The first generation stars are the massive short-lived monsters that came about early in the history of the universe, when H and He were the only building blocks around.
The second generation formed amid the ashes of the first gen stars, definitely more elements to work with but we get stars with thousands (to hundreds of thousands) times less metallicity than our own Sun.
Third generation stars tend to be metal rich by definition.
We can't know what we don't know, but, the steady progression of technological
development would eventually lead to a point where the understandings and
hardware required for such efforts are available. We can't speak to the will to employ
these technologies, but the extrapolation is reasonable.
Last edited by Trakar; 2011-Jan-12 at 07:25 PM. Reason: double word correction
Earth’s temperature, size, orbital stability, and the presence of oceans and land
abundant life on Earth from methane and ozone out of thermal equilibrium
intelligent life from the effects of pervasive agriculture, extensive metal working and coal burning
they might be able (from their far more sophisticated understanding of biological and social evolution, and industrial pollutants) to determine our state of technological development.
These are capabilities we will begin to deploy perhaps in this decade, and the full extent of which are conceivable within a century.
For there not to be any deliberate attempts at communication would require monolithic behavior within all the groups within all 100 civilizations. Such attempts would not be expensive for such a civilization. The Arecibo radio telescope in Puerto Rico, has a one megawatt radio transmitter which could be picked up an Arecibo sized receiver at 320 light years. The observatory has a budget of about $10 million per year. I would be pretty surprised if we could not send a considerable more powerful transmission at considerably less cost by 2200.
There might be hundreds of thousands of entities in each of the 100 postulated advanced civilizations that would be capable of spending the equivalent of a few million dollars per year on such a project. It seems most implausible that, amongst these millions of entities, none would send messages, perhaps to all nearby planets that have identified technological civilizations.
There could be innumerable motives for such an undertaking: academic curiosity, altruism, spreading the Good News, sending their obituary, for instance. Some might be delusional and think they are communicating with their ancestors.
Whatever, it seems far likelier that a bunch of these entities would send us a message rather than maintain stony and boring silence. It only takes one.
"The Fermi Paradox: An Approach Based on Percolation Theory" - Geoffrey A. Landis - http://www.geoffreylandis.com/percolation.htp
Stephen Hawking: Why Isn't the Milky Way "Crawling With Self-Designing Mechanical or Biological Life?" - http://www.dailygalaxy.com/my_weblog...ical-life.html
"An instrument-based method to search for extraterrestrial interstellar robotic probes" - http://www.sunstar-solutions.com/sun...BIS-SETV01.pdf
"The search for extraterrestrial intelligence" - http://www.bioinf.uni-leipzig.de/~il...gy_nature5.pdf
Temporal Aspects of the Interaction among the First Galactic Civilizations: The "lnterdict Hypothesis" - http://www.users.globalnet.co.uk/~mfogg/fogg1987.pdf
[table one is of interest - I know it is oft repeated, but this provides a good RoT guide for common considerations of how long galactic colonization takes]
"The Grand Analogy: History of the Idea of Extraterrestrial Life" - http://www.bigear.org/CSMO/HTML/CS05...ll.htm#cs05p02
Not anything that is required reading for further discussion, just some basic background reading/reference considerations for this general thread.
They did not show their work!The analysis is based on two key assumptions. First, it is assumed that interstellar travel is possible, but difficult, and thus that there is a maximum distance over which colonies can be directly established.
Once again, beginning with an assumption of interstellar travel and then proceeding onward. They did not show their work!Once an advanced ETI civilization has overcome certain major technological challenges, like practical interstellar travel, what might the probe missions invovle and what behaviors might be observed?
It amazes me how easily skeptical some people are with regards to abiogenesis (an established occurrence) but then throw that scientific attitude completely out the door when the topic of interstellar travel arises (an unproven possibility).
No, thank you for the links! I find the topic fascinating.Not anything that is required reading for further discussion, just some basic background reading/reference considerations for this general thread.
What we do know is that some of the mater found on earth are not from the solar mass of sol.
Is the chemistry/physics well known as to how stars initially comprised of just Hydrogen and Helium upon their Supernova'd deaths gave rise to new elements who in turn upon their demise gave birth to further new types of metals?
Will 3rd generation stars like Sol (or bigger ones) upon their deaths continue this trend of spawning still further heretofore unknown metals? If so, does this somehow increase the going-forward (yes billions of years downstream) potentiality for life in the universe as the presence of metals increases?
