Here's why:

* Decreasing distance: This is the most obvious factor - if two objects are getting closer, the risk of collision increases.

* Constant bearing: If the bearing (the direction from one object to the other) remains the same while the distance decreases, it means the objects are moving on a direct collision course.

* Changing bearing: If the bearing is changing, it means the objects are not directly approaching each other. This might indicate they are passing by or moving away from each other. However, a very small change in bearing, especially when combined with decreasing distance, could still mean a collision is likely.

Example:

Imagine you are driving on a road and see another car coming towards you.

* Decreasing distance: The distance between you and the other car is getting smaller.

* Constant bearing: The other car appears to be staying in the middle of your lane. This indicates a potential head-on collision.

* Changing bearing: If the other car starts drifting slightly to the right or left, the bearing changes. However, if this change is small, you still might be on a collision course.

Conclusion:

While decreasing distance is a strong indicator of potential collision, a constant or slightly changing bearing combined with decreasing distance significantly increases the risk of a collision.