Fermi paradox - Alex Semenov's classification

[Spaceception]

Just now, fredinno said:

I do a lot of reading on Habitable planets though.

Saaaaame.

[Aethon]

You're doing just fine Polnoch.  We understand English isn't your first language.  

[Mikki]

"Pike" case might be the thing. And, as in frame of time itself, 2 sufficiently developed civilisations meeting up in a galaxy while beeing able to travel interstellar and communicate with each other (friendly...) looks very questionable... winning the lottery ten times in a row looks more possible.

For a species capable of travelling interstellar it shouldn`t be too difficult discovering the remains of other higher developed civilisations... but even that would be utter luck, a planets surface changes itself alot in 100 million years for example.

Shaking hands or claws or tentacles together... alive...? I guess that no, sadly.

My opinion : E.T.s?- Sure, but the real question is "From when until when?"

[KerBlammo]

I think industrial civilizations are quite rare, and even if they are there we can't detect them.  If there was an Earth like planet orbiting Alpha Centauri we probably wouldn't know it given our available tools.  The Sci-Fi trope of aliens watching "I love Lucy" 50 light years away is not possible given today's technology.  The radio waves are just too weak to be detected across interstellar space.  Sure if we aimed a very powerful transmitter at a point in the sky it might be detected, but we're not doing that, at least not very often.

Life on Earth apparently arose quickly after things settled down enough for the ground to be solid and stuff stopped falling out of the sky in vast quantities. But for billions of years that life was barely more advanced than pond scum.  And once more complex life did arise it did not immediately start constructing TV studios and making and broadcasting sit-coms.  Dinosaurs dominated the planet for tens of millions of years and there is no evidence they were highly intelligent or capable of making the simplest of tools.  

The human species might have been around for the last million or so years but its only in the last few 100 years have we had anything like the technology to announce our presence to any who might be listening (and so far except for a few brief transmissions we have not done so).

So if the Earth is at all typical (and of course thats the still the big unknown) and even if there are billions of Earth like planets supporting life in this galaxy there would still only be a handful of technological civilizations out there and if they are at all like us they aren't talking.

[tater]

Yeah, and beamed transmissions are over short time intervals. Alines beam a signal towards Earth, and let's say there is enough beam-slop that they can cover the entire sky in about a year with a few hours broadcast in each solid-angle they broadcast into. If we are not looking at them during that few hours (plus the travel time of the signal, obviously) we don't see them. Now, you can take some optimistic value, and multiply by a few million possible worlds over the 3-400 billion in the galaxy, and maybe there are signals zipping past earth fairly frequently... then you need to know how often we survey the sky for those signals, and we can see what the chances are that SETI is looking the right direction when a signal happens to zip by.

We're basically re-deriving the Drake equation.

I tend to think that simple life is probably incredibly common, but multicellular life is relatively rare.

[PB666]

7 minutes ago, tater said:

Yeah, and beamed transmissions are over short time intervals. Alines beam a signal towards Earth, and let's say there is enough beam-slop that they can cover the entire sky in about a year with a few hours broadcast in each solid-angle they broadcast into. If we are not looking at them during that few hours (plus the travel time of the signal, obviously) we don't see them. Now, you can take some optimistic value, and multiply by a few million possible worlds over the 3-400 billion in the galaxy, and maybe there are signals zipping past earth fairly frequently... then you need to know how often we survey the sky for those signals, and we can see what the chances are that SETI is looking the right direction when a signal happens to zip by.

We're basically re-deriving the Drake equation.

I tend to think that simple life is probably incredibly common, but multicellular life is relatively rare.

I don't even think simple life is common, it think you have two planets in our systen with a fortuitois star and arrangement of planets that may have tolerated lifes start twice. There are three planets in our habitable zone, two are currently dead. That basically goes to showvthat once life starts there is more than eve chance that it will promptly die. 

I'de like someone to prove me wrong, all ibsee is exoplanet jubilee with each new duscovered followed by, well, no its really just a hot barren planet orbiting and unstable star that probaly does not have an atmosphere and we think it was blown away a few seconds after the star went bright. 

