How far outward can we rule out intelligent life?

[rootone]

So far we haven't detected an exoplanet which shows a strong potential for being habitable, they mostly have been 'Hot Jupiters'.
There are a small number of discoveries which are more Earth-like, but we don't really know much other than they are orbiting their star at a safe distance and might be rocky rather than gas giants.
This is mainly because our present technologies for studying exoplanets are at a very early stage.
Doubtless this will improve, but until it does improve any directed signalling whold have do be done more or less randomly.
That obviously reduces a lot the chances of being successful.

 

[Jenab2]

This is reminiscent of the Fermi paradox - where are they - If intellligent life is rampant, why have we not already detected their radio signals? The most likely answers are 1] radio communication is rare, 2] intelligent beings are rare. If we choose to dismiss option 2, then we must come up with a reason for the lack of radio detection. Contenders include 1] the universe is too vast for radio signals to be detectable beyond short distances; 2] we are the crown jewel of intelligent beings within radio detection distances; 3] we are too moronic to recognize an intelligent signal; 4] we are the only ones dumb enough to paint a radio bullseye on ourselves in a universe teeming with exploiters and predators. Our ability to generate radio signals detectable across many light years allows us to rule out option 1. Option 2 can be eliminated on anthrocentric grounds. That leaves my personal favorites, options 3 and 4, as the most reasonable explanations

Choice 2 might be correct. Anthrocentrism doesn't mean 'false'; it only means go carefully. Even a biased mind is right once in a while.

 

[newjerseyrunner]

I think the most likely solution to the Fermi Paradox is the "they're made of meat" argument. We're too primitive to be considered civilized life. The universe is probably littered with animals that almost made it, but didn't. If our obsession with medicine is anything to go by, our self preservation instinct extends to our technology, and since that's a driving force of evolution of greater beings, I would expect species to embrace some sort of digital immortality not soon after it's invented. What could a being that's hundreds of thousands of years old have to talk about with an ape that can barely understand it's place in the universe.

An elite American special forces team could spy on an ancient Roman battalion without much effort, I see no reason that an alien species couldn't observe us from afar without us knowing.

 

[DavidLloydJones]

Let's assume there is a planet out there with life equally intelligent as humans that is putting in the exact same amount of effort to detect alien life that we are. Their science and technology also developed in line with human technology. Given that we're looking and they're looking, what is the closest this planet could be to us given that we don't know about them (yet)? Any guesses?

Seems to me they have to be at least thirty light-years away. Any civilization at our level of ability and confusion will spend at least thirty years debating a loud reply once they find out about us. If they'd been on Mars, their thirty years would have been up some time ago, so they're not there at least.

-dlj.

 

[Bernie G]

What could a being that's hundreds of thousands of years old have to talk about with an ape that can barely understand it's place in the universe.

Love.

 

[Alltimegreat1]

Seems to me they have to be at least thirty light-years away.
-dlj.

Thanks for specifically answering my question.

 

[dougfgd]

We are receiving coherent radio signals regularly with modulation that are 4 milliseconds long inconveniently they that turn up at random intervals.
The signals have been traveling for millions of years and we don't know if they contain useful information. Will make a good basis for science fiction story.
My story uses the information to decode frozen entanglement for instantaneous hyperspace communication.

 

[ThomasLLS]

We may or may not be the most intelligent beings in the universe. The point of creating this thread was to determine how far outward from the earth/sun scientists would feel safe about saying there is no human-equivalent intelligent life. I was hoping to get some more specific answers, even if merely based on intuition. The observable universe has a diameter of some 90 billion light years.

What if there were humans just like us living on a planet 100 light years away from Earth (with the same telescopes and radios and satellites) who were also interested in finding alien life? Would we have detected them by now?

