Monday, February 18, 2008 | Science : Astronomy | print version

Potentially Habitable Planets Are Common, Study Says

by National Geographic

Thanks to James Dowse for the link.

Reposted from:
http://news.nationalgeographic.com/news/2008/02/080219-planets-life.html

Aalok Mehta in Boston, Massachusetts
National Geographic News
February 18, 2008

More than half of the sunlike stars in the galaxy could have terrestrial planets with the potential to harbor life, a new study suggests.

The research, announced yesterday at a meeting of the American Association for the Advancement of Science in Boston, Massachusetts, is just one of a set of recent findings that suggest the roster of potential life-harboring worlds is huge—even in our own solar system.

"Our observations suggest that between 20 percent and 60 percent of sunlike stars form rocky planets like our solar system's," said Michael Meyer, an astronomer at the University of Arizona, at a press briefing Sunday.

Meyer and his team used NASA's Spitzer Space Telescope to study heat from the dust around sunlike stars of various ages, much like looking at "the smoke you see rising from chimneys in Boston on a cold day."

Such hot dust implies that larger rocky bodies are forming and colliding in the "messy" business of planet formation, Meyer explained.

Planet-forming dust was found at one to five times the distance from the sun to Earth, Meyer said (see an interactive map of the solar system.)

The dust was also seen in young stars but was absent from most stars older than 300 million years—a perfect fit with current models of planetary formation, he added.

(Read related story: "Newborn Planet Found Orbiting Young Star" [January 3, 2008].)

The study will appear in an upcoming edition of the Astrophysical Journal Letters.

Earth-Size Refugees?

At the briefing, scientists also advanced the possibility that our solar system contains hundreds or even thousands more dwarf planets like Pluto, hidden from view in the distant region known as the Kuiper belt.

There is a growing body of evidence that the poorly understood region contains several Earth- or Mars-size planets and many tinier bodies, said NASA planetary scientist Alan Stern, adding that this could very well be a "new Copernican revolution" in our understanding of planets.

"What we thought is, our outer solar system is actually our middle solar system," Stern said.

It would be a vindication for Pluto, which was recently "demoted" from full planet status by astronomers after a lively and controversial debate.

Pluto might be the best known representative of a third major class of planets, the dwarfs, "which could be far more common than either the terrestrial or gas giant planets," Stern said.

The initial solar system was quite cluttered with small bodies, he explained, but these were swept out as the four gas giant planets—Saturn, Jupiter, Uranus, and Neptune—finished forming.

Evidence for that can be seen in Uranus, which is lying almost on its side compared to the other planets, Stern said.

It must have been struck by a massive object several times the mass of Earth—an extraordinary coincidence if there were only a few such bodies around.

Exploring the Kuiper belt will be a slow process, Stern pointed out, as the objects in it are extremely difficult to find because of their distance from Earth.

These worlds would mostly be rocky bodies with icy surfaces, though larger ones might be able to harbor gassy envelopes.

But there is also the possibility that some could have "warm, wet interiors," Stern said.

Some scientists think it is "likely Pluto has an ocean in its interior, as does [Jupiter's moon] Europa and many of the other satellites of other planets," Stern said.

In the future, we might focus the search for life on such worlds, which could be far more common than planets like Earth with liquid water on their surface, he added.

Slow Search for Life

But directly detecting the kinds of planets that could harbor life remains a huge challenge, said Debra Fischer of San Francisco State University.

Such planets fall into an "anti-sweet spot," she said—far too small to detect using any of the common planet detection methods, which have so far found about 250 or more extrasolar planets.

But scientists have reasons to remain optimistic, she said.

If a planet with the right mass is found at the right distance from a star—in the so-called Goldilocks zone, where it is neither too hot nor too cold—most of the work is done.

"The raw materials for life are common," she said. "Water is probably the most common molecule in the universe."

