Another step towards answering the question of life's origins - science

[Elixir]

I saw this on my Edge front page regarding new ideas and work about the start of life on Earth

MSN

“I think that we need more experimental approaches to explore the geochemical context of the planet when life was born.”

My money is on myriad viable pathways, of which only one or a few can endure in the presence of others. The “creation” of life is probably not the miracle; the miracle would be its continuation in any given environment.

 

[Swammerdami]

While re-reading Nick Lane's wonderful book The Vital Question: Why is life the way it is? I was struck by how good his prose is. The following -- which sheds much light on thread topic -- may belong in the "Beautiful Snippets of Text" thread.

Only hydrothermal vents provide the requisite conditions, and only a subset of vents – alkaline hydrothermal vents – match all the conditions needed. But alkaline vents come with both a serious problem and a beautiful answer to the problem. The serious problem is that these vents are rich in hydrogen gas, but hydrogen will not react with CO₂ to form organics. The beautiful answer is that the physical structure of alkaline vents – natural proton gradients across thin semiconducting walls – will (theoretically) drive the formation of organics. And then concentrate them. To my mind, at least, all this makes a great deal of sense. Add to this the fact that all life on earth uses (still uses!) proton gradients across membranes to drive both carbon and energy metabolism, and I’m tempted to cry, with the physicist John Archibald Wheeler, ‘Oh, how could it have been otherwise! How could we all have been so blind for so long!’

Let's calm down and finish. I said that reduction potentials both constrain and open the conditions under which life should evolve. . . .
[Swammi's emphasis]

 

[Elixir]

isn't it true that only a god can smack neutron stars together?

I’ve been told that they’ll smack themselves together if you can get them close enough.

 

[bilby]

isn't it true that only a god can smack neutron stars together?

I’ve been told that they’ll smack themselves together if you can get them close enough.

Anyone who thinks it's difficult to get neutron stars to collide, hasn't grasped the gravity of the situation.

 

[Shadowy Man]

isn't it true that only a god can smack neutron stars together?

I’ve been told that they’ll smack themselves together if you can get them close enough.

Anyone who thinks it's difficult to get neutron stars to collide, hasn't grasped the gravity of the situation.

Given the masses involved, it'll require quite a grasp!

 

[Jokodo]

isn't it true that only a god can smack neutron stars together?

I’ve been told that they’ll smack themselves together if you can get them close enough.

Anyone who thinks it's difficult to get neutron stars to collide, hasn't grasped the gravity of the situation.

I'm sure you know this and are just willing to accept a small inaccuracy for a pun, but other readers may not: getting two dense objects with a small cross-sectional area to smack together in the emptiness of space is surprisingly hard. 99.999999% of the time, they'll circle each other on a hyperbolic path, exchange some momentum, and continue their journeys in different directions than they started out, but with the same relative velocity, never two meet again except maybe half a revulsion around the galactic core later at the other end of the Milky Way.

Even getting them to enter an orbit around each other is hard, and requires a third object to take up the excess momentum. The sun could "catch" a brown dwarf crossing the solar system - but under must plausible scenarios, that would involve ejecting Jupiter at high velocity.

It's a bit easier to get objects to merge that are already in orbit around each other to smack, but it ain't gravity don't the job, its the breaking effect of the gaseous medium that sends them on a slow inward spiral, that over many eons can get small enough for even objects as dense as a neutron star to end up on orbits that are mathematically inside each other's surface.

None of this applies to fuzzy objects like gas clouds and galaxies. Whether neutron stars qualify as such is left as an exercise to the reader.

 

[Bomb#20]

Anyone who thinks it's difficult to get neutron stars to collide, hasn't grasped the gravity of the situation.

I'm sure you know this and are just willing to accept a small inaccuracy for a pun, but other readers may not: getting two dense objects with a small cross-sectional area to smack together in the emptiness of space is surprisingly hard. 99.999999% of the time, they'll circle each other on a hyperbolic path, exchange some momentum, and continue their journeys in different directions than they started out, but with the same relative velocity, never two meet again except maybe half a revulsion around the galactic core later at the other end of the Milky Way.

A circle has no end.[/nerd*]

(* Oh who are we kidding. Nerd is forever.)

 

[Loren Pechtel]

It's a bit easier to get objects to merge that are already in orbit around each other to smack, but it ain't gravity don't the job, its the breaking effect of the gaseous medium that sends them on a slow inward spiral, that over many eons can get small enough for even objects as dense as a neutron star to end up on orbits that are mathematically inside each other's surface.

None of this applies to fuzzy objects like gas clouds and galaxies. Whether neutron stars qualify as such is left as an exercise to the reader.

Neutron stars will eventually smack due to losing energy to gravitational waves. It's a pretty slow process until the end, though. Same problem for supermassive black holes and galactic mergers--once they have ejected all the stars between them shedding the remaining energy takes a long time.

 

[lpetrich]

Biochemists now have software to guess protein folding and so on. When can we expect the carbon atom to be modeled well enough to predict the shapes of amino acids, etc.? I imagine a detailed model which starts from fundamental parameters like the Fine Structure Constant

α = 0.0072973525693.​

Over how broad a range of α would carbon's chemistry be versatile enough to support complex life?

Silicon is sometimes compared to carbon, but the details of their chemistry are very different. Carbon oxidizes to CO₂, the fizz in soda pop. SiO₂ is quartz rock. 6-rings of silicon exist ( Silabenzene#Hexasilabenzene) but their shapes are quite different from carbon rings.

How much would the parameter α need to change before it is Silicon, and not Carbon, which allows the complex chemistry needed for life?

The FSC supplies overall scaling, but is otherwise insignificant. What is really responsible for all the chemical structure that we find is a combination of:

• Electrons have spin 1/2, making them fermions
• Atomic nuclei are much smaller than electrons and much more massive

That first property is what makes electrons stack up in atoms, making electrons' shell structure in atoms, and it also makes chemical bonds involve pairs of electrons. That shell structure also explains ions, atoms with extra or lacking electrons.

One can find atoms' energy scale and size scale by doing simple dimensional analyss.

Kinetic energy = p² / (2*me) where p is the momentum = hbar / r, where r is the size.

Potential energy = e² / r where e is the elementary electric charge and I've folded into its definition sqrt(4*pi*(permittivity)).

Since kinetic energy ~ potential energy, by the virial theorem if nothing else, we have

hbar² / (me * r²) ~ e² / r

One can easily solve for r, giving hbar² / (me * e²) -- the Bohr radius

The energy is me * e⁴ / hbar² -- twice the Rydberg energy

Since the FSC a = e² / (hbar * c) -- c is the speed of light in a vacuum -- this gives us

Size = (hbar/(me*c)) / a -- the first term is the reduced Compton wavelength of the electron

Energy = (me*c²) * a² -- the first term is Albert Einstein's famous equation.

One can continue further with such estimates, finding the vibrational and rotational energies in terms of electronic ones:

E(vib) = sqrt(me/Mn) * E(ele)
E(rot) = (me/Mn) * E(ele)

where Mn is from the masses of the nuclei involved in the vibration or rotation.