Widdekind

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Planetary Mass Growth Rates, in Proto-Planetary Disks, are calculated to be (C.A.Scharf. Extra-Solar Planets & Astrobiology, pg. 89): [math]\frac{dM}{dt} = \pi \; R^{2} \left(1 + \left( \frac{v_{esc}}{v_{rel}} \right)^{2} \right) \; \rho_{disk} \; v[/math] And (ibid., pg. 102): [math]\rho_{disk} \; v \approx \sigma_{disk} \; \omega[/math] where: [math]\sigma_{disk} \approx 1700 \; \left( \frac{D}{1 AU} \right)^{3/2} \; g \; cm^{-2}[/math] We assume that the average Relative Impact Velocity (vrel) is equal to the Keplerian Disk Velocity (v)*. * This can be verified, by assuming that all potential Impactors possess, at the beginning of their planet-ward trajectories, the Keplerian Disk Velocity at that Orbital Distance; and, that said potential Impactors impinge upon the Proto-Planet from all directions equally. Then, by integrating over Velocity Space, the Average Relative Velocity turns out to be just the Keplerian Disk Velocity. We may now estimate the Planetary Formation Time-Scales: [math]\tau \equiv \frac{M}{\frac{dM}{dt}}[/math] for the Planets & Dwarf Planets* in our Solar System. * http://en.wikipedia.org/wiki/Dwarf_planet RESULTS: Planet Formation Time-Scales are plotted against Planet Orbital Distances in the attached figure. We find that: Terrestrial Planets -- formed over hundreds of thousands of years Gas Giants -- formed over tens of millions of years Ice Giants -- formed over hundreds of millions of years Kuiper Belt Objects -- formed over billions of years In particular, please ponder the pronounced "dips" corresponding to both the Asteroid- & Kuiper- Belts. This may imply, that the Giant Planets "stole" material from adjacent disk regions, thereby "strangling" Planetary Growths there. Note, too, that the Outer Kuiper Belt Dwarf Planet Eris, with an estimated Planetary Formation Time-Scale exceeding the age of the Solar System, may still be (albeit slowly) accumulating material through collissions. ANALYSIS: The Ice Giants, being depleted in Hydrogen & Helium compared to the Gas Giants, are thought to have formed after the Sun's Solar Wind blasted out the Lighter Elements from the Planetary Disk (citation needed). That "sweeping out" happened when the Solar System was tens of millions of years old*. This is completely consistent with the above results, which indicate that the Ice Giants took hundreds of millions of years to form. * http://www.scienceforums.net/forum/showthread.php?t=40703 The roughly-linear main trend indicated has a slope of roughly 5/2, indicating that [math]\tau \propto D^{5/2}[/math].

There's an important "common" word, shared by both those statements. Please explain to me, how you conclude that they are "importantly" different. I would say, that there is a significant "possibility", not "probability". The very word "probable" / "probably" connotes a likelihood in excess of 50%. Such a claim exceeds the limits of present primitive observations, which can only "hint" & "suggest". But, present observations are completely consistent w/ abundant Life, making the possibility worthy of serious consideration. That's all I said -- "Life is likely to be likely". All the "hints" of which we're aware "suggest" that Life is likely to be likely. That's not an opinion, but a promising possibility suggested by present observations, to anybody w/ an open mind. Adhering stringently to a "Rare Earth" hypothesis, in the face of present observations which (weakly) favor the converse, is a (mildly) pre-judged position. ANALOGY: After one inning (or even 1/2 inning), Life is leading Rare Earth 1-0. So, if you had to bet, you'd (barely) prefer Life. That's all I said. To quote Br. Guy Consolmagno, SJ (Intelligent Life in the Universe -- Catholic belief & the search for extra-terrestrial Intelligent Life), "we don't know, we don't know, we don't know, we don't know" (which words apply both to Alien Life & Alien Intelligent Life). But, it's completely possible, so there's no reason to a priori prefer Rare Earth. That seems be a source of some concern, for other people posting about this important topic. It seems that there is some sort of preference for the position, "bah humbug, we Humans are all there is, in all the Cosmos" (my words). Hypothetically, that position could be the case. It could be correct. But, it could also be incorrect, and present primitive observations, which are witnessing repeated "hints" & "suggestions" for frequent Life, tend to imply the opposite position. ADDENDUM: Just to be blunt, it is my opinion, that if I could get people drunk on a cocktail of Vodka & Truth-serum, I could quickly get them to say, "bah humbug, we Humans have the whole entire complete Cosmos to ourselves, there's nothing doing anywhere else, never has been, never will be, we Humans are the pinnacle of all Creation, somebody has to be Tops and it just so happens to be my species". It is also my opinion -- as I am suspicious of such self-spoken beliefs -- that, as according to Folk Wisdom, "there's always a bigger fish". These are my opinions regarding Intelligent Life, which are only opinions, b/c I cannot conclusively answer Fermi's Paradox (if they [Alien Intelligences & Civilizations] are everywhere, where are they?). But, for basic primitive microbial-caliber Life-forms, I can graduate from "opinions" to "possibilities" based upon "hints & suggestions" of actual observations. Everybody posting so far, seems to mutually agree, that Intelligent Life "should" be less frequent than more primitive types of Life. That, then, seems to be a common ground which everybody here can accept.

