Do you believe in possibility of life in other galaxies?

Nov 18, 2020
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With over a hundred billion galaxies in the universe. It is hard for me to believe that there is not at least one other solar system with life. Especially, when some scientists claim that they have already found some exoplanets that can be like Earth.
 
Mar 4, 2020
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It depends on your view of the probability of life coming or evolving from non-life. It also depends on how you define, and how much faith, you have in many probability studies.

The last I checked, there was zilch probability, that life could have evolved on earth. Hence the comet life seeding theory.

But the thinking changes from decade to decade. It seems to be more of a want, than an answer. Because the ONLY evidence of life elsewhere.......is probability.

Can probability, prove probability?
 
Nov 18, 2020
83
12
55
It depends on your view of the probability of life coming or evolving from non-life. It also depends on how you define, and how much faith, you have in many probability studies.

The last I checked, there was zilch probability, that life could have evolved on earth. Hence the comet life seeding theory.

But the thinking changes from decade to decade. It seems to be more of a want, than an answer. Because the ONLY evidence of life elsewhere.......is probability.

Can probability, prove probability?
I`ve read an article that the Earth-like planet was found. "Earth Like Planet Found orbiting Proxima Centauri" by Al Paslow, published Sept.1, 2016; updated June 12, 2017, Mystic Sciences. Amazing detailed online article with artist illustration. So on some of those exoplanets that have been discovered by scientists some forms of life can live. I guss there is such possibility. Unfortunately we cannot check it(
 
Nov 18, 2020
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I`ve recently watched the video about NASA`s the most expensive telescope. James Webb Space Telescope is considered to be the most technological and most advanced space telescope that is made for discovering exoplanets. I guess such project gives us the possibility to study those exoplanets and possibly it will help us find some forms of life on other planets. https://en.wikipedia.org/wiki/James_Web ... _Telescope
 
Jan 27, 2020
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I`ve recently watched the video about NASA`s the most expensive telescope. James Webb Space Telescope is considered to be the most technological and most advanced space telescope that is made for discovering exoplanets. I guess such project gives us the possibility to study those exoplanets and possibly it will help us find some forms of life on other planets. https://en.wikipedia.org/wiki/James_Web ... _Telescope
I'm not quite sure how the James Webb Telescope will be able to detect life, as it has been designed to detect light in a relatively narrow range in the mid-infrared, at wavelengths ranging from 0.6 micrometers to 28.5 micrometers, for the following reasons:
  • high-redshift objects which have their visible emissions shifted into the infrared
  • cold objects such as debris disks and planets which emit most strongly in the infrared
  • this band is difficult to study from the ground or by existing space telescopes such as Hubble
But trying to assess the possibility of extraterrestrial life, it is unknown how abundant such life is across the universe, or whether such life might be complex or intelligent.

On Earth, the emergence of complex intelligent life required a preceding series of evolutionary transitions such as abiogenesis, eukaryogenesis, and the evolution of sexual reproduction, multicellularity, and intelligence itself. Some of these transitions may be seen as extraordinarily improbable, even in conducive environments. The emergence of intelligent life late in Earth's lifetime is thought to be evidence for a handful of rare evolutionary transitions, but the timing of other evolutionary transitions in the fossil record is yet to be analyzed in a similar framework. Using a simplified Bayesian model* that combines uninformative priors and the timing of evolutionary transitions, we demonstrate that expected evolutionary transition times likely exceed the lifetime of Earth, perhaps by many orders of magnitude.

The original argument, suggested by Brandon Carter, concerns the idea that intelligent life in the Universe is exceptionally rare, assuming that intelligent life elsewhere requires analogous evolutionary transitions. Arriving at the opposite conclusion would require exceptionally conservative priors, evidence for much earlier transitions, multiple instances of transitions, or an alternative model that can explain why evolutionary transitions took hundreds of millions of years without appealing to rare chance events. Although the model is simple, it provides an initial basis for evaluating how varying biological assumptions and fossil record data impact the probability of evolving intelligent life, and also provides a number of testable predictions, such as that some biological paradoxes will remain unresolved and that planets orbiting M dwarf stars are uninhabitable.

