Interstellar travel?

[Berzerker]

You're right, thats what it looks like. There's a theory about snowball Earth that says we mostly froze over ~650 mya and sure enough most of the land was at the south pole. I imagine the ice sheet down there was gigantic.

 

[red_elk]

Yes, RNA world hypothesis... read about that a while ago.
These molecules can act both as a catalyst (ribozymes) and as a storage of genetic information.
They are simpler than DNA and require less complex mechanisms to replicate, than proteins.
Good candidate for the first self-replicating structures.

 

[Berzerker]

Okay, at the beginning of the video 3.3 bya the first land mass is tiny. A chunk of Africa and Australia, I assume that craton where the diamond mines are located in SA. But thats a few hundred million years after life appeared. Were there any land masses back then? I dont get the impression land was available, other than maybe some islands. That would mean vents are a more likely breeding ground.

 

[Kaitzilla]

until we find pre-late heavy bombardment life (ie over 4 bya) I'm inclined to believe it was the late heavy bombardment that gave life its start. So why would massive impacts around 4 bya start life but not the impact that gave rise to the Moon?

People don't really know what 4 billion years means.

If I gave someone 1 second to explain all of the evolution that life on Earth went through from 2008 to 2018, and then another 1 second to go over evolution on Earth from 1998 to 2008, we can get through 6000 years of lifes' evolution on Earth during humans' recorded history in about 1 minute.

To get through 4 billion years going back a decade every second, we wouldn't get through all 4 billion years until 3P.M. on February 13th, 2031.
To go back to the Big Bang when the universe was created would take until 10P.M. on March 4th, 2062.

 

[Samson]

In what appears from CFC's point of view perfect timing, a paper has come out (currently only on the pre-print server arxiv.org so not yet peer reviewed) that uses Bayesean maths to try to estimate the probability of intelligent life in our galaxy as having a confidence interval of 53%-99.6% and in the observable universe at 39%-85%. I have not read the paper, and probably could not if I tried. I cannot explain how the upper bound of the confidence interval can be lower for the universe than our galaxy or how you can come up with such numbers. However this is an indication that trying to put such probabilities on in is not such a vain hope as some here indicate.

Pre-print paper here.
Powerpoint presentation by the authors (surprisingly readable) here.

 

[EnglishEdward]

In terms of detecting intelligent life i.e. receiving signals, detecting mega structures; it may be that
the studies definitions are such that the observable universe for their purpose is smaller than the galaxy.

That would explain why the two ranges of percentages are that way round.

 

[Samson]

In terms of detecting intelligent life i.e. receiving signals, detecting mega structures; it may be that
the studies definitions are such that the observable universe for their purpose is smaller than the galaxy.

That would explain why the two ranges of percentages are that way round.

It would. However this graph from the presentation would indicate that is not the case, and it has a higher probability of being alone in the galaxy than the universe.

 

[red_elk]

I cannot explain how the upper bound of the confidence interval can be lower for the universe than our galaxy or how you can come up with such numbers.

The given confidence intervals are for the probability that we are alone, e.g. no other developed civilization exists in our galaxy or observable universe.

 

[Manfred Belheim]

Well, I wasn't trying to conclusively prove it. I'm only saying that there are no evidences that abiogenesis is such an extremely rare event, so that it would make Earth's life unique in all Universe.

Isn't that a bit like insisiting that a coin locked away in a sealed box is most likely heads, because there's no evidence that it's tails?

 

[red_elk]

Isn't that a bit like insisiting that a coin locked away in a sealed box is most likely heads, because there's no evidence that it's tails?

In the absence of evidence, there is a substantial probability that the coin is heads.

 

[uppi]

In what appears from CFC's point of view perfect timing, a paper has come out (currently only on the pre-print server arxiv.org so not yet peer reviewed) that uses Bayesean maths to try to estimate the probability of intelligent life in our galaxy as having a confidence interval of 53%-99.6% and in the observable universe at 39%-85%. I have not read the paper, and probably could not if I tried. I cannot explain how the upper bound of the confidence interval can be lower for the universe than our galaxy or how you can come up with such numbers. However this is an indication that trying to put such probabilities on in is not such a vain hope as some here indicate.

Pre-print paper here.
Powerpoint presentation by the authors (surprisingly readable) here.

I assume no one has clicked on your first link, yet, because it leads to a completely different paper (I think there is a 4 missing at the end). I was wondering how amorphous Nd-Fe alloys are supposed to be connected to the Drake equation until I clicked on the second link.

The numbers you quote aren't the probability bounds for intelligent life in our galaxy / the universe, but the reverse: the bounds for us being alone. That explains why the numbers are higher for our galaxy and the universe.

They get the numbers from all the existing estimates and claim that if you do proper statistics on them, the uncertainty (with 30 orders of magnitude!) is even larger than the distribution on the final values in the literature ("just" 8 orders of magnitude). According to them, it is even more of a vain hope to multiply all these factors and arrive at a realistic estimate after a proper analysis than it seems at first glance.

In addition, they claim that if you take the uncertainties of the factors seriously, you automatically end up with a long-tail distribution. That means that unless you are able to seriously constrain all the factors, you will always end up with a significant probability that we are alone.

 

[Manfred Belheim]

In the absence of evidence, there is a substantial probability that the coin is heads.

Hmm. Well that isn't really the same thing, but also it's not hard to think about how the situation could be set up such that that's not true at all.

 

[red_elk]

Hmm. Well that isn't really the same thing, but also it's not hard to think about how the situation could be set up such that that's not true at all.

We don't know exactly how the situation is set up. If we do, then we have an evidence. Otherwise we cannot discount any possibility.

It's incorrect to say we know 'nothing' about the possibility of life in the Universe. It's true that the information we have now doesn't allow us to make 100% conclusions, but until life is discovered we have range of estimations which are gradually improving in accuracy. The article posted by Samson is one example of scientific approach to this hypothesis.

 

[Manfred Belheim]

Well I haven't read it, but if uppi's summary is accurate then it doesn't sound as though it adds much to the "it's really likely there's life elsewhere" argument.

Anyway my point of contention was with your reasoning that lack of evidence for A somehow implies that B is more likely, despite the fact that there's an exactly equal lack of evidence for B.

 

[red_elk]

Well I haven't read it, but if uppi's summary is accurate then it doesn't sound as though it adds much to the "it's really likely there's life elsewhere" argument.

The article estimates the confidence interval between 15%-61%, for developed intelligent life in observable universe. Which is a significant probability by any means.
Uppi's summary adds details about the shape of distribution and high amount of uncertainties.

Anyway my point of contention was with your reasoning that lack of evidence for A somehow implies that B is more likely

This is not my reasoning, as I explained above.
Lack of evidence for A implies that we can't make conclusion "B is extremely unlikely".

 

[Manfred Belheim]

Still haven't read it, but even the abstract says this:

... we find a substantial probability of there being no other intelligent life in our observable universe, and thus that there should be little surprise when we fail to detect any signs of it. This result dissolves the Fermi paradox, and in doing so removes any need to invoke speculative mechanisms by which civilizations would inevitably fail to have observable effects upon the universe.

 

[red_elk]

Still haven't read it, but even the abstract says this:

Yes, and it's perfectly in line with everything what I've said here.

 

[Manfred Belheim]

Guess we must be in agreement then

 

[Azem.Ocram]

I sincerely believe that hummanity is the only civilization in the galaxy. I also believe that simple life is likely to exist on earth-likes and super-earths.