> Talking about this just made me realize
>something, though.
> Your calculations assumed 80 earth years and
> derived a figure for spaceship years. Shouldn't
> you have assumed 80 spaceship years and then
> calculated earth years?

It was you who assumed initially that the 80 years was "ship time". Diane merely said she saw on TLC that a journey to Alpha Centauri at .1c would take a round trip of 80 years. I took that to mean Earth years and not ship years, as I knew intuitively that .1c wasn't going to make much difference time-dilation wise.

But, if you want to assume 80 years as ship time, then all you have to do to figure out "Earth" time is multiply times gamma, or 1.006, and you get 80.48 years. The "actual" value I got for "ship time" when assuming 80 years Earth time was 79.52, so either way, it's the same.