Wait.. 90 billion light years? Isn't it estimated that the big bang happened around 14 billion years ago? Therefore we should suppose that 90 billion light years away from us there should be nothing at all, at least for now.
I think that we cannot be the only intelligent beings in the entire universe, there should be another civilization out there and if they are more intelligent than us they most likely know about our existence.
Anyway, this beliefs that there are intelligent beings like us somewhere out there, in the known space, have no proof whatsoever (I believe them though).
But the human race always wants to look out there, and imagine we are not alone.

 

[phinds]

Wait.. 90 billion light years? Isn't it estimated that the big bang happened around 14 billion years ago?

This is a common misconception until you understand the basics of cosmology. The universe is expanding. The objects that are 47 billion light years from us now were MUCH closer when they emitted the light that is getting to us now and they have move very much farther away during that time.

Therefore we should suppose that 90 billion light years away from us there should be nothing at all, at least for now.

This shows an even more fundamental misunderstanding. The observable universe is not expanding into anything. The universe is possibly infinite, possible just many many orders of magnitude larger than the observable universe. Also, for what you say to be true, we would have to be at the center of the total universe which is staggeringly unlikely. Google the Cosmological Principle.

 

[Alltimegreat1]

How can we tell that the most distant objects we can observe are 45 billion LY away when the light we can view from them now was emitted from less than 13.7 billion LY away?

 

[ThomasLLS]

This is a common misconception until you understand the basics of cosmology. The universe is expanding. The objects that are 47 billion light years from us now were MUCH closer when they emitted the light that is getting to us now and they have move very much farther away during that time.

This shows an even more fundamental misunderstanding. The observable universe is not expanding into anything. The universe is possibly infinite, possible just many many orders of magnitude larger than the observable universe. Also, for what you say to be true, we would have to be at the center of the total universe which is staggeringly unlikely. Google the Cosmological Principle.

Understood, so we should consider the observable universe much much smaller than the actual universe, and the observable universe measures 94 billion light years aproximately (considering it a straight line).

 

[phinds]

Understood, so we should consider the observable universe much much smaller than the actual universe

yes, that's what I said.

and the observable universe measures 94 billion light years aproximately (considering it a straight line).

yes, 94 billion light years diameter. Your "straight line" would seem to suggest you are thinking of a radius, as in "straight line from here".

 

[rootone]

How can we tell that the most distant objects we can observe are 45 billion LY away when the light we can view from them now was emitted from less than 13.7 billion LY away?

Because the light of these distant objects is red shifted due to the expansion of space.
From the amount of red shift it is possible to determine how long ago the light was emitted, and from that we can deduce where they would be now if they still exist.

 

[ThomasLLS]

Yes, I expressed myself badly, I meant the diameter.

 

[Alltimegreat1]

Alright, but how far away were these most distant observable objects today from the Earth when they emitted the light we see today?

 

[Jenab2]

I think the most likely solution to the Fermi Paradox is the "they're made of meat" argument. We're too primitive to be considered civilized life. The universe is probably littered with animals that almost made it, but didn't. If our obsession with medicine is anything to go by, our self preservation instinct extends to our technology, and since that's a driving force of evolution of greater beings, I would expect species to embrace some sort of digital immortality not soon after it's invented. What could a being that's hundreds of thousands of years old have to talk about with an ape that can barely understand it's place in the universe.

An elite American special forces team could spy on an ancient Roman battalion without much effort, I see no reason that an alien species couldn't observe us from afar without us knowing.

I hold the opinion that our kind of life is ineluctably biological. If we create computer-mechanical life, we do not transition ourselves to it. Rather, we facilitate our own replacement by it. Our devices were originally conceived as our tools, what we use to extend our perceptions and our powers while we, ourselves, remain biological organisms. We are, by nature, more than our wants and our wills, and although evolution will sooner or later change us, we will remain us only so long as we remain biological.