Yes, it might...
Why isn't the Milkyway teaming with life ? or where are the aliens ? Can only be answered by approximation's of facts unknown.
I think the 'best' answer still is... It might be. We have not seen any sign of it yet does NOT suggest its not. Does it ?
Under this circumstance (one galactic civilization), it’s required, for us not to be aware of ETs existence, that they not only do not colonize, but do not visit (even with robotic agents), do not communicate, do not have any visible engineering projects and not enough energy leakage anywhere and anyway so as to be obvious. It also assumes monolithic behavior within the civilization. They would be spread across millions, maybe billions, of worlds, separated by tens of thousands of light years and time, and they would all act the same. That does not seem likely.
Each world could have hundreds of thousands of various types of groups and entities that could spend the equivalent of a few million dollars a year on communication with worlds identified as having a technological civilization. Across the galaxy there could easily be trillions of such entities. And they all act the same. That does not seem likely.
Some such entities might also send visitors—robotic or staffed—from motives of altruism, curiosity, enlightened self-interest, from religious, ideological, philosophical and other enthusiasms
Brane Worlds, the Subanthropic Principle and the Undetecability Conjecture.
Abstract: In the recent article ‘Conflict between anthropic reasoning and observation’ (gr-qc/0303070) Ken D. Olum, using some inflation-based ideas and the anthropic premise that we should be typical among all intelligent observers in the Universe, arrives at the puzzling conclusion that ‘we should find ourselves in a large civilization (of galactic size) where most observers should be, while in fact we do not’. In this note we discuss the intriguing possibility whether we could be in fact immersed in a large civilization without being aware of it. Our conclusion is that this possibility cannot be ruled out provided two conditions are met, that we call the Subanthropic Principle and the Undetectability Conjecture. The Subanthropic Principle states that we are not typical among the intelligent observers from the Universe. Typical civilizations of typical galaxies would be hundreds of thousands, or millions, of years more evolved than ours and, consequently, typical intelligent observers would be orders of magnitude more intelligent than us. The Undetectability Conjecture states that, generically, all advanced civilizations camouflage their planets for security reasons, so that no signal of civilization can be detected by external observers, who would only obtain distorted data for disuasion purposes. These conditions predict also a low probability of success for the SETI project. We also argue that it is brane worlds, and not inflation, what dramatically could aggravate the ‘missing-alien’ problem pointed out first in the fifties by Enrico Fermi.
Where the telescope ends, the microscope begins. Which of the two has the greater view?
What I find strange is the reluctance to consider abiogenesis as fact. Are we unconsciously allowing for a theistic origin of life on Earth, which in turn allows for no natural abiogenesis? Either it happens and is a natural process or it does not and is not.
The difficulties with the Fermi paradox, if one accepts abiogenesis as fact, relate to interstellar travel, mean distances between advanced civilizations, and so forth. If, say, there is only one advanced civilization per galaxy, we may never have experimental proof nor contact, but that does not disprove abiogenesis.
Life's around out there, somewhere.
For each man, according to the measure of his intelligence, must speak what he can speak, and do what he can do. - Alfred, King of Wessex
Calm down, have some dip. -George Carlin
Yes, whether or not we attain proof of advanced ETs, it is clear our universe is naturally geared to produce life, and it likely happened as soon as the right ingredients were available.The difficulties with the Fermi paradox, if one accepts abiogenesis as fact, relate to interstellar travel, mean distances between advanced civilizations, and so forth. If, say, there is only one advanced civilization per galaxy, we may never have experimental proof nor contact, but that does not disprove abiogenesis.
Life's around out there, somewhere.
Where the telescope ends, the microscope begins. Which of the two has the greater view?
(note - it is technically possible for a first gen star to form right now, it just has to form in a region that hasn't picked up the ashes from stellar evolution through the last 13 Billion years or so)
Second Gen stars are much like Third gen stars, in that they come in a variety of sizes and life spans, the primary difference is in proportion of elements heavier than H/He. There is no definitively clear second/third gen dividing line, and this is one reason the Sun is occassionally still listed as a 2nd gen star. (as noted above, second gen is more of a composition issue than a time of formation issue)
We know that our Sun formed about 5 billion years ago, and at that time it was probably among the earliest stars with its level of metals to form (not the earliest, but among the early examples of this type of star). Star metallicity, however, may well be a double edged sword with too little and too much both being potential negatives with regards to the potential for life to arise among their planetary systems.
