Are Aliens Listening? Evidence for Intelligent Life in Space

[Chronos]

Even assuming aliens have the same sensory capabilities as humans - which seems fairly reasonable. There is an unbounded parameter space for language to emerge. How many languages exist, much less have ever existed, on this planet; hundreds, thousands, more? Each language has a unique history of development. They all began with a few basic sounds or gestures followed by subtle manipulations thereof, all based on the unique culture heritage of its native speakers. And this does not even address the issue of interpreting written language We have enough trouble figuring out other human languages; e.g., WWII Japanese v Navajo language, and almost no clue how to interpret the language of other animals: after all, they don't make noises or engage in ritual behaviors because of the survival value in alerting predators to their presence. It would be incredibly difficult to translate an ET language, or even recognize it as language - and vice versa. A pattern recognition algorithm may suggest data content in a message, but little else. I understand the hostile universe concept, as does Stephen Hawking, but risk taking cannot be eliminated from any effort to advance and prosper.

 

[lpetrich]

I'll now consider analog vs. digital reverse engineering.

Analog signals are fairly easy to reverse engineer, since their content parallels the original content, and since video signals have horizontal and vertical synchronization signals that stand out from the content signals.

Digital signals are much more difficult to reverse engineer for these reasons:

• Data compression. In summary, it gets rid of redundancy. But while it reduces the number of bits to transmit, it also deprives the signal of clues that reverse engineers could use.
• Error-correction coding. That involves adding extra bits so that if some of the bits get corrupted, there will still be enough to reconstruct the signal.
• Encryption. Without knowledge of the encryption algorithm, breaking it will be VERY hard.

So all that an extraterrestrial eavesdropper will be able to tell about digital broadcasts is that those broadcasts are present. That's true not only of radio and TV, but also of the Internet.

 

[sophiecentaur]

We could in principle develop telescopes that could filter out the background noise.

There are some very practical limits to this. You can use very directive receiving arrays (telescopes) but diffraction is a fundamental limit. You cannot necessarily distinguish between a wanted signal (with an unknown format) and the random signals from the same direction. By reducing the bandwidth of a receiver, you can improve the signal to noise ratio but you very soon get down to a bandwidth of fractions of a Hz and the information content of such a signal would be of not much use for making sense of your received signals. Imagine taking a Megawatt analogueTV signal and trying to make sense of what's in a 1Hz bandwidth part of the signal. You could perhaps recognise the frame repeat rate if you swept it very slowly with a spectrum analyser set to 1Hz b/w. There is an even greater problem spotting signals used in modern communication systems. Digital signals are deliberately profiled to maximise the rate of information transfer and such signals are very random looking and hard to distinguish from random noise.
The probability becomes very low of spotting a likely looking source when you are effectively scanning the whole of space with a pencil (if you are lucky) beam and taking days and days to scan the received signal in each beam position.
Now we have spotted many planets in Goldilocks Zones, we could avoid aimless scanning in all directions by looking just at them with our radio telescopes but success would require their civilisations would need to be only a thousand years (or less) out of step with ours for us to miss each other.
If a channel could be identified in one direction (i.e. we hear them or they hear us) then the recipient would find it very interesting (and throw them into blind panic, no doubt). But how many years / generations / millennia would be involved in a meaningful two way conversation? That puts a maximum limit on the 'relevance' of anything we (or they) could receive.
Scifi media have explored so many possibilities of communication. At present, I think the more likely scenario would be a more advanced civilisation spotting us (the basic OP scenario) but what if they are not very far away - near enough to come and have a look within a few centuries? That is one of the scariest scenarios I could ever contemplate. "Independence Day' with no happy ending.
Edit: I see that @lpetrich has made my point about the difference between various signalling systems; a cross post and very well put.

 

[nikkkom]

Diffraction limit problem can be overcome with interferometric telescopes. In space, there are no hard limits how large your baseline can be. Millions or even billions of kilometers are possible.
Space-based antennae are also not limited to diameters of about ~150m for steerable and ~500m fixed antennas, as they are on Earth.

