An object moving through the sky at a far distance from you is moving through 3D space. It appears to you to move in 2D space because of the fact that the image is being projected onto the back of your eyes, and our eyes aren't far enough apart to discern depth beyond a certain distance.
That object could appear to turn "90 degrees" in _two dimensions_ when actually it changes course by a smaller angle in 3D space.
Imagine a satellite is heading straight for you. It would appear to not be moving at all. Now imagine it is moving toward but slightly below you. It will now appear to be moving slowly "straight down" from your perspective, but actually, it could be moving towards you at high speed.
Now imagine there is a small impact with the satellite that causes it to bump up and right slightly from its current trajectory. It might now suddenly look like it's moving entirely rightwards, from your perspective, but it is still moving towards you.
This is hard to explain without visualisation, but completely explains all of these anecdotes about sudden direction changes.
This is exactly what I thought about when reading about the UFO sightings of the Roswell era. Less than 30 years after the biplane era, there were secret jet engine aircraft projects screaming around the Southwest desert at near Mach speeds and aircraft in production well over 500 mph. See one of those flying low almost directly toward you at night would look appear as if it is floating or barely drifting across the sky. If it then had a moderate course change left or right, it would appear to you to go from floating to extreme speeds with almost instant acceleration.
Right. I try to apply Occam's Razor in these scenarios. Either aliens fly around in the sky regularly enough that I've witnessed it multiple times, or there's something about perspective that I just don't fully understand (not meaning to throw shade on OP here).
That object could appear to turn "90 degrees" in _two dimensions_ when actually it changes course by a smaller angle in 3D space.
Imagine a satellite is heading straight for you. It would appear to not be moving at all. Now imagine it is moving toward but slightly below you. It will now appear to be moving slowly "straight down" from your perspective, but actually, it could be moving towards you at high speed.
Now imagine there is a small impact with the satellite that causes it to bump up and right slightly from its current trajectory. It might now suddenly look like it's moving entirely rightwards, from your perspective, but it is still moving towards you.
This is hard to explain without visualisation, but completely explains all of these anecdotes about sudden direction changes.