[magnemoe]

2 hours ago, Nibb31 said:

What if FTL simply isn't possible, which rules out interstellar travel by making it so impractical that it is not worth the effort.

Another option is the Dark Forest hypothesis: There is a 50/50 chance that another species is hostile and wants to wipe you out, so it's best to keep quiet.

Or there might be a predator species out there that considers any other species a threat and destroys them preemptively just in case. They might even have some form of time travel, so they can go back and destroy others before they are even capable of making contact.

 

Apes or angels, either they think stars are holes in the sky or they have tech to do interstellar missions a long time. 
First is no danger, second could have wiped you out long ago if they was interested. 

[tater]

34 minutes ago, PB666 said:

I don't even think simple life is common, it think you have two planets in our systen with a fortuitois star and arrangement of planets that may have tolerated lifes start twice. There are three planets in our habitable zone, two are currently dead. That basically goes to showvthat once life starts there is more than eve chance that it will promptly die. 

I'de like someone to prove me wrong, all ibsee is exoplanet jubilee with each new duscovered followed by, well, no its really just a hot barren planet orbiting and unstable star that probaly does not have an atmosphere and we think it was blown away a few seconds after the star went bright. 

"Common" is relative. 9 planets, 3 of which (and as many moons) in the habitable zone and one has life. Forget the habitable zone, even. There are about 100 planets and moons of which maybe 20 are of a decent size in the solar system (barring more largish stuff out in the Kuiper belt). Only 1 has life. If life was a million times more rare than that 1%, we're still talking about 400,000 worlds with life in our galaxy. Of course even that life might be very simple indeed. I tend to think that intelligence is fairly rare, with just the right combination of circumstances available. Heck, we all owe our existence to a single collision between 2 cells at some point a couple billion years ago. Then, on top of that, we had the "reset" button hit a few times along the way... pretty amazing.

The universe, OTOH, is vast. There are more galaxies in the universe than stars in our own, so even with just a few hundred thousand worlds with life in one, that makes thousands of trillions in the universe.

[magnemoe]

47 minutes ago, Mikki said:

"Pike" case might be the thing. And, as in frame of time itself, 2 sufficiently developed civilisations meeting up in a galaxy while beeing able to travel interstellar and communicate with each other (friendly...) looks very questionable... winning the lottery ten times in a row looks more possible.

For a species capable of travelling interstellar it shouldn`t be too difficult discovering the remains of other higher developed civilisations... but even that would be utter luck, a planets surface changes itself alot in 100 million years for example.

Shaking hands or claws or tentacles together... alive...? I guess that no, sadly.

My opinion : E.T.s?- Sure, but the real question is "From when until when?"

Raises another question, why should it go extinct if it was interstellar? It can loose an solar system and survive, 

[PB666]

27 minutes ago, tater said:

"Common" is relative. 9 planets, 3 of which (and as many moons) in the habitable zone and one has life. Forget the habitable zone, even. There are about 100 planets and moons of which maybe 20 are of a decent size in the solar system (barring more largish stuff out in the Kuiper belt). Only 1 has life. If life was a million times more rare than that 1%, we're still talking about 400,000 worlds with life in our galaxy. Of course even that life might be very simple indeed. I tend to think that intelligence is fairly rare, with just the right combination of circumstances available. Heck, we all owe our existence to a single collision between 2 cells at some point a couple billion years ago. Then, on top of that, we had the "reset" button hit a few times along the way... pretty amazing.

The universe, OTOH, is vast. There are more galaxies in the universe than stars in our own, so even with just a few hundred thousand worlds with life in one, that makes thousands of trillions in the universe.

Yes, but its not a matter of what our system is, the average detected system has gas giants inside the habitable zone. Our system is highly unusual, that we know of because it has relatively small rocky planets inside the habitable zone. I can buy 400,000 in our galaxy that have some point in their existence life, most of those worlds orbited stars that died or blew up or snuff out because an adjacent star blew up.