One of the oldest arguments against SETI is the biological contingency argument (Simpson, 1964): the evolution of anything similar to humans has a minuscule probability since biological evolution is dominated by contingency, is radically open-ended, and has no determinism or tendency toward intelligence. Even in similar environments, the chance of getting “humanoids” is minimal, and most environments will be vastly different. This is the same argument used by Mayr in his debate with Sagan: out of the approximately 50 billion species on Earth, only humans evolved intelligence, suggesting a low probability (Mayr, 1995a, 1995b, 1995c).

Carl Sagan (1995) countered by noting that if there are enough possible pathways, even individually very unlikely paths can in sum give a high probability of an intelligent outcome. He also noted that extrapolating from our case is either valid, and we should expect Earth to be an average sample, or it is improper to extrapolate, in which case Mayr's argument fails. While the biological contingency argument can be attacked in other ways, for example, by emphasizing convergent evolution (Puccetti, 1968; Morris, 2003), and supported by noting the lack of convergent evolution toward human-like intelligence in the fossil record (Lineweaver, 2009), the key issue is how representative the Earth's biosphere history is (Rospars, 2013).

Brandon Carter proposed a simple model of evolutionary transitions to describe the process of intelligent life emerging. The model proposes that intelligent life requires n “critical steps,” each of which occurs at some rate λ. He further stipulates that λ−1 > τ⊙, so that the probability per unit time of the critical step is low enough that the time it takes for each critical step will typically exceed the lifetime of the star. A number of interesting properties follow from this model. First, the probability that the final transition occurs at time t is proportional to tn, so that the final critical step is likely to occur toward the end of habitable time remaining. Second, the amount of time remaining will be roughly equal to τ⊙/(n + 1), allowing one to estimate the number of critical steps that occurred in Earth's evolutionary history simply by knowing the amount of time left in Earth's habitable lifetime.

When Carter originally proposed the model, it was thought that the biosphere could last for another 4 billion years, which in turn suggested that there were likely only one or two critical steps in our evolutionary history. Subsequent improvements in climate models led to additional research that suggested that the time remaining is substantially shorter, on the order of 1 billion years (Caldeira and Kasting, 1992). A number of researchers have returned to Carter's critical step model and re-estimated the number of critical steps predicted by the remaining lifetime of the biosphere. Watson (2008) found that the best fit was with four critical steps, while Carter (2008) suggested between five and six. Waltham (2017) went further to demonstrate that models up to 12 critical steps still fall within a 95% confidence interval. Using the Carter model without further hard steps [e.g., just abiogenesis, as in Lineweaver et al. (2002) and Spiegel and Turner (2012)] produces significantly different estimates from including hard steps (Flambaum, 2003). The hard step model can also be combined with estimates of the window length (Lingam and Loeb, 2019), or even possible early windows for abiogenesis that later close (Lineweaver and Davis, 2003).

There are a number of reasons why the probability of an evolutionary transition could change over time. Perhaps most importantly, some evolutionary transitions may have required high oxygen concentrations as a source of energy, and oxygen concentrations have changed dramatically over Earth's history (Holland, 2006). The fact that oxygen concentrations have became high enough to support humans only in the past 800 Myr or so has led to some speculation that a planetary oxygenation time is the primary rate-limiting step to intelligent life (Catling et al., 2005). Relatedly, complex life on land requires shielding from ultraviolet radiation, and the emergence of an ozone layer has also been hypothesized to be a rate-limiting step that is correlated with stellar evolution, undermining Carter's original argument (Livio, 1999).

To test this, we adjust our model so that the transition rates change over time. The most dramatic example of this is a model in which the final evolutionary transition to intelligent life has a probability of zero until vertebrates on land emerge (340 million years ago), and that transition has probability zero until Phanerozoic oxygen concentrations are reached (800 million years ago). This model essentially tells us that these transitions occurred fairly rapidly once oxygen concentrations were high enough, and the results show a much larger peak around fast rates, suggesting a higher probability of intelligent life emerging in the right conditions. However, even these faster transition times are not enough to exclude extremely slow rates. Overall, accounting for a changing environment in terms of oxygen concentrations does not seem to be sufficient to overturn our key results.

after oxygenation.jpg

Posterior distribution if we assume two transitions that were made possible only after high oxygenation levels. Given the late oxygenation of Earth's atmosphere, these transition times are short, resulting in higher posterior probability on faster rates. However, arbitrarily slow rates are still not excluded. (Bottom) Posterior distribution if we adopt the self-indication assumption, and weight all parameter combinations by their probability of obtaining intelligent life. Only parameters that are consistent with intelligent life are assigned high probability, and extremely slow rates are ruled out entirely. Color images are available online.