There is yet room for improvement in the human kind by biological means. The major impediments are ideological, not theoretical or practical. It seems that every time someone says 'eugenics,' someone else says 'Holocaust,' and the discussion rapidly attenuates, dissolves, or mutates. The betterment of unknown billions of people yet to be born is judged to be of less importance than the present condition or the civil rights of a few millions who live now. Those future people don't get to vote on whether they shall be born strong or weak, constitutionally sound or prone to illness, with senses acute or impaired, or of great intelligence or retarded. And so what can be done, and what should be done, is never done.

 

[newjerseyrunner]

Love.

Chimps love each other, think you could have a stimulating conversation with one?

Alright, but how far away were these most distant observable objects today from the Earth when they emitted the light we see today?

45 billion light years, that's the definition of the Hubble Radius.

 

[Rubidium_71]

Humans ruling things out isn't necessarily the final word on a subject, even on our own planet. Just ask a coelacanth. (or see https://en.wikipedia.org/wiki/Living_fossil)
As far as detection goes, how do we know other civilizations would use radio waves to communicate? Especially given how impractical the radio method is when applied to interstellar distances. It could be that there is another, currently unknown method that other life forms use to communicate between the stars and we simply haven't discovered it yet.
It's also possible that some of the subsurface oceans here in the Solar System might contain some fairly intelligent creatures as well. We'll never know until we actually check.

 

[AgentSmith]

Love.

They would not know we were "apes" until communication had commenced, assuming they had not picked up old broadcasts of Mr. Ed and My Mother the Car.

 

[newjerseyrunner]

Humans ruling things out isn't necessarily the final word on a subject, even on our own planet. Just ask a coelacanth. (or see https://en.wikipedia.org/wiki/Living_fossil)
As far as detection goes, how do we know other civilizations would use radio waves to communicate? Especially given how impractical the radio method is when applied to interstellar distances. It could be that there is another, currently unknown method that other life forms use to communicate between the stars and we simply haven't discovered it yet.
It's also possible that some of the subsurface oceans here in the Solar System might contain some fairly intelligent creatures as well. We'll never know until we actually check.

I think the fact that we can't see anyone else using radio waves is evidence towards that. Say the Alcubierre drive idea actually can work, it'd actually be faster and more secure to send a ship with a message than to beam it across the universe with radio waves.

While it's remotely possible that some sort of intelligence lives under subsurface oceans, we can use laws of physics to determine that it's astronomically unlikely. Complex life requires a great deal of energy density and tidal forces alone couldn't generate that.

They would not know we were "apes" until communication had commenced, assuming they had not picked up old broadcasts of Mr. Ed and My Mother the Car.

No, they wouldn't know we were apes until observation had commenced. That may have started thousands of years ago for all we know. If I were immortal and wandering the universe, I'd drop probes at any planet that even had the potential to evolve technological beings. That's the nice thing about immortality, eons are irrelevant. If a curious being or species stumbled across our little planet millions of years ago, they may have been observing us that entire time.

 

[Ralph Dratman]

This is reminiscent of the Fermi paradox - where are they - If intellligent life is rampant, why have we not already detected their radio signals? The most likely answers are 1] radio communication is rare, 2] intelligent beings are rare. If we choose to dismiss option 2, then we must come up with a reason for the lack of radio detection. Contenders include 1] the universe is too vast for radio signals to be detectable beyond short distances; 2] we are the crown jewel of intelligent beings within radio detection distances; 3] we are too moronic to recognize an intelligent signal; 4] we are the only ones dumb enough to paint a radio bullseye on ourselves in a universe teeming with exploiters and predators. Our ability to generate radio signals detectable across many light years allows us to rule out option 1. Option 2 can be eliminated on anthrocentric grounds. That leaves my personal favorites, options 3 and 4, as the most reasonable explanations

Or, successful technological civilizations use radio only for a few decades to a few centuries, because there is a better method of communication we do not know about yet.

 

[Ralph Dratman]

[QUOTE="Would an aquatic species use radio?[/QUOTE]
An aquatic species with tool-making and tool-using capabilities comparable to ours might use radio. The gaseous atmosphere on the surface of our planet would seem like a kind of low-level outer space to such creatures, but their capabilities certainly might grow to allow them to roam pretty freely on land and in the air. Hint to this species: dry off before you start building electronics.

