if there was no relative motion, they would not collide. That's the definition of relative motion- there is a relative motion between the 2 objects. Boatbum said it correctly. 2 objects on same course at same velocity is the only case of no relative motion. Every other case, it is the sum of their relative velocities. Appearance of an object on a constant bearing does not change that fact that there is relative motion between the 2 objects
Another Collision.
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if there was no relative motion, they would not collide. That's the definition of relative motion- there is a relative motion between the 2 objects. Boatbum said it correctly. 2 objects on same course at same velocity is the only case of no relative motion. Every other case, it is the sum of their relative velocities. Appearance of an object on a constant bearing does not change that fact that there is relative motion between the 2 objects
In a head on collision the car is right in front of you till the point of impact. No relative change in bearing but a crash none the less.
Picture a boat crossing in front of you 1000 yards ahead and 1000 yards to your left (port for purists). His relative bearing is 45 port. Time goes in and he is 500 yards ahead and 500 yards left, still at a 45 port bearing. More time and he is 1yard ahead and 1 yard left, still port 45.
More time and it doesn't matter he is in your cockpit.
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Which brings us back to the Original Post:
How did it happen that all parties, of two separate "units" ( bridge and "the weapons center" ) NOT recognize the threat and respond.
Only conclusion possible, very poor training and or management. ( Of everyone aboard was drugged... )
It is bad enough that the bridge failed, but more distressing is that those in charge of the weapons did not recognize and respond to the threat. ( Not that they should shoot, but it was a threat, regardless, and it needed to be "serviced" in an appropriate manner )
How did it happen that all parties, of two separate "units" ( bridge and "the weapons center" ) NOT recognize the threat and respond.
Only conclusion possible, very poor training and or management. ( Of everyone aboard was drugged... )
It is bad enough that the bridge failed, but more distressing is that those in charge of the weapons did not recognize and respond to the threat. ( Not that they should shoot, but it was a threat, regardless, and it needed to be "serviced" in an appropriate manner )
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If you are talking about relative motion in terms of distance, yes. If you are talking about motion in terms of bearing no there is no change in motion when on a constant relative bearing. The brain will discount distance when relative bearing is constant, because it is not a perceived threat.
Constant relative bearing is how collision avoidance software makes decisions. That is why they have vector arrows on the symbology on the screen.
I agreed with that notion when posted above, and AMEN now. Our brain "sees" what it thinks it needs so see.
"Contact moving (Relative bearing change)? Better flag that."
"Contact still where it was? Good, move on."
"But Contact seems Bigger! Ignore."
I don't think we will have much of an idea of what really was happening with these 2 vessels unless we eventually see their simultaneous tracks.
My guess is the tanker was too limited in maneuverability , and since the US was claiming they lost or "may have lost" steering until right after the collision , the Navy vessel likely changed course into the path of the tanker. But the tracks would reveal a lot.
Aside from all the human error and negligence, those below-waterline bulbous bows have been wreaking havoc on Navy hulls and seamans' lives
My guess is the tanker was too limited in maneuverability , and since the US was claiming they lost or "may have lost" steering until right after the collision , the Navy vessel likely changed course into the path of the tanker. But the tracks would reveal a lot.
Aside from all the human error and negligence, those below-waterline bulbous bows have been wreaking havoc on Navy hulls and seamans' lives