 

[stefan r]

Diffraction limit problem can be overcome with interferometric telescopes. In space, there are no hard limits how large your baseline can be. Millions or even billions of kilometers are possible.
Space-based antennae are also not limited to diameters of about ~150m for steerable and ~500m fixed antennas, as they are on Earth.

When the source signal is less than 1 photon you have a hard limit. A Dyson sphere sized dish would probably nice long range. They could also use a longer exposure time.

If single photons are appearing occasionally you still lose the message. I suspect that would foil an interferometer too.

 

[happyhacker]

I like to think that it is probable that any life on other planets will have evolved (given the same Big Bang time scale, same physics applying, etc.) at the same rate everywhere. If there is intelligent life on an adjacent star(s) then I assume they would be at the same technological state of advancement. Therefore our signals would have crossed and if detectable and the source descernable a response would be most likely to be returned (would humans?). Then we are stuck exchanging information likely to little effect until a common language is devised. I would be interested as to the best way of transmitting these signals - a powerful xmtr. on the moon perhaps?

Do we invite some advanced race to come and see what a mess we are making of things? Unlikely there are such beings IMO as above. But if the are let's hope they don't have the conquering mindset of us humans!

 

[phinds]

I like to think that it is probable that any life on other planets will have evolved (given the same Big Bang time scale, same physics applying, etc.) at the same rate everywhere.

that is a completely unwarranted assumption and extremely unlikely (the rate, not the physics)

If there is intelligent life on an adjacent star(s) then I assume they would be at the same technological state of advancement.

Particular nonsensical.

 

[happyhacker]

Justify your responses! And how can it be unwarranted in this context?

 

[berkeman]

Justify your responses! And how can it be unwarranted in this context?

No, it is you that must justify your assertions by showing us links to the mainstream scientific articles that are making such statements. That's how the PF works...

 

[Bandersnatch]

I like to think that it is probable that any life on other planets will have evolved (given the same Big Bang time scale, same physics applying, etc.) at the same rate everywhere. If there is intelligent life on an adjacent star(s) then I assume they would be at the same technological state of advancement.

Consider the timescales involved - humans as a species have existed for a few hundred thousand years. Civilization for a few thousand. Technological civilization a few hundred.
Even if you assumed* that it takes precisely the same route for life to go from abiotic to civilization capable of communication on each and every planet, all you need is for their stellar system to coalesce from its molecular cloud a mere million years earlier or later to put unimaginable technological distance between us and them. What if it happened a billion years earlier?

*this assumption is similarly implausible, since there's no good reason to think that for civilization to develop life must go through the same evolutionary path and same extinction events, and same glaciations, same tectonic history... pretty much everything is a free variable.

For example, imagine where Earth's life would be today if there was no K-T extinction event (because the asteroid missed the planet)? Would descendants of dinosaurs develop civilization millions of years earlier? Or maybe intelligence would never appear in the form necessary for technological societies?

 

[happyhacker]

Thanks for you response. I'm wondering how the OP justified those points made.

 

[phinds]

Thanks for you response. I'm wondering how the OP justified those points made.

He absolutely did not. He made an assumption (a very unlikely one) and discussed what might happen if his unlikely assumption just happened to be true. That is not even remotely the same as categorically stating, as you did, that the assumption is valid.

He said

if aliens were searching the heavens ...

 

[rootone]

It is completely plausible that elsewhere in the Universe a life form could exist that is similarly or more highly advanced to what there is on Earth.
The problem is that it could be long in the past or future, and so far distant in space that communication is not remotely possible.

 

[stefan r]

It is completely plausible that elsewhere in the Universe a life form could exist that is similarly or more highly advanced to what there is on Earth.
The problem is that it could be long in the past or future, and so far distant in space that communication is not remotely possible.

I think the physics question should be "what range is it possible". Of course somethings might be further away. Expansion of the universe will also cut off a lot of places and prevent them from ever receiving a signal from earth.

Might help to narrow down to one signal. The Taldom transmitter broad casts at 261 kHz with 2.5 MW. Wikipedia says this is the largest on earth. Perhaps limit receiver size to diameter of planet earth.