I’m not sure about Tarsney’s model in particular, but on the model I use in The Edges of Our Universe, a year’s delay in setting out towards the most distant reaches of space results in reaching about 1 part in 5 billion fewer stars before they are pulled beyond our reach by cosmic expansion. If reaching them or not is the main issue, then that is comparable in value to a 1 in 5 billion existential risk reduction, but sounds a lot harder to achieve.
Even in a model where it really matters when one arrives at each point in space (e.g. if we were merely collecting the flow of starlight, and where the stars burning out set the relevant end point for useful expansion) I believe the relevant number is still very small: 4/R where R is the relevant radius of expansion in light years. The 4 is because this grows as a quartic. For my model, it is 3/R, where R is 16.7 billion light years.
I’m not sure about Tarsney’s model in particular, but on the model I use in The Edges of Our Universe, a year’s delay in setting out towards the most distant reaches of space results in reaching about 1 part in 5 billion fewer stars before they are pulled beyond our reach by cosmic expansion. If reaching them or not is the main issue, then that is comparable in value to a 1 in 5 billion existential risk reduction, but sounds a lot harder to achieve.
Even in a model where it really matters when one arrives at each point in space (e.g. if we were merely collecting the flow of starlight, and where the stars burning out set the relevant end point for useful expansion) I believe the relevant number is still very small: 4/R where R is the relevant radius of expansion in light years. The 4 is because this grows as a quartic. For my model, it is 3/R, where R is 16.7 billion light years.