PDA

View Full Version : Summing up the Fermi Paradox solutions for new and old alike.



Noclevername
2014-May-29, 07:14 AM
We make a lot of references to the Fermi paradox here on the Forum, and it may be confusing for newbies.

Here's what it means: http://en.wikipedia.org/wiki/Fermi_paradox


The Fermi paradox (or Fermi's paradox) is the apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilization and humanity's lack of contact with, or evidence for, such civilizations.[1] The basic points of the argument, made by physicists Enrico Fermi and Michael H. Hart, are:
The Sun is a young star. There are billions of stars in the galaxy that are billions of years older;
some of these stars probably have Earth-like planets[2] which, if the Earth is typical, may develop intelligent life;
presumably, some of these civilizations will develop interstellar travel, a technology Earth is investigating even now, such as that used in the proposed 100 Year Starship;
at any practical pace of interstellar travel, the galaxy can be completely colonized in a few tens of millions of years.

According to this line of thinking, the Earth should already have been colonized, or at least visited. But no convincing evidence of this exists. Furthermore, no confirmed signs of intelligence (see Empirical resolution attempts) elsewhere have been spotted, either in our galaxy or in the more than 80 billion other galaxies of the observable universe. Hence Fermi's question, "Where is everybody?"[3]


We also argue about it a lot here. Yet again and again, we hear some of the same arguments repeated over and over again. So to provide a basic list of the most common proposed potential explanations offered as to why we haven't seen them, here's a page from waitbutwhy.com:

http://waitbutwhy.com/2014/05/fermi-paradox.html


In taking a look at some of the most-discussed possible explanations for the Fermi Paradox, let’s divide them into two broad categories, those explanations which assume that there’s no sign of Type II and Type III Civilizations because there are none of them out there, and those which assume they’re out there and we’re not seeing or hearing anything for other reasons:

This thread will, hopefully, serve to familiarize new posters and visitors (and well-established posters who have simply not talked about this topic before) with the already-proposed ideas so often made, because we do tend to see a lot of "But what about X, I'll bet you never thought of that!!" --when X is an old familiar speculation that we've chewed over dozens of times in numerous threads. The thread and its links will help give a broad overview without having to read through many, many posts in long and rambling threads in the Life In Space subsection (Not that reading through threads before posting is at all a bad thing, quite the contrary, but some of those threads are very long and winding, often touching on subjects only tangentially connected with Fermi's Paradox).

Hlafordlaes
2014-May-29, 10:38 AM
Interesting and nice approach to framing things to see if we might ramble less and learn more (speaking in meta- terms, not in reference to the citations.) I've always thought that just one or two stickies at the start of some forums might be a good idea, as long as not overdone.

[At the same time, we can see any thread can go looney fast, as is now doing the one on AI (or with signs of it heading in that direction). Just can't think of any way short of highly interventionist moderation that could do away with that, but that would be worse than the problem itself.]

At any rate, kudos for the good intentions, and here's hoping for a content and not rule-oriented sticky policy some day.

Noclevername
2014-May-29, 11:53 AM
Interesting and nice approach to framing things to see if we might ramble less and learn more (speaking in meta- terms, not in reference to the citations.) I've always thought that just one or two stickies at the start of some forums might be a good idea, as long as not overdone.

[At the same time, we can see any thread can go looney fast, as is now doing the one on AI (or with signs of it heading in that direction). Just can't think of any way short of highly interventionist moderation that could do away with that, but that would be worse than the problem itself.]

At any rate, kudos for the good intentions, and here's hoping for a content and not rule-oriented sticky policy some day.

Thank you. I agree that a set of "the basics for beginners" stickies might be helpful (especially if locked); However, I also fear that such a list will soon bloat out of control and take up more space than the actual discussion threads, as everyone tries to be "helpful" and add their pet theory.

Perhaps a basic FAQ, also locked, could be started, and added to only with moderator permission and content approval.

ShinAce
2014-Jun-02, 02:59 AM
It sounds like we'd have to change things around from 'forum' oriented to 'wiki' oriented.

