I read the book "Alone in the Universe" by John Gribbin recently. He argues that the conditions that produced intelligent (sort of) life on earth are incredibly rare, so this explains the "Fermi paradox": if there are aliens out there, why don't we see them? (assuming as seems reasonable, that we don't).
He gives a lot of plausible reasons for why the rareness of life. Like, only a certain part of the Milky Way is a good home for life. Our planet has a magnetic field that shields it from the solar wind - charged particles that stream out of the sun. Continental drift may not be common, and it's crucial for regulating the concentration of carbon dioxide in the atmosphere, which is a kind of natural thermostat for Earth. He thinks there were serendipitous mass extinctions of life forms that were unlikely to become intelligent, like the Ediacarans. They were a weird kind of multicellular life that were around before the Cambrian. Strangely shaped things. And so on.
Some of it is very questionable to me. Like, he thinks that land life is much more likely to become technological, and that the reasons are obvious. I'm not sure what the obvious reasons are and I looked online and didn't find them. I wondered if part of the reason was that aquatic creatures would be less likely to develop hands, but then I found that octopi can manipulate objects with their tentacles. A lot of technology wouldn't work underwater, but being underwater would make some things easier, too. Aquatic intelligent creatures might be very good at spatial thinking since they live in 3 dimensions. He mentions the idea of an advanced civilization putting self-replicating machines out into the universe that would colonize everything in time, and report back what they found to the home planet. So why aren't there self-replicating alien machines on Earth, if there are alien civilizations? But I'm not convinced that an advanced civilization would necessarily want to do this, or that it would be at all practical or feasible.
He talks about a dinosaur called Troodon, which lived right before a 6-mile wide rock (probably) smashed into the earth, causing the end-Cretaceous extinction. He says based on its brain size, Troodon was about as smart as a small baboon. So the dinosaurs were on their way to evolving intelligence when they were wiped out.
It would be interesting to speculate what an intelligent creature that Troodon could have evolved into, would have been like. They might have been more warlike than us (NOT a happy thought) since they were carnivorous and we evolved as omnivores. Carnivores generally seem to be rather aggressive towards others of the same species.
There are obviously a lot of pitfalls with arguing that life is rare, based on lucky accidents that produced us. Evolution is very creative, and examples of convergent evolution show how the same solution to a problem that life is faced with, are found over and over. Why shouldn't intelligence be a solution that convergent evolution finds over and over, on different planets, even? And, different solutions to different problems posed by different circumstances, could be found by alien life, and the limitations of our imagination are no argument against this.
To me, the slow speed of light compared to the size of the cosmos seems a good reason why we'd be left alone by Them. The Milky Way galaxy is about 100,000 light years in diameter. One could perhaps make a good argument that other intelligent life would exist on a roughly similar time scale to us, so that 100,000 years would look like a long time to Them, too.
If it's true that conscious life is very rare, then it returns the specialness to us that science took away so much, by discovering the hugeness of the universe, that the sun and stars don't revolve around us, etc. The wonderful nature of our world is partly explained by the fact that we are here to see its wonders - which is made possible by the enormous size of the universe.
For me, thinking about this kind of spacey thing is a mind-refreshing relief from the humdrum forced on me by health problems. And you can enjoy exploring the cosmos too in your imagination.
We haven't got to far away from earth as yet - and so I would have thought that it is safe to assume that nothing much can traverse the massive expanse of space. Unless perhaps it is very small - and I think we already have evidence for very small life forms arriving on earth.
The galaxy has been around for a long time. The fact that we cannot visit other stars is not the point. The question is, if it's possible at all (and it is), then why hasn't someone else already done it?
This might take us to a discussion of UFO's. You have said it is in fact possible for a life form to visit other solar systems. As such, how do you know that some of the unexplained UFO's have not been the result of visits from other solar systems?
John, unexplained UFOs are simply that. Rememer the times when unexplained phenomena were attributed to god's intervention? We need a rigorous, scientific expaination, not a pop fantasy myth. There is no proof that we have been visited by aliens. But the yearning we have for superior beings to visit us is fascinating. Are we waiting for the gods to appear?
Roman, I don't know how you could have so grossly and totally misunderstood the comment. Are you sure you read it in context? I think you owe it to yourself to reanalyze it. I hope I don't have to explain it word for word.
John, I'm sorry for misunderstang your comments.
Whenever I see "UFO" in a discussion about space travel, and visits from aliens, a red flag pops up and I regard any further discussion null and void.
Your first sentence made me think that you considered UFOs a serious topic for discussion. You then mentioned space travel, and then reinforced my opinion that you take this seriously with "how do you know that some...UFOs have not been the results of visit...?"