Being an atheist would still allow the possibility that abiogenesis is very improbable; say the reciprocal of the number of stars in the observable universe. Or even the reciprocal times 10^ -9. Either probability would handily explain the Fermi paradox.
That examples of more than one abiogenesis have not been found on Earth or anywhere else in our solar system suggests that the probability of abiogenesis occurring may not be high.
How is it possible to draw probability conclusions from one example and within a very limited and incomplete theoretical structure?
I was away since Christmas eve until today, so I'm replying to a
post from December 27. I see that others have replied to it, but
I haven't read those replies yet.
You personally might expect to see evidence of intelligent ET
life in many places if it were common, but even you would not
expect to see it "everywhere". You did not say what you
actually meant. You meant that you would expect to see
evidence in many places. I do not share that expectation,
since there is no good reason for it.
have originated elsewhere and have been brought here rather
than originating here. I disagree. There is no reason to think
that the relative commonality of intelligent ET life would make
independent origin and development of life on Earth improbable.
Given that the evidence we do have suggests that life did
independently originate and develop on Earth, we can surmise
that the same has happened elsewhere. We cannot surmise that
its happening elsewhere made it unlikely to happen here.
very quickly, and that human technology has developed to its
current level even more quickly. I do have hope that humans
will be able to communicate with and maybe even travel to
other star systems. I have no idea how long it will take, if it
ever comes about. First contact may have been made today,
and we'll find out all about it in the morning news. Or we might
give up looking and never make contact.
assertion, most of which you know nothing about.
I'll repeat that: It is completely unknown how long a
civilization can last or is likely to last, and completely
unknown what a civilization can accomplish, will accomplish,
or is likely to accomplish during its existence.
sort of evidence that we should have seen if intelligent ET
life is common.
Earth is easy to see from low Earth orbit. From the distance of
the Moon, or farther, radio transmissions are probably the only
detectible evidence of intelligent terrestrial life. At the distance
of Mars, those radio signals are incredibly difficult to detect.
At the distance of Proxima Centauri, there is almost no hope at
all of detecting intelligent life on Earth. Just detecting that the
Earth exists would be an impressive accomplishment.
at all for your expectation.
What evidence would you expect to see? You have given
no indication, which suggests that your expectation is based
also to die off. I think intelligent life is probably quite common in
the Universe and in our Galaxy. I hope that definitive evidence of
it will be found in my lifetime, and I'll do what I can to make that
happen. It certainly won't happen if people stop working on it.
-- Jeff, in Minneapolis
"I find astronomy very interesting, but I wouldn't if I thought we
were just going to sit here and look." -- "Van Rijn"
"The other planets? Well, they just happen to be there, but the
point of rockets is to explore them!" -- Kai Yeves
The gap between what we know is common and what remains unique has been shrinking noticeably over the past few decades.
The Implications of the Early Formation of Life on Earth - http://arxiv.org/PS_cache/arxiv/pdf/...807.4969v1.pdf
The fact that life arose surprisingly early after the formation of the Earth can be used as evidence
for the hypothesis that abiogenesis is easy, and hence supports the conclusion that life is common
in the universe. However, the evidence is not as conclusive as has been claimed. Specifically,
this study has highlighted the fact that knowledge of the early abiogenesis time on Earth is still
compatible with the following hypothesis: that life is extraordinarily rare in the universe, perhaps
even only on Earth, and we observe early abiogenesis due to chance (we’d have to be moderately
lucky, but not obscenely so). This conclusion differs from Lineweaver & Davis (2002) because they
unwittingly made overconfident prior assumptions. Hence, unless there is a direct detection, the
answer to the perennial question “are we alone” remains “nobody knows”.
The energetics of genome complexity - http://www.nature.com/nature/journal...ture09486.html
Memo to all, let's keep the religious part out of this discussion.
The discussion of whether or not there is a theistic bias is completely inappropriate here.
Also, as you cannot know all theists, all general remarks can be insulting to some of them.
All comments made in red are moderator comments. Please, read the rules of the forum here and read the additional rules for ATM, and for conspiracy theories. If you think a post is inappropriate, don't comment on it in thread but report it using the /!\ button in the lower left corner of each message. But most of all, have fun!