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1. Comment #129188 by SamKiddoGordon on February 18, 2008 at 8:49 pm

They know that organic molecules are in the nebulae all over the universe. I think that life will be found to be widely disperse, seeded from these naturally forming molecules, many varieties, viruses, rna, dna. If the conditions are at all favorable, the pre-biotic hydroponic soup gets a few seeds an voila, life. these seeds help in the diversification of life, and have been shown to match with periods of meteoric activity. The conditions were ripe here, the seeds, well, are star dust.

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2. Comment #129204 by SPS on February 18, 2008 at 9:19 pm

It could be that we'll find signs of extraterrestrial intelligence by way of the Allen Telescope Array before finding life within our own solar system. Either way, it's somehow encouraging to think that we may not be alone even if our closest neighbors turn out to be bacteria.

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3. Comment #129235 by tacitus on February 18, 2008 at 10:12 pm

I'm all for SETI and the boost to the program the ATA will provide, but I suspect we've got a better chance of finding signs of life in other solar systems via a new generation of optical telescopes first.

Many are predicting that we will be able to directly image a nearby Earth-like planet by the year 2020. Once you can see such planets, even though they'll only be a pixel or two across in the sensors, you should be able to begin examining the make up of their atmospheres by studying their spectra. Certain chemical signatures could provide strong evidence of biological and even technological processes going on on the surface of such planets. We won't be able to see much (though we might in a few more decades) but we should have a strong indication of whether life is there or not.

The Golden Age of planetary astronomy is barely beginning. There should be some fun times ahead though we'll probably have to be patient for a little while longer!

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4. Comment #129292 by Mitchell Gilks on February 19, 2008 at 1:00 am

Holy crap! This is huge, I am so excited. All I want is to see extraterrestrial life before I die, yes, I don't care what. Be it becteria, or little green men, even fossils from mars would do it for me. I just want to see it, and know what they are made, of, and how they worked. What their structure consists of and so forth. Just, before I die I really really want to know. This makes me optimistic! Here's hopin'!

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5. Comment #129326 by Adam Morrison on February 19, 2008 at 1:33 am

Lol. I can't wait for the day they find extraterrestial bacteria or other microscopic life.

'Satan just put it there to test our faith!'

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6. Comment #129429 by rod-the-farmer on February 19, 2008 at 5:57 am

Every time one of these "more planets found" articles appear, I wonder if there is someone updating the Frank Drake Equation. Surely the ratios have changed in recent weeks/months.

I too am a SETI supporter, and have several computers at home running the software, plus I have created a team of some colleagues who do SETI as well.

http://setiathome.berkeley.edu/

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7. Comment #129444 by Ian Bamlett on February 19, 2008 at 6:28 am

There has been a drip, drip, drip effect of this kind of story for some time now.

Letting it percolate into our consciouness.

Preparing us.

They are coming.

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8. Comment #129447 by Steve Zara on February 19, 2008 at 6:33 am

I too am a SETI supporter, and have several computers at home running the software, plus I have created a team of some colleagues who do SETI as well.

Sorry to be a downer, but my feeling is that SETI via the search for messages is just not going to work, unless a civilization spends some time deliberately sending them out to announce itself. If it doesn't, then communication across the vastness of space is going to tuned so as to be most efficient - it will use maximal compression and the lowest possible power: It will be indistinguishable from barely detectible noise.

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9. Comment #129452 by annabanana on February 19, 2008 at 6:43 am

I think that life will be found to be widely disperse, seeded from these naturally forming molecules, many varieties, viruses, rna, dna.

I don't think they'll be finding viruses floating around as it seems that the origins of viruses are misplaced pieces of DNA that are specific to a small group of organisms that are usually fairly closely related. This is why we don't get viruses that our dogs and cats and plants have, but can contract things like bacteria and parasites. I'm sure that what I've given is a bit of an over-simplification, but I just wanted to point that out. ;-)

EDIT: I should have said "misplaced pieces of DNA or RNA" as it can be either...

