How Many Alien Civilizations Are Out There? A New Galactic Survey Holds a Clue. (nationalgeographic.com) 93
Here's a good sign for alien hunters: More than 300 million worlds with similar conditions to Earth are scattered throughout the Milky Way galaxy. A new analysis [PDF] concludes that roughly half of the galaxy's sunlike stars host rocky worlds in habitable zones where liquid water could pool or flow over the planets' surfaces. From a report: "This is the science result we've all been waiting for," says Natalie Batalha, an astronomer with the University of California, Santa Cruz, who worked on the new study. The finding, which has been accepted for publication in the Astronomical Journal, pins down a crucial number in the Drake Equation. Devised by my father Frank Drake in 1961, the equation sets up a framework for calculating the number of detectable civilizations in the Milky Way. Now the first few variables in the formula -- including the rate of sunlike star formation, the fraction of those stars with planets, and the number of habitable worlds per stellar system -- are known. The number of sunlike stars with worlds similar to Earth "could have been one in a thousand, or one in a million -- nobody really knew," says Seth Shostak, an astronomer at the Search for Extraterrestrial Intelligence (SETI) Institute who was not involved with the new study.
Astronomers estimated the number of these planets using data from NASA's planet-hunting Kepler spacecraft. For nine years, Kepler stared at the stars and watched for the brief twinkles produced when orbiting planets blot out a portion of their star's light. By the end of its mission in 2018, Kepler had spotted some 2,800 exoplanets -- many of them nothing like the worlds orbiting our sun. But Kepler's primary goal was always to determine how common planets like Earth are. The calculation required help from the European Space Agency's Gaia spacecraft, which monitors stars across the galaxy. With Gaia's observations in hand, scientists were finally able to determine that the Milky Way is populated by hundreds of millions of Earth-size planets orbiting sunlike stars -- and that the nearest one is probably within 20 light-years of the solar system.
Astronomers estimated the number of these planets using data from NASA's planet-hunting Kepler spacecraft. For nine years, Kepler stared at the stars and watched for the brief twinkles produced when orbiting planets blot out a portion of their star's light. By the end of its mission in 2018, Kepler had spotted some 2,800 exoplanets -- many of them nothing like the worlds orbiting our sun. But Kepler's primary goal was always to determine how common planets like Earth are. The calculation required help from the European Space Agency's Gaia spacecraft, which monitors stars across the galaxy. With Gaia's observations in hand, scientists were finally able to determine that the Milky Way is populated by hundreds of millions of Earth-size planets orbiting sunlike stars -- and that the nearest one is probably within 20 light-years of the solar system.
Use earth as average lack of all other evidence (Score:5, Interesting)
One thing about these projections is based on the idea that Earth is the Average outcome of these conditions.
I could see Alain Life Forms, Most places will just have life like Bacteria and Algae (but not Bacteria and Algae because they would have a different evolutionary cycle). And some may have what we consider advanced animals. But being as far as we know, Earth over 5 billion years had only one Animal that created a Civilization. While past periods would leave enough time for other animals to evolve into something that we would consider a civilization.
Perhaps we as Human are Unique in the Universe. Or perhaps it is our own arrogance prevents us from seeing other things that are different as Civilized.
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Objection! Assumes facts not in evidence. It has not yet been established that humanity is actually civilized.
Re: Use earth as average lack of all other evidenc (Score:2)
How can we be uncivilised if we defined the term itself?
Do you have some outside jurisdiction to refer to?
Q?
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I think it's reasonably clear from examining all of nature that there are other species on the planet that exhibit some of the same characteristics or behaviors that would be attributed to civilization. It's merely a case of to what degree those characteristics are expressed.
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We have defined a lot of things that we aren't. Have you heard the song about the purple people eater? (Don't worry, it only eats purple people.)
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But what if we defined colors wrong too...
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My nightmares have multiplied... to infinite and beyond.
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Objection! Assumes facts not in evidence. It has not yet been established that humanity is actually civilized.
Your objection is noted and denied. It's not been established that humanity is logical and your argument is based in logic.
