That is pretty depressing. Perhaps others like ourselves are trying to find us. Perhaps we live in a universe has built in features that prevents us from communicating. Perhaps life like ours is very rare in the universe. Sometimes I feel like we live in a lonely void. Perhaps that is sad. Perhaps if we could get along with each other we would be more succesful in finding the answer...
I think it somewhat depends what you're looking for. Since we're only scanning radio frequencies (AFAIK), we're already constrianing ourselves to radio communications, which may only last for just a few centuries during the lifetime of a technologically-capable species (from the time they first invent radio communication devices to the time they invent something better).
Now I agree that as their technology advances, they will find increasingly better ways to encode and compress their transmitions, to the point they are very hard or even impossible to distinguish from noise (unless you know exactly what to look for, which they must, and we don't). However, in the earlier stages, such encoding is bound to be far less significant. So this doesn't entirely eliminate our chances of detecting such communications, but only limits them (albeit siginificantly) since from a window of opportunity of a few centuries, we drop to one of only a few decades, or even years.
The more critical issue, is whether such communications, especially in their early non-encoded stages, will be sufficiently powerful for us to detect at all?
Do they want to know us?
Do they want us to know them?
Even if there is little chance of success with SETI, it's still worth doing. Multiply the very small chance of finding anything by the enormous impact any such find would have, and it becomes a worthwhile search.
And even a negative result proves something. If you can say something like, "There is no planet within 200 light years of Earth, that is transmitting radio signals like the Earth is.", that's worth knowing.
Radio waves aren't only transmitted to carry information. Some of the most powerful radio signals leaving Earth come from radar transmissions. With radar, you often just belt out as much power as possible, either in pulses, or in a narrow sweeping beam. There's no encoding. The idea is just to 'shine' the brightest beam of radio you can up into the sky, to maximise the chance of seeing some of it bounce back off an aircraft, or whatever.
If ET wanted to talk to us they would realize just how backwards we were and compensate for it, wouldn't they? Also what if there's another civilization out there at the same stage as us: before they got efficient with their technology? It seems there are still very many tangible reasons to scan the skies even if ET is ahead of us in technology.
I think it is rather simple really- we now know that our own technology will likely very soon accelerate to a point were we are encoding our communication- and our very selves into the structure of spacetime itself- down in the fundemental processes which weave spacetime and matter fields into existence- something like artificial spin-networks perhaps
the probability is that technological civilizations only dable in things like fire/ the wheel/ and radio for a brief cosmic moment before they quickly figure out how to start customizing their own universe how they see fit-
things like intersteller spaceships and radio communications between worlds are an illusion of civilizations stagnating at post-industrial levels of technology for aeons-
if intelligence doesn't go extinct- it almost certainly develops past such simple notions and weaves it's being directly into the fundamental structures of the cosmos- the inevitable end of intelligence bootstraping natural processes is eventually controlling/manipulating/utilizing ALL possible Cosmic processes-
if you want to find alien communications- your best bet would be to look for networked "artifacts"- basically ordered structures in the vacuum and in the spacetime around us at subatomic scales- but such structures would probably not react with the matter we use- nor be detectable by any method we currently know- so we probably won't find them until we are at that level of maturity ourselves [?]
If our world is constantly making components smaller and less resistant for data speed then maybe they are doing the same thing, but there cell phones are running 20k or so faster than ours ? (computer cables) Fiber Optics use light impulses with nearly unlimited bandwidth that we know of and travels much faster because of less resistance. If we can make a reciever capable of picking up signals 20000 times our technology then maybe well pick up something. I wonder what 2,361,183,241,466,822,622,848 cycles per second will do :) sincerely Dymium
We could still distinguish the signal from the background radiation, reguardless of the size of the signal. We maybe not be able to understand it or capture all of it but we could tell that the signal wasn't natural.
According to Moore's Law that will only take about 21 and a half years.
