Aliens

What would be extremely interesting is if an alien showed similarities in some part of its physiology or biochemistry, showing the possibility of either common descent, or convergent evolution. For example, if you have life in vaguely similar conditions to those on earth, are legs the best method of locomotion?

That would be cool to find out, even if legs (or whatever) were completely different in actual anatomy. Also, we can only think of the world in terms of our own senses, but aliens would probably have others (given the number of things there that are sensable) The most obvious is the possibility for seeing other bits of the electromagnetic spectrum, or if the workings of the eyes and ears were reversed (our eyes sense three wavelengths with high directionality, our ears sense thousands of wavelengths with vague directionality.)

Coatsy wrote

I think the possibility of life on another planet, given the nature of the universe, is not just possible, but entirely probable.

Seconded.

[Sternwallow]

haushibo wrote

Anyone have any idea where the typical idea of an alien(large head compared with body, large slanted eyes, etc.) came from? Does that spring purely from the human imagination or is there any truth to reports of people having spied such things?

To my mind these sightings could mean either that:
1. Someone made this up one day and people found it to be a rather fetching image, so it stuck and has lived on in popular culture(similar to unicorns).
Or
2. Aliens really do exist and people have seen them.

Option two seems the more interesting of the two, though one too has to say something about how ideas get propagated through a culture if, in fact, they are fictional.

In the 60's(?), there were all sorts of different alien descriptions, short, furry, big headed, stick-figure thin childlike, 9' tall, big eyes, tiny eyes, no eyes. Then a guy named Whitley Strieber wrote a supposed non-fiction description of his abduction, "Communion", which became very popular. On the cover was an artist's composite of various "races" of alien, the gray, head with tiny chin and "wrap-around" eyes. That became the template for many later tales of abduction and contact and it is now stuck in the culture.

[Sternwallow]

FishFace wrote

What would be extremely interesting is if an alien showed similarities in some part of its physiology or biochemistry, showing the possibility of either common descent, or convergent evolution. For example, if you have life in vaguely similar conditions to those on earth, are legs the best method of locomotion?

That would be cool to find out, even if legs (or whatever) were completely different in actual anatomy. Also, we can only think of the world in terms of our own senses, but aliens would probably have others (given the number of things there that are sensable) The most obvious is the possibility for seeing other bits of the electromagnetic spectrum, or if the workings of the eyes and ears were reversed (our eyes sense three wavelengths with high directionality, our ears sense thousands of wavelengths with vague directionality.)

The very basis of life might be very different. We talk about the Earth being in the perfect zone for life, liquid water etc., but other very different systems of chemicals become mutually reactive under different conditions. For example silicon is not at all well suited as the basis for our kind of life, but, at much higher temperatures it can form many bonds the way carbon does for us. It would not be hard to imagine a "litholitic" (not "organic") ecology.

Fred: "Honey, it's time to go to the nursery,... I mean quarry to pick up baby Eldon."
Ethyl: "OK. And bring back some oil-shale from the store. We're running low on 'Slipry-Grit' floor polish."

[Victus]

I forget the name of the program, but there was something on the discovery channel about robot probes reaching an alien planet. The species used a type of sonar (they had no eyes) despite relatively good lighting. It was an amazing program.

Tenspace wrote

Are there aliens? I think the Copernican Principle applies here. What's so special about a small planet attracted to an average sun somewhere in a spiral arm on a galaxy that's really not that massive, and one of billions of such galaxies just in our little corner of the universe, and there are billions of little corners of the universe out there, and maybe even billions of little corners of other universes too, then yes, I'd say that we would be fools to think that we are the only intelligent life in the entire universe.

But suppose it takes an Earth-like planet to give rise to intelligent life, that there are 10^20 Earth-like planets in the observable Universe, and that the probability of intelligent life arising is something like 1 in 10^25. Probability is against 2 of these planets having done so, but for one of them to do so is not all that unlikely. Now, although any one of those 10^20 Earth-like planets could have given rise to intelligent life, in this scenario, only one of them would have. So it would be possible for only 1 instance of intelligent life to exist in the Universe, even though the Copernican Priniciple (the principle of mediocrity) would still apply. And whichever that one otherwise-insignificant planet might happen to be would be the one that the only intelligent life in the Universe found itself on. Earth could be completely insignificant in all aspects except one: we could be the only intelligent life in the Universe.