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Still lacking data on other parameters (Score:2)
Yes, the analysis sets good limits on one of the parameters in the Drake equation, probability of a star having a rocky planet in the habitable zone. But two other critical parameters-- what are chances it develops life? what are the chances the life develops to become a technological civilization?-- are still completely guesswork.
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...are still completely guesswork
Well, not completely guesswork. Even though we only have a sample-size of 1, we actually do know some relevant details about that sample. For example, if life first appeared very soon after the Earth's crust cooled, that would tell us something very different about the chances that life will develop than if life appeared at some other point in the Earth's history. And if technology evolved gradually, that would tell us something very different than if technology waited for eons, and then suddenly exploded.
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Again, that's only if you make the assumption that the events which unfolded on earth which produced civilized life represent an average case for life or civilizations in the first place.
While we have no reason to speculate that it is not, we also have no reason to suspect that it is.
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I mean FFS with your attitude you probably don't believe you need to wipe your ass
selection bias [Re:Still lacking data...] (Score:2)
That's completely wrong. We do not need to assume that it's an average at all. What we are doing, which is rational and not unfounded, is to assume that the events and their timelines, are part of the range of possibilities of such progress,
Right so far.
and it is more likely than not that the range experienced here is of within several orders of magnitudes,
Unfortunately not.
The problem is selection bias: we wouldn't see ourselves if we weren't there to see ourselves.
we don't have any reason to think that what we see here is representative to within orders of magnitude. If we were the only one in the universe, or if we were one of a heptillion, either way when we look out we see ourselves with probability one.
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Re: selection bias [Re:Still lacking data...] (Score:2)
> we don't have any reason to think that what we see here is representative to within orders of magnitude.
Yes we do.
No, we do not. There is a 100% chance of our seeing that we are in the location we are, regardless of the actual probability of our being where we are. This is selection bias.
Your point being seemingly that we would cannot make any kind of judgment on the relative probabilities of our local system being unique (based on non-universality of physics?)
If we could derive the origin of life from the laws of physics, that would be an argument. But we can't. We do not, at the moment, know the chemical pathway by which self-reproducing chemistry originated. There are many hypotheses, but none supported by evidence. (Keep in mind that we are trying to understand an event t
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It is quite simple. You look for the evolutionary reason why intellectual evolution overtook physical evolution. Over the period of time we evolved from a far more primitive species to the current transitional state species, the change was cyclic ice ages causing major changes in habitable zones for the various species inhabiting each zone. This tens of thousand of years cycle, over twenty thousand years for ice ages and over ten thousand years for the current warm period.
This quite clearly would favour in
Re:Still lacking data on other parameters (Score:5, Interesting)
Geoffrey.landis vouchsafed:
Yes, the analysis sets good limits on one of the parameters in the Drake equation, probability of a star having a rocky planet in the habitable zone. But two other critical parameters-- what are chances it develops life? what are the chances the life develops to become a technological civilization?-- are still completely guesswork.
It appears more and more certain that life is an emergent property of our Universe. Where it can arise, it will do so. So I don't think it's entirely unreasonable to posit that the percentage of rocky planets in habitable zones that develop life at some point in their evolution is pretty close to 100%.
As for ones that then go on to evolve intelligent life that's capable of developing a space-faring civilization, I also suspect that that unknown value is very, very small. After all, there's been life on this planet of one form or another for at least 3.7 billion years now, and humans didn't evolve until just the past million years or so. Had there been no K-T bollide, there's a good chance that dinosaurs would still be the dominant lifeforms hereabouts - and it's worth noting that they had the joint to themselves for the best part of 180 million years, without ever inventing so much as a Roman candle in all that time.
Basically, I think we're probably an accident. There might be others like us in our galaxy, but, unless we figure out FTL, there's a depressingly-high probability that they'll be extinct long before we make contact with them.
Or, y'know, vice-versa ...
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>It appears more and more certain that life is an emergent property of our Universe
I hope you're right... but on what basis?
We only have one example, and all searching has come up with nothing. Lots and lots of rocky plants with liquid water aren't life.
If in the Drake Equation, the odds of life sparking is zero (or so close to zero that Earth is unique in the universe) - the other variables don't help.
