Intelegent life in the Universe, how common is it?

[DanS]

And we continue to make progress. We are about to make fossil fuels useless as an energy source. Although we will still need them for plastics, a very real plague on the environment. And with SpaceShipOne's happy launching to the edge of recognized space, and the whole program cost *less* then Russia charges people to ride in the third seat of a launch to the ISS, there is hope that we will have non-governmental avenues to reach space.

It seems quite possible that there will be 2 manned private orbital space programs within the next 5-10 years: SpaceX, if they can launch their rockets safely; and a russian outfit, possibly Dnepr, assuming that Bigelow helps fund an overseas competitor to SpaceX for assured access to LEO.

[Last Conformist]

To avoid further confusion, I thought I'd post the version of Drake's I'm familiar with:

N = R*fp*ne*fl*fi*fc*L

N = # of civilizations in the Galaxy capable of interstellar communication.
R = # of Sun-like stars born in the Galaxy per year.
fp = Proportion of these that have planets.
ne = Proportion of planetary systems that have a inhabitable planet.
fl = Probability of life arising on an inhabitable planet.
fi = Probability that intelligent life develops on a planet with life.
fc = Probability that an intelligent life form develops the capacity for interstellar communication.
L = Remaing life expectancy civilizations after they have reached the capacity for interstellar communications, in years.

Only, R and L can be bigger than one, and R is, as said, supposed to be about ten.

[reds4ever]

I know this isn't inthe equation, but should n't R allow for the fact that 'Sun type' stars can only support life as we know it within a certain timeframe?

ie not at the start and end of its 'life'

[DanS]

There *are* no experts in interstellar travel here.

Speak for yourself, Earthling.

[Last Conformist]

Originally posted by reds4ever
I know this isn't inthe equation, but should n't R allow for the fact that 'Sun type' stars can only support life as we know it within a certain timeframe?

ie not at the start and end of its 'life'

Nope. That's, in principle handled by the other factors.

[Boris Godunov]

Originally posted by Dauphin
We are not discussing meaningful contact, we are discussing detection.

Whatever, but distance is still a major consideration when you're talking some species 10,000 ly away as opposed to one 4 ly away. The further away a sentient species is from us, the less likely detection will be, simply based on the fact that any intelligent species is going to concentrate detection efforts in nearby star systems as opposed to ones halfway across the galaxy. The reason "meaningful contact" is important is that another species presumably wouldn't be so bothered about detecting intelligent life that was so far away it couldn't have meaningful contact. What would really be the point of that?

@Boris Gudonov: If the alien race was actively searching for other intelligences, they would presumably leave a probe in each system potentially capable of supporting life permanently.

And again, depending on how distant the alien race was, the likelihood of said probe being here can be remote. There might be 400,000,000,000 stars in our galaxy to check out. Even with a million probes, the odds of them finding our star are remote.

[OliverFA]

It depends on the civilizations density factor choosen in the options screen

[Dauphin]

Originally posted by Boris Godunov


Whatever, but distance is still a major consideration when you're talking some species 10,000 ly away as opposed to one 4 ly away. The further away a sentient species is from us, the less likely detection will be, simply based on the fact that any intelligent species is going to concentrate detection efforts in nearby star systems as opposed to ones halfway across the galaxy.

So you are saying that because there are nearer stars that can be inspected an alien race will inspect them first? Certainly very likely. This does not mean that its the distance or travel time that is important though. This is what I have been driving at- If stars were spaced on average 1 light day apart (meaning that a star 4 light years aways was the equivalent of 6,000 light years away in our present galaxy) do you think that a star 4 light years away would be the first choice destination? From your post I would think you would say no and I would agree. Its actual distance has not changed, neither has the time it takes to reach there.. From this would you not agree that its not the absolute distances involved that are of first importance.


Edit -

The reason "meaningful contact" is important is that another species presumably wouldn't be so bothered about detecting intelligent life that was so far away it couldn't have meaningful contact. What would really be the point of that?