Thanks for the reference ! GENERAL QUESTION: If Pulsars can sport "secondary planets" (born post-explosion), have Exoplanets similarly been seen orbiting White Dwarves ??

I only pursued the "semi-Relativistic" scenario some more, "for fun", "to see what happened". Would you (DH) please explain how GR can account for Martin's observation, that the "GPE" gained by particles sinking into Gravity Wells can be radiated away ?? For, if "GPE" is fictitious, akin to Coriolis Energy, then, how could GR account for a particle being able to produce Light Energy as it nears other massive bodies ?? Where could that Radiated energy come from, if not from the fictitious GPE ?? (Thanks again in advance.)

I never said that. I said, "all the evidence available, at present, is completely consistent w/ Life being abundant". That's all I said, nothing more. So, Life could be inevitable & frequent... and, if it were inevitable & frequent... then things would look exactly like they do look ("the raw materials for Life are abundant"). Again, the available evidence is completely consistent w/ Life being abundant. Again again, that's all I said. Who's assigning specific probabilities ? All I said was, "if Life was frequent across the Cosmos, then the first few primitive observations to appear would be Life on Earth, possible Life on Mars, & copious quantities of Organics across the Cosmos". This is precisely what we do see, completely consistent w/ Life being common across the Cosmos. Er go, in the absence of any understanding of Abiogenesis as you said, we have no A Priori reason to prefer "Life-Phobic" positions. For example, our primitive & puny present comprehension of our position is completely consistent with their being Microbial Life, in at least trace amounts, on every single planet in the whole Universe. Even the Hot Jupiter Exoplanets could support some sort of Extremophiles in their Atmospheres -- we don't know. I mention this example, b/c it's equally consistent with their being no Microbial Life, on any planet in the Universe, beyond Earth. So, see what I'm saying ? Even so, in loose language limited by keyboard & ASCII, our presently-known Data Set looks like this: Life, Life?, Life???, ?????????????????????????????????????????????????????????????????????????????????? All I'm saying, is that is completely consistent with an "Objective Truth" of: Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life... And, it is slightly, but importantly (you agree, yes?) more consistent with all that Life, than the diametrically opposite "Objective Truth" of: barren world, barren world, barren world, barren world, barren world, barren world, barren world, barren world, barren world, barren world... SUMMARY: Completely Barren Cosmos Hypothesis: barren world, barren world, barren world, barren world, barren world, barren world, barren world, barren world, barren world, barren world... Life-is-Everywhere Hypothesis: Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life, Life... Primitive Present Observations: Life, Life?, Life???, ?????????????????????????????????????????????????????????????????????????????????? CONCLUSION: We can already exclude the Completely Barren Cosmos Hypothesis. We cannot yet exclude the Life-is-Everywhere Hypothesis. Present Observations infinitesimally favor Life being everywhere (or at least quite common).

For a power-law IMF, the you must increase the exponent [math]\alpha[math] above about 4.5, before you start getting M-L Ratios of order 100-1. Note, in particular, that you must increase the IMF exponent above four (4), from the Luminosity-Mass estimate (L* ~ M*4). Without doing so, although the bigger brighter stars are less frequent (M*-2.3), they still produce much more radiation (M*2.3 x M*+4 = M*+1.7). Thus, in sum, you get such huge quantities of radiation, even from a few such stars, that it depresses the M-L Ratio. Only if bigger & brighter stars were incredibly infrequent ([math]\alpha[/math] ~ 4.5+), would even their incredible brilliances be offset by so many smaller dimmer stars as to darken the whole population.

