Kevbo

Current science pins the age of the universe at close to 13.7 billion years since the Big Bang. The Earth, in more or less its present body of mass, has been around approximately 4.5 billion years. We, as humans, are arguably the most intelligent form of life on this planet, and our technology has only reached "space-age" in the past century.

If we use an analysis of the Earth, our most easily observed planet, to determine the possibility of life on other planets, we might gain some interesting insight on the problem. Our planet has existed for roughly a third of the time that the universe has been in operation in its current form. Here are some questions that arise from this:

• What "generation" of planet is our Earth? (i.e. how many generations of stars are required to generate the elements found on our planet necessary for sustaining life and allowing space-travel technology?)
• Is evolution on our planet typical of any planet that is endowed with a similar situation for sustaining life, both in speed and outcome?
• Is there a way that evolutionary probabilities relating to the development of organisms capable of space-travel can be calculated?
• Is it possible for organisms with advanced technology to transcend the Big Bang or temporal reality, coming from other universes? Is this substantiated with known physics?
• Should we take the lack of solidly confirmed encounters with extraterrestrial intelligence as an evidence of lack?
• Given our observed technological progress, what is our time horizon for reaching the nearest star? The nearest galaxy?
• How is our technological prowess regarding space travel developing versus the expansion of the universe?

Please feel free to answer any or all of these questions or pose your own.

Wounded King

Ill address a couple of your points.

Until we have more than one instance of the evolution of life I dont see how we can make any predictions about how likely it is to occur. But if abiogenetic events only rely on certain chemical conditions and enough time in order to occur then there is nor reason to assume it is much less prevalent than the number of eath like planets. Then again there may be an unknown number of other conditions which will allow life to come about that we dont know of, and there is always panspermia.

As for the probability of species evolving to the level required for space travel, we hardly even have one example of that happening so far.

And absence of evidence should never be taken as evidence of absence.

Ovazor

It's not possible to say that something is typical without a fairly large sample size. With just one known example this question cannot be answered. Of course, when no other data exists, it might be a reasonable quess to assume that what happened here is among the more likely paths.

No.

No and no. Travel between two different universes is impossible; if it was possible the two would be part of same universe.

It means that there has been no encounters with extraterrestrial intelligences. It is not evidence of lack of such intelligences, but would indicate that such intelligences are very rare, use technology which we cannot detect at distance, or they take special care to not to encounter us.

Nearest star: unmanned probe in a couple of centuries. Nearest galaxy: never.

Unless, of course, it turns out to be possible to tralvel faster than light. There is very little reason to suppose FTL travel is possible, and plenty of reason to think it is impossible.

Friar Bellows

At least two, I think. One to create the heavy elements when the first generation star goes supernova, and the other to create the planet (and the second generation star). Astronomers use terms like Population I, II and III to denote progressively older generations of stars.

No one knows.

No.

No one knows.

No, the parameter space we've investigated so far is laughably small.

Our current level of technology? Thousands of years for the nearest star. Billions for the nearest galaxy. In other words, forget about it.

Not quite the right question to ask. The stars within our galaxy and the galaxies within our Local Group aren't expanding away from us. They're gravitationally bound together. But how is our technological prowess regarding space travel developing? Not at all. Chances that humans will one day colonise other star systems? Bupkes.

Friar Bellows

And just on "The Possibility of Meeting Extraterrestrial Intelligence". Even if we did, would we notice? Read Stanislaw Lem's "Fiasco" and "His Master's Voice" for fiction on this theme.

Asha'man

Well, kinda sortof. This is a really rough guess type of analysis, not even an order-of-magnitude type of thing, but here are my thoughts:

Single celled life appeared on this planet relatively quickly, perhaps a billion years after the planet formed. Much of those first billion years don’t really count, since the planet was not really in a hospitable state. I’d conclude that, given reasonable conditions, the formation of single celled life is not horribly difficult.

Single celled life then sat around doing nothing for a couple of billion years. Ok, it didn’t really do nothing, but it did remain relatively simple. I may be remembering wrong, but it seems to have taken longer to go from simple life to complex life than it did to go from no life to simple life. From this, I’d conclude that the jump from simple life forms to more complex ones isn’t inevitable or particularly likely.

Once we start to see complex life, things really exploded. In only a few hundred million years, the complexity managed to reach intelligence. I’d say that intelligence is probably an inevitable outcome of complex life, fairly likely. Going from simple intelligence to a technological society took even less time. I’d rate that as very likely, then.

Lastly, we have the utterly unknown time it takes to reach space travel. This might be achievable in the next 500 years, or the hard speed limit of the universe may mean that space travel is forever out of reach. Personally, I think there will be no escaping the speed of light limitation, and nothing but robotic probes will ever leave our solar system. Anything more might be possible, but nobody will ever want to pay for it, so it won’t happen.

Shadowy Man

This is where the problem lies. No one really knows what "reasonable" conditions are necessary for the formation of life, and how commonly found those conditions are.

Kevbo

One way we might be able to investigate more about the possibilities of evolution would be creating very high-fidelity computer models. If we can really nail down the processes that drive evolution and we have enough computing power, we can run evolution through several hundred pathways and see what pops up. Life on this planet as is seems highly dependent on natural disasters also, so maybe those could be added in at random as well.