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10. Comment #129462 by Steve Zara on February 19, 2008 at 7:01 am

I don't think they'll be finding viruses floating around as it seems that the origins of viruses are misplaced pieces of DNA that are specific to a small group of organisms that are usually fairly closely related. This is why we don't get viruses that our dogs and cats and plants have, but can contract things like bacteria and parasites. I'm sure that what I've given is a bit of an over-simplification, but I just wanted to point that out. ;-)

It is a pretty good summary. General viruses are hard to evolve as viruses have to react to certain receptors on a cell to enter it and reproduce, and these receptors can be pretty specific to a group of animals. This is why pandemics where viruses spread to humans from other animals are quite rare, (although when then do happen they can devastating).

Your point also illustrates why Fred Hoyle's idea that we regularly get diseases from space is ludicrous.

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11. Comment #129467 by annabanana on February 19, 2008 at 7:08 am

Yes, Steve. This is why we haven't experienced a pandemic of bird flu since the virus would have to cross the bird-human barrier probably multiple times before it became an issue.

I was/am looking into graduate school for microbiology/virology. :-)

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12. Comment #129473 by Steve Zara on February 19, 2008 at 7:17 am

Yes, Steve. This is why we haven't experienced a pandemic of bird flu since the virus would have to cross the bird-human barrier probably multiple times before it became an issue.

And even more, it would have to transmit efficiently human to human....

The Hoyle suggestion illustrates for me an interesting form of compartmentalisation - how a truly great scientist in one area can be, frankly, an embarassment when they try and dabble in others. This reminds me of when the biologist Jack Cohen visited a conference of astronomers discussing the chance of finding life elsewhere. He could not believe what he was hearing, and said something like "would you mind if I gave a lecture here on black hole theory - I am qualified, I am a biologist".

I was/am looking into graduate school for microbiology/virology. :-)

I specialised in microbiology in my biochemistry degree (partly because I did not want to do anything nasty with animals). I really enjoyed it, and there is so much more for you to know now. The genetics of these organisms is utterly amazing.

There are good places in Europe, by the way!!

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13. Comment #129486 by Adam Morrison on February 19, 2008 at 7:43 am

Just expect to pay through the nose if you're doing a graduate degree in the UK and you're not a UK or EU citizen (I know I did!)

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14. Comment #129489 by annabanana on February 19, 2008 at 7:50 am

Yes, I would expect so. I've yet to figure out what or when I'm going to do. I need to get some lab experience before I go to graduate school, it seems. I was supposed to volunteer at a program here, but the professor has been very lax about getting back in touch with me.

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15. Comment #129493 by al-rawandi on February 19, 2008 at 7:57 am

Any recommendations on bartending schools?

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16. Comment #129500 by annabanana on February 19, 2008 at 8:14 am

Bartending school, eh? Why on earth do you want to know that?

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17. Comment #129501 by Epinephrine on February 19, 2008 at 8:18 am

@rod-the-farmer

*Gasp*
Surely, at RD.net we *evolve* a team of colleagues :P

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18. Comment #129503 by annabanana on February 19, 2008 at 8:23 am

Epinephrine...I meant to tell you that I like your new avatar. It's much less menacing than the other one. You look like a normal human now. ;-)

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19. Comment #129507 by Charles Bradlaugh on February 19, 2008 at 8:33 am

This may be a bit of a tangent, but it reminds me of what i thought was the weakest part of TGD: the anthropic principle idea. i can see 'the universe is so big, the law of averages suggests there must be another world like this one somewhere' in a kind of phillip pullman way, but i didn't see how it fitted into 'therefore a god didn't create this one.'

if someone can explain, as simply as possible, i'd be really grateful. apologies if i'm wildly off-topic or being stupid.

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20. Comment #129512 by al-rawandi on February 19, 2008 at 8:39 am

Anna,

I am no scientist, so I figure grad school would consist of a bartending school.

PhD in Mixology! (I already have an honorary PhD in Drikology... from Princeton no less)

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21. Comment #129514 by annabanana on February 19, 2008 at 8:43 am

Science is the only area they offer in grad school?[/sarcasm]

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22. Comment #129518 by al-rawandi on February 19, 2008 at 8:50 am

anna,

Fine.

