[xelasnave]

Originally Posted by bojan

This is an old hat, Alex..
Have a look at this explanation.
http://mentock.home.mindspring.com/twins.htm
Pure and simple.

This one is more complex, but essentially the same.. and yes, it is from wikipedia.. but not everything found there is bad :-)
http://en.wikipedia.org/wiki/Twin_paradox

Thank you Bojan I like Wikipedia particularly all the stuff they have in blue

alex