If Barbour had told Einstein to give him a call back in seven minutes, Einstein might have asked: Your minutes or mine? If Barbour had been calling, say, from a spaceship moving at close to the speed of light, or one perched at the lip of a black hole, Einstein would find that each of Barbour’s minutes would last far longer than his. There is no universal reference clock that both Barbour and Einstein could agree on.Exactly!
It frustrates me to no end that some people miss this important part of physics.
I get flack for not getting the lawn cut yet, when in effect, on MY time it is already cut!
I constantly have to make people realize that their time is simply different than mine.