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View Poll Results: Are we alone in the Universe, based on the evidence at hand?
We are almost certainly alone. 1 6.25%
We are probably alone. 2 12.50%
We are probably not alone. 12 75.00%
We are definitely NOT alone. 2 12.50%
All the life is Planet X 3 18.75%
Multiple Choice Poll. Voters: 16. You may not vote on this poll

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  #51  
Old 11-05-2019, 01:27 PM
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Default Re: A Sample of...One

PBS Spacetime is my jam!
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  #52  
Old 05-20-2020, 06:12 PM
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Default Re: A Sample of...One

Dr. David Kipping, a proponent of the rare earth theory, recently published a new paper, "An Objective Bayesian Analysis of Life’s Early Start and Our Late Arrival," that re-examines the odds of abiogenesis and the emergence of intelligent life here on Earth.

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Abstract
Life emerged on Earth within the first quintile of its habitable window, but a technological civilization did not blossom until its last. Efforts to infer the rate of abiogenesis, based on its early emergence, are frustrated by the selection effect that if the evolution of intelligence is a slow process, then life’s early start may simply be a prerequisite to our existence, rather than useful evidence for optimism. In this work, we interpret the chronology of these two events in a Bayesian framework, extending upon previous work by considering that the evolutionary timescale is itself an unknown that needs to be jointly inferred, rather than fiducially set. We further adopt an objective Bayesian approach, such that our results would be agreed upon even by those using wildly different priors for the rates of abiogenesis and evolution—common points of contention for this problem. It is then shown that the earliest microfossil evidence for life indicates that the rate of abiogenesis is at least 2.8 times more likely to be a typically rapid process, rather than a slow one. This modest limiting Bayes factor rises to 8.7 if we accept the more disputed evidence of 13C-depleted zircon deposits [E. A. Bell, P. Boehnke, T. M. Harrison, W. L. Mao, Proc. Natl. Acad. Sci. U.S.A. 112, 14518–14521 (2015)]. For intelligence evolution, it is found that a rare-intelligence scenario is slightly favored at 3:2 betting odds. Thus, if we reran Earth’s clock, one should statistically favor life to frequently reemerge, but intelligence may not be as inevitable.
TLDR; life is 9x more likely than no life, but the ratio of life vs intelligent life is 3:2.

Also TLDR, instead of reading any of this you can just watch the video of Kipping explaining how he arrives at this conclusion. :recline:

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  #53  
Old 05-20-2020, 08:10 PM
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Default Re: A Sample of...One

In my opinion, it's bullshit. He starts by admitting that no one has any idea for the values of fL and fI. Then after building a series of elaborate arguments on this shaky foundation and single data point, he convinces himself that he now has a better idea than before. It's wishful thinking with an elaborate disguise of complex statistics.

I look forward to his next in-depth analysis concerning how many angels can sit on the head of a pin.
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  #54  
Old 05-21-2020, 10:27 AM
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Default Re: A Sample of...One

I don't think the stubble works for him. Maybe he's going for lockdown-chic (and what I assume is a cardigan looks more like a dressing gown), but he's got a good voice and a strong jaw and the Desperate Dan look just lets him down.

Yes, I'm saying he'd be prettier if he just went along with my prejudices.
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Old 05-21-2020, 11:06 AM
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Default Re: A Sample of...One

Wtf is going on at 17:35+? He says the objective Bayesian prior [probability] curves up at the corners and one of the extremes is most likely to be the correct answer. But I didn't see any justification for this - no background detail - so it seems like handwavium "and then a miracle happens". But this is absolutely central to his argument, isn't it?

Nice shirt though.
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  #56  
Old 05-21-2020, 08:55 PM
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Default Re: A Sample of...One

Given we've had a couple of recent threads on SETI-related topics, it might be time to dust off this old thread, which is still pretty relevant today, over fifteen years later.

No reason for it not to be relevant, I suppose: during the last fifteen years we've found that planets orbiting other stars are very common - probably even Earth-sized planets - and we've detected no alien signals. Other than that, no new data to go on: just fresh speculation.
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  #57  
Old 06-06-2020, 01:04 PM
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Default Re: A Sample of...One

Quote:
Originally Posted by ceptimus View Post
In my opinion, it's bullshit.
IMO, that's too strong. I suspect he's wrong (I've only watched the vid, haven't read the paper or worked through the details), but I think the argument sheds some light and is academically interesting.

For me, the interesting and likely good point is that while we may have only one data point, it is not a random data point, and that gives us some more information. This has the fancy name of "the weak anthropic principle", but it's really just a way of saying the sampling strategy is non-random in a particular way.

Where I think he's wrong is that he sneaks in an assumption that all life-bearing and all civilization developing planets are more similar than not, but I don't think this is supportable. Why shouldn't some planets have a much longer habitable window than Earth's? What about planets with vastly different amounts of water on the surface?

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Originally Posted by JoeP View Post
Wtf is going on at 17:35+? He says the objective Bayesian prior [probability] curves up at the corners and one of the extremes is most likely to be the correct answer. But I didn't see any justification for this - no background detail - so it seems like handwavium "and then a miracle happens". But this is absolutely central to his argument, isn't it?
It's funny, the video spends a bit of time talking about this prior, and then he says that you get the same results using a different prior anyway so I'm not sure of the point of all that. So no, it doesn't seem to be central to the kind of analysis he's doing, which is basically to say that, given everything else, certain parameters are more likely to have values at one end of the scale than the other (by a certain factor).

Objective Bayes and the Jeffreys prior are a thing, but AFAIK (which is only a little) they're not universally accepted as the best way to go.
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  #58  
Old 06-06-2020, 08:01 PM
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Default Re: A Sample of...One

I was thinking recently about alien signals and if we’re even looking at the right things. Here on earth I presume if we ever learn how to better harness particles like neutrinos, or other dark-matter like particles that might be out there, that we would be using those instead of light for certain communication, since a neutrino based internet could send signals straight through the earth making the farthest connection the earths diameter instead of half the circumference or more.

Obviously it’s a bit of an alien of the gaps idea, but we are currently hunting the skies without a full understanding what’s fundamentally out there.
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  #59  
Old 06-07-2020, 11:51 PM
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Default Re: A Sample of...One

Also, this just in. The Sun is apparently way calmer than other sun-like stars.

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Magnetic activity on the Sun leads to solar flares, coronal mass ejections, and other space weather that affects Earth. Similar activity on other stars may determine the habitability of any orbiting exoplanets. Reinhold et al. analyzed brightness variations of stars observed with the Kepler and Gaia space telescopes to infer their activity levels (see the Perspective by Santos and Mathur). They found that the Sun was less active than most of the 369 solar-type stars in their sample (those with the most similar physical properties). It remains unclear whether the Sun is permanently less active than other stars of its type or if its activity levels vary over many thousands or millions of years.
Yet another Goldilocks factor, or another aspect of the "stability of the Sun as a star" factor, as to why we are here but extraterrestrials apparently are not.
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