 

[Chronos]

I agree an evolving technological civilization may only utilize radio for a brief time, but, they would surely realize exo civiliations would likely utilize this technology at some point during their development - encouraging them to listen for, and perhaps even broadcast radio signals. The devlopment of electrical technology in an undersea environment would obviously progress in a different way and rate than it did for human civilization, but, it would surely occur for an advanced civilization.

 

[write4u]

I recently watched a very interesting program, which approached the problem of biochemical molecules from a purely chemical viewpoint. The link is to a formal lecture by Robert Hazen, at the Carnegie Institute for Science.

Robert Hazen

• Senior Staff Scientist at Carnegie Institution for Science
• Washington D.C. Metro Area

• This is a recorded video of the lecture itself, but I found it on YouTube. In the past, the fact that something is shown on YouTube automatically disqualified the link as "unreliable". But after receiving several notifications inviting me to return to the Physics Forum, I'll give it one more shot. It might give some new insight into the almost certain occurrence of biochemical molecules on other planets.

Before ruling this link out, I request that a moderator with expertise in chemistry review the clip before rejecting this very interesting lecture, which precisely addresses the OP question.
(if you want to skip the lengthy introduction start @ 25:00)

 

[Promytius]

I'd add that the "Universe" is infinite, as there cannot be a 'container' with nothing beyond it; our local 90 billion chunk is filled, teeming with life and always will be; add the infinite number of other intelligent planets, and contact is always possible. There may be life very close to us, but on the galactic plane and therefore very obscure. Also out tiny little chunk of under 100 solar years of transmissions is a pathetically insignificant "noise" to detect. Perhaps not where, or how close, but rather when, and how recent.
Finally, so far, what we've broadcast may not be of any interest, even to nearby neighbors, especially if they are significantly 'different' than we are. It is perfectly plausible (except to hubristic homo sapiens) that a civilization has no interest in such a 'young' and primitive planet such as ours; maybe we just don't rise to the level of interest.
So, my answer is: how far outward can we rule out intelligent life? We cannot, all the way to forever, they all are theoretically reachable. Stop thinking in only 3 dimensions for an answer.

 

[Promytius]

Wait.. 90 billion light years? Isn't it estimated that the big bang happened around 14 billion years ago? Therefore we should suppose that 90 billion light years away from us there should be nothing at all, at least for now.
I think that we cannot be the only intelligent beings in the entire universe, there should be another civilization out there and if they are more intelligent than us they most likely know about our existence.
Anyway, this beliefs that there are intelligent beings like us somewhere out there, in the known space, have no proof whatsoever (I believe them though).
But the human race always wants to look out there, and imagine we are not alone.

YUP, 90 billion; blame it on the Dark.

 

[write4u]

My baseline is the earth, where insects had mastered flight 600 million years ago. We need only look at the variety of surface, aquatic, and flight capable organisms very early on to get an idea of what is not only possible, but probable that biochemical interactions occur everywhere conditions allow for the formation of biochemical molecules, the building blocks of life.

 

[skylon7]

Maybe we could change our definition of life a little bit... Like how do we not know that the gaseous forms in space aren't a form of life? Or robots... Maybe not life like humans in most ways, but I think that humans/animals aren't the only "living" things out there. Like planets, they are born in a sense, and they can die in a sense, and during their life they complete tasks like growing and changing their structure without much outside help. Twists my mind a bit to think about this...

 

[Snerdguy]

Intelligent life is probably widespread. It is time that makes it unlikely that we will find any beyond our own. Every bit of evidence we have suggests that life is fleeting. It begins and ends in an extremely short time relevant to the existence of the universe. The conditions which bring about life occur randomly during relatively minuscule periods of time over billions of years and since nothing remains constant, they end. Its sad to say that only our arrogance makes us look to the distant future of our sun dying and our colonizing space and the human species going on forever, because life just doesn't work that way. So, it's entirely possible that the signals of intelligent life passed us long before we were ready to receive them and ours will also miss their window to reach another species, falling before or after a minutely narrow period of time. Life could have come and gone as far out as we can see and we would still miss it and our species will be gone before others are ready to detect us. We our just a bunch of sparks in a very big fire.

