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Old Jan 8th 2013, 06:46 AM
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Default 17 billion neighbours

The aspect of astronomy that occupies itself with the search for exoplanets, i.e. planets that orbit stars other than our own Sun, is arguably the most fruitful endeavour in science at the moment, second perhaps only to the LHC. The rate at which such planets are found is very high and accelerating. In this thread from not four years ago the tally was 346. Today the tally is 854 - there's a catalog of them here - and there are at least 18,000 more candidates.

There's not only a rapid increase in numbers but also an ever increasing refinement in technology and techniques that allows to discover ever smaller planets. The smallest ones confirmed have less than twice the mass of Earth. Any day now an "Earth-copy", at least in size and position vs. its star will be found.

All this new information has given the possibility of making an educated guess at the number of such Earth-like planets there are in the galaxy where we hang out. The Keppler team announced such an estimate at the meeting of the American Astronomical Society. The number is no less than 17 billion. This is an order-of-magnitude estimate of course. It may be 1.7 billion, it may be 50 billion in reality. But the essence is that such planets are abundant.

The magnitude of this number recalls the age old question: "Where is everybody?", a question formalized as the Fermi paradox. When one puts a number as high as 17 billion in probabilistic equations one would expect to find a veritable circus of activity in the galaxy. But we've only observed complete silence. So something's amiss here. But what?

There's an extensive list of the possibilities in the aforementioned article on the Fermi paradox. I'll consider a few here.
  • Earth (life) is unique
It's not impossible but every anthropocentric or religiously motivated such argument has so far been proven wrong. Earth is not the center of the universe, the Sun is not the center of the universe, humans are just another animal, and so on.
The result that planets are ubiquitous confirms that the formation of planets is well understood and that it is a process that is similar in the entire galaxy and probably in the entire universe. Billions of planets have the same conditions for life as Earth had. There should be life on many of them.
  • Technological civilizations are unique/extremely rare
This possibility has more merit. The leap from single cell life to multicellular life is in my opinion much bigger than that from non-life to single cell life. The latter is just chemistry with components that are available in abundance. The former is an organizational, abstract event. It occurring may be quite rare. Other than that, even Earth has so far only developed a single species with at least the potential to engage in interstellar communication. Dinosaurs e.g. were around for over 200 million years and the smartest of the enormous number of species that produced was about as thick as a chicken.
  • Technological civilizations are very short lived
Given what the one sentient species on Earth has done to its habitat in a few thousand years, and assuming that humans are not especially psychotic, this has to be considered as a real possibility.
  • The place is just too big
While galaxies are the cities of the universe, where hundreds of billions of stars are amassed, the distances between the houses of that city, i.e. the stars that make up the galaxy and their planets, are still astronomical (no pun intended). A light year is an almost inconceivable distance and even with 17 billion 'Earths' the closest one of those might still be 10 or more light years away. How to get there is an extremely fundamental problem that cannot be solved by extrapolating current technology. And science fiction solutions are just that, science fiction. Wormholes e.g. could be conceivably used to transmit information through but anything that has mass and relies on spatial integrity would be torn apart by extreme tidal gravity.

As mentioned before, there are other possibilities, from age old religious ones to typical Internet conspiracy theories. See the linked Wiki-article for those.

So what do you all think? Where is everybody ?
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Old Jan 8th 2013, 01:50 PM
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Default Re: 17 billion neighbours

Quote:
Originally Posted by Dominick View Post
The aspect of astronomy that occupies itself with the search for exoplanets, i.e. planets that orbit stars other than our own Sun, is arguably the most fruitful endeavour in science at the moment, second perhaps only to the LHC. The rate at which such planets are found is very high and accelerating. In this thread from not four years ago the tally was 346. Today the tally is 854 - there's a catalog of them here - and there are at least 18,000 more candidates.

There's not only a rapid increase in numbers but also an ever increasing refinement in technology and techniques that allows to discover ever smaller planets. The smallest ones confirmed have less than twice the mass of Earth. Any day now an "Earth-copy", at least in size and position vs. its star will be found.

All this new information has given the possibility of making an educated guess at the number of such Earth-like planets there are in the galaxy where we hang out. The Keppler team announced such an estimate at the meeting of the American Astronomical Society. The number is no less than 17 billion. This is an order-of-magnitude estimate of course. It may be 1.7 billion, it may be 50 billion in reality. But the essence is that such planets are abundant.

