
Calculator to estimate how many civilizations are in our galaxy if you haven't already done it.
A) Civilizations capable of getting here are easily capable of observing us without us knowing. They are visiting us and/or I have been probed.
B) Life is far more rare than is often expected. The universe, or our galaxy may be extremely sparsely populated.
C) I have mystical or spiritual beliefs that there is no life anywhere in the universe but Earth.
D) Our understanding of phsyics and technology is mostly complete and it is exceedingly difficult or impossible for civilizations to travel or communicate between stars.
E) We are boring or primitive or have been quarantined by other civilizations.
F) It's just really big out there. We'll find someone eventually.
G) Other