Why do you think we have not detected extraterrestrial radio signals?

Question

There are trillions of stars in our galaxy alone, billions of galaxies in our known universe, and already over two-hundred extrasolar planets discovered. Many scientists and astronomers have predicted (based on the volume of extrasolar systems) that it is an almost certainty that extraterrestrial life exists, and even probably that the universe it teeming with life.

SETI has been in operation for decades and has so far detected only the single WOW signal. With radio waves occurring in nature and being an obvious method for communication, why do you think we have yet to detect an alien version of "I Love Lucy" bouncing throughout the cosmos?

Answer 1

They're going out of their way to avoid us.

Answer 2

The WOW signal may have been the strongest, but it's not the only candidate signal.  I don't have statistics handy, but years ago, the SETI@Home group had performed follow up observations of over a thousand candidates.  WOW was followed up without success also.

I think we're expecting moderately broad band noise.  It has too look narrow band enough to distinguish it from cosmic noise.  But it has to be distinguishable by the aliens too.

I doubt we're looking at the right frequencies.  I doubt that we're anywhere near sensitive enough.

But i expect that there are aliens out there.  And i expect that they communicate with each other.

Here's a strategy that might work.  When we see a nearby supernova, we could broadcast a signal in the other direction.  We expect ETI to be interested in the supernova, and they'd see our signal too.  So we should target around supernovae, and other phenomenon for unusual activity.

Answer 3

The question you're asking here is known as 'Fermi's Paradox', and basically boils down to 'Why aren't the aliens here yet?'. There are a wide variety of possible explanations, and considering which are the most likely is a highly interesting intellectual exercise. Here are some theories:

1. Intelligent life is extremely rare, and we're the only intelligent life in the Universe.

2. Intelligent life is fairly rare, and for some reason chooses not to expand throughout the Universe but rather to stay in a relatively small area of the Universe.

3. Intelligent civilizations almost always destroy themselves before expanding into the rest of the Universe. Possible methods of destruction include nuclear war, natural or artificial disease pandemics, reproducing nanomachines (which proceed to consume the entire surface of their home planet, along with all the intelligent beings living there) or highly destructive physics experiments (such as, possibly but unlikely, our own Large Hadron Collider).

4. Intelligent civilizations are fairly common, but use some advanced form of communication that our telescopes either can't see at all or perceive as just being random, natural signals.

5. Intelligent civilizations are fairly common, and they are deliberately shielding us from receiving their signals for some reason.

6. Intelligent civilizations are fairly common, but some natural phenomenon is preventing us from receiving their signals (maybe something to do with the Pioneer Anomaly?).

7. Intelligent civilizations tend to develop extremely advanced technology and use it to transport themselves into other universes with different laws of physics that better support their existence.

8. The rest of the Universe isn't really the way it looks according to our telescopes; some natural or artificial phenomenon (maybe something to do with the Pioneer Anomaly?) makes the conditions out there appear larger, more hospitable to life or more permeable to radio waves than they really are.

9. Some intelligent force is consciously preventing intelligent life from arising elsewhere in the Universe.

Out of these, items 7, 8 and 9 fall into the 'weird' category, where the effects involved are significantly outside our normal understanding. Personally I think items 4 and 7 are the most likely possibilities. Items 1, 2, 6, 8 and 9 are all highly unlikely, for a variety of reasons. Keep in mind that the true answer may involve more than one of the above explanations, or some other explanation we haven't thought of yet.

Answer 4

Note I'm just kidding:

The alien intelligence that takes over my body when i'm black out drunk left me a note saying that they use telepathic relay crystal to communicate over vast distances.

Answer 5

On at least two occasions and probably more,signals have been detected.In the 1920s a national day of radio silence was observed.A team of civilian scientists and another group from the US Army listened for signals.Both groups received some rather odd signals which to this day have not been deciphered.In July 1976 a SETI group received a verifiable signal.It was reported in The New York Times.The next day the government shut down the project.  

Answer 6

  Technological societies like ours may not be that long lived.

  If the closest alien was 500 light years away and they sent a signal 700 years ago the signal would have passed by earth before we had the technology to detect it.

Answer 7

um...

radio communication was surpassed rather quickly by us once we first employed it's use...

what's to say aliens didn't have the same thing happen?  

