Please excuse this slightly tangential attachment!!!
Suppose the day eventually arrives when a technological civilisation is discovered. Which type would it most probably be?
- Type 0, as ours is right now.
- Type I, as ours will be if we hold things together for another couple of hundred years.
- Type II, which is said to lie more than 3000 years in our future.
- Type III, which could be a 1,000,000 or more years down the road.
Two factors to take into account when answering that are (a) the cosmological time scale, (b) the age of our own technological civilisation.
Let's make two assumptions:
(1) The first planets suitable for the evolution of life were accreted around the first of the second generation stars 10 billion yrs ago
(2) It takes 5 billion years to evolve a technological civilisation.
That allows the possiblity that the civilisation could currently be anything up to 5 billion years old. I think, therefore, that:
(1) The probability of discovering a Type 0 or Type I is very close to zero.
(2) There's a slightly better but still very small chance of finding a Type II.
(3) There's a high probability of a great predominance of Type III (or higher). But they may not be easily detectable. Their activities may be indistinguishable from (other) natural phenomena.