The fact that the universe is very big isn't material, or that our galaxy is very big, is also immaterial. Space travel is not easy, and pretty much half of the habitable galaxy is too far away to view. Even more so, if you go out to Pluto's orbit and point a big telescope at earth how much will you here, alot, alittle, mostly alot of cell phone static.  So lets all scale this down to the next variable, how much life exist in places that we might actually care about, let's say, in the next million years (assuming that going across the galaxy at 0.10 the speed of light would be a fantastically great achievement) We can basically draw a circle 10,000 ly (you cannot travel constantly you have to land, rebuild and then venture out) around our sun and describe that as the we might care zone. Ok the galaxy is 300,000 ly across its 900 times that size, and you reduce that 400,000 down now to 500 systems have life and intelligent life maybe 1, 0.1, 0.01 etc. Then we can look at it from the point of view of intelligent life lucky enough to moved to another star maybe 1/100, 1/1000, 1/10000. Or we can ask the question in a circle of say 7500 ly, how many starts are close enough and produce a big enough signature that we might observe that signature from earth. 

Here's another metric. Life has been on this earth for 3.8 billion years, however in 500 million years or less, all life including intelligent life is likely to be gone. So in the 4.2 billion year timeframe, At most intelligent life only exists for 11% of that time max, and that is only on one of three planets inside of the habitable zone, therefore even in deluxe habitable stars the odds of actually seeing intelligent life is not good. If we are more practical, it not likely that life sentient life will exist on this earth for a fraction of that time, we either become space fairing soon, or its like the sentients will die out, which a resource issue for the next sentient to come along. In fact if we take the current measure for 200,000 of the last 3.8 billion years has life sufficiently progressed that we could carry on a conversation if the materials for conversing were provided for us, and less than 150 years since the famous EM experiment demonstrating that electomagneti pulses can be communicated. So our range for sentient proportion is from about 150 to 500,000,000 of 4.3 billion proper. Its not good statistics for concluding that sentient life can be found. Earth has had life on it for 3.3 billion years, but only sentient life for 200,000 that metric is 6 x 10-6. But if you peg - this planet might be habitable, which means if falls in the goldilocks zone, and then 1/6 bodies of our habitable zone have life and the one that has life has sentient life for only 1/160,000 of its total quantifyable existence, the 500 habitables in the We care zone is not impressive.

I am waiting for someone to prove me wrong, but if I am an alien life form that just happened to notice a blue planet with a O2/N2 atomsphere were they expect C02/N2/Methane I would probably ignore further investigation of that planet until more signal information was available. I might even have a odds going in the Alien Vegas if the sentient life existed and  about how long that sentient life might exist, and send a meager coke can probe out to signal when life went phzzzt.

 

 

 

 

[Mikki]

26 minutes ago, magnemoe said:

Raises another question, why should it go extinct if it was interstellar? It can loose an solar system and survive, 

... lets imagine a hypothetical spacetravelling species encounters a planet similar to their origin homeworld by the means of chemical and physical properties and makes it with little or more effort to adapt themselfes and restart their cycles of reproduction. Would they immediatly move further ahead interstellar to search for more habitable places?

Probably yes, with even more effort than before, but still, a period of maybe 10000 years of interstellar travelling in a diminishing small area of the milky way might be the final era of such an species due to many problems. It remains pure guesswork.

[tater]

11 minutes ago, PB666 said:

long post

 

I don't disagree, actually. I'm not saying we're likely to detect such life, I'm saying that it's likely out there, even if we won't, or can't ever detect it. That said, my 400k number was predicated on life being a million times less likely than in our solar system (utterly arbitrary with no data at all).

I think the paradox is very sensitive to initial assumptions.

Also, you are right that the window of time when we could communicate is short, and that's on top of the discussion about how much time they could beam a signal to any particular place in the galaxy, so even if they were trying hard to contact others, those others would have to be:

1. In the timeframe of their history where they could look, and were looking.

2. Happened to be looking at the broadcaster at just the right time (likely infinitesimally small compared to even #1) to notice the transmission.

