by Jenab » Thu 14 Oct 2004, 12:41:55
$this->bbcode_second_pass_quote('mmm', 'I')f Titan is covered in LNG, doesn't that mean that Natural Gas is not a fossil fuel (produced from decaying plant/animal matter)? And if LNG isn't a fossil fuel, doesn't that mean coil and oil are also probably not fossil fuels as well, since they are often not found together?
There is such a thing as primordial
methane, which formed in the interstellar medium prior to the collapse of the gas cloud that became the sun and planets of our solar system.
The universe probably appeared as the result of the required uncertainty in vacuum energy states. There's a physical law called the uncertainty principle that says that the product of changes in energy level and the length of an interval of time cannot exceed a certain (very small) number. What that means is this: while it is permitted for something to add up to zero energy when all its component parts are summed, the distribution of the positives and negatives must remain open to flux.
Hence, even in a "perfect" vacuum, there's always this boiling of energy potentials, as electric and magnetic fields randomly vary within. We don't see this turbulence because it takes place on a quantum scale, much too small for our eyes to notice, and the fluxes tend to cancel each other out by the time you reach the scale of size that we are equipped to deal with.
Our universe might be a result of that boiling: a bubble of spacetime having contents that add up to zero, or almost, which from the outside might pop in-and-out of existence so fast that it wouldn't be noticed, but which from the inside seems to persist because
we adjudge "time" to be a dimension that the universe has in ample measure.
Anyway, the first thing to appear within our universe was a sea of pure radiation, probably having a blackbody distribution, but with a characteristic temperature so high that the peak of that distribution was far off in the high gamma-ray spectrum. Shazam! Let there be light.
Now, when radiation is composed of photons that energetic, what tends to happen is something called pair production. Photons find themselves unstable under Bose-Einstein statistics, so some cosmic gremlin comes along and changes a sign in the denominator of those statistics, so that they click over to Fermi-Dirac statistics, at which time they are no longer photons, but quarks, anti-quarks, electrons, positrons, neutrinos, or anti-neutrinos.
(I'm not all that wise about how pair production actually happens; I just know that it does, so I invented the gremlin to cover my ignorance.)
Of course, there's some early matter-antimatter annihilation, which produces some secondary gamma radiation. But after all is said and done, the universe has a net surplus of matter, in the form of quarks and leptons, to go with the radiation which is now mostly composed of photons under 1 MeV.
(Neutrinos and electrons are among the more important leptons.)
The quarks team up with other quarks and become bonded with the strong nuclear force, forming muons (2-quark particles) and baryons (3-quark particles). Protons are probably the most important of the baryons thus produced. Some of the protons capture electrons and become neutrons, a time reverse of the beta-decay process.
Also, a few protons and neutrons happen to locate each other to form deuterium and helium nuclei.
Now hydrogen is simply a proton. When it has an electron to go with it, it is "neutral hydrogen." Without the electron, it's "ionized hydrogen."
At first, the temperature of the universe is too high for electrons to form stable orbits around protons, so all the matter in the universe is ionized, which means, among other things, that space isn't yet dark, or black. It's white-hot. Everywhere glows.
But as space keeps expanding, the positive energy of the radiation in it must spread over more volume, which brings the temperature down. When the temperature falls under 3000 Kelvin, electrons start clicking into stable energy states around protons, and matter shifts from the plasma state into the un-ionized gaseous state.
Gravity has been working all this time to pry the clouds of plasma, and then gas, into clumps, using the initially small asymmetries in the spatial distribution of material as leverage. The clouds of hydrogen and helium fall into great big clumps, which have internal asymmetries of their own. So the great big clumps fission into smaller clumps, each of which contract under its own gravity, and this process of fission and contraction continues until galaxies and stars are born.
The first stars contain nothing heavier than helium. The big ones of those go through their whole life cycle creating those heavier elements through nucleosynthesis, and finally explode as supernovas. The galaxies meanwhile still contain a fair bit of unaccreted gas in the form of nebulae, and the exploding supernovas send massive waves of heavy-element enriched gas through them. This not only laces those nebulae with carbon, nitrogen, oxygen, and other elements, it also causes a shock-wave compression of the nebula, which might increase the density of the nebula to the point where it can contract under its own gravity into new stars.
The later generations of stars, then, have metals. (Stellar astronomers refer to all elements heavier than helium as "metals," which means they don't speak quite the same language that chemists do.) The planets that form around these later stars also contain stuff like carbon, nitrogen, oxygen, etc.
Now, it often happens inside of nebulae, that the lonely carbon atom will encounter, and shack up with, some number of willing hydrogen atoms. That's how methane forms in interstellar space. More complicated molecules have also been known to form, but methane is among the more common molecules. But as the density of a nebula grows in response to gravitational accretion, say, into a planet like Jupiter or a moon like Titan, it becomes more likely that the lonely carbon atom will get lucky in finding hydrogen atoms to consort with.
That's why there's so much primordial methane in the outer solar system.
But Earth formed too close to the sun for it to keep its
primordial methane. The sun got rid of it by two processes: thermally agitated escape and photochemical dissociation. All the methane on Earth, or anyway, the great preponderance thereof, is the result of chemical reactions that took place later, and most of those reactions are those that produced the other fossil fuels. Methane is a paraffin, the simplest one. The others are ethane, butane, propane, pentane, hexane, heptane, octane...gasoline, kerosene, etc.
Jerry Abbott