Intelligent alien life

[Dave]

True, though seriously, if Silicon could build polymers like Carbon can I think we would see them naturally on Earth. We do see complex Silicon molecules and they are called Rocks. Despite old Star Trek episodes, you can watch them for a long time without them moving very far.

The other possible chemical substitution that is discussed is liquid Ammonia as a solvent instead of Water. That would be a seriously cold world in which I doubt we could survive ourselves.

[J-WO]

I'm pretty sure there has to be intelligent alien life out there. And I can't rule out the possibility some civillisation has figured out FTL. Who can say?
But what I can't figure out is that, if the above is true, why would any vessel have to enter Earths atmosphere to investigate? A culture that can travel faster than light could probably read my DNA from the comfort of Pluto's orbit, surely.

[J Riff]

Right, J-Wo. And the idea that Aliens would even come here personally is questionable.. they would send beings grown in vats, to go pick up whatever it is they wanted. What could they want here? They can probably connect to the internet and watch TV from Proxima Centauri and learn that there is nothing worth coming here for.

[J-WO]

Glee has probably made us the pariah of the Milky Way.

[Dave]

Or, too far away from the hyperspace bypass for anyone to bother turning off!

[skeptical]

A few years back, I carried out a simple exercise. I was interested in the question of how long it would take humanity to totally colonise the Milky Way galaxy to the point of overpopulation.

The answer depends on the assumptions you put into the model. I assumed no FTL travel, but a cruising speed between stars of 0.2C. I discovered that population growth was not limiting. The times involved were so great that population size would grow more than enough. I also assumed that, if a star system had no habitable planets, humans would simply build artificial habitats in space, such as giant rotating cylinders, using local raw materials. Thus, my assumption that expansion was not limited by planets available.

The answer, depending on assumptions, was somewhere between 400,000 years and 10 million years.

The shortest time (400,000 years) was based the assumption that humanity went bananas and devoted itself to little more than expansion. This would be achieved by sending billions of probes at 0.2C to all corners of the galaxy. Each probe would contain frozen embryos and advanced robots able to create new habitats, and thaw, and educate the embryos.

Anyway, back to aliens. This gives us a time scale for alien expansion, also. If we postulate just one alien species in our galaxy that is aggressively expansionist, then it would colonise the entire kaboodle within 10 million years. This time is a mere eye blink against the age of the galaxy.

Hence the Fermi Paradox. Where the hell are they?

Simplest answer is that advanced life forms are sufficiently rare that no such aggressively expansionist species has evolved in our galaxy.

[jojajihisc]

The main problem I have with the Fermi Paradox is that, as Robert A. Freitas Jr. states, the paradox

implicitly construes the absence of extraterrestrials on Earth as positive evidence of their nonexistence

A bigger problem is that we at least know that intelligent life does exist in one place so it seems more likely it should exist in another than not at all.

[skeptical]

joja

The Fermi Paradox is a question, not an implication. There are numerous suggested answers, none of which we can test. I have suggested that the most likely answer is that intelligent aliens are rare. I did not say they don't exist.

However, with 200 billion star systems in the Milky Way, and a lifetime of 5 to 7 billion years, if aliens were common, there seems no reason why they would not have visited our solar system, and settled here.

Outside the Milky Way galaxy, there are more galaxies than we can even estimate in number with any accuracy, but at least hundreds of billions. Even if intelligent aliens are rare, they almost certainly exist there.

The thing is that, assuming Einstein was correct, and nothing can go faster than light, then those aliens would not be able to visit our galaxy. Even the closest large galaxy outside the Milky Way - Andromeda - is 2 million light years away. At 0.2C, a space vessel would take 10 million years to cross between. That seems to me to be pretty much impossible.

[jojajihisc]

Originally Posted by skeptical

The Fermi Paradox is a question, not an implication.

That's right, it is a question and I could have included that in the quote I gave as Freitas mentions it. Here is the expanded quote.

Fermi's question "Where are they?" implicitly construes the absence of extraterrestrials on Earth as positive evidence of their nonexistence elsewhere in the Universe.

However, you may have also misunderstood how the word "implicitly" was used in the quote. It's used as an adjective to modify "construes" the noun. The quote isn't saying the paradox is an implication it is describing what the paradox does. I guess my only point here is that the question is not very sound because the absence of evidence for alien's existence is not itself evidence for their nonexistence.

I should also say that I agree with your final statement where you said

Simplest answer is that advanced life forms are sufficiently rare that no such aggressively expansionist species has evolved in our galaxy.

[mosaix]

The straight answer is that we don't know - nobody knows - so any explanation put forward is guesswork.

My guesses as follows: there are billions of galaxies out there, each with billions of stars and each star has the potential for planets. With all those planets I guess that the accident of life has probably been repeated somewhere. Intelligent? I don't know.

Have we been / are we being visited? Given that Earth is just one planet amongst all the rest, I find it unlikely that aliens could find us and, even if they've detected our radio / TV transmissions, I don't think there has been enough time to travel here. So my guess is that unidentified flying objects remain just that - unidentified but not alien.

Other things that persuade me against UFO's:

1) Why haven't they contacted us? If they're hiding they're not very good at it. If their 'mothership' is invisible then why aren't their 'scout craft'?

2) Why are all their craft different shapes and have different characteristics? Maybe there's more than one set of aliens studying us? I think that is even more unlikely.

One thing about the human psyche that shouldn't be forgotten is that when presented with something that we haven't yet explained people will tend to come up with an explanation that fits with a previously held belief that they would like to be proved to be true.

I know this isn't the case with everybody, but in the past 'sightings' have been taken to have religious significance, nowadays they have alien significance.

I would love us to discover alien life in the universe. I think Mars is the best bet and that it is microbial. I just hope it happens in my lifetime.

[jojajihisc]

Originally Posted by jojajihisc

It's used as an adjective to modify "construes" the noun.

Or rather it's an adverb modifying the verb. That's what I get for trying to give a grammar lesson.

[JDP]

Still waiting for signs of intelligent terrestrial life. My money's on the dolphins.

:-D

[Doctor Crankenstein]

Skeptical, there is one problem I have with your experiment.

Surely a race that is advanced enough to populate an entire galaxy would be intelligent enough to realise the dangers of overpopulation? Furthermore, who says they have the same sense of curiosity and explanation that humans do? Perhaps they are quite content sitting in their small corner of the galaxy playing Pazaak.

[JDP]

The Fermi Paradox relies on the assumption that an alien (super?)intelligence would allow us to see signs of its existence. They might be happier for us to remain in ignorance, á la the Zoo or Planetarium Hypotheses...

[skeptical]

To Dr. Crank.

Sure, there may be intelligent species sitting at home and playing philosopher. However, it seems to be a law of nature that every species has a drive to disperse. An intelligent species would have individuals willing and keen to explore outside what we consider to be the norm. Humans certainly have enough individuals willing to put their lives at risk to go somewhere no-one else has ever been.

It seems to me that, while a few species might be happy stay-at-homes, others will be expansionist. If there have been more than a tiny number of intelligent species in our galaxy, over 6 billion years, it would be strange if some had not explored and colonised widely. With a maximum of 10 million years to fully populate the entire galaxy, we should have no problem seeing signs of those beings.