The magnitude of this number recalls the age old question: "Where is everybody?", a question formalized as the Fermi paradox. When one puts a number as high as 17 billion in probabilistic equations one would expect to find a veritable circus of activity in the galaxy. But we've only observed complete silence. So something's amiss here. But what?

There's an extensive list of the possibilities in the aforementioned article on the Fermi paradox. I'll consider a few here.
  • Earth (life) is unique
It's not impossible but every anthropocentric or religiously motivated such argument has so far been proven wrong. Earth is not the center of the universe, the Sun is not the center of the universe, humans are just another animal, and so on.
The result that planets are ubiquitous confirms that the formation of planets is well understood and that it is a process that is similar in the entire galaxy and probably in the entire universe. Billions of planets have the same conditions for life as Earth had. There should be life on many of them.
  • Technological civilizations are unique/extremely rare
This possibility has more merit. The leap from single cell life to multicellular life is in my opinion much bigger than that from non-life to single cell life. The latter is just chemistry with components that are available in abundance. The former is an organizational, abstract event. It occurring may be quite rare. Other than that, even Earth has so far only developed a single species with at least the potential to engage in interstellar communication. Dinosaurs e.g. were around for over 200 million years and the smartest of the enormous number of species that produced was about as thick as a chicken.
  • Technological civilizations are very short lived
Given what the one sentient species on Earth has done to its habitat in a few thousand years, and assuming that humans are not especially psychotic, this has to be considered as a real possibility.
  • The place is just too big
While galaxies are the cities of the universe, where hundreds of billions of stars are amassed, the distances between the houses of that city, i.e. the stars that make up the galaxy and their planets, are still astronomical (no pun intended). A light year is an almost inconceivable distance and even with 17 billion 'Earths' the closest one of those might still be 10 or more light years away. How to get there is an extremely fundamental problem that cannot be solved by extrapolating current technology. And science fiction solutions are just that, science fiction. Wormholes e.g. could be conceivably used to transmit information through but anything that has mass and relies on spatial integrity would be torn apart by extreme tidal gravity.

As mentioned before, there are other possibilities, from age old religious ones to typical Internet conspiracy theories. See the linked Wiki-article for those.

So what do you all think? Where is everybody ?
I'm not a scientist, so correct me if I am wrong on this one.

The distance/scale issue seems to be the big problem. Even if we take your conservative estimate of 1.7 billion planets that is a lot. It seems to me that we are pointing a radio telescope at a point we have made an educated guess about and hoping that signal reaches said point in time to be received by an intelligent civilization that may or may not exist. there are a lot of guesses in there and the universe is a very big place. To boil this down, it seems that we have to find the right planet, at the right time, send a signal using the right method/technology, hope that signal reaches the planet at the right time, and then hope said alien civilization returns a signal to us using the right technology at the right time.

I'm not saying all that isn't possible, but, as the wiki article pointed out we, we haven't been trying for all that long. It will probably take a while for all those conditions to line up properly.
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Old Jan 8th 2013, 02:16 PM
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Default Re: 17 billion neighbours

It could also be that intelligent life is quite unique as you point out dominik. I think that this is a possibility that we might have to accept.
a refutation of this would be if we were able to cook an intelligent being. So far, we are trying but with no success either.
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Old Jan 8th 2013, 06:47 PM
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Default Re: 17 billion neighbours

I posted this comic a couple of weeks ago. It seems highly relevant to this topic.
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File Type: jpg CalvinHobbes.jpg (201.7 KB, 7 views)
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Old Jan 8th 2013, 06:50 PM
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Default Re: 17 billion neighbours

For God's sake, they may well be intelligent even if they haven't managed to send messages to us, or visit us.
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Old Jan 8th 2013, 07:16 PM
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Default Re: 17 billion neighbours

Quote:
Originally Posted by Dominick View Post
The aspect of astronomy that occupies itself with the search for exoplanets, i.e. planets that orbit stars other than our own Sun, is arguably the most fruitful endeavour in science at the moment, second perhaps only to the LHC. The rate at which such planets are found is very high and accelerating. In this thread from not four years ago the tally was 346. Today the tally is 854 - there's a catalog of them here - and there are at least 18,000 more candidates.