I stand corrected.

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23. Comment #129519 by Epinephrine on February 19, 2008 at 8:50 am

-annabanana,

Thanks, I saw both you and Steve update your avatars and thought, "why not?" I don't normally post pictures of myself online (not even on facebook, where I have relentlessly un-tagged myself from all photos) but this place is so friendly that it seemed better than being renovation-man forever :)

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24. Comment #129522 by Steve Zara on February 19, 2008 at 8:57 am

This may be a bit of a tangent, but it reminds me of what i thought was the weakest part of TGD: the anthropic principle idea. i can see 'the universe is so big, the law of averages suggests there must be another world like this one somewhere' in a kind of phillip pullman way, but i didn't see how it fitted into 'therefore a god didn't create this one.'

if someone can explain, as simply as possible, i'd be really grateful. apologies if i'm wildly off-topic or being stupid.

It isn't off topic, and I didn't think it was handled that clearly in TGD.

The problem is this: Is the Universe "tuned" for us to be here? And, if so, does this imply a "God"?

People have tended to consider that tuning meant Earth-like planets, which may have been rare. It looks like they probably aren't. But the discovery in recent times of "extremophiles" - organisms that can live at what is (at least to us) extremes of heat, cold, pressure, vacuum, acidity and alkalinity, suggests that life really could turn up just about everywhere where there is liquid water, and that could be all over the Solar System (and that is just carbon-based life). The term Anthropic Principle covers a multitude of sins, from a simple self-evident argument that there must have been at least one Earth-like planet, because we are standing on it, to weird claims that the existence of life somehow "made" the universe the way it is. It also includes a tendency to consider the conditions we live in to be special, which does not make sense, as for some life forms even here on Earth, they would be toxic.

It is looking increasingly like life is very robust and could exist all over the place. So, the real problem may not be the existence of life, but the existence of a universe with the right laws of physics to allow the physical and chemical complexity required for life to arise.

That is another topic altogether, but to summarise briefly: the complexity of those laws of physics is far, far less by an almost unimaginable degree, than the complexity of a mind (such as that of a God). So it makes more sense to claim that the universe "just exists" than a creator God.

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25. Comment #129557 by swordsbane on February 19, 2008 at 9:55 am

I find it odd to call these potential planets "habitable" though. I mean I admit that they are certainly going to be more habitable than say... Venus or Jupiter, but on the other hand, what sort of data do we have on probable atmospheric composition and pressure? Is Venus an abberation as close as she is from the sun or is Earth the abberation and Venus is more common instead? If it's common, those likely candidates look a lot less likely.

I think it would be a cool project for SETI to have a look at a few of the closer stars that are good candidates for "Eartlike" planets and work on getting a signal of some sort beamed to them. Thirty - fifty light years out seems like a good bet and it has the potential to actually reach someone on the other end of the call within an acceptable span of time. I think it's past time we started talking instead of just listening.

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26. Comment #129586 by Quetzalcoatl on February 19, 2008 at 10:50 am

Swordsbane-

it's entirely likely that "Earthlike" planets out there will have entirely different atmospheric compositions to ours. Offhand, I think that the current oxygen-nitrogen atmosphere the Earth has is its "third". One of the major dirvers behind the introduction of oxygen to our atmosphere may have been plants giving it off as a by-product. If alien plants use different chemical reactions, then the atmospheres are likely to be different.

Tacitus-

I agree that telescopes are our best bet. That's why I was pissed when NASA cancelled the Terrestrial Planet Finder.

Rod-the-farmer-

Sorry to be a downer, but I agree with Steve. Even if an alien civilisation is sending out signals, the chances of us listening in the right section of the sky at the right time are remote.

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27. Comment #129588 by snoov on February 19, 2008 at 10:52 am

All.

I agree with steve when he says something like what Paul Davies writes in 'Are we Alone?', that if we are to be taken as an example, there could be many many intelligent beings out there listening to nobody transmitting!