What we need before we can answer the question in any meaningful way is numbers and facts. Is intelligent life limited to carbon-based life as we know it? Must a planet be Earth-like for intelligent life to arise on it? How many Earth-like planets are there? What is the probability of intelligent life arising?

[Tenspace]

DinaNoun wrote

But suppose it takes an Earth-like planet to give rise to intelligent life, that there are 10^20 Earth-like planets in the observable Universe, and that the probability of intelligent life arising is something like 1 in 10^25. Probability is against 2 of these planets having done so, but for one of them to do so is not all that unlikely.

Where are you getting your numbers from? We could surmise that the probability of life arising on an Earth-like plant is one in ten as well; short of dusting off Drake's equation, I know of no reliable way to discern those numbers.

Once you provide a surface area as big as Earth's for life to arise, you create another set of probabilities. It could very well be 1:1 when viewd on a planetary scale, or why just planets? We could even consider star systems as the target population.

Tenspace wrote

[DinaNoun,] Where are you getting your numbers from?

I was supposing ("But suppose it ..."). As I pointed out at the end of my post, I don't believe we have the numbers and facts needed to make a legitimate estimate of how many intelligent civilizations there are in the observable universe.

And the typical astronomers' logic - "There MUST be other intelligent life out there because there are billions and billions of stars" - simply doesn't work because we do not know what the probability of intelligent life arising is. Lots of people have taken guesses, but that's not legitimate. If the true probability is 1 in a million, then yeah, there are probably lots of intelligent civilizations out there. If it's 1 in a trillion trillion then there's not likely to be more than one.

The question really isn't about life, or even intelligent life. Given the size of the universe, I would consider both extremely likely. The real question is whether or not there is technology developing intelligent life. Consider for a moment, there have been billions of species of life on the planet, only one has developed technology. Also consider, neanderthals were around twice as long as humans and never developed technology. That could be much more rare and we simply do not have the database about other planets to speculate what is normal and what isn't in terms of the universe.

Victus wrote

I forget the name of the program, but there was something on the discovery channel about robot probes reaching an alien planet. The species used a type of sonar (they had no eyes) despite relatively good lighting. It was an amazing program.

The name of the show is Alien Planet and it is still my favorite show that the Discovery channel has ever done.

Here is a preview for anybody interested in the show
http://www.youtube.com/watch?v=JYTIEDDVVE0

Also a torrent for anybody who wants to see the full version
http://www.torrentspy.com/torrent/29...t_tvrip_BiTSrg

I highly recomend anybody who has an interest in this topic to watch the show. You won't be disappointed.

[Sternwallow]

Cap'n Awesome wrote

The question really isn't about life, or even intelligent life. Given the size of the universe, I would consider both extremely likely. The real question is whether or not there is technology developing intelligent life. Consider for a moment, there have been billions of species of life on the planet, only one has developed technology. Also consider, neanderthals were around twice as long as humans and never developed technology. That could be much more rare and we simply do not have the database about other planets to speculate what is normal and what isn't in terms of the universe.

We just keep discovering new parameters, like life by undersea vents and under miles of rock, and we update the probabilities accordingly. The probabilities jumped nicely when the first extra-solar planets were discovered and each new one adds its increment to our guesses.
A figure that decreases the effective probability is the huge distances. For other intelligent life to be meaningful, it must be near enough to communicate. A hardy race from Bellatrix (a.k.a. γ Orionis) about 350 years ago, started their vacation cruise to Earth. Being polite, they radioed ahead for reservations. They won't be here for another 800 years at their best speed but it won't matter because we couldn't receive their signal 108 years ago so we won't be leaving a light on for them. (their home star is only 243LYs away).

Cap'n Awesome wrote

The question really isn't about life, or even intelligent life. Given the size of the universe, I would consider both extremely likely. The real question is whether or not there is technology developing intelligent life. Consider for a moment, there have been billions of species of life on the planet, only one has developed technology. Also consider, neanderthals were around twice as long as humans and never developed technology. That could be much more rare and we simply do not have the database about other planets to speculate what is normal and what isn't in terms of the universe.

I dont think that they would be all that different from us, or even more advanced...it could be that we are the most advanced of all the lifeforms.

Theres people on Zargon X talking about the earthlings are coming and scaring there children with Predator VS Earthman stories.

[HeathenLifer]

I was just reminded of a Futurama where some aliens were watching earth tv via our radio signals, then came to earth to see how it ended, or something like that.. Point is, Wonder what they'll know about us before they get here. "Honey, the map says 'turn left at 'Mad About You'."