My personal favorite would be that we were seeded here by aliens. They knew they would need a pit stop between long interstellar travels. The only to guarantee a bountiful supply of left handed proteins and amino acids was to plant them here themselves. It would be funny if all this time spent looking for aliens we had the telescope pointed the wrong way around.

redshifter
2014-Jun-02, 05:35 PM
Question about the so called 'Fermi Paradox' and the use of radio for contacting E.T.: How much power does it take to send a radio broadcast to a nearby star, say 15 ly away? How about 1000 ly? Also, I assume a radio dish that broadcast to this hypothetical star would need to be pointed directly at it?

In other words, it seems like the scenario where E.T. figures out where we are because they caught I Love Lucy broadcasts from a few decades ago seems implausible to me. One because the broadcast power isn't nearly enough to reach a nearby star, two because the broadcasts might not even be pointed such that E.T. could pick them up. And this assumes they're even listening in the first place.

I've discussed this with someone a while back, this person denied the existence of E.T. anywhere because we should be picking up all these broadcasts from all over the place if E.T. did exist. AFAIK, the only way we'd pick up any broadcasts from E.T. is if:
1) The broadcast was sufficiently powerful
2) The broadcast was aimed right at us
3) The broadcast was at a specific frequency that could be picked up against 'background noise'

So, even if the universe was full of E.T. with radio transmission technology, it does not follow that we would be picking up all sorts of radio transmissions unless we just happened to be in E.T.'s line of sight and they happened to be broadcasting with sufficient power and at a frequency that doesn't get lost in background noise.

This doesn't even factor in how long E.T. broadcasts via radio before moving on to something else, etc. This is just about the issues around interstellar communication/broadcasts via radio.

Do I have this right? Please correct me if I'm wrong.

mkline55
2014-Jun-02, 05:48 PM
Question about the so called 'Fermi Paradox' and the use of radio for contacting E.T.: How much power does it take to send a radio broadcast to a nearby star, say 15 ly away?
Define 'radio broadcast'. Stars send out radio broadcasts all the time. Theoretically, a single radio-frequency photon can travel at least 10 billion light years. However, a recognizable 'broadcast signal' with any sort of intelligent message relies on a minimum density of photons to make the message intelligible at the receiving end.

swampyankee
2014-Jun-02, 05:56 PM
"Fermi and Frost (http://www.baenebooks.com/chapters/9781625791078/9781625791078___3.htm)"

redshifter
2014-Jun-02, 07:32 PM
Define 'radio broadcast'. Stars send out radio broadcasts all the time. Theoretically, a single radio-frequency photon can travel at least 10 billion light years. However, a recognizable 'broadcast signal' with any sort of intelligent message relies on a minimum density of photons to make the message intelligible at the receiving end.

By 'radio broadcast' I guess I mean transmitting messages through a dish/antenna such as what a radio or TV station would do. I'm curious as to how much power it would take to broadcast a number of light years (say anywhere from 20 - 1000) and be receivable by a dish/antenna. I'm barely a layperson as far as knowledge in this area, I might not even be asking the right questions.

ShinAce
2014-Jun-03, 01:17 PM
The carrier signals we use in radiowave broadcasts is quite recognizable and could be detected to large distances given the right conditions. The information encoded in it has essentially 0 chance of being decoded at any appreciable distance.

Could they detect an episode of I Love Lucy? Yes, if they tried really hard and were close enough. Could they watch an episode of I Love Lucy? Forget about it.

Look at New Horizons. At the distance of Pluto, it will take about 6 months to transmit 8 gigabits of data. At the distance of Jupiter, it is 38 times faster than that and could transfer its entire memroy buffer in about a week. At the distance of another star, we should basically be sending slow Morse code.

Extrasolar
2014-Jun-03, 05:43 PM
By 'radio broadcast' I guess I mean transmitting messages through a dish/antenna such as what a radio or TV station would do. I'm curious as to how much power it would take to broadcast a number of light years (say anywhere from 20 - 1000) and be receivable by a dish/antenna. I'm barely a layperson as far as knowledge in this area, I might not even be asking the right questions.