"UFOs" and "Aliens" are conjoined twins, and a large portion of the population strongly believe that we have, and are being visited by aliens. This is a tragic commentary about our science education and makes me very prickly.
Sorry if I misread this,
At the very least, it would be a crap shoot. We could end up finding a consumptive race, like the one in Independence Day, or we could find an enlightened race that would want to bring us up to their technological and social level, like some of us would. How to tell, before we meet them?
There are 200 to 300 billions of stars in the milky way galaxy and around 100 billion galaxies, many with over a trillion stars. That's a whole bunch of opportunities for life and intellegent life to evolve. My own view is that life is an intergal part of cosmic evolution and is a common occurance.
Can biologists and physicists learn each others language?
"Like, he thinks that land life is much more likely to become technological, and that the reasons are obvious. I'm not sure what the obvious reasons are and I looked online and didn't find them."
I can (only recently, and I'm kind of proud of that) understand why Gribbin thinks it's obvious and why many people would not find it obvious. I'm much more attuned to the physical sciences than I am to the biological ones (I'm working hard to bridge that gap but it's a slow process), but I have come to realize that the word "technology" can mean entirely different things to different readers. If the writer/reader has a stronger background in biology, anthropology, etc.; they will tend to interpret "technology" as the use of tools to accomplish a goal. If the writer/reader has a stronger background in physics, astronomy, etc., (and especially if we're talking about contact with an alien civilization); technology means using electromagnetic fields to transmit information.
So, a water-world civilization could obviously make use of all kinds of technology in the biological sense, but it would obviously be close to impossible for them to master technology in the astrophysical sense (e.g. build a radio telescope).
I would tend to agree with Joshua, at this point I would find it really hard to put a probability on there being wide spread intelligent life in the universe. In fact, given the distances involved and the likely data loss that would occur if when trying to communicate, I'm not sure if it will ever be possible to even know the likelihood.
However, I think it's fun to think about and here is some new data for thought: http://www.livescience.com/26212-life-precursor-chemical-found.html
a water-world civilization could obviously make use of all kinds of technology in the biological sense, but it would obviously be close to impossible for them to master technology in the astrophysical sense (e.g. build a radio telescope).
Again, there is nothing obvious about John Gribbin's assertion, which is that technological life wouldn't develop on worlds that are covered with water.
First, there's no obvious reason to exclude "land" being created by life! There are many floating life forms in the ocean, and no obvious reason that they couldn't under some circumstances become a stable permanent floating island. It might be a giant sieve scooping the ocean for food.
There's a HUGE middle ground here, where we just don't know. Some people apparently believe that technological life "must" be common simply because there are so many planets that are roughly like Earth.
Some people believe that technological life "must" be extremely rare because they don't see how it would develop differently from how it did on Earth. Again, the limits of one's imagination are not an argument! (which also applies to the "intelligent design" claims that such and such could not have evolved naturally)
Even for lifeforms that live in water, I haven't heard a good argument against becoming technological (including generating EM waves). Evolution has come up with many bioluminescent marine organisms, so there seems no reason to exclude EM waves used in sophisticated ways by marine organisms. Why not form metal underwater? We do deep-sea drilling, so why couldn't a technological marine civilization build things on land, or create land for some reason? How about flying animals evolving on a marine world, and eventually developing technology?
John Gribbin does make some good arguments that there's MUCH more than meets the eye, to make a world capable of developing technological life. Such as having a magnetic field; a near-circular orbit; even continental drift. The stability of our world is very unusual, and even in our very stable world, life has been incredibly battered, with massive extinctions, from being smashed by asteroid and other catastrophes. Humans almost went extinct; about 74,000 years ago there were only about 10,000 people left of reproductive age!
As for wolves evolving hands - again, I never said they would evolve hands if they became arboreal, nor did I say they could evolve hands in the northern forests. However having evolved from arboreal ancestors, there is no clear reason to exclude them becoming arboreal again, and eventually evolving hands (which would happen along with the plant life evolving around them). Retractable claws are useful for large arboreal creatures, and maybe those genes persist in wolves - there are arboreal canids with retractable claws.
One thing I wondered about, is to what extent the possibility persists of regaining something that is lost in evolution. There are snakes that have re-evolved legs, for example, so the leg-making genes weren't totally lost went snakes lost their legs.
Yes, I love the idea that alien technological life, the staple of sci-fi, is almost certainly out there somewhere. Not necessarily in our galaxy; but the universe is so huge that it seems certain that the miracle of our existence must have happened again in some galaxy. And maybe there are alien civilizations that are searching for other intelligent life. It's only recently that we have been broadcasting our TV programs to outer space and advertising our existence to the universe at large - so They might not have any idea we're here, for a long time.