Two twins are separated; one remains on Earth while the other flies off into space at nearly speed c.

As twin-1 watches his brother rocket away from the planet, he perceives his brother as "aging slower". After a couple'a years pass, twin-1 would be 2 years older whilst his space-bound brother ages by just two weeks.

The paradox arises when one takes relativity at face value, and realizes that the space-bound twin could very well say that from his frame he was at rest, while it was the Earth that moved at nearly the speed of light. If so... how do we know which is actually aging slow, and which is actually going to be the full two years older at the end of the trip?

Twin Paradox Resolution

I find it easier to just direct somebody to see the appropriate math for themselves rather than attempt to post it on this forum... It's too damn messy!

• So, Mark, who is younger then: John or Bob? - alexander - October 31, 2001 - 17:31 UTC
  • Motion is not symmetric in this case... - smartguy - October 31, 2001 - 20:18 UTC
    • John and Bob are in SYMMETRIC situation. - alexander - October 31, 2001 - 20:46 UTC
      • Oh yes, excuse me for not directly answering the question... - smartguy - October 31, 2001 - 22:29 UTC
        • Don't argue with Alex - doctordick - November 1, 2001 - 16:22 UTC
          • Mark (and Dick) - alexander - November 1, 2001 - 18:46 UTC
            • Alex, this case is symetric, however you fail to realize... - smartguy - November 1, 2001 - 19:39 UTC
              • Alex, I think the thing that troubles you... is that... - smartguy - November 1, 2001 - 23:53 UTC
                • So, there is no "sloving of motion trough time" - alexander - November 2, 2001 - 01:06 UTC
                  • As far as I know... - smartguy - November 2, 2001 - 19:12 UTC
                    • Way incorrect. Proper past/present/future is ABSOLUTE. - alexander - November 2, 2001 - 20:11 UTC
                      • Alex, Alex, Alex... - smartguy - November 2, 2001 - 21:08 UTC
                        • Pretty impressive - harvey1 - November 2, 2001 - 21:26 UTC
                          • Thanx a lot Harv!! - smartguy - November 2, 2001 - 21:46 UTC
                        • Ditto - luis_hamburgh - November 2, 2001 - 22:28 UTC
                        • Mark, "proper" is a relativistic term. It means - alexander - November 3, 2001 - 17:34 UTC
                          • If it means anything to you... - smartguy - November 3, 2001 - 18:51 UTC
                            • Ouch! (nt) - harvey1 - November 4, 2001 - 03:58 UTC
                    • Yes, but proper height/width/length are ALSO ABSOLUTE - luis_hamburgh - November 2, 2001 - 22:27 UTC