I've seen maths that sum this up by doing a calculation of a 1 megawatt signal to Alpha Centauri. An array on a planet around Alpha Centauri to detect a signal from Earth would need to be ~10 kilometers. Also, since we send out lots of different signals all the time within the same frequencies, the signal might just as well mimic noise when mixed together. If there is a planet where specific frequencies are sending out a planet wide signal equal to several megawatts, then that would be more detectable. Otherwise, I don't think we send anything that would be detectable all the way out to 20 LY. If we were going to send any intentional signal, it would probably have to be because we detected one first and know where to transmit to. I'm not even sure that the amount of listening SETI does is a significant portion of what could be listened to. I'm sure there is some analogy like 'its like looking for starlight at noon' or something like that.

Hlafordlaes
2014-Jun-03, 06:40 PM
Question about the size of dish ~ would the calculations above also lend themselves to capture scenarios via scattered small dishes, as we do for some things? Would that make the issue of targeting us specifically slightly less a problem?

Noclevername
2014-Jun-03, 06:51 PM
My personal favorite would be that we were seeded here by aliens. They knew they would need a pit stop between long interstellar travels. The only to guarantee a bountiful supply of left handed proteins and amino acids was to plant them here themselves. It would be funny if all this time spent looking for aliens we had the telescope pointed the wrong way around.

The first problem with this concept is that on long interstellar journeys, it's far more difficult to make a "pit stop" than to just keep cruising. You'd need to decelerate and then re-accelerate up to interstellar travel speed, which wastes a lot of delta V.

This also presumes that the aliens regularly use the same flight path for billions of years, which makes little sense when stars (including us) are constantly moving around in various directions. Sol wouldn't be in the same place twice over such a long run.

Extrasolar
2014-Jun-03, 07:04 PM
Question about the size of dish ~ would the calculations above also lend themselves to capture scenarios via scattered small dishes, as we do for some things? Would that make the issue of targeting us specifically slightly less a problem?

Yes, this is what SETI has. Many small dishes that are combined. 42 6-meter dishes.

http://www.seti.org/faq#ata1

The Vary Large Array has 27 25-meter dishes making a (virtual) antenna that is 36 km.

http://www.vla.nrao.edu/

It has a sensitivy of a dish that is 130 meters across. I don't know exactly how that relates to picking up a signal though.

Noclevername
2014-Jun-03, 09:36 PM
In keeping with the purpose of the thread, IE educating those unfamiliar: Since the Paradox is about why we have not been visited or colonized, expanding the discussion into signal strength and SETI might be a bit of a derail IMO. But if you want to get into the topic, the reasons why we have not detected signals boils down to either "there are no signals to detect" or "there are signals we cannot detect"*; basically, corollaries of the same reasoning as to why we have not been visited.

* This includes signals in the past that we did not receive because we either had yet to exist, or had not yet invented radio. It would also include incoherent signals, signals that have not yet reached us, or signals that use a different medium or pattern than we are looking for.

Extrasolar
2014-Jun-03, 10:46 PM
In keeping with the purpose of the thread, IE educating those unfamiliar: Since the Paradox is about why we have not been visited or colonized, expanding the discussion into signal strength and SETI might be a bit of a derail IMO. But if you want to get into the topic, the reasons why we have not detected signals boils down to either "there are no signals to detect" or "there are signals we cannot detect"*; basically, corollaries of the same reasoning as to why we have not been visited.

* This includes signals in the past that we did not receive because we either had yet to exist, or had not yet invented radio. It would also include incoherent signals, signals that have not yet reached us, or signals that use a different medium or pattern than we are looking for.

Where does it say that the Fermi paradox is only about visitation again?

Edit: And why is there apparantly an answer for the paradox that specifically includes extra terrestrial signals, if the paradox is only about visitation and/or colonization?

Noclevername
2014-Jun-03, 11:25 PM
Where does it say that the Fermi paradox is only about visitation again?

Per the OP:
According to this line of thinking, the Earth should already have been colonized, or at least visited.


Edit: And why is there apparantly an answer for the paradox that specifically includes extra terrestrial signals, if the paradox is only about visitation and/or colonization?

It's my answer for the sideline discussion, not the paradox.

Extrasolar
2014-Jun-03, 11:40 PM
Per the OP...


Well, maybe a debate about wikipedia's ability to define a paradox differently than the paragraph that precedes it can wait for another day, and I'll respect your wish to keep the discussion to a scope limited to that definition in this thread.