Click on the link and go to Drake's equation. Load the interactive version so you can play with the parameters (how many suns have planets, how many planets can support life, how many lifeforms can develop intelligence, etc). Then look at our own history (how long have we been transmitting in radio frequencies, and how soon will we outgrow that...) Once you start getting even a little bit conservative, the numbers of communicating species drops dramatically. SETI may not be a winning proposition. Remember that whales are quite intelligent, and they communicate through acoustic signals through water, and can't be detected from the Moon , much less from Proxima Centuri. There is no guarantee that we can detect any extra-solar intelligent life, unless they decide to visit.
Well, the Drake equation is based on so much speculation that its tough to use it to prove anything. Its just interesting to play with.
Regarding whales - they wouldn't meet SETI's definition of "intelligence" since they don't use tools or technology of any kind.
ceptimus and Andromeda both also have good points - radar signals (especially military - Aegis especially is directional, transient, and very powerful) are very powerful, and we should not discount the possibility of a beacon. While right now a few megawatts for a beacon seems like a lot of wasted power, in 100 years, a few megawatts probably won't seem like much.
You have to consider though, how fast does radar technology evolve? How long till we switch to something else, especially in military? E.g. passive radars rely on the reflections of common radio communication signals, which brings us back to the communication side..
EDIT: As for beacons - assuming we're looking for civilizations roughly at the same development stage as us, what is the chance we'll detect a deliberate radio beacon, considering we have not set one up ourselves?
Have we not? We have been transmitting on SW and VHF & UHF for a considerable time now. How long before our calling card is returned a la 'Contact'?
Humans have sent 2 deliberate signals to the stars and both were designed to be received and understood.
And then there's our unintentional signals from all our radio chatter.
So, there is still hope of finding other civilizations.
Perhaps we won't tap into their interpersonal communications, but we can still listen for their deliberate signals & unintentional artifacts.
I'm not sure what we have been transmitting.. I was talking about a signal specifically intended for possibe ETs to detect. If we have sent something like this (like Phobos seems to suggest), then I stand corrected.
Considering the distances involved, I figure it would take a while.. :uhh:
if "tricks" are possible and the aliens have a way to cheat lightspeed- their response or they themselves might get to us just hours/days/weeks after they recieve ours-
since we are just beginning as a technological civilization- whoever is out there is most likely to have been there a LOOOONG time before us- and would posess some serious god-tech- and there are so many conjectured ways to cheat- such as manipulating space instead of moving- or finding natural wormholes already connected to far regions than can be adapted for signals- etc-
An 'optical SETI' project is underway (go visit the Planetary Society's website for details).
At least one of the deliberate attempts to communicate involved sending an 'image' in the direction of a globular cluster (M13?), by radio (Arecibo?) - the signal was VERY powerful.
Lots of (military) satellites communicate using spread spectrum coding schemes (similar to the CDMA third-generation standards now being deployed in mobile (aka cell) telecoms networks); while decoding an intercepted signal is hard to nearly impossible, detecting the signal is easy (one of the seti websites has some very nice images and discussion of this; even amateur hams can 'see' the satellites).
The underlying assumption in SETIs is 'just like us'; if you start straying away from 'us', then it becomes increasingly difficult to have any confidence in detection or the meaning of null results.
However, the best thing about SETI (esp the SETI@Home project, and its receivers on Arecibo) is the 'incidental science' ... not only did SETI@Home lead to BOINC - a wonderful 'fast forward' in grid computing, esp for science projects - but the SETI data can be mined for unusual or not-seen-before signals of a quite natural kind. Never underestimate the value of serendipity!
I would expect a compressed message would still have certain patterns to it that aren't common in the static of the universe. Even if we couldn't decode it, I think we would know it's a weird event and could find intelligent patterns. But I think things will be SO different in say 5000 years (~1/2000000 the age of stars/planets) that we won't be doing the same things as other species. I also don't think a species of extreme intelligence would be looking for intelligence like us. They would be doing what we're doing, looking for equal or greater. Even that depends on so many things.
BTW, I guess I like the idea of the Drake equation but I think it is completely wrong because it assumes the universe is infinitely old and that stars form at the same rate at all times and that civilizations all go extinct.
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