Re:Still lacking data on other parameters (Score:4, Insightful)
I suspect the GP is correct simply because I don't believe in magic. There's nothing about Earth or the Solar system that should make them *that* unique in the universe. There hasn't been any actual "searching" yet, but we ought to have some answers within a couple of decades. Once we can analyze exoplanet atmospheres, we'll be able to detect some signatures of life. And eventually someone will go turn over a few rocks on Mars, in some area that was hospitable in the distant past.
Even though life may be ubiquitous, I do expect "civilization" to be vanishingly rare because we have one example of that among billions of species that have existed on this planet. In that sense we're likely alone.
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In response to my assertion:
It appears more and more certain that life is an emergent property of our Universe
MrLogic17 inquired:
I hope you're right... but on what basis?
In large part, based on the presence of a number of organic molecules in interstellar gas clouds [wikipedia.org]. Plus the abundance of carbonaceous chondrites both in the asteroid belt and elsewhere in our local star system (which also show promise of complex, organic molecules in their makeup - molecules that passage through our atmosphere cook to the point that the chemistry of carbonaceous meteorites may be different after they crash into our planet than it was before they
Re:Still lacking data on other parameters (Score:4)
In the history of the biological world, mostly it has been single-celled organisms in the mud. Some of this is likely just survivorship bias. We only get to see the few things that die in a way that leaves behind traces, like oil and coal and giant skeletons of ancient monsters stomping through flower-less and grass-less forests of ferns.
The two things this history tells us is that:
The local equivalent of hairless monkeys with ray guns are not expected.
But we may see some interesting takes on seafood. If the Universe is full of edible sushi that's just a bonus.
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I agree with you. Single celled life is easy, and probably plentiful.
Complex life, let alone intelligent life is highly unlikely.
Read the details in my comment [slashdot.org]
Not zero [Re:Still lacking data...] (Score:2)
Geoffrey.landis vouchsafed:
Yes, the analysis sets good limits on one of the parameters in the Drake equation, probability of a star having a rocky planet in the habitable zone. But two other critical parameters-- what are chances it develops life? what are the chances the life develops to become a technological civilization?-- are still completely guesswork.
It appears more and more certain that life is an emergent property of our Universe
Since life emerged, in the trivial sense of the word "emergent" this is obvious.
Where it can arise, it will do so.
Unfortunately, we don't know this. Data is lacking. We know that life emerged once. So we can say "Where it can arise, it has done so on at least one occasion."
So I don't think it's entirely unreasonable to posit that the percentage of rocky planets in habitable zones that develop life at some point in their evolution is pretty close to 100%.
Of course you can posit that. We just don't have any statistics to back it up. The problem is that the observation has a selection bias: we see that life emerged here because if life hadn't we wouldn't see it.
The observation we have is consistent with 100%, with 1%, or
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what are chances it develops life? what are the chances the life develops to become a technological civilization?-- are still completely guesswork.
We've narrowed it down to more than zero at least.
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Most places will just have life like Bacteria and Algae
Not the same. It is guessed that bacteria-like life is common, as it appeared earth in Earth's history. However, we have no evidence that life began more than once on Earth - so it could still be vanishingly rare.
Algae is totally different. Algae is complex life, Eukaryotes, which may have taken a billion years or so to evolve, after the first bacteria.
We may find the galaxy to be swarming with worlds covered in bacteria-like organisms, but never find anything as complex as algae.
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That is also my take on it: single celled life is easy and emerges pretty quickly (~ 0.5 Billion years after bombardment ended). So for over 3 Billion years there were only lots of single celled life.
However, multicellular life is totally different story. For that to emerge requires two rare events that each happened exactly once in earth's history: the engulfment of one cell by another, and continuing to live within the host cell, with its own much reduced genome: the mitochondria, and the chloroplast.
Each
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What makes you think other living things have not created civilizations?
Just cos we use tools, that doesn't mean other animals can't use tools.
Just cos we can communicate, that doesn't mean other animals don't.