So you think it not worth finding intelligent life unless its with a couple of hundred light years? I would think any discovery would be welcome at the present time, and even more so if nothing is found within our galactic neighbourhood.

[smacksim]

And more good news for the 'I don't think looking is a waste just because of Drake's guess being only a guess' group:
Cassini at Slashdot

[Boris Godunov]

Originally posted by Dauphin
So you are saying that because there are nearer stars that can be inspected an alien race will inspect them first? Certainly very likely. This does not mean that its the distance or travel time that is important though.

It does matter, though, as the alien race does not have limitless resources (they're not gods, as far as we know), and you reach a point of diminishing returns whereby exploring out a great distance isn't going to be fruitful. That's why I brought up what would be the use of finding an intelligent species that was so far away there couldn't be "meaningful contact." Why would an advanced raced expend so much effort to find something that would serve no purpose?

This is what I have been driving at- If stars were spaced on average 1 light day apart (meaning that a star 4 light years aways was the equivalent of 6,000 light years away in our present galaxy) do you think that a star 4 light years away would be the first choice destination? From your post I would think you would say no and I would agree. Its actual distance has not changed, neither has the time it takes to reach there.. From this would you not agree that its not the absolute distances involved that are of first importance.

But stars are not spaced average 1 light day apart, they're spaced many, many light years apart. When you get down the practical physics, it only makes sense that the further a star system is from an alien race, the less likely it will be they will explore said system, especially when you have hundreds of billions to explore.

To reverse your scenario, let's talk about exploring other galaxies. Given enough time, sure, you could get a probe from one galaxy to another. But would this be of any practical or scientific use? How would you even get the data from it? So isn't the distance between galaxies an inhibiting factor for sending probes to them?

[:) Smiley]

What's with the idea that it'd stop with a probe? If aliens behave in the ways we know intelligent life (namely us) do, following the probe will be subdivisions, Hard Rock Cafes, bad movies, and other hard-to-miss things.

Heaven help them (and us), if true.

Ya didn't know? We Americans are actually from outer space. We apologize assigning this world such a incompetent administrator in the last couple of years.

[DanS]

The universe is a mind-blowingly big place. Admittedly, doing the probe thing on a 156 billion ly diameter space would be impossible. But it seems quite doable on the 100,000 ly diameter milky way galaxy containing 400 billion stars and some galaxies in our local area.

The idea is that these probes would self-replicate, i.e., would require no additional resources from Earth other than listening in. Indeed, the probes would populate space even if human beings no longer existed. However, it seems likely that we would send out new probe revisions every year to keep up with technology or to survey new aspects of these star systems.

[reds4ever]

Originally posted by smacksim
And more good news for the 'I don't think looking is a waste just because of Drake's guess being only a guess' group:
Cassini at Slashdot

WOW! Thats BIG news!!!

[DanS]

We Americans are actually from outer space.

Beam me up, Scotty!

[Last Conformist]

Boris Gudonov

And again, depending on how distant the alien race was, the likelihood of said probe being here can be remote. There might be 400,000,000,000 stars in our galaxy to check out. Even with a million probes, the odds of them finding our star are remote.

A million probes, however, are very few. As I've tried to show in my previous posts, for a civilization capable of building self-replicating interstellar probes - and from our present technological horizon, that does not appear to be a very difficult feat - it would be relatively easy to put a probe in orbit around every star in the galaxy.

Now, you might argue that there might have not been any such civilizations around 40 million years ago, but there might be plenty now. This is possible, but hugely unlikely; the galaxy hasn't changed noticeably during the last 40 million years, and the civilization density would be expected to be much the same. If there weren't any around 40 million years ago, we should expect it to be next to none around today.

(I appear to've commited some arithmetic error in arriving at 18 million years, BTW; to reach 400,000,000,000 stars in the way I described, we'd rather need 39 million years. Does not change anything wrt my argument, however; this is still a short time on the galactic timescale.)