There's not only a rapid increase in numbers but also an ever increasing refinement in technology and techniques that allows to discover ever smaller planets. The smallest ones confirmed have less than twice the mass of Earth. Any day now an "Earth-copy", at least in size and position vs. its star will be found.

All this new information has given the possibility of making an educated guess at the number of such Earth-like planets there are in the galaxy where we hang out. The Keppler team announced such an estimate at the meeting of the American Astronomical Society. The number is no less than 17 billion. This is an order-of-magnitude estimate of course. It may be 1.7 billion, it may be 50 billion in reality. But the essence is that such planets are abundant.

The magnitude of this number recalls the age old question: "Where is everybody?", a question formalized as the Fermi paradox. When one puts a number as high as 17 billion in probabilistic equations one would expect to find a veritable circus of activity in the galaxy. But we've only observed complete silence. So something's amiss here. But what?

There's an extensive list of the possibilities in the aforementioned article on the Fermi paradox. I'll consider a few here.
  • Earth (life) is unique
It's not impossible but every anthropocentric or religiously motivated such argument has so far been proven wrong. Earth is not the center of the universe, the Sun is not the center of the universe, humans are just another animal, and so on.
The result that planets are ubiquitous confirms that the formation of planets is well understood and that it is a process that is similar in the entire galaxy and probably in the entire universe. Billions of planets have the same conditions for life as Earth had. There should be life on many of them.
  • Technological civilizations are unique/extremely rare
This possibility has more merit. The leap from single cell life to multicellular life is in my opinion much bigger than that from non-life to single cell life. The latter is just chemistry with components that are available in abundance. The former is an organizational, abstract event. It occurring may be quite rare. Other than that, even Earth has so far only developed a single species with at least the potential to engage in interstellar communication. Dinosaurs e.g. were around for over 200 million years and the smartest of the enormous number of species that produced was about as thick as a chicken.
  • Technological civilizations are very short lived
Given what the one sentient species on Earth has done to its habitat in a few thousand years, and assuming that humans are not especially psychotic, this has to be considered as a real possibility.
  • The place is just too big
While galaxies are the cities of the universe, where hundreds of billions of stars are amassed, the distances between the houses of that city, i.e. the stars that make up the galaxy and their planets, are still astronomical (no pun intended). A light year is an almost inconceivable distance and even with 17 billion 'Earths' the closest one of those might still be 10 or more light years away. How to get there is an extremely fundamental problem that cannot be solved by extrapolating current technology. And science fiction solutions are just that, science fiction. Wormholes e.g. could be conceivably used to transmit information through but anything that has mass and relies on spatial integrity would be torn apart by extreme tidal gravity.

As mentioned before, there are other possibilities, from age old religious ones to typical Internet conspiracy theories. See the linked Wiki-article for those.

So what do you all think? Where is everybody ?
If hypothetically, there were another earth with a species at the same technological level as humans doing what humans do, and assuming it had existed at the right time based on its distance (e.g. 10 years ago if it's 10 light years away, 100 years ago if its 100 light years away...etc), how far away would they have to be before we wouldn't "hear" them anymore? And how many of these supposed 17 billion planets are in that radius?

I mean, if we were 30 light years away from ourselves, would we be picking up on radio waves from the 1980s? Or at least able to tell that "hey! That's not just random background noise!"

The fact that we haven't "met" any aliens doesn't really strike me as remarkable. Maybe FTL travel is simply not possible, no matter how advanced one's technology. It seems more curious that we haven't "heard" anyone else, or even the echoes of anyone else. Or at least it seems curious to me; but then, I obviously don't know much about it.
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Old Jan 8th 2013, 08:31 PM
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Default Re: 17 billion neighbours

Quote:
Originally Posted by Non Sequitur View Post
I'm not a scientist, so correct me if I am wrong on this one.

The distance/scale issue seems to be the big problem. Even if we take your conservative estimate of 1.7 billion planets that is a lot. It seems to me that we are pointing a radio telescope at a point we have made an educated guess about and hoping that signal reaches said point in time to be received by an intelligent civilization that may or may not exist. there are a lot of guesses in there and the universe is a very big place. To boil this down, it seems that we have to find the right planet, at the right time, send a signal using the right method/technology, hope that signal reaches the planet at the right time, and then hope said alien civilization returns a signal to us using the right technology at the right time.