If you are talking about buildings, ant hives are pretty large and are build artifically by the ants. Same for bees. Depending on the hive, some of the ant hives are probably equal to maybe a 100 story building (in terms of the average ant's height). Just cos we don't see them use tools, does not mean
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Once an alien civilization reaches a Kardashev-2 level, it will unavoidably emit an IR signature that will be visible for millions of light-years. We have scanned 100,000 galaxies [scientificamerican.com], containing total of more than a quadrillion stars. Even if only one in a million planets evolves to the K2 level, there should be billions of them in range. Yet we have found ... nothing.
Perhaps none of them build K2 structures. Perhaps the laws of physics are different than what we believe.
But Occam's razor says that the mos
Re:Place AND Time (Score:4, Interesting)
That's assuming that the Kardashev scale is valid, and something life will advance through. Perhaps there is another route? For example, life will inevitably discover that we live in a simulation, begin to converse with the simulation-builders, and ask to be let out of the sim.
Or, life discovers how to translate consciousness into pure mathematics, requiring no substrate or even a universe to live in.
Or, life discovers how to encode itself into the warped space-time surrounding black holes.
Which is all just another way of saying "No one is out there." But "No one is out there" is not incompatible with the view that "Life may transcend the physical universe fairly quickly after gaining civilization" which DigiShaman put forth.
So you two are arguing at right angles to each other. You may both be correct.
Re:Place AND Time (Score:5, Insightful)
Or that search is poorly informed to begin with. We assume a civilization 2,000 years more advanced than us will be constricted to the same energy demands and energy sources as we will. But 100 years ago nuclear power was a complete unknown. 200 years ago, we didn't know about electrical power. And ~300 years ago we didn't even have steam engines. So the idea that we have any idea of what the energy consumption profile of a civilization 1000 years more advanced than us will look like is simply absurd.
Actually it's a bit worse than that. Dyson spheres are, according to our current understanding of physic and engineering, impossible to build (the tensile strengths required are beyond any existing physical material). So looking for Dyson spheres is a search motivated by our current understanding of physics and engineering, for something which cannot exist according to our current understanding of physics and engineering. So either our current understanding is wrong, in which case we have no reason to think Dyson spheres exist, or it's right, in which case we know they don't exist.
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Dyson spheres are, according to our current understanding of physic and engineering, impossible to build
When people talk about "Dyson Spheres" they are rarely referring to a single rigid shell. Of course, that is impossible.
A Dyson Sphere usually means a system of orbiting satellites encompassing a star. Even Freeman Dyson used it that way in his original paper.
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Once an alien civilization reaches a Kardashev-2 level, it will unavoidably emit an IR signature that will be visible for millions of light-years.
That is nonsense. The IR radiation wont be bigger/more intense than the sun it is drawn from.
Seriously: second law of physics, conservation of energy. Some mundanes call it the first law even.
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That is nonsense. The IR radiation wont be bigger/more intense than the sun it is drawn from.
Indeed it will not. But the wavelength of the light will be different, and more importantly, it will be at a combination of wavelength and intensity that does not exist in nature.
The problem is not that we can't differentiate between bright IR sources that are K2s or natural, but that we aren't seeing them AT ALL.
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You are aware that K1, K2 etc are SF designations?
Why would anyone build a K2 - K4 structure?
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You are aware that K1, K2 etc are SF designations?
The terms were originally used in SF. The terms are now used by astronomers and exo-biologists.
Why would anyone build a K2 - K4 structure?
Lebensraum.
A Dyson Sphere constructed at 1 AU would have an area more than a trillion times the surface of the earth.
That would mean 140 earths for every human.
Cool.
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But you are aware that the planet is approaching an equilibrium of population?
We certainly do not need Lebensraum.
And I would be genuine surprised if there is even single Dyson Sphere in this universe. No one - except a SF author - would ever build one.
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We certainly do not need Lebensraum.
Speak for yourself. I want my own planet.
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I can look in my basement, perhaps I find a small one for you :P
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But Occam's razor says that the most likely reason we don't see anyone is that no one is there.
No, it does not.
Occams's razor days: the simplest solution to a problem is most likely the true one.
And in this case it is: we can not detect them. Opps.