What I want to know is, how far away are these planets, how long does the light we see take to reach us and what is the probability of a mode of communication that can deal with these distances?

Is it not the case that light from our own sun takes between 3 and 4 minutes? Proxima Centauri is 4.3 light-years from the Sun, so at light speed a conversation is hard. I don't know if there is any way of doing it faster but both parties would have to share the method - I think so - would that mean someone would have to make the trip' deliver the technology?

I seems unlikely.

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28. Comment #129592 by hoops mccann on February 19, 2008 at 10:56 am

Charles Bradlaugh says:

"This may be a bit of a tangent, but it reminds me of what i thought was the weakest part of TGD: the anthropic principle idea. i can see 'the universe is so big, the law of averages suggests there must be another world like this one somewhere' in a kind of phillip pullman way, but i didn't see how it fitted into 'therefore a god didn't create this one.' "

I don't think that the anthropic principle concludes that there is no god, only that devine action is not *necessary* to create things that are highly unlikely. Even highly improbable events become inevitable when the universe of possibilities is large enough. We know that it's greater than zero since we exist, so sheer size and expanse of time make it possible for life (and universes) to exist without needing (super)intelligent creators.

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29. Comment #129593 by Quetzalcoatl on February 19, 2008 at 10:56 am

Snoov-

Is it not the case that light from our own sun takes between 3 and 4 minutes?

Roughly 8 minutes.

would that mean someone would have to make the trip' deliver the technology?

Yep, they'd have to make the journey first, probably travelling slower than light. It seems unlikely, but with sufficient determination it could be done.

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30. Comment #129643 by Adam Morrison on February 19, 2008 at 12:05 pm

Hey Anna,

As far as what you can do to pay or get funding, I can give you a couple pieces of advice;

- Apply early, I'm not sure if you're from Canada or the US (or somewhere completely different) but most of the major grants need the application submitted a year before your grad studies begin. Many also need a letter or two of recommendation (some more, I think I needed 6 when I applied for the Rhodes IIRC).
- Volunteer even outside your field, it still helps, but within your field is still essential.

It can be pretty tough to get funding still. I graudated with a double honors undergrad and a first class GPA, was a president of an undergrad student association, volunteered for years at a historic recreation facility in my hometown, was on dept. council, etc, etc, and I didn't get any funding. Mind you archaeology and anthropology usually get minimal grants.

If you're Canadian I'd suggest going to Alberta for a year and working in the oil-fields or pipeline trades. It's pretty terrible work and the people are generally meth-heads or worse, but you can make insane money.....

Whoah, sorry, my advice seems pretty depressing.
(edit)
Getting a grad degree is nothing but sunshine and rainbows!!!!

That's better

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31. Comment #129657 by Epinephrine on February 19, 2008 at 12:33 pm

I had little problem with funding, I was in neuroscience; we have pretty decent funding for grad students with good grades, and the research assistantship/teaching assistanships help enormously. I'm not sure how it works at other schools, but it was ~30 dollars an hour to do TA work.

Clearly the answer is to come to Canada and get an NSERC scholarship.

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32. Comment #129926 by chuckgoecke on February 19, 2008 at 7:01 pm

The sad thing is that alien civilizations looking and listening for us here on earth only will have about a 100 year window of time when we are leaking radio energy out into space, basically the 1920's to the 2020's.(Out of a 14 billion year universe life and a 4 billion year earth habitability.) The rate that cellular, satellite, and fiber optic networks are replacing broadcast radio and TV, we will very soon not be leaking much radio energy out into the universe. Likewise we listeners for other civilization have this severe constraint on us, plus the possibility that many if not most other civilizations may not want to be listened to. Maybe they are worried about Borg-like super robot civilizations that assimilate other civilizations that they encounter( ie. find, by listening for), and spread across the universe like an ultra slow virus. Scary!

Maybe we should all observe the WWII poster with a GI holding up his cup and saying, "How about a nice cup of shut the fuck up".

