If the communication lifetime of civilizations in our galaxy is 10,000 years and our galaxy is 13 billion years old, what is the chance of us detecting another intelligent civilization now?
A) 1 in 13,000
B) 1 in 1,300,000
C) 1 in 1300
D) 1 in 130,000

Question

Quizplus · Accepted Answer

If the communication lifetime of civilizations is 10,000 years, then the chance of us detecting another intelligent civilization now would depend on the fraction of the galaxy's history during which communication is possible. Since the galaxy is 13 billion years old, this fraction would be 10,000 / 13,000,000,000, or 1 in 1,300,000. Therefore, the best choice is B.

If the Communication Lifetime of Civilizations in Our Galaxy Is