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The universe is old enough that entire civilizations could of come up to our point and already dropped back down. We've been here a scant time of even our planet's history. A fraction of the time of the dinosaurs even.
The universe may be teaming with life but the time span is so incredible that we may never find anyone ever.
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As far as I know, Dinosaurs never were a "civilization".
If they had one, it is most peculiar that there is no evidence of one.
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A lot can change over 65 MILLION years. If an asteroid from space the size of that which hit the dinosaurs happened today, do you think in 65 MILLION years you would find much evidence of our current civilization?
Seems unlikely to me. We don't even know everything about Mesopotamia, our first "ancient" civilization. That was only a scant 6 thousand years ago. We are talking 65 million years here.
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Considering the Sun and the earth is roughly 5 billion years old, your idea makes no sense.
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The universe is 13+ billion years old.
Also, the conditions necessary to form civilized life are not as old as the earth.
An analogous question ... (Score:5, Insightful)
What are the odds that you would have met Abraham Lincoln?
The universe is 13.8 billion years old.
Modern humans have been around 50,000 years.
Civilization is about 5,000 years old.
Abraham Lincoln:
Born February 12, 1809
Died April 15, 1865
Sorry.
Those reading this missed it by THAT much.
--
For us to find "life as we know it," we are going to need a lot of coincidence.
None (Score:1)
Next question.
If only we could travel to them quickly (Score:2)
Window of opportunity (Score:2)
Others have skirted the question, but one I'd like to see a scientific answer to is the odds of an alien civilization concurrently existing with us. You have to guess at how long it takes to develop a civilization, and at how long a civilization might last, but I'm sure someone in the field can make a better stab at such guesses than I can...
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Again, sample size of 1. Currently cooking our own planet out from under us.
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Rather more accurate to say that we're cooking ourselves with the planet.
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Others have skirted the question, but one I'd like to see a scientific answer to is the odds of an alien civilization concurrently existing with us.
Even concurrency won't help if the distances are too vast. Groups like SETI and the Drake Equation are considering only planets within the galaxy, but even that puts the span at about 100,000 light years. Consider where humanity was --- or even if it could be considered humanity --- 100,000 years ago. Settling of the Fertile Crescent was about 5000 years ago, it's 20 times farther back. Then consider where we could possibly be in a hundred centuries. The Milky Way is far too vast. Even the Orion Arm is too
Re: Window of opportunity (Score:2)
And if you look at our own use of radio, the ability of alien detection is decreasing over time. Early radio transmissions were both powerful and blatantly artificial. But they were also extremely inefficient in information density. Now we're using more sophisticated encoding schemes in order to approach the Shannon limit and as a result, our radio transmissions are approaching random noise in appearance. Add in the general reduction in power if the radio transmitters, and we'll be effectively non-detectabl
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Now we're using more sophisticated encoding schemes in order to approach the Shannon limit and as a result, our radio transmissions are approaching random noise in appearance. Add in the general reduction in power if the radio transmitters, and we'll be effectively non-detectable from a radio point of view.
That doesn't apply to all radio signals. Some military radars are very powerful, and very directional. The phased array radar at Eglin AFB Site C-6 [wikipedia.org] can put out 32 MW in a beam only 1.4 degrees wide. If hunting for asteroids with active radar becomes a big thing (as it might in the future), we could get more detectable, not less.
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We have detected planets or likely planets on about 10% of them.
Because the the others have their planet in orbits we can not detect. That is all.
There is no plausible reason that not nearly _every_ solar system has planets.
People ignore the assumptions (Score:3)
1) There are so many Galaxies (estimates range from 100-200 billion) that even if there is only life on one planet in the Milky way ( 100-400 billion stars, averaging about 8 planets per star) then there should likely be life in the universe, if not the galaxy.
2) Difference between life and intelligent life, and defining intelligence. Chimps, orangutans, gorillas, dolphins, crows, macques, octopi, sea otters, elephants, and some rodents (degus) all use tools, so Earth has at least 10 species on earths that use tools. So chances are pretty good that a quasi-intelligent species will exist on each planet.
3) Communicative intelligence - i.e. something we could talk to and get full sentences rather than simplistic ideas, are rarer. A few apes and birds have convinced people that they can communicate in sentences. Say 1.? species on Earth count.
