I haven't read the book, does it answer these points: There are only 76 type A stars within 100ly of us (100 light years because we've had powerful radio about

I haven't read the book, does it answer these points: There are only 76 type A stars within 100ly of us (100 light years because we've had powerful radio about that long). So even assuming every star had a civilisation capable of destroying us, that's only 76 of them. Similarly, we've had primative life on earth for millions of years. If a civ exists that can detect primative life and wishes to destroy it, it would have done so by now on earth since the milky way is only about 100k ly across. That's without getting into whether technological development is actually exponential, whether it caps out or how fast it is...