New blog 28-07-2013: Summer School Alpbach 2013: "Space Weather: Science, Missions and Systems"
> determine their existence, size and orbital parameters
> infer the existence of oceans (bluer), continents (redder), and even vegetation (plants reflect light more strongly at near-infrared wavelengths than in normal visible light)
> detect out of thermal equilbrium methane, oxygen, ozone and nitric oxide
We may even be able to detect industrial gases and other pollutants, which could, not only reveal the presence of intelligent life, but allow approximations of the technological abilities of such a civilization.
Some of this may have to wait for the next decade, the 2020s. Although cost, completion and capability estimates of incomplete or unbuilt projects are always dubious, it seems likely that many of the goals of outstanding space and astronomical projects will be met by then; especially considering all of the various technologies, funding sources and involvement of many different nations and institutions.
If we look even a short way into the future--say the next century--we should have immensely increased capabilities in identifying the existence and characteristics of extrasolar planets, of detecting life from an analysis of atmospheric gases and other properties of such objects. We may also be able to develop a good grasp of the stage of evolution of such life based on our increasing knowledge of evolutionary biology and social development. We should be able to identify signals of agriculture, metal working and industrial pollutants.
Based on what we have done, expect to do in the near future and should be capable of a bit further into the future, it seems to me that we should, eventually, have very little trouble detecting a technologically advanced civilization out to several hundred light years, if not considerably further.
Last edited by Bobunf; 2011-Jan-14 at 07:15 AM.
This century we may find another abiolgenesis on Earth or elsewhere in out solar system; but I would hardly call that outcome a certainty, and I think the probability declines with time. This century we may hear from ET, but I would hardly call that a certainty. This century we may figure out how abiogenesis works; but I would hardly call that a certainty.
If we don't find another biogenesis in our solar system, that doesn't mean that it didn't occur here or elsewhere. But such lack of evidence will constrain the probabilities.
The other line of evidence is the Fermi paradox. That we've had no contact with ETs doesn't mean they don't exist; but it does constrain the probabilities.
There are weak hints: life started early on Earth, complex organic molecules and extrasolar planets abound; but we haven't seen a second abiogenesis; and we haven't seen any ETs.
In the absence of a theoretical understanding of abiogenesis, how can anyone say abiogenesis is inevitable or certain?
The only way to resolve this issue is to discover an undeniable instance of another abiogenesis. This is why there is so much interest in the biochemistry of Titan and also in the "shadow" evolution recently suggested by the arsenic-based chemistry recently announced by NASA.
Abiogenesis could actually be very common yet still unique within our system. If that is the case, the gap may never be fully closed absent ET contact. I think you and I are in considerable agreement on this point.
For the Fermi Paradox to be real (i.e. a paradox), you are required to accept two independent assumptions... 1) abiogenesis & intelligence are relatively common and 2) either interstellar travel is possible or technological civilizations are extremely long-livedThe other line of evidence is the Fermi paradox. That we've had no contact with ETs doesn't mean they don't exist; but it does constrain the probabilities.
There is reason to believe that 1) is true and 2) is false, thus eliminating the paradox without constraining the probability for abiogenesis.
cogito ergo sum?In the absence of a theoretical understanding of abiogenesis, how can anyone say abiogenesis is inevitable or certain?
The probability for finding evidence of another abiogenesis event on Earth may plausibly be declining, but we have hardly even looked in the rest of the solar system. As far as we can tell, life requires liquid water and we have not looked any of the places with liquid water yet (a very difficult challenge).This century we may find another abiolgenesis on Earth or elsewhere in out solar system; but I would hardly call that outcome a certainty, and I think the probability declines with time.
So far, our only evidence consists of Martian rocks which might have come from places where there used to be liquid water...but this is extremely limited evidence. Consider taking a random rock from Earth--chances are extremely high that it contains no fossils of any sort. So, even if life used to be abundant on Mars we would need to have been lucky to see any fossil evidence of it in our limited Martian samples.
So, we're still at a very early stage in which our probability of finding abiogenesis elsewhere in the Solar System is increasing.
For 2) to be false, two things are required: Interstellar travel must be impossible AND technological civilizations are short-lived (by some definition of short-lived; use your own since you're making the claim).
Thus, you need to provide two arguments--one argument that interstellar travel is impossible and another argument that technological civilizations are short-lived.
(Note that we humans have already sent five spacecraft on interstellar journeys.)