It took approximately 4.5 billion years for a series of evolutionary transitions resulting in intelligent life to unfold on Earth. In another billion years, the increasing luminosity of the Sun will make Earth uninhabitable for complex life. Intelligence therefore emerged late in Earth's lifetime. Together with the dispersed timing of key evolutionary transitions and plausible priors, one can conclude that the expected transition times likely exceed the lifetime of Earth, perhaps by many orders of magnitude. In turn, this suggests that intelligent life is likely to be exceptionally rare. Arriving at an alternative conclusion would require either exceptionally conservative priors, finding additional instances of evolutionary transitions, or adopting an alternative model that can explain why evolutionary transitions took so long on Earth without appealing to rare stochastic occurrences. There are a number of other testable predictions, including that M dwarf stars are uninhabitable, that many biological paradoxes will remain unsolved without allowing for extremely unlikely events, and that, counterintuitively, we might be slightly more likely to find simple life on Mars.

We can conclude that intelligent life is exceptionally rare and that we may possibly be the only intelligent civilization within the observable universe, so long as we assume that intelligent life elsewhere requires similar evolutionary transitions. Although this may seem like a large assumption, there are good reasons to believe that many evolutionary transitions have universal properties (Levin et al., 2017). It also follows if we reason that our civilization is typical. If there were substantially easier evolutionary pathways to intelligent life that did not require such evolutionary transitions, we should expect to observe this easier evolutionary history instead. Although it is hard to show beyond doubt the absence of extraterrestrial intelligence, so far all of our astronomical data are consistent with being alone (Tipler, 1980).

* Bayesian statistics is a particular approach to applying probability to statistical problems. It provides us with mathematical tools to update our beliefs about random events in light of seeing new data or evidence about those events.

In particular Bayesian inference interprets probability as a measure of believability or confidence that an individual may possess about the occurance of a particular event.

We may have a prior belief about an event, but our beliefs are likely to change when new evidence is brought to light. Bayesian statistics gives us a solid mathematical means of incorporating our prior beliefs, and evidence, to produce new posterior beliefs.
Bayesian statistics provides us with mathematical tools to rationally update our subjective beliefs in light of new data or evidence.
This is in contrast to another form of statistical inference, known as classical or frequentist statistics, which assumes that probabilities are the frequency of particular random events occuring in a long run of repeated trials.

A Bayesian analysis of transition times

The objective is to estimate evolutionary transition rates, given how long it took to complete each transition. This can be found by using a Bayesian update as follows:



where t is the sequence of transition times t1,…,tn, β denotes our β parameters, and P(β) is a prior density over the expected transition time parameters. The term P(t|β), the probability of observing transition times t given the parameters β, is equivalent to the likelihood function as follows:


However, this likelihood function needs to be renormalized to account for the fact that we can only observe these data if all evolutionary transitions occurred before the end of Earth's lifetime. Accounting for this sample bias can be done by dividing the likelihood L(β|t) by the probability that all transitions occurred within the lifetime of Earth. If L is the lifetime of Earth, then our adjusted likelihood function is as follows:



where
is the probability that all transitions occur before the end of Earth's lifetime.

