Text 644, 154 rader
Skriven 2004-11-04 11:50:00 av Tomhendricks474 (1:278/230)
Ärende: Re: First Mutation Was Bi
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<< > Secondly no chemical system can adapt to a non cyclical heat source.

A simple replicator doesn't need to adapt. It just survives nicely.
So your point is moot.
 >>

TH
Huh? - how does it magically survive?
Put it on a bunsen burner for 1000 hours and tell me
how good its replicating.

<< Most solar radiation is infrared, and most of the rest is visible
light. UV is a small fraction. IR and visible light don't directly
initiate chemical changes. When an IR or visible light photon strike a
chemical, most of the time it merely jiggles the atoms a bit, causing
them to wobble and/or rotate. This local motion is coupled to other
molecules, whereby the energy is shared. We measure these small random
motions as thermal energy. When enough thermal energy accumulates, a
state change occurs, solid to liquid to gas. Also most chemical
reactions run faster at higher temperatures. But in the absense of
anything to upset the equilibrium chemical mixture, no significant
chemical reactions occur. Evaporation of water from one location and
condensation at another location can cause some chemicals to become
more concentrated in one place than another, but there's nothing for
any of them to react against, so crystallization is the most
interesting thing that ever happens.

But a single UV photon directly breaks a chemical bond, creating an
unstable radical or ion or atom which tends to initiate new chemical
reactions with other chemicals it encounters. Likewise the very high
temperatures present in geothermal vents and in crashed
asteroids/comets cause changes beyond simple state change, gross
disruption of molecules to form active radicals/ions/atoms.

TH
It also destroys just about anything made.

 In
conclusion it isn't the total amount of energy that's important for
this discussion, it's only the amount of UV radiation that reaches the
surface of the ocean and breaks chemical bonds, plus the amount of
chemical bonds broken via geothermal vents and asteroid/comet crashes
(and perhaps lightening strikes also may be significant, I don't know).

TH
No heat alone can denature nucleotides or unfold proteins etc.
But, OK take the sun out and tell me your origin theory?

rem
So you need to get better figures that don't compare the total amount
of energy (mostly IR/vis) but *only* the UV from the Sun, against the
other sources of chemical bond-breaking.

TH
Why fight the obvious Sun to fulfill some very hard
to back up  temporary vent theory in an in hospitable
envionrment?

> The energy source can do one of 3 things - continually get hotter -
> everything burns up

rem
No, it doesn't work like that. As an object gets hotter, it radiates
more energy, and for any given input of energy there's an equilibrium
temperature where radiation equals input so it doesn't get any hotter.

TH
What? If any prebiotic material continually gets
hotter and never stops getting hotter - it'll burn up.
Life chemistry happens in a very narrow range of temperature. Way outside of
that range, and it'll
not work.


> continually get colder, everything shuts down

rem
Same logic. If the initial temperature is hotter than equilibrium, it
radiates more than it receives, so it it cools toward equilibrium.

If it continually cools it shuts down.Life can't
happen at absolute zero.

> randomly gets hotter and colder - no chem system can adapt to random
> actions

Only if the energy input randomly varies. I assume that's what you
mean. But this is moot because adaption isn't needed for a simple
replicator.

TH
Yes it is. The environment will destroy it.
Put your replicator in the middle of the sun
and tell me how it survives.
Put it at absolute zero and tell me how it survives.
The only scenario where it will survive is a
 non random heat cycle at a specific temp
of liquid water 0-100C.

> cyclical heat cycle - the only thing that fits.

rem
A cyclical heat cycle only causes temperature to vary in a cyclic way,
which might produce a back-and-forth state change (evaporation and
condensation). But it doesn't invoke any chemical changes, any bond
breaking,

TH
What? PCR is a heat cycle that breaks bonds.

rem
 unless the temperature gets very very hot, like thousands of
degrees, much hotter than you're talking about from Solar radiation,
but much like geothermal vents (deep inside) and asteroid/comet crashes
(immediately adjacent to crashed material) produce. If you want to
claim that heat change is the only source of "interesting" chemistry
during the pre-biotic times, then you've eliminated the Sun completely
as a cause of abiogenesis. But if you include UV-induced bond-breaking,
the the Sun is back in the game.

> Thermal vents have all kinds of problems associated with them.
'
rem
I'm still waiting for your argument to that claim.

Others make it better than I.
They are very unstable heat cycles that have no
dry aspect to them - most scenarios need
both a wet /dry aspect for polymerization.
Just getting to a replicator - as wonderful
as that is - isn't enough - there are all kinds
of problems with that.
Vents today IMOd are shoreline life adapted
to undersea conditions.
Vents may help produce the necessary monomers,
but they also sterilize the entire ocean in
a very short time - they destroy what they create.







 >>
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