4) Advanced life that can get off their planet is what we really want, but I would say that is 0.99 species on Earth count as we no longer have the capability to get to the moon, but that will likely change back to 1.0 before my nieces die, as we are working on it again.
5) Within reasonable distance where an adult could send a message and get an answer before his new born child becomes an adult. That is unlikely to happen, as we have been blasting radio waves out into space for more than 80 years and got no response.
One more thing, the most important technology for space travel to become possible is MEDICAL technology. Light speed is a harsh rule, but there is no such harsh rule for life extension. We can probably build something to move humans at 0.1 C, (solar sail and/or antimatter engines could do this0 allowing us to take 40 years to get to the nearest star and another 40 to get back.
So we need a solid 110+ year life expectancy to visit another world and return or better yet colonize. THAT is totally possible. Some humans already live that long, but we need to make it the norm and with a guaranteed healthy, active quality of life to actually colonize other worlds. Not to mention a better, transportable fully recyclable biosphere to get there without running out of water, air, and food.
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I see no reason for assumption 5.
You could build a generational ship, why would it be a requirement that it must be achieved in a single human life time?
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Generational ships are far harder to build and organize than a single person ship. We might use them to colonize planets more than 20 light years away, but they are an unnecessary expense for anything less than 20. So our first colonization attempts will likely not be them.
Things you need for a generational ship, that you do not need for normal ships.
1) Far better life support that will last for 200+ years, rather than 80
2) Soylent Green issues - you can't throw away the high quality organics in a human
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Medical technology is critical for humans to explore the stars. Its not clear an alien species would have a similar lifespan, or care whether it, or its descendants survived the trip. One can also imagine various synthetic lifeforms created specifically to allow space travel (eg robots) which might have no practical life limit.
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I wouldn't be so sure about the second item on your list. On Earth life developed almost as soon as it possibly could early in Earth's history. However, for about the first 3.5 billion years, Earth was limited to simple, single-celled organisms, with complex lifeforms a relatively recent development. That life developed so quickly on Earth bodes well for life developing on other planets too, but for multicellular life to take so long to development kind of suggests that might be a hard step on the evolut
How many? It's easy! (Score:2)
https://en.wikipedia.org/wiki/... [wikipedia.org]
I've done half the work, now count them yourself!
How long are the stages? (Score:2)
It is entirely possible that the "stages" of advancement, once a certain level of intelligence is reached, are fairly short. Perhaps being a massive radio beacon only lasts a few hundred years?
Given the short window of time that detectable EM may be emitted you might miss millions of civilizations simply because you were not listening when they were transmitting.
The idea that a species 2000 years more advanced than us would use radio waves as the basis for communications seems absurd considering a tighter f
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And the power levels are being reduced across the board by the "powers that be".
The power levels were never very high to begin with, not on an interstellar scale. We can barely make out planets in other solar systems; are we really capable of picking up radio transmissions at planetary or interplanetary power levels from other worlds, even tightbeam transmissions that happen to point directly at us?
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The power levels were never very high to begin with, not on an interstellar scale. We can barely make out planets in other solar systems; are we really capable of picking up radio transmissions at planetary or interplanetary power levels from other worlds, even tightbeam transmissions that happen to point directly at us?
Voyager 2 transmits at 22 watts and it's 17 light-hours out now and we can still hear it. Just recently we can talk to it again and get the expected programmed responses to commands still, not just a beacon. Now, that's knowing what we're looking for of course, but it does give us practice at picking real signals out of an ocean of galactic radio noise. The hardware and software required to do both actually exist and are being used. They're not just theoretical.
So... within certain power levels, yes, we
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So... within certain power levels, yes, we should be able to detect and differentiate modulated signaling at interstellar distances
That's... kind of comforting to know.
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Planetary radio transmissions from Earth run into the tens of megawatts combined. Even after the inverse square law takes its toll, we can be heard from quite a long way out now.
As I mentioned elsethread, the military phased array radar at Eglin AFB Site C-6 can transmit 32 MW in a beam 1.4 degress wide. I don't know how obviously artifical it is.