See: https://dailygalaxy.com/2021/03/the-aliens-before-us-we-are-not-the-first-technological-civilization-or-are-we/#utm_source=rss&utm_medium=rss&utm_campaign=the-aliens-before-us-we-are-not-the-first-technological-civilization-or-are-we

See: https://www.liebertpub.com/doi/10.1089/ast.2019.2149

See: https://www.quantstart.com/articles/Bayesian-Statistics-A-Beginners-Guide/

See: https://www.mathworks.com/help/stats/bayesian-analysis-for-a-logistic-regression-model.html;jsessionid=651855aa7c4c808bdf0975efb713

We have come a long way from Frank Drake's original equation on the probability of extraterrestrial intelligence. Which is the following:

{\displaystyle N=R_{*}\cdot f_{\mathrm {p} }\cdot n_{\mathrm {e} }\cdot f_{\mathrm {l} }\cdot f_{\mathrm {i} }\cdot f_{\mathrm {c} }\cdot L}

where:

N = the number of civilizations in our galaxy with which communication might be possible (i.e. which are on our current and past light cone) and where:

R∗ = the average rate of star formation in our galaxy
fp = the fraction of those stars that have planets
ne = the average number of planets that can potentially support life per star that has planets
fl = the fraction of planets that could support life that actually develop life at some point
fi = the fraction of planets with life that actually go on to develop intelligent life (civilizations)
fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L = the length of time for which such civilizations release detectable signals into space

See: https://www.seti.org/drake-equation-index

andromeda m31.jpg

The Andromeda Galaxy. Image credit: Ivan Bok / CC BY 4.0.

When we look up in the night sky and the Andromeda Galaxy, M31 or NGC 224, swims into view in our field glasses, will someone on a planet in one of the habitable zones orbiting a stable G 2 star like our sun be looking back at the Milky Way, or whatever they call our home, wondering the same thing? Will they also have a forum where they can question the many possible pathways life has taken from RNA to intelligence contemplating the cosmos? Or are we, as I fear and they might also, alone.

Hartmann352
 
Mar 4, 2020
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I`ve recently watched the video about NASA`s the most expensive telescope. James Webb Space Telescope is considered to be the most technological and most advanced space telescope that is made for discovering exoplanets. I guess such project gives us the possibility to study those exoplanets and possibly it will help us find some forms of life on other planets. https://en.wikipedia.org/wiki/James_Web ... _Telescope

I can't wait til Webb gets operational. I predict it will confirm my earlier predictions. The farther we look, the denser it gets.
 
Nov 18, 2020
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NASA`s the most expensive telescope James Webb Space Telescope will be able to detact forms of life on some of exoplanets but still, it give us a hint at probably some planets that can have life
 
Apr 5, 2021
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At the present time we have absolutely no evidence of life anywhere else except on the Earth. So if we use evidence as our criteria then I'd have to say 'No'. Using statistics and probability of billions and billions of galaxies, containing billions and billions of stars, that contain billions and billions of planets is just, conjecture. But then your question did ask, do you 'believe in the possibility' of life in other galaxies, which I would have to then answer 'Yes', there is always the 'possibility' of life in a different galaxy. The conundrum is a religious person could counter there is as much evidence for an Almighty God as there is for alien life. Both involve a belief system.

I was answering the question posed "Did I Believe There Was Life In Other Galaxies" My analogy to God was just an analogy, and was not meant to be a referendum on religion or does God exist. Many highly intelligent people believe there is intelligent life 'out there', yet those same people deny the existence of God even though the evidence for both is the same., or some people could legitimately argue maybe even a bit stronger for God because there is varied life here. When evidence for 'life out there' is cited, it's always cited as a statistical and probability of so many galaxies x so many stars x so many planets must = life. I don't agree that that's evidence, it's just conjecture! As for believing in God, I have found most people are taught this concept as children, and not a belief they come to by and in of themselves thru judging the evidence. Again, the thread was "Did I Believe There Was Life In Other Galaxies".

With over a hundred billion galaxies in the universe. It is hard for me to believe that there is not at least one other solar system with life. Especially, when some scientists claim that they have already found some exoplanets that can be like Earth.
bearnard,
Your belief seems to be the majority belief and for the reason you stated, yet it's still just statistical and probability, not evidence. just conjecture.
 
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Nov 18, 2020
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bearnard,
Your belief seems to be the majority belief and for the reason you stated, yet it's still just statistical and probability, not evidence. just conjecture.
Unfortunately, I cannot show you any evidance, of this theory. Talking about life on the exoplanets that can be Earth-alike it`s just a conjecture. These planets are too far and we don`t know it for sure the only think we can do is presume and make some hypothesis.
 

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