Noclevername
2014-Jun-03, 11:51 PM
Well, maybe a debate about wikipedia's ability to define a paradox differently than the paragraph that precedes it can wait for another day, and I'll respect your wish to keep the discussion to a scope limited to that definition in this thread.

I appreciate that. Personally, I don't think it is a paradox at all, just expectations built on faulty logic. But I'm in danger of derailing my own thread now, so I'll stop there.

Noclevername
2014-Jun-04, 06:42 PM
A well-timed XKCD: http://www.xkcd.com/1377/

Noclevername
2014-Jun-04, 07:04 PM
And on that note, bringing back a relevant classic: http://xkcd.com/638/

FarmMarsNow
2014-Jun-06, 10:47 PM
Have you ever heard of Fermi's Internet Paradox? It posits that with so many billions of internet connections there ought to be at least one intelligent lifeform trying to contact us....

oh and there's another called the Fermi Dating Paradox....

Noclevername
2014-Jun-07, 05:05 AM
Is it related to the FerYou Paradox?

swampyankee
2014-Jun-07, 09:36 AM
Have you ever heard of Fermi's Internet Paradox? It posits that with so many billions of internet connections there ought to be at least one intelligent lifeform trying to contact us....

oh and there's another called the Fermi Dating Paradox....

The Fermi Internet paradox is easy: the Internet destroys intelligent life by non-violent means.

iquestor
2014-Jun-07, 11:57 AM
Have you ever heard of Fermi's Internet Paradox? It posits that with so many billions of internet connections there ought to be at least one intelligent lifeform trying to contact us....

oh and there's another called the Fermi Dating Paradox....

that's like arguing: "with so many billions of cats in the world, there should be at ;least one of them ought to be an alien trying to contact us..."

Noclevername
2014-Jun-07, 12:14 PM
that's like arguing: "with so many billions of cats in the world, there should be at ;least one of them ought to be an alien trying to contact us..."



You mean this documentary film (http://en.wikipedia.org/wiki/The_Cat_from_Outer_Space)? It has of course, like anything alien-related, been suppressed by The Government.

And by the estate of McLean Stevenson, who left MASH because he felt being typecast was "hurting his movie career". Which this film was the high point of.

Marakai
2014-Jun-08, 10:33 AM
A humourous take on F.P. :

http://www.tor.com/stories/2010/08/the-fermi-paradox-is-our-business-model

Barabino
2014-Jun-17, 07:14 PM
And on that note, bringing back a relevant classic:

http://imgs.xkcd.com/comics/the_search.png

I agree with that strip: if a galactic civilization exists, Iexpect it to rely on FTL-, and not radio-, communications... or more probably only isolated planetary civilizations exist...

Noclevername
2014-Jun-17, 08:49 PM
or more probably only isolated planetary civilizations exist...

There's a very wide spectrum of potential between "galaxy-wide" and "planet-bound". A civilization encompassing many planets, moons, asteroids, and artificial habitats across one star system is plausible to envision.

Barabino
2014-Jun-18, 05:29 AM
yes, but it's not an interstellar civilization anyway...:-/

Van Rijn
2014-Jun-18, 08:00 AM
We also argue about it a lot here. Yet again and again, we hear some of the same arguments repeated over and over again. So to provide a basic list of the most common proposed potential explanations offered as to why we haven't seen them, here's a page from waitbutwhy.com:

http://waitbutwhy.com/2014/05/fermi-paradox.html


I'm not impressed. He uses the Kardashev scale as a measure of technological capability, for one thing. He says " if 1% of intelligent life survives long enough to become a potentially galaxy-colonizing Type III Civilization, our calculations above suggest that there should be at least 1,000 Type III Civilizations in our galaxy alone" - but that's a thousand civilizations each using as much energy as the *entire galaxy* produces naturally. What, I wonder, does he think would happen in the long term if there were that many civilizations so profligate with energy?

He mentions exponential growth, but he doesn't consider the limits of exponential growth. For instance, if you have something that could convert the mass of the Earth to machines in a few centuries, it only takes a few more to convert the entire mass of the sun (or solar system - it's about the same thing) to machines. Sure, maybe such a civilization could spread a bit, but it isn't going to be around long.

