I've written this twice, months apart from scratch. Failed both times. I'll bet this is a trivial mistake! The attachment is .nb, identical to this paste, below.

(Twin Paradox)

(* dilation =tprime/time *)

(natural units, c=1 ; v in fraction of c )

(* At v = .999 c, etc. *)

v = 0.999; dilation = 1/ ((1 - (v^2))^0.5)

v = 0.999999; dilation = 1/ ((1 - (v^2))^0.5)

v = 0.999999999999; dilation = 1/ ((1 - (v^2))^0.5)

v = 0.999999999999999999999999; dilation = 1/ ((1 - (v^2))^0.5)

22.3663

707.107

707115.

Power::infy: Infinite expression 1/0. encountered. >>

ComplexInfinity

FullForm[dilation]

\!( TagBox[ StyleBox[ RowBox[{"DirectedInfinity", "[", "]"}], ShowSpecialCharacters->False, ShowStringCharacters->True, NumberMarks->True], FullForm])

dilation = N[1.000000000000000000000000/ ((1.000000000000000000000000 - (0.999999999999999999999999^2))^(1/ 2)), 1000]

Power::infy: Infinite expression 1/0.*10^-12 encountered. >>

ComplexInfinity

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