They use the number of stars in the observable universe instead of the number of stars in the whole universe. This ruins their calculation. I wrote a little more here
But the lower bound of this is still well below one. We can’t use our existence in the light cone to infer there’s at least about one per light cone. There can be arbitrarily many empty light cones.
They use the number of stars in the observable universe instead of the number of stars in the whole universe. This ruins their calculation. I wrote a little more here
We can take it as a calculation for ‘number of technological civilizations in our past light cone’, whose messages we could receive.
But the lower bound of this is still well below one. We can’t use our existence in the light cone to infer there’s at least about one per light cone. There can be arbitrarily many empty light cones.