The previous considerations refer to the best case,
namely the maximum number of „Earths 2“ in the galaxy.
If you take the figures determined for civilizations,
then things look even worse.
According to sentence 15.2.3, a maximum
number of 169  2556 civilizations can be expected.
For 169 civilizations, the average distance is 5,296 light years.
That would also be the maximum average distance to another civilization.
SETI only covered a space of around 55 light years. So you would have
to send or wait at least 5,241 more years so that we would
get the answer in 10,537 years.
With 2556 civilizations, the average distance is 2,141 lightyears.
That would also be the maximum average distance to another civilization.
SETI only covered a space of around 55 light years. So you would have
to send or wait at least 2,086 more years so that we would
get the answer in 4,227 years.
Overall, we would have to search and wait with SETI for
an average of between 4227 to 10537 years before we get an answer.
According to Chapter 16.5, only civilizations of a certain level
of development use electromagnetic signals. According to
Theorem 15.3.3, 16  243 comparable civilizations
could exist on habitable „Earth 2“ in the galaxy.
For 16 civilizations, the average distance is 11,620 light years.
That would also be the maximum average distance to another civilization.
SETI only covered a space of around 55 light years.
So you would have to send or wait at least 11,565 years
so that we would get the answer in 23,185 years.
With 243 civilizations, the average distance is 4,692 light years.
That would also be the maximum average distance to another civilization.
SETI only covered a space of around 55 light years.
So you would have to send or wait at least 4,637 more
years so that we would get the answer in 9,329 years.
Overall, we would have to search and wait for an average
of between 9329 and 23185 years with SETI before we get an answer.
