Again, moving at 30km/s relative to the original firing point is the objective and accurate answer. I'm not going to say "relative to the Dark Energy located at the original firing point." because a narrator doesn't actually need to maintain a physical frame of reference for even a nanosecond to calculate the speed of an object. How can the location of the original firing point be more unreliable and ambiguous than the 500 meter ship that's moving backwards? I mean, they're basically exactly the same thing. The only difference is that the latter alters the calculations massively and gives very damning implications for other space battles in Halo. You yourself have said "the motion of the Frigate is irrelevant" after all.tsassi wrote:This doesn't answer my question. "The original firing point" is uniquely defined only at the time of firing. After that it's ambiguous and depends on your choice of coordinates.TheDeathSummer wrote:Relative to the location of the original firing point is fine.
See, there's this concept of a coordinate system where you define an origin, a base point, and then at any point in time you tell where an object is by how far and in what direction it is from the origin. You can have different coordinate systems, these coordinate systems move relative to each other, and "speed" is only defined with respect to a given coordinate system.
Consider this: there is a train moving past a station. In the train there is a bottle on a table. There is a man sitting in the train. The origin of his coordinate system is where he sits. In his coordinate system, the bottle is stationary, it is not moving relative to him, the direction and distance of the bottle to him is always the same, it has zero speed. There is another man on the station. He also has his own coordinate system, where his position is the origin. Because the train is moving relative to him, and the bottle is in the train, it is moving relative to him, the distance between him and the bottle is growing, its speed is greater than zero. These two men observe a different speed for the bottle, because they are measuring the speed in different coordinate systems.
Crucially, one has to understand that there is no absolute universal coordinate system. No coordinate system is better, or more correct than another. The speeds measured by the two men are both correct. There is no such thing as the "true" speed of the bottle.
Normally, on Earth when we say something is moving, we really mean that it is moving relative to the ground. So if I say "the train was going 50 m/s", everybody understands that it was going 50 m/s relative to the ground, because that's a convention we've implicitly agreed upon. Our coordinate systems in which we measure the speeds of things on the ground are all stationary relative to each other. However, this convention hardly makes sense when we are hundreds of light years away from Earth in the middle of space, because we can't even see the ground on Earth. So, the question "moving relative to what?" becomes relevant. And the "what" has to be a concrete object. You can't say, "oh, relative to this point" because that "point" depends on your chosen coordinate system, so it's circular reasoning.
And so we get back to my question: moving at 30 km/s relative to what object in the scene?
And I'll ask again, what issue do you take with "It's fallacious to fire an M1911 off the back of the Shanghai Maglev and then calculate and apply the bullet speed to every gun on earth."?