So even if my 1M times less likely was made a few orders of magnitude more likely, the chance of contact would be tiny, possibly infinitesimal. 

[Bill Phil]

6 hours ago, Nibb31 said:

What if FTL simply isn't possible, which rules out interstellar travel by making it so impractical that it is not worth the effort.

Another option is the Dark Forest hypothesis: There is a 50/50 chance that another species is hostile and wants to wipe you out, so it's best to keep quiet.

Or there might be a predator species out there that considers any other species a threat and destroys them preemptively just in case. They might even have some form of time travel, so they can go back and destroy others before they are even capable of making contact.

 

We could potentially build a vehicle with about 11.7% C exhaust velocity. It would have to be done centuries from now, yes, but it's not impossible. If we brake with a magsail, then we could use .117C for the cruise to the star. Or .1C, leaving some extra leftover deltaV. We could potentially go slower, allowing us to send generation ships. 

You don't need FTL for interstellar travel. We could, if we so desired, launch a generation ship using NPP within a century. 

[PB666]

7 hours ago, Nibb31 said:

What if FTL simply isn't possible, which rules out interstellar travel by making it so impractical that it is not worth the effort.

Another option is the Dark Forest hypothesis: There is a 50/50 chance that another species is hostile and wants to wipe you out, so it's best to keep quiet.

Or there might be a predator species out there that considers any other species a threat and destroys them preemptively just in case. They might even have some form of time travel, so they can go back and destroy others before they are even capable of making contact.

 

If you survive long enough and you have a dedicated space faring culture, then it is possible to wait a few 100,000 years until another star passes close to the sun, at which point you could travel 1 ly or so and the expand a space fairing culture. If you kept doing this at the rate of say 3 per million years you could move away from our position hitchiking stars at aroud 3000 m/s giving an idea how fast you could expabd, each expansion, by definition would create a new species. 

I think our interstellar future should give up on this fixation with habitable, what you really want is resource available systems. 

[tater]

Obviously if you can do generation ships, then you don't need a planet (just as for colonies you don't need Mars, just build a habitat that spins), build Rama, lol. That said, if you want a planet, and habitable planets are indeed very, very rare, then that expands on the Dark Forest's premise. He doesn't mention that specifically, instead saying life is common, and expands indefinitely, but real estate is finite. In reality, life can be fairly uncommon, but good real estate is more rare still, hence don't stick your head up.

[Spaceception]

Just now, tater said:

 build Rama, lol.

Rendezvous with Rama? That book is excellent, I finished it in less than 6 hours

[magnemoe]

3 hours ago, tater said:

Obviously if you can do generation ships, then you don't need a planet (just as for colonies you don't need Mars, just build a habitat that spins), build Rama, lol. That said, if you want a planet, and habitable planets are indeed very, very rare, then that expands on the Dark Forest's premise. He doesn't mention that specifically, instead saying life is common, and expands indefinitely, but real estate is finite. In reality, life can be fairly uncommon, but good real estate is more rare still, hence don't stick your head up.

If you don't need planets why don't stay in your solar system and save the energy, yes you might do this a few times but not something you continue doing. 
Yes it you are close to the dryson swarm level it start making sense but this has not been detected.

On the other hand we are on the edge of discovering earth like planets, in not to long we will have an decent map, someone who go interstellar will have maps of the actual exoplanets. Its pretty hard to hide planets. 

One part I agree in, why move to an crappy planet

[Stargate525]

6 hours ago, PB666 said:

Yes, but its not a matter of what our system is, the average detected system has gas giants inside the habitable zone. Our system is highly unusual, that we know of because it has relatively small rocky planets inside the habitable zone.

Hold on a moment. The reason we've found a lot of stars with that configuration is that a fast, heavy planet close into the star makes it wobble more perceptibly than an earth-sized one. It's a self-selection bias based on one of the ways we find planets.

The biggest problem with the drake equation is that all of its inputs are guesses. I skimmed the beginning of the article, but I personally couldn't wade through the broken English.