He also doesn't mention economics and why that could (and I'd say almost certainly would) be very important.

There are quite a few other things he doesn't mention. He certainly is making common arguments, but he is leaving out a lot of important issues.

Noclevername
2014-Jun-18, 08:35 AM
There are quite a few other things he doesn't mention. He certainly is making common arguments, but he is leaving out a lot of important issues.

Well, yes, that's why I said it's just to familiarize beginners with "the basics". It's hardly meant to be a comprehensive counter-argument. The rest of this thread is here to fill out details.

profloater
2014-Jun-18, 10:23 AM
This is a Poisson type distribution, large number of trials but vanishingly small chance of intelligent life. That may be a Goldilocks argument but the sequence of near extinctions plus the moon being just right, plus the glaciations, makes simple life likely but intelligent life very unlikely. Then the high chance of repeated near extinction for intelligent life. Then the chance of intelligent life realising it is not intelligent to invite competition. Fish indeed may be as high as it gets usually.!

KABOOM
2014-Jun-18, 01:19 PM
What is intelligent life? We have many species on Earth that have pretty amazing intelligence. However, humans are the only species that has meaningful "foresight" as an evolved attribute. The ability to ponder the future (beyond one's near term meals and shelter) and execute plans to alter the future path that would otherwise have occurred. Testing has shown that are closest primate relatives lack this attribute in any significant way.

If we believe that "natural selection" is a universal law, it might take an extremely rare confluence of circumstances to even begin to "select" for an attribute as nebulous as "foresight".

That coupled with the lack of economic "return on investment", vast distances, etc make galactic conquest something that probably doesn't happen.

profloater
2014-Jun-18, 03:01 PM
as in big disappointment for first interstellar expedition at huge cost, to find top protoearth has reached slime moulds. Of course you have to say its a huge success.

Noclevername
2014-Jun-18, 05:57 PM
as in big disappointment for first interstellar expedition at huge cost, to find top protoearth has reached slime moulds. Of course you have to say its a huge success.

If the ship crosses light-years and can still function at all, it's a pretty huge success.

Noclevername
2014-Jun-18, 06:04 PM
yes, but it's not an interstellar civilization anyway...:-/

No, but it makes it markedly easier (not easy, just easier) to achieve interstellar travel. A system-wide economy would have the resources for building starships; a single world would not. And when you don't need planets, you don't have to worry about whether the destination has "suitable" worlds. There's also the slowboat method for fairly close stars, just send a habitat hopping from comet to comet across the Oort cloud until it bumps up against another comet cloud. It may take hundreds of generations, but on the timescale given by Fermi, that's not much.

Barabino
2014-Jun-18, 07:09 PM
I suspect that being proficient in interplanetary flight is not a significant advantage for interstellar travel :-( it's about 4 orders of magnitude :-/

profloater
2014-Jun-18, 08:49 PM
This is a Poisson type distribution, large number of trials but vanishingly small chance of intelligent life. That may be a Goldilocks argument but the sequence of near extinctions plus the moon being just right, plus the glaciations, makes simple life likely but intelligent life very unlikely. Then the high chance of repeated near extinction for intelligent life. Then the chance of intelligent life realising it is not intelligent to invite competition. Fish indeed may be as high as it gets usually.!Hey xkcd agrees with me! (see FISH)

Noclevername
2014-Jun-18, 08:54 PM
I suspect that being proficient in interplanetary flight is not a significant advantage for interstellar travel :-( it's about 4 orders of magnitude :-/

Good thing that's not what I said, then. Please re-read post # 36.

Thanatos
2014-Jun-25, 08:56 AM
I can hardly imagine anything more dangerous than drawing the attention of something with inconceivable energy resources.

Noclevername
2014-Jul-26, 04:03 PM
I can hardly imagine anything more dangerous than drawing the attention of something with inconceivable energy resources.

Interstellar travel will require inconceivable (to us) energy. If they have that kind of energy resources, and yet have NOT destroyed themselves, they will likely have a high degree of self control and a strongly socialized capacity to isolate, tolerate or ignore the unpleasant.