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300 Million Is Probably An Underextimate (Score:3)
"A new analysis concludes that roughly half of the galaxy's sunlike stars host rocky worlds in habitable zones where liquid water could pool or flow over the planets' surfaces"
Given that we've discovered 3,000+ planets by the Kepler's occultation technique, and the requirement that to be discovered that way, the planet's ecliptic plane must EXACTLY intersect the Earth, the only reasonable conclusion is that planets are LITERALLY as common as dirt out there, and that the "roughly half" estimate is probably a bit low.
We can't guess yet how many are rocky (although we already know that SOME are) or are in the "habitable zone". But our solar system has nine planets, and some other systems have "several", so with probably a TRILLION planets in the Milky Way, , I'd guess that there are more than a paltry 300 million potentially habitable worlds are out there.
Civilizations? We can't even guess. There are at least 4 "intelligent" species on Earth, but humans are the only "generalist" species that makes tools. (Dolphins, octopus, and elephants don't have hands and can't "manipulate" their environment.)
Time is V A S T (Score:3)
You think intersteller distances are vast -- time is moreso. For how long do you think humans will remain a recognizable civilization? We've been broadcating radio for ~100 years, maybe a thousand more? That is 0.00006% of the 20 billion years the universe has existed.
To have life was we know it, planets also have to be the right composition, Carbon, oxygen, iron and traces. Likely only from 3rd gen stars.
We will probably never know (Score:2)
It is unlikely that any civilization will broadcast radio waves strong enough for us to detect against the background of all the other electromagnetic radiation in the universe.
Not surprising. (Score:1)
42 (Score:1)
is the answer.
36 (Score:2)
nft
Why ask? it doesn't matter.. (Score:2)
I suppose it's an interesting question to ask, but if you look at the situation, there is no importance to the question.
Physics says, assuming Einstein's famous theory is correct, you cannot go faster than light. IF this is true (and it likely is) we are never going to visit or be visited by an alien civilization. The travel time is just too long so there is no way anyone can practically make the trip.
So zero chance there is any meaning or impact to the actual answer to the question being asked. It doe
Re: (Score:2)
I don't know that I'd say never to the question of will humans ever encounter alien life. We're just now beginning to gear up to explore our own little neighborhood in the solar system, but that technology will improve and grow. The chances that at some point in the future we as a species develop generation ships and begin to spread through the galaxy are above zero. And while it's not going to happen in my lifetime for sure, nor likely yours, if we really do establish a permanent colony on the moon and
Galactic Survey (Score:2)
It may take a while to get back responses from the Delta Quadrant
I'm sorry... (Score:2)
How Many Alien Civilizations Are Out There? A New Galactic Survey Holds a Clue.
It most certainly does not. There is now way in hell, at our current technological level, we could even begin to even guess at the number of alien civilizations in the universe.
Simply don't know (Score:2)
We know a lot about what planets are out there.
We have a very weak guess as to how often life evolved - based on it appearing on earth pretty soon after conditions ware habitable.
We have no idea how often complex life evolves. No idea how often intelligence evolves. No idea how often civilization develops or how long it lasts.
So at least 3 completely unknowns multiplied. We continue to collect information and some of those unknowns may get narrowed down, but at the moment there is no basis for making an e
Terrible news (Score:2)
Re: (Score:2)
Agreed. If one out of 10 planets COULD support life, and we find 10% of those actually DO support life, but there's no obvious sign of intelligent life anywhere that looks like the sort of civilization/technology we can extrapolate from the human technology curve, that pretty much says there's a great filter not too far in our future. Either that, or advanced civilizations are hiding for good reason.
Angels and pins (Score:1)
May as well ask how many angels.
For the time being, no one knows what the probability is that life will form under any particular set of conditions. So, estimates of earth-like planets are nice, but mean nothing.
On the other hand, the numbers of anything in the known universe, much less the parts we can't see, are, well, astronomical. With such numbers, pretty much any low but not absurdly low probability event has or will occur. How often is the part that we can't estimate.
By the evidence, the civilization count is... (Score:1)
We may not have gathered all the evidence, though.