OT: Extrasolar planets discovered directly

[narf poit chez BOOM]

Oh well. It was fun while it lasted.

[Hunpecked]

Certain considerations suggest that the odds of finding a contemporary alien technological civilization in our galaxy are less than we might think. Far from being typical, our solar system may be a very special place:

Only a fraction of star systems are "friendly" to life as we know it. Blue/white giants burn out much too quickly for life to become established on any orbiting planets. Altair, for example, would be a poor prospect, despite its being the (fictional) home of the Krell in the film "Forbidden Planet." Red dwarfs, which I understand are much more abundant than Sol-like stars, have such a narrow "habitable zone" that planets are unlikely to remain within it year-round. Most stars are part of multiple-star systems, most of which will have no habitable zone whatsoever. Planets orbiting single stars that are more variable than our sun may suffer extreme climate variations that make even primitive life unsustainable.

It's been suggested in recent years that Jupiter and Saturn are exactly the right size in exactly the right orbits to sweep up space debris that would otherwise cause much more frequent mass extinctions on Earth.

Planets with more axial tilt than the Earth may suffer yearly climate variations too extreme for "higher" life forms to develop. Supposedly our unusually large (relative to its primary) moon helps stabilize the Earth's axis.

Speaking of the moon, I recall a Larry Niven story based on the premise that the moon facilitated life on Earth by sucking off some of our dense early atmosphere, which otherwise would have made the planet a "greenhouse" similar to Venus. I can't vouch for the scientific validity of this concept. I also recall an article by (I believe) Isaac Asimov in which he suggested that tide pools (the moon again) may have acted as a crucial transition zone in the evolution of air-breathing animals.

Our galaxy may have a "habitable zone" analogous to the zone around a star. Too close to the galactic center, and an otherwise habitable planet may be periodically sterilized by supernovas, radiation bursts, etc. from the relatively dense population of nearby stars or the black hole at galactic center. Too far from the center, and the abundance of "metals" (elements with atomic number above 2) may be too low to produce stellar systems with such life-essential elements as carbon, nitrogen, and oxygen. Depending on the width of this zone, the vast majority of our galaxy's stellar systems may be unsuitable for life on this basis alone.

Life apparently developed on Earth as early as 3.5 to 4 billion years ago, but remained "primitive" until about half a billion years ago. This suggests that under the right conditions the odds of developing life are high, but development of "higher" life forms is much less likely. This idea was used in the film "Mission to Mars", which explained the so-called "Cambrian explosion" of complex life forms as alien seeding.

Some of these ideas (and others) are discussed at

http://www.spacedaily.com/news/life-00z1.html

[Slick]

Don't give up just yet.

[Renegade 13]

Do you know something we don't...??

[Atrocities]

Hunpecked said:
Certain considerations suggest that the odds of finding a contemporary alien technological civilization in our galaxy are less than we might think. Far from being typical, our solar system may be a very special place:

Only a fraction of star systems are "friendly" to life as we know it. Blue/white giants burn out much too quickly for life to become established on any orbiting planets. Altair, for example, would be a poor prospect, despite its being the (fictional) home of the Krell in the film "Forbidden Planet." Red dwarfs, which I understand are much more abundant than Sol-like stars, have such a narrow "habitable zone" that planets are unlikely to remain within it year-round. Most stars are part of multiple-star systems, most of which will have no habitable zone whatsoever. Planets orbiting single stars that are more variable than our sun may suffer extreme climate variations that make even primitive life unsustainable.

It's been suggested in recent years that Jupiter and Saturn are exactly the right size in exactly the right orbits to sweep up space debris that would otherwise cause much more frequent mass extinctions on Earth.

Planets with more axial tilt than the Earth may suffer yearly climate variations too extreme for "higher" life forms to develop. Supposedly our unusually large (relative to its primary) moon helps stabilize the Earth's axis.

Speaking of the moon, I recall a Larry Niven story based on the premise that the moon facilitated life on Earth by sucking off some of our dense early atmosphere, which otherwise would have made the planet a "greenhouse" similar to Venus. I can't vouch for the scientific validity of this concept. I also recall an article by (I believe) Isaac Asimov in which he suggested that tide pools (the moon again) may have acted as a crucial transition zone in the evolution of air-breathing animals.

Our galaxy may have a "habitable zone" analogous to the zone around a star. Too close to the galactic center, and an otherwise habitable planet may be periodically sterilized by supernovas, radiation bursts, etc. from the relatively dense population of nearby stars or the black hole at galactic center. Too far from the center, and the abundance of "metals" (elements with atomic number above 2) may be too low to produce stellar systems with such life-essential elements as carbon, nitrogen, and oxygen. Depending on the width of this zone, the vast majority of our galaxy's stellar systems may be unsuitable for life on this basis alone.

Life apparently developed on Earth as early as 3.5 to 4 billion years ago, but remained "primitive" until about half a billion years ago. This suggests that under the right conditions the odds of developing life are high, but development of "higher" life forms is much less likely. This idea was used in the film "Mission to Mars", which explained the so-called "Cambrian explosion" of complex life forms as alien seeding.

Some of these ideas (and others) are discussed at

http://www.spacedaily.com/news/life-00z1.html

Thank you. You put into word the many things that I have seen that had conviced me that we are a rare accident out side the normal plan of the universe. Thank you.

[Atrocities]

I should also point out that we have no direct proof that there isn't life out there, but the evidence at hand makes the likelyhood that there is that much less likely. Also, who is to that the universe itself is not, or is a life form?

Granted we know so very little about the subject that for all intents and purposes we are but single celled ameba's compared to the human body.

[Strategia_In_Ultima]

Hunpecked, you are right about the fact that most planets cannot support human life..... but who says that all life has to be carbon-based and has to exist in an Earth-like environment to survive? I believe that silicon-based life - even intelligent life - will not be very rare, since silicon is IIRC relatively abundant. Also, if these (possibly crystalline) life forms exist, it will be likely that because of their tough physique, they will be able to survive in climates instantly lethal to a human being. For all we know, crystalline life forms exist on Venus. Why shouldn't it exist? What proof is there that silicon-based or crystalline life is impossible on our sister planet? For all we know, we might be in a Galaxy, even a SYSTEM, abundant with life of innumerable sorts! Give me proof that it is impossible for life forms to exist on Jupiter? Gaseous masses perhaps, or even solid life forms in the methane oceans? And to those who say that the pressure there would be too high and the radiation lethal, I say: look at the animals who live at the bottom of oceanic trenches. They survive at extreme pressures, if you take them to the surface they will actually explode. Also, there are microbes known to be able to resist radiation lethal to a human. So IMO there is no good reason why it would be impossible for life to exist even in this very system. It would be life of a kind as of yet unknown to us, but it WOULD be life.

[Renegade 13]

It's all a matter of life as we know it.

[Strategia_In_Ultima]

And then why should we be ignoring life as we do NOT know it? IM(NSH)O this is a VERY bad thing.....

[Renegade 13]

We should not ignore it. But it is difficult to predict the incidence of life in the universe when we do not even know all the viable forms it could take.