
How a star explosion may have shaped life on Earth (2015) - dnetesn
http://oceans.nautil.us/feature/562/the-secret-history-of-the-supernova-at-the-bottom-of-the-sea
======
ferros
The more I read and learn the more I realise how little we know about
everything that surrounds us and existence itself.

It truly is humbling.

~~~
jcims
Start watching the complexity of energy management in a cell or how the immune
system works or how cancer cells implement countermeasures to bypass all of
the evolved mechanisms against it (yet remain viable). It's beyond ridiculous

Honestly I just struggle with the overall statistical likelihood of life
evolving. I've tried to get folks to engage on my thinking here but it never
happens. I don't know where I'm off.

One example. The number of interactions per second in water is roughly the
mean molecular velocity divided by the mean free path times the number of
molecules. For a mole of water (~18g) that's approximately 590 m/s *
1/3.1e-10m * 6.02e23 or ~1.15e36 interactions per second. Per kg of water
that's ~1.15e36 * (1000/18) = ~6.4e37. Given that most chemical reactions
related to the formation of life are going to happen in solution in water,
this seems like a reasonable place to start on this journey.

Expanded across all of the water and entire biomass of the earth (in kg) for 5
billion years, this is 1.15e36/kgs * (1.4e18kg + 6e14kg) * (360024365*5e9)s =
2.5e71 potentially life-forming molecular interactions in water on planet
earth's history. We're just spitballing here so let's square that to account
for any bullshit that I missed.

6.25e142 'interesting' molecular interactions on earth since it was a sphere
of magma.

I know this is broken but just roll with the idea for a second.

Given 6.25e142 molecular interactions total, let's assume that's the upper
bound of base pairs of DNA stacking on each other (reality is obviously many
many many order of magnitudes less). A+C+A+G, then A+C+A+T, then A+C+T+A, etc
etc. Let's further assume that the absolute minimum number of base pairs
required for a critter to reproduce is 1/10 the smallest observed genome. The
smallest i can find is Carsonella ruddi with 160k base pairs. Let's split that
down to 16k base pairs just for shits and giggles and assume that most of it
can be random and still result in a living reproducing organism. The only
constraint i'm going to ask for is that there are one or more critical
sections that need to be reasonably correct for the DNA to be viable.

The question is what is the likelyhood that all of these interactions are
going to create one of those critical sections?

There are four nucleotides that make up dna, commonly labled as A, C, G and T.
The possible combinations of these nucleotides grow exponentially with the
length of the sequence. 4 base pairs have 4^4 combinations, 10 base pairs have
4^10 combinations. etc etc. What if we assume perfectly uniform distribution
of random variations (obviously broken), what's the maximum length of
'critical section' that we can guarantee will get at least one shot at life.

log₄(6.25e140)=237

237 nucleotides is the limit to where our mythical mix master could explore
all possible combinations and any one of those has a 100% chance of being
realized. (Keep in mind that this is individual nucleotides, not genes. A
single gene typically starts at 1000 nucleotides, our 'most simple organism'
Carsonella ruddi has 160,000 base pairs, and the human genome has ~3 billion
base pairs.)

What this tells me is that you cannot have a 'critical section' in ANY gene or
DNA sequence that is more than 237 nucleotides long and attribute the source
of that sequence as some kind of statistical certainty...from there it starts
to become a function of chance. The degree to which it is chance depends on
what kind of sequence you need to find to get life moving. (ANd this is
completely ignoring the fact that DNA is not living, it needs all sorts of
mechanisms around it to actually function) This is all true also if you limit
the scope of your investigation to the planet earth.

If you expand it to all of the atoms across the entire universe assuming it's
one giant blob of water, just expand the middle term from ~1.5e18kg to
1.5e53kg and the length to 15 billion years. You wind up with max critical
section length of 355 nucleotides.

Again i'm sure something is wrong with my thinking. But my mental model is
that we are operating somewhere along an infinite stream of events of
trillions of universes and we are unbelievably special/unique. OR the universe
is much more bizarre than we even remotely understand.

¯\\_(ツ)_/¯

~~~
throwaway_pdp09
The weakness _may_ be down to your assumption that the simplest form of life
then is equivalent to the simplest form of life you personally can find now.

. Life has to do a lot of things now that maybe the first reproducing cells
needn't, like defending itself from other life.

. There may be simpler forms of life that exist currently that we are unaware
of...

. ...or maybe not, because each time it gets created it gets eaten by much
more advanced life around it.

. We don't even know what life really is.

etc. etc. I get the feeling you're perhaps paving the way for a theistic
argument. If you don't believe that god the creator exists, the proof that
life is possible regardless of your stats is all around you.

(None of my arguments are novel)

~~~
jcims
Thanks for the reply. I definitely feel that my idea of where it started is
polluted by where we are now. However, the minimum viable product for
evolution is essentially 'trait inheriting chemical structure' and even the
simplest examples that we have of that today are _incredibly_ complex.

>I get the feeling you're perhaps paving the way for a theistic argument. If
you don't believe that god the creator exists, the proof that life is possible
regardless of your stats is all around you

Nope. It's really not. There's no way for me to prove it, and I'm glad you
said it out loud so it could be addressed, but it's really not. This honestly
came to me out of my career in information security and tangents into
encryption. If you think of those 'critical sections' as passwords or
encryption keys to life, our current thinking just seems to be totally fucked
by impossibly small probabilities.

The place where the ball settles in the saddle for me is panspermia OR that
there is something that we don't quite understand in general about emergent
phenomena that drives 'chance' in a certain direction.