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33. Comment #129930 by tooltroll on February 19, 2008 at 7:18 pm

. . . but when they finally discover one, the sea will be exactly the wrong shade of pink. . .

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34. Comment #129944 by sent2null on February 19, 2008 at 7:48 pm

As I read this article I thought of an old idea I had concerning the evolution of planetary systems. We know that the stuff of which we and our planet are made is composed of mostly heavy elements fused into existence in the cores of the first few generation of stars that went Nova prior to the formation of our system 5 billion years ago.

This tells us that the chemistry of our system is intimately tied to the composition and organization of the previous star clusters and molecular clouds that existed in the region where our system was given birth. It should be possible to calculate probabilities for the percentage composition of various elements based on assumptions of what existed in the previous generation of stars and how those stars gave birth to the "dust" from which latter generation systems like ours formed.

It should be possible to study the many billions of stages of star formation we see (and through spectroscopy are able to make detailed measures of elemental composition) in clusters all over our galaxy to determine a measure of the generated "seed" matter that will result once the stars in the chosen system evolve. We know a great deal about the fusion of heavy elements in star cores, I think enough to come up with estimates of how much stuff is spewed into the surrounding space. By combining these measures with the knowledge of the existing surrounding stars mass and nebular composition we should be able to make a better approximation of the composition of any planets that will form in the vicinity of a selected star in a chosen cluster. Knowing the composition we should also be able to determine the type (rocky or gaseous) of planets most likely to evolve in a given region from the previous elemental composition. It sounds like a mountain of a problem but it seems to me the seeds for a solution lie all around us at various stages of development. It will just take some diligent investigation and correlation to divine out the patterns.

Any astronomers know if any such programs are in progress? It would be really cool if one day we had a planet formation calculator that could be used to evolve systems given an initial state of molecular hydrogen , forming stars and matter from previous generation stars. Maybe some enterprising graduate student reading this will answer the call!

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35. Comment #129948 by teddydef4 on February 19, 2008 at 7:58 pm

Anna,

What school(s) are you looking at?

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36. Comment #129961 by Rational_G on February 19, 2008 at 8:16 pm

1. The anthropic principle doesn't explain anything.

2. SETI searches are worth doing.

3. Planets are ubiquitous.

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37. Comment #130012 by Mitchell Gilks on February 19, 2008 at 10:37 pm

Wam, bam, thank you ma'am! Rational_G! "It's over already?" "Just what are you implying?" "...nothing, nothing at all..."

"I am an automaton nuclear neo-human android, you may call me "A.N.N.A.!". You cannot confuse my programming with your all-female sex orgy, let us kung fu fight!"

I couldn't help myself.

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38. Comment #130044 by Adam Morrison on February 20, 2008 at 12:56 am

Michell;

Classic, just classic

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39. Comment #130100 by KesheR on February 20, 2008 at 4:47 am

Even if the chances are incredibly remote.

Even if some civilization could find us and destroy us.

Even if there are no results for years.

The opportunity to know there are other intelligent beings out there is so important, so dramatic, that it has to be tried.

I RUN SETI.

Repeat with me.

I RUN SETI.

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40. Comment #132479 by chuckgoecke on February 24, 2008 at 8:04 pm

I am all for SETI. I wish they would reinstate federal funding for it. My previous post was just to emphasize that it really is like looking for a needle in a giant haystack. But hopefully, there are lots of needles....

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41. Comment #173148 by logicalbasedreality on April 30, 2008 at 12:37 pm

Lol. I can't wait for the day they find extraterrestial bacteria or other microscopic life.

'Satan just put it there to test our faith'

Yeah but god in his omniscience would have known that but been unable to stop Satan from doing that which negates his all-powerfulness. Its the same all over the universe, I guess :-).

I asked a IDiot when it happens would Jesus be the savior for that planets life as well. He said well they had better accept him as their lord and savior or they wont get into heaven. You had better bet there will be xians clamoring to be the first on a newly formed planet to convert the locals and save them! LOL!

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