Drake Equation: How Many Of Them Are Out There?L= average lifetime (in years) that a civilization remains technologically active. How long will the civilization use radio communication? Will they be around long enough to send messages and get a reply? Even if we manage to take better care of the Earth and each other, our technology is changing so we may not use radio communication. It used to be that our television and music/talk broadcasts were "over the air" using radio and microwaves. Some of that radio/microwave energy leaked out into interstellar space (that may be why all of the extraterrestrials are staying away). Those broadcasts are now happening mostly via cable. Now the voice communication that used to be via cable is now happening mostly with radio/microwaves (land lines vs. cellular phones). There is also the fact (yes, I use "fact") that individual species have changed and died out as their environment changed. Humans will be very different in a million years from now (if we survive that long). Because of the huge interstellar distances in the Galaxy, the
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