[magnemoe]

11 hours ago, tater said:

I don't disagree, actually. I'm not saying we're likely to detect such life, I'm saying that it's likely out there, even if we won't, or can't ever detect it. That said, my 400k number was predicated on life being a million times less likely than in our solar system (utterly arbitrary with no data at all).

I think the paradox is very sensitive to initial assumptions.

Also, you are right that the window of time when we could communicate is short, and that's on top of the discussion about how much time they could beam a signal to any particular place in the galaxy, so even if they were trying hard to contact others, those others would have to be:

1. In the timeframe of their history where they could look, and were looking.

2. Happened to be looking at the broadcaster at just the right time (likely infinitesimally small compared to even #1) to notice the transmission.

So even if my 1M times less likely was made a few orders of magnitude more likely, the chance of contact would be tiny, possibly infinitesimal. 

Radio emissions are hard to detect unless directed, you might be lucky and pick up fragments from an directed antenna as the sender planet rotates, but this would be to rare and infrequent for regular seti use. 
We are reducing the number of high effect radio transmitters and move towards low power cell structures.
Lasers are probably better in space, its already movement in this direction. 

However planets with oxygen atmosphere and water can be detected far away, yes this shows life not technology but life will be more common. 

[tater]

Yeah, I know, but O₂ is not intelligence. If we're talking about the Fermi paradox, detecting such worlds without making an intelligent life determination merely increases the paradox (now we have a word of likely life... but no aliens walking around stealing trashcans (as I recall, that was the cartoon they were discussing up at LANL).

Your point about directed broadcasts seems to mirror mine. With narrow lobes, the number of hours any such a society could spend broadcasting at any particular distant star is very small---and that means it's wasted effort as the potential recipients would have to be looking just for the few hours when the signal arrives.

The combination of the 2 points would be to look at, and broadcast to, planets with O₂ selectively, I suppose. Then you can dwell on them longer in transmission since there are far fewer. Still chances are that we could easily miss the call. If you dial random phone numbers (land lines only), and let it ring twice then hang up, you're vastly more likely to have a person answer than a SETI call even though many people will be at work when you call

[Polnoch]

22 hours ago, tater said:

The galactic crossing time for a probe like New Horizons is on the order of a billion years. Light is just 100,000 years.

We've not been looking terribly long, and any sufficiently powerful signal from far away would necessarily be directional, which limits any civilization's ability to broadcast often to the same parts of the sky... so even if they were all trying, we'd have to be looking in their direction during the short timeframe when they were broadcasting in our direction. How long would you dwell on a given area if broadcasting, and what solid angle would you be broadcasting into? 

Communications in this way is non-trivial.

 

I not agreed with this conclusion, because New Horizon hasn't goal to have a big delta-v with Sun, and cross  Galaxy with very big speed. Please recall about Voyager program, and about ion/plasma engines(it's not fantastic, and it exist!). I think, It's not difficult to create something, which can cross galaxy during some of millons years - we can use ionic engines, and Obert's maneuvers using Jup, may be, using Sol.

I think, argument about "achieve stars impossible" not correct. May be we'll never achieve it, but not because it is impossible.

Alex Semenov wrote about Greate Filter, but in explanations of his formulas, I think, he made mistake: Greate Filter not only about Swan, but also about Pikes. In pikes, we have P₂~0 - civilizations exist(P₁ = 1), but doesn't create the Wave of Mind. If Create Filter exist, and if it in our future (if it in our Past, we probably live in Swan case), we, our civilization, must be destroyed, and we can't create the Wave, because we will died.

If we'll create the Mars Colony in next years, it may be evidence, proof, about we can create the Wave of Mind by technology reasons.

But may be we live in Crawfish, inside alien's mind zone? May be nearly us is civilization-predator, and other civilizations to be silent, because they was killed by predator or fear of being discovered by Z=1/2 predator?

Also we can live inside mind zone, if we alive... inside computer simulation May be our Universe is simulation on layer of elementary particles? And space around us empty, because it's interesting for persons, who running our simulation?