Answer 8

We have not detected signal for one of two reasons:

1) They extraterresterials don't want us to hear them.  They don't want us to find them

2) Extraterresterials don't exist.

Any planets that have been discoverd have not been proven to contain life.  In fact, ALL of the ones so far "discovered" are believed to be super-sized gas giants, like Saturn.  NO ONE has yet discovered a planet that is anything even close to earth.

In fact, most of the discovered planets can't even bee seen with telescopes.  Scientists THINK that they are there because their orbits makes their suns "wobble".  This also shows that the planet, if we could see it, is HUGE, and not a small, tidy world like earth.

The fact is, there are a great many things that have to be just exactly right for life as we know it to live on this planet:

A "yellow sun" of the same size and intensity.

Planet orbits at exactly the same distance from the sun

The presence of large planets to "sweep" asteroids out of the way.

The planets magnetic field cannot be too strong or two weak.

and so on.

As it turns out, these circumstances are pretty unique!  Scientists are now beginning to think that instead of "thousand" of planets with "hundreds" of living worlds, we may in fact be one of only 10 or 20, and those others are so far distant that we won't ever hear form them.

Answer 9

i believe it's nearly impossible for there not to be life somewhere else.

the government knows things tht they aren't going to tell us cuz we might panic or something. i hate it. i was watching the discovery channel (they act like they're telling everything but u can tell they're keeping stuff from us) and they said they found a spacecraft crashed on earth with two unrecognizable creatures in it. they said they took them to the lab for further analysis. but the thing is i want to kno what happened after tht u kno? to answer ur question, i think they might hav different signals or might be too far away or they aren't as smart as us to build them. i hope this helped

Answer 10

teh signals are too weak.

we are listening on the wrong frequency.

we are listening for the wrong things.

there are no signals to pick up.

our most efficient communication systems sound like noise. maybe theirs do too.

Answer 11

Adding to Tina's comment, we don't have a reason for aliens to contact us; we're not that famous.

Answer 12

There maybe many many planets out there, but chances are intelligent life requires a very Earth like environment which vastly decreases the viable worlds in the universe. Not only that but as a species mankind has only existed for a fraction of the history of Earth and our sun. Compare the 4 billion so years of life on Earth to the 100 years mankind has been broadcasting radio signals. So even if there are a billion Earth like worlds (I think that is a VERY generous estimate too) in our galaxy right now only 25 of them currently have a civilization broadcasting (this is a very rough estimate as mankind will most likely be broadcasting into the foreseeable future unless it we are wiped out, but I'm getting to that). Thats 25 worlds spread out evenly over the entire galaxy. Even if we knew wear to look with our radio telescopes it can be assumed most if not all of these worlds are too far away to distinguish their signals from the other natural sources of radio static.

I also have a little theory of my own. Look back to the years mankind has been broadcasting... a certain even comes to mind that would have changed the world we live in today quite drastically should it have turned out differently... the Cuban missile crisis. Mankind came within a hair's width of annihilating itself and all the survivors would be again hundreds of years away from re-attaining current technology. I believe that any species intelligent and ambitious enough to develop an technologically advanced civilization is likely to annihilate itself before spreading to any other worlds. If the bombs don't fall then they are likely to use up all their natural resources and then digressing in technology (mankind is probably going to go this course).

In summary, intelligent species may be very common throughout history, but they are very likely to wipe themselves out or digress technologically making the window for us to observe them with our very limited radio telescopes very small.

Answer 13

The simple truth is that the probability of picking up electromagnetic radiation containing sophisticated information from another civilization on another planet is extremely small.  While there are estimates of the number of such civilizations (Drake equation), the fact is that so far we have no way of determining the probability of such a finding when we have no physical evidence whatsoever of life on any other planet.  That is, with a sample of only one planet (earth), there is no way to estimate the probability of finding another planet with intelligent species that use radio waves for communication.

Answer 14

Tina is on the right track.

I would add that your assumption that radio waves being an obvious method of communication may be wrong.

For all we know, that method of communication may be a passing phase of an advanced civilization.

We may yet discover a much more efficient means of interstellar comms, that will make radio transmissions seem like smoke signals.

Maybe using wormholes... or quantum entanglement.