it would just result in a splinching.