33 minutes ago, tater said:

Yeah, I know, but O₂ is not intelligence. If we're talking about the Fermi paradox, detecting such worlds without making an intelligent life determination merely increases the paradox (now we have a word of likely life... but no aliens walking around stealing trashcans (as I recall, that was the cartoon they were discussing up at LANL).

 

I think, we need to wait new Scopes - new Europe's 40m, new U.S. in Hawaii, 30m, and Jams Webb. This devices provides us abilities to fix more variables of  Drake's formulas. But founding or not founding O2 planets not permit to us to exclude life, using alternative bio-chemistry (for example, live probably can exist on Titan, Saturn's satellite... It can based not on H₂0)

11 hours ago, Spaceception said:

Rendezvous with Rama? That book is excellent, I finished it in less than 6 hours

Could you please explain, who is Rama?

[Polnoch]

15 hours ago, Bill Phil said:

We could potentially build a vehicle with about 11.7% C exhaust velocity. It would have to be done centuries from now, yes, but it's not impossible. If we brake with a magsail, then we could use .117C for the cruise to the star. Or .1C, leaving some extra leftover deltaV. We could potentially go slower, allowing us to send generation ships. 

You don't need FTL for interstellar travel. We could, if we so desired, launch a generation ship using NPP within a century. 

 

Argeed. But has a 0.1c doesn't require to produce the Wave of Mind. Ships of generations or achieve immortality by H+ social movement technologies, or by artificial mind (or by deployed in computer digital brains of humans) can provide us to create the Wave without technologies of 0.1c speed 

10 hours ago, Stargate525 said:

I skimmed the beginning of the article, but I personally couldn't wade through the broken English.

I'm sorry  Can I try to explain? Could you please tell, which sentences is most difficult to understanding? I'll try to re-write it.  

Edited April 7, 2016 by Polnoch

[Spaceception]

Just now, Polnoch said:

Could you please explain, who is Rama?

Rendezvous with Rama is a novel by Arthur C. Clark written in the 70s about a large alien ship that entered the solar system.

And humanity is a  multi planetary species that rendezvous with Rama to figure it out

Edited April 7, 2016 by Spaceception
I'm holding a baby

[magnemoe]

3 minutes ago, tater said:

Yeah, I know, but O₂ is not intelligence. If we're talking about the Fermi paradox, detecting such worlds without making an intelligent life determination merely increases the paradox (now we have a word of likely life... but no aliens walking around stealing trashcans (as I recall, that was the cartoon they were discussing up at LANL).

Your point about directed broadcasts seems to mirror mine. With narrow lobes, the number of hours any such a society could spend broadcasting at any particular distant star is very small---and that means it's wasted effort as the potential recipients would have to be looking just for the few hours when the signal arrives.

The combination of the 2 points would be to look at, and broadcast to, planets with O₂ selectively, I suppose. Then you can dwell on them longer in transmission since there are far fewer. Still chances are that we could easily miss the call. If you dial random phone numbers (land lines only), and let it ring twice then hang up, you're vastly more likely to have a person answer than a SETI call even though many people will be at work when you call

yes O2 is not intelligent life just life. Also agree that keeping an telescope on an planet with O2 for an extended time is far more effective than hunting blind. 
An non directed signal will have to be idiotic strong if it can be picked up over interstellar distances. unlikely that aliens will direct an signal at us so best option is to look for random stuff in our direction. 

Fermi paradox has an problem with the last part as it assume an short life length for an civilization, not only typical pessimism but also assuming that aliens has the exact same problems as us. Minor example: an alien with far better noses like us will be more sensitive for pollution and  wherefore have less problems with it, add that most mammas has better sense of smell than us. 
Others has gone the other way, why has not alien colonized the galaxy. 

[Polnoch]

Rendezvous with Rama is a novel by Arthur C. Clark written in the 70s about a large alien ship that entered the solar system.

 

Thank you. I delayed Arthur Clark, because I want to read it in English, and I waiting level up of my lang/vocabulary, to have fun reading without use vocabulary in each pages.