I'm not saying all that isn't possible, but, as the wiki article pointed out we, we haven't been trying for all that long. It will probably take a while for all those conditions to line up properly.
We're sending all over the place, not just to specific locations. Our radio waves are dispersed in any direction, save possibly for the poles. As for listening, SETI is dependent on the direction the static Arecibo Observatory is pointed to. With the wobbles of the planet taken into account that gives this range of research:



The pink band is the region of origin of SETI signals. Dynamic radio telescopes can of course point to any place.

We've been sending and receiving roughly speaking for 60-70 years. That results in an Earth-centred sphere with a radius of 60-70 light years which could be called our radiosphere. In that region of the galaxy there are traces of our communication and it's also roughly the sphere we've listened to. Now, the figure of 1.7 billion 'Earthies' translates to about one per 60 stars. As you can see in this list, there are more than 500 stars within 50 light years from Earth. Statistically there should thus be at least 8 or more 'Earthies' in our radiosphere. That's eight potential civilizations that could have heard from us or vice versa.

There's also the possibility that we could have picked up signals from (much) farther away if those signals left at their system at the right time. For instance, if a civilization was sending radio signals 525 years ago from a system 500 light years away, those signals could have been picked up 25 years ago. (That's not quite correct actually, I should explain it relativistically but I'll spare you (and me !) that).

It's true that we haven't been listening and paying attention all that long but with these new numbers for potentially habitable planets for life-as-we-know-it it does begin to seem eerily quiet in our neck of the woods of the galaxy.
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Old Jan 8th 2013, 08:34 PM
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Default Re: 17 billion neighbours

Quote:
Originally Posted by shekib82 View Post
It could also be that intelligent life is quite unique as you point out dominik. I think that this is a possibility that we might have to accept.
The longer it takes, the more that option comes to the forefront indeed. 'T would be a shame in my opinion.

Quote:
Originally Posted by shekib82 View Post
a refutation of this would be if we were able to cook an intelligent being. So far, we are trying but with no success either.
I don't think that would refute the above. It's still only one place where it originated.
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Old Jan 8th 2013, 08:36 PM
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Default Re: 17 billion neighbours

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Originally Posted by Michael View Post
I posted this comic a couple of weeks ago. It seems highly relevant to this topic.
Wouldn't that be the final blow to human hubris ? "Sorry, guys, but you guys are under quarantine since you're the second nuttiest place in the galaxy." (2nd nuttiest because if we were the nuttiest of all, we'd feel special again).
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Old Jan 8th 2013, 08:45 PM
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Default Re: 17 billion neighbours

Quote:
Originally Posted by dilettante View Post
If hypothetically, there were another earth with a species at the same technological level as humans doing what humans do, and assuming it had existed at the right time based on its distance (e.g. 10 years ago if it's 10 light years away, 100 years ago if its 100 light years away...etc), how far away would they have to be before we wouldn't "hear" them anymore? And how many of these supposed 17 billion planets are in that radius?
See previous post.

Quote:
Originally Posted by dilettante View Post
I mean, if we were 30 light years away from ourselves, would we be picking up on radio waves from the 1980s? Or at least able to tell that "hey! That's not just random background noise!"
Definitely. All the signals that we do receive are understood. Sources are things like pulsars, quasars, supernovas and even interstellar dust. The rest is just static (actually a left over from the Big Bang). Any signal with structure would immediately stand out. There have been a few inconclusive candidates for that such as the Wow! signal. But none have ever been confirmed or repeated.

Quote:
Originally Posted by dilettante View Post
The fact that we haven't "met" any aliens doesn't really strike me as remarkable. Maybe FTL travel is simply not possible, no matter how advanced one's technology. It seems more curious that we haven't "heard" anyone else, or even the echoes of anyone else. Or at least it seems curious to me; but then, I obviously don't know much about it.
I too consider interstellar travel an impossibility. And I agree that the radio silence is a more worrying aspect. Worrying if one wants to find other civilizations that is. Some will no doubt call it a relief.
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