 

[AgentSmith]

AgentSmith said: ↑
They would not know we were "apes" until communication had commenced, assuming they had not picked up old broadcasts of Mr. Ed and My Mother the Car.

newjerseyrunner said:
No, they wouldn't know we were apes until observation had commenced. That may have started thousands of years ago for all we know. If I were immortal and wandering the universe, I'd drop probes at any planet that even had the potential to evolve technological beings. That's the nice thing about immortality, eons are irrelevant. If a curious being or species stumbled across our little planet millions of years ago, they may have been observing us that entire time.

They could know we were at a very low technological state if they could just communicate with us. Since immortal beings would be even rarer than intelligent ones, we can safely ignore that scenario on probabilistic grounds. Observation would entail communication back to the home planet(s) by an AI, unless they had a base hidden on the moon with natural beings "manning" it. Then you have to make some assumptions such as cloaking technology, undetectable signals, invisible resupply ships or super-capable 3D printers and such. Its all possible, but not very probable. I would be happy to be proven wrong, if they would just come out and be friendly. But there is that damned Prime Directive.

 

[rootone]

Stop thinking in only 3 dimensions for an answer.

How do you propose any kind of communication even if it's only one way, with beings whose existence is not within our known observable Universe?

 

[StoneBurner]

Points about relative weakness of radio signals well taken. Don't know what the sun's power output is in kilowatts, but probably more in any band than anything we'll build! Point about radio being obsolete - doubt. As technology progresses here on earth, electromagnetic spectrum frequencies get MORE used, not less. As for predators - that assumes Einstein was wrong, and FTL travel possible. Could be, but that's not the way to bet.

 

[write4u]

Chimps love each other, think you could have a stimulating conversation with one?

Well, not about science, but yes, Koko, that remarkably intelligent Gorilla, is able to commuicate how she feels, what she wants, named her kittens (substitutes for babies). She has a sign vocabulary of some 1000 words and understands some 2000 *spoken* words, and is capable of teaching her Gorilla companions how to sign properly. Do we need to understand quantum to be a "person"?

Bonobo Chimps will not only voluntarily share but facilitate access to food. An experiment was performed with 2 Bonobos, separated by a fence with a door which could only be opened from one side.
The Bonobo in the compartment with the lock was given a bunch of bananas. When the Bonobo on the *closed* side indicated it wanted to eat also, the Bonobo with the bananas opened the lock and allowed her companion to enter her compartment and both sat close together sharing in the abundance .
Not only was this a clear sign of altruism, but it also required analysis of the problem and the correct action to *do a friend a favor*.
While this may seem rudimentary logic, such as in human children, it clearly demonstrates that apes are capable of assessing and solving a problem.

 

[write4u]

How do you propose any kind of communication even if it's only one way, with beings whose existence is not within our known observable Universe?

How about a model of the Fibonacci Sequence? 1 1 2 3 5 8 13 21 34 55... This could easily be communicated digitally over extremely long distances.

 

[ancient1physicsevy1]

I'm not saying just right there in our Backyard. I'm saying that they might be existing beyond our Solar System.

the backyard concept or very nearby is more possibly closer to the truth, moon or same solar system ' . the moderator has not clear stated that alien or different life forms verse human form exist or not exist. (aside from all the natural species on Earth and in oceans) the moderator has not seen a gray alien or he goes cautiously about that issue, for it is not comfortable to know about or see for real . it leaves one with much questions , shock , aware of many lies or avoidance's . they do exist ' and they are highly advanced both in technology and mental abilities . let's see if the moderator allows this note.