How Many Extra-Solar Civilizations?

star field

7 Civilizations, Past: 110 Billion

If the assumptions are modified by raising the civilization lifetime to 500,000 years, the cumulative number of civilizations emerging into the Galaxy rises to 110 billion (Table 4).

Table 5: Cumulative Civilizations, Assumptions 3
Civilization Time Available, years  5,500,000,000
Planet Civilizations Emerging, per year                       0.02
Total Number of Civilizations    110,000,000
Available Sequential Time-slots                5000
Assumed Civilization Lifetime, years           500,000
Concurrent Civilizations


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