Relative speed

Here is the Queen Elizabeth passing the identical Queen Victoria out in the Atlantic. We'd been tipped off that it was about to happen. Things happen slowly at sea but this happened twice as fast as expected. We were steaming north at 20 knots. She was steaming south at 20 knots. That means that the distance between us was shrinking at 40 knots. That was our relative speed. To us, we could have been still with the Elizabeth approaching at 40 knots. To them, the Elizabeth was still and we were approaching at 40 knots. That was all fine until Einstein got hold of it and started thinking about what would happen when you get to the speed of light .... but that's another story.