An excellent point [the fact I entirely agree with Drake on this point has NOTHING to do with my use of the term 'excellent']. The window of opportunity to detect EM signals from our civilization [and presumably any others out there] may be very narrow - perhaps no more than a couple centuries [our time].
Not really, I'd give it atleast a few thousand. You forget Voyager 2.
"Their little universe is very young, and its god is still a child. But it is too soon to judge them; when We return in the Last Days, We will consider what should be saved.'"
This phrase is the epilogue of the novel "3001 the final odyssey", I have an english edition of this book
What about the dramatic increase in the amount of RF power transmitted by mobile ('cell' to our US friends) base stations? And all those military radars, aren't they the most powerful radio transmissions on Earth? Do they all get reflected off the ionosphere? How about the GPS system (and the future Galileo one)? And TRDS? Space-based military comsats?
OK, so our SETI friends will have a great deal more difficulty decoding milsat transmissions than the Jerry Springer show, but maybe it's better that way?
Cell phones!!! What??? They don't even work on this planet half of the time.
How does the level of high power activity compare to that of the 1960's or 1980's? I would think that the number of high strength transmitters is dropping or will drop significantly; as is suggested by the report. As for military RADAR, would we recognize such a signal from another planet? I didn't think this would compare to the characteristics of TV or radio as being necessarily from an intelligent source.
Just because radio telescopes are the humans best idea for finding other civilizations, doesn't mean that the aliens agree. Maybe they have such advanced technology that they can optically see faster than the speed of light, through anything, including our atmosphere. Maybe they're watching you right now. Though that sounds far fetched, you should at least consider that maybe there is a detection method that we have not thought of yet.
Even if more and more people are using cable/sattelite for their TV, it doesn't mean that radio wave transmissions are being phased out altogether and will completely cease in the near future.
Still though, how is the "window of opportunity" only a couple of centuries long? The signals we send out will travel through space indefinitely. Aliens still could intercept "Jerry Springer" and detect us 10,000 earth years from now, right?
We can all have great fun (or maybe great pain) speculating to our hearts' contents, but how does any one of us move beyond speculation to something that can actually be tested (or observed)?
The 'two century window' is real, if indeed Earth ceases to be a source of high-powered, omni-directional EM in the radio part of the spectrum. While it may be true that a trend to move 'free-to-air' radio and TV broadcasts to cable has started, and that this would certainly reduce the radio energy from Earth, it doesn't follow that the Earth (and the space nearby) will become radio-quiet! Consider mobile phone (aka cellphones in the US), satellite transmissions (for a wide variety of reasons), military radars (among the most powerful single sources, ever), even radar astronomy.
The window is still narrow because any given observer will only have a couple centuries or so to dial us in before the signals strong enough to detect and recognize as being of intelligent[?] origin fly past them.
We probably shouldn't worry about the 2 century limit too much. Until we develop wireless electrical power transmission, the Earth will emit with a distinct frequency signature, especially in the 50-60 Hz range. Our standardized AC electrical distribution frequencies are going to make a HUGE blip on any casual scan. You can thank Tesla for that one - Edison wanted to power the world with DC.
Is the solar system transparent to 50-60 Hz radio? IIRC, the interplanetary plasma - at least within Saturn's orbit - absorbs this. Or maybe I'm thinking of the ionosphere - doesn't it act as a very good mirror for these frequencies?
True, however, if the laws of physics are indeed the same everywhere, then radio waves will remain a simple, cheap, and effective means of transmitting information over interstellar distances...for humans or aliens. Even if they have more advanced methods, they still might keep their alien ears to the radio frequencies in their search for more primitive technological civilizations.
A couple of centuries for any given alien planet. It takes time for radio signals from Earth to reach that planet and eventually, the signals will pass it by and continue onto more distant regions of the universe, getting ever fainter. It's like a train passing by you...the beginning and end of the train marking the beginning and end of the radio signals from Earth. A particular alien planet will only have a limited window to catch the signal before it passes by.
Are we even pretty sure we want to be found? i mean what if they find us and become hostile?
You would think if they were advanced enough to travel here, they would not consider us much of a 'threat' [think NATO vs a neanderthal tribe]. You would also like to think such an advanced civilization would not find anything here that is so highly prized and otherwise unobtainable it would even be worth the trip. You would also like to think they would be more civilized than to go around pounding on defenseless primitive societies. More likely we would viewed like we would view a hitherto unknown marine species. Something to study, not eat.
So we should all go back to Iridium...
A good question. But with all the radio noise eminating from our activities (inadvertantly), the cat is already out of the bag. We have only sent a couple deliberate signals (and some people had the same concerns you do).
Let us devoutly hope that they do not have human-like social traits. Our species' track record regarding the treatment of more primitive cultures at the hands of technologically-societies is pretty dismal. Kill them, steal their land, ruin their habitat and destroy their means of sustenance....and that's to other human beings! It is conceivable that aliens could regard us as valuable only as museum specimens and start killing and collecting us like the Victorian-era explorers killed birds and butterflies. :surprised
Search for another blue planet
New small planets found.
The hunt has just begun. The nasa probes should be interesting, especially the terrestrial planet finder. Unfortunately, will have to wait awhile for that one. The Kepler Mission is, however, scheduled to launch in 2007. By the time it is all said and done, I think we will have a hard time finding stars that do not have planetary systems. Thirty years ago people thought I was nuts when I admitted to believing that proposition [they couldn't get me to bite on the tooth fairy, though]. Not that they were wrong, just for the wrong reason.
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