Circumstance and perception...
So about this question I have about being able to discover ourselves. Is it possible? I'm using the Cassini spacecraft as an example because as far as my limited research tells me, it's the farthest scientific instrument in space that we still have full use and functionality of. I'm quite sure some physics or astronomy scholar could correct me on the details but the arguments that could come up in this question I believe are futile. And my last disclaimer for the moment, I know Cassini's mission isn't to try and find life outside our solar system... Just go with it.. Mmm-k?
As we look back at earth from a vantage point of say, the moon, could we determine there is intelligent life on our planet? Well, by mere matter of circumstance we could easily determine that. We could see the lights (maybe) on the night side of the earth, we may be able to see or detect satellites in orbit, or even intercept a radio wave or other non-natural emitting forces that are unique to the human race. But could we detect human beings? If this planet was still only occupied by dinosaurs and other prehistoric creatures, could we determine it from any distance of multiple astronomical units?
Farther out, we see a view of earth from Cassini. It looks like what we know of as a star in the sky. Using very accurate and ingenious technological instruments, we may be able to decipher wavelength properties, red or blue shifting, rotational periods, basic elements, average temperature... etc. etc. etc. But again, can we detect ourselves ignoring the bias that we obviously know we are here?
If there is another form of intelligent life in our universe (which I personally have faith that there is), how could we detect it if they don't use wavelength based communication or refine and manufacture metals for technological advancement. Maybe this other life form realizes that fire itself may be bad for the environment. (Argue that after standing downwind from a campfire). Maybe they are smart enough to realize that the process of refining and manipulating natural resources for purposes of greed and power is destructive to their race as a whole. Maybe this other life form is in a place where there is no resource to refine such as that which we know. (Gold, coal, copper, fossil fuel, etc.). Without being able to detect things which we may relate to intelligent life, how can we tell?
Without the circumstantial evidence that we may observe of our own planet from a viewpoint outside our solar system, how could we detect the life form energy of human beings?
Wavelengths of any definition is really a property of energy acting in a certain manner. It comes across as light or radiation or even noise. In my limited study of physics and astronomy, it seems that although there are many methods to measure and determine properties and existence of energy, energy itself has yet to be defined. What if the energy that we know of isn't the only thing in existence. What if the dark matter in which we don't understand is made up of something completely 'out of this world'? We can measure properties and actions of energy as we know it, but could the data we derive from the instruments we know of be anomalous to something not yet discovered?
The same energy that gives us life, also gives life to disease, despair, emotion, love, hate and everything in between. We can measure electrical impulses from the human mind to correlate specific activity to certain brain functions, but it's like hearing static on your radio from a lightning strike and trying to determine everything about lightning from that one anomalous reading.
I was given a comment from a reader to propose this to Neil Tyson and I actually fully intend on doing so. First, I must get myself out of the middle of BFE, and second I want to propose the question in a fashion that doesn't make me sound like an asshole. This isn't a question to dispute or challenge the knowledge and intelligence of anyone, it's a question to explore something I believe doesn't get quite as much face time as it should. The answers we are looking for in so many aspect of our life are closer than we know. We have to do more than simply open our eyes...