| To be concrete, suppose the event of the rocket leaving Earth is at the point (0,0,0,0) in our coordinate system, and the rocket travels inertially (without acceleration) to the point (5,4,0,0). The rocket immediately turns around, and follows an inertial trajectory back to Earth, arriving at the event (10,0,0,0). The interval between (0,0,0,0) and (5,4,0,0) is, as we have seen, 3. Suppose this corresponds to an elapse of three years according to the onboard clocks. The return trajectory from (5,4,0,0) to (10,0,0,0) also has an interval length 3, corresponding to another three years elapsed. So the astronaut twin arrives back having aged six years, and having had all the experiences that correspond to six years of life. | | To be concrete, suppose the event of the rocket leaving Earth is at the point (0,0,0,0) in our coordinate system, and the rocket travels inertially (without acceleration) to the point (5,4,0,0). The rocket immediately turns around, and follows an inertial trajectory back to Earth, arriving at the event (10,0,0,0). The interval between (0,0,0,0) and (5,4,0,0) is, as we have seen, 3. Suppose this corresponds to an elapse of three years according to the onboard clocks. The return trajectory from (5,4,0,0) to (10,0,0,0) also has an interval length 3, corresponding to another three years elapsed. So the astronaut twin arrives back having aged six years, and having had all the experiences that correspond to six years of life. |
| [[Concept]]ual frames of the [[universe]] are only relatively true; they are serviceable scaffolding which must eventually give way before the expansions of enlarging [[cosmic]] comprehension. The understandings of [[truth]], [[beauty]], and [[goodness]], [[morality]], [[ethics]], [[duty]], [[love]], [[divinity]], [[origin]], [[existence]], [[purpose]], [[destiny]], [[time]], [[space]], even [[Deity]], are only relatively true. God is much, much more than a Father, but the Father is man's highest concept of God; nonetheless, the Father-Son portrayal of [[Creator]]-[[creature]] relationship will be augmented by those supermortal conceptions of Deity which will be attained in [[Orvonton]], in [[Havona]], and on [[Paradise]]. Man must think in a mortal universe frame, but that does not mean that he cannot envision other and higher frames within which thought can take place. | | [[Concept]]ual frames of the [[universe]] are only relatively true; they are serviceable scaffolding which must eventually give way before the expansions of enlarging [[cosmic]] comprehension. The understandings of [[truth]], [[beauty]], and [[goodness]], [[morality]], [[ethics]], [[duty]], [[love]], [[divinity]], [[origin]], [[existence]], [[purpose]], [[destiny]], [[time]], [[space]], even [[Deity]], are only relatively true. God is much, much more than a Father, but the Father is man's highest concept of God; nonetheless, the Father-Son portrayal of [[Creator]]-[[creature]] relationship will be augmented by those supermortal conceptions of Deity which will be attained in [[Orvonton]], in [[Havona]], and on [[Paradise]]. Man must think in a mortal universe frame, but that does not mean that he cannot envision other and higher frames within which thought can take place. |