Arbogast

"Should we take the lack of solidly confirmed encounters with extraterrestrial intelligence as an evidence of lack?"


First off, here is my personal bias, faith and prejudice. I consider it quite possible I am wrong...

What follows is conjecture and idle speculation...

This I freely admit, what the naysayers rarely admit freely, is that they make equally extrordinary claims, ie the rarity of alien species, with equally thin observational evidence of the solar system and nearby stars.



Many Alien Animals have evolved to technological species. Such species will wish to fill any ecosystems they are able. They will build colonizing spacecraft, and radiate to the stars. Even if travel can only reach 0.01% the speed of light, they will have spread huge distances in a few million years, which is really a short time. Therefore, we are already surrounded by one or more alien civilizations. UFO tales and Ancient Astronauts are only myths, mankind has no accurate record of encounters with such creatures. (If such an encounter occured, mankind would likely learn things they could never imagine, truth being stranger than fiction, therefore, alien stories are not strange enough to be true. Picture a Chimpanzee trying to imagine a trip on the Space Shuttle before ever seeing a man or leaving his rainforest) Contact has not occured because they are either uninterested or wish to allow us to evolve on our own. They already know more about us than we know about ourselves, if they have any interest.

Whether or not they exist in our Solar System is an open question. Although it seems likely an advanced alien civilization does not exist in our solar system, in reality we have little data. We can safely say it is unlikely any of the other planets are inhabited in a major way. If they have evolved to have no need of anything but an artificial environment, it is possible a significant alien population exists in our solar system, although this is unlikely. It is quite possible the solar system has an unobtrusive alien prescence. Mankind would be wholly ignorant of a clandestine alien scientific outpost (with living creatures or more likely machines). Likewise, there could be any number of alien archeological sites on other planets and moons, that mankind would know nothing of.

The fact that we have been left alone (undisturbed or relatively undisturbed, we cannot say, due to sketchy knowledge of human and earth history) does suggest one thing. That the dominant alien species in our stellar neighborhood prefer a different ecosystem than is available on earth. If our planet were attractive to aliens, we would not have been left here to inhabit it. Therefore, the aliens in our neighborhood live either in artificial environments (many humans are beginning to live very isolated lives from the natural world) or in a ecosystem very different from earth (and most likely, any of our Solar Systems planets). (This could be useful to SETI researchers, who probably dont, in future years, need to focus their studies on Earth Like planets)

The alien lack of interest is not surprising. With the simplest machines, they could observe and compile a detailed history of earth. With advanced science, they probably could have looked at our apelike ancestors millions of years ago, and predicted the rise of man within narrow parameters. They are old and advanced compared to man. We are foolish to think we would have anything interesting to say to a civilization that developed space travel 10's or 100's of millions of years ago. We naively assume that because we know nothing of them, they know nothing of us. They are not hiding, when we develop slightly better astronomy, and can make out small details on planets and artificial objects on neighboring stars, we will know. SETI Radio Astronomy is important for the attempt, and may make a lucky discovery ( more likely from the radiation from engineering projects on a scale we can barely concieve, than from a deliberate broadcast). But SETI is unlikely to find a signal. If an alien civilization wished to signal us, they would have forseen our rise 100,000 years ago, and sent a robot to our solar system, and would merely broadcast to us on our normal communications equipment

In conclusion, our species is nearly blind. Our knowledge of the details of the planets and moons in our solar system are vague. Mankind has no clue what sort of solar systems make up the local stars. We see shadows of a few huge planets. Cities the size of the moon could be ordinary in other solar systems, we wouldn't have a clue. Our sketchy written history goes back a few millennia. It is documented with photographs and such less than 2 centuries. We are blind in the present, and ignorant of the past. All we really know for certain is there is no obvious alien presence in our solar system, and that alien civilizations on other stars are not bathing our planet with very high powered, obvious radio signals. That is not much data to take the HumanoCentric view that we are the most advanced species in our neighborhood. It is probably a laughable idea, like the idea that Jerusalem is the Center of the Universe.

I compare our circumstance to a Neanderthal looking out over the Atlantic, who paddles out a few hours on a log, returns, and informs people there Absolutely is nothing but water and fish out there.

Anyway, there is a speculative answer to the question.

BioBeing

I agree with your thinking in general, but just wanted to extrapolate even further here...

Assume that you are correct, and that the rate limiting step is the conversion of single celled life to multicellular. Once there, everything snowballs. Imagine two planets (Earth plus one other) that form at about the same time, with similar expectancies of abiogenesis occuring. Now assume that rate limiting step was extra slow on Earth, for whatever reason. It is possible that an alien race may have made the jump in the half the time - say 1 billion years instead of two. That gives them quite an advantage!

Then, there will be the planets that takes twice as long as the earth - we'll be a bit ahead of them.

To my mind, given virtually an infinite number of planets in the Universe, it seems likely that there will be plenty of all of these types of planets - thus there will be species billions of years more "evolved" than us.

The question then becomes, will we ever meet them?