I deny the accuracy of that assertion. We can do better than merely "one local observation"... albeit, barely better. For, we can see Life on Earth... possible Life on Mars... and copious quantities of Organic Chemicals across the Galaxy. CONCLUSION: I would agree, that a "completely primitive" Cave Man, looking out across Ice Age Europe, and saying, "Man, I'm convinced there's Life across the Cosmos", actually would be "extrapolating from one local observation to the whole Universe". But I deny that that is what Mankind is doing today, having, as we do, partial information, from across the Cosmos, all of which could be construed as completely consistent, with Life being abundant across the Cosmos. Present data is doesn't settle the issue, but it hints & suggests more strongly for frequent Life, as for its miraculous rarity (which would, incidentally, violate the Copernican Principal). Merged post follows: Consecutive posts merged According to NASA, Thus, brashly applying these statistics to Mars, all its Methane could quite conceivably come from Life. Why is the "simplest" explanation a non-Biological one? What is so "complicated" about "hey, man, Martian microbes make Methane" ? Is not there some sort of preconceived "Life-phobia" in such assertions ? W/o being flippant, I see it, as an assumption, that admittedly more complex Bio-Chemical Processes must be more rare. For, as afore-cited, on Earth, the exact converse is true -- the more complex Bio-Chemical Processes produce most of the Methane. Therefore, from my current understanding, I deny the assumed equivalence of "Complexity <=> Rarity".

(Thanks DH for the fuller, Relativistic, explanation.) Brashly combining Newton & Einstein again, would deny the existence of Black Holes. For, from our Escape Velocity Equation, Relativistically revised, we have that: [math]KE = -U[/math] [math]\left( \gamma - 1\right) \; m \; c^{2} = \frac{G \; M}{R}[/math] And, the LHS of that equation is unbounded. Thus, for any positive & finite Mass & Radius, you can find some finite Relative Velocity ([math]0 \leq \beta \leq 1[/math]), such that your KE exceeds your GPE. CONCLUSION (?!?): Sufficiently relativistically-fast particles can always plow up out of any Gravity Well. Only the sufficiently slower particles would be bound back to the Gravitating Body. Likewise, Light could be claimed to Gravitate, by Mass-Energy Equivalence: [math]F_{g} = - \frac{G \; M \; \left(\frac{h \; \nu}{c^{2}}\right) }{R^{2}}[/math] However, for Light, there would still be some sort of Black Hole criterion, requiring: [math]h \; \nu > \frac{G \; M \; \left(\frac{h \; \nu}{c^{2}}\right)}{R}[/math] [math] 1 > \frac{G \; M}{c^{2} \; R}[/math] which would seem to make the "Schwarzschild Radius" half of its Relativistic value (being the same radius, at which a massive body's GPE exceeds its RME-eq., as per previous posts).

According to the Science News article I cited: According to a diagram from the NASA article I cited, the maximum Magnetic Field Strength the MGS detected was 1200 nT (roughly 4% [math]B_{\oplus}[/math]). CONCLUSION (?): While Mars' Remnant Magnetism is much weaker than Earth's Dynamo-driven Planetary Magnetic Field, it's still much greater than Earth's own Remnant Magnetism. Does this imply, that Earth's Planetary Magnetic Field inhibits Crustal Magnetism upon this planet ?

Mars' Planetary Magnetic Dynamo, generated by Core Convection, apparently dissipated by about 3.8 billion years ago: And, the collapse of Core Convection is likely linked to the collapse of Plate Tectonics (from Mantle Convection), at about the same time: Thus, on Mars, all Convection Currents completely stopped by about 3.8 billion years ago, when Mars was merely ~3/4ths of a billion years old. REVISION of THEORY: Mars being some ~60 times less Convective than Earth (Ra ~ 0.016), Convection-driven processes, and in particular Plate Tectonics, stopped on Mars much sooner than upon this planet. To wit, the Martian Mantle did once Convect, but only in the deep past. REFERENCES: http://www.nasa.gov/centers/goddard/news/topstory/2005/mgs_plates.html http://www.sciencenews.org/sn_arc99/5_1_99/bob2.htm

That's true, and those Chemical Properties determine specific details, like Melting Points & Heats of Fusion. However, I'm only speaking in generalities -- water is "molten ice", much as magma is "molten rock". And, icy worlds will have "molten ice", much as rocky worlds will have "molten rock". NOTE: From the above figure, you can estimate the size of Uranus & Neptune's Rock-Ice Cores, by simply projecting them, straight down, onto the Rock-Ice Curve. That amounts to keeping the mass constant, but reducing the radius. This is a "zeroth order" approximation, implicitly assuming that the atmosphere doesn't mass much. Visually, it looks like both Uranus & Neptune's cores are roughly 1/2 [math]R_{\oplus}[/math] smaller in radius that the whole planets. Since both of these "hidden planets" are quite big (~ 10 [math]M_{\oplus}[/math], ~ 3 [math]R_{\oplus}[/math]), perhaps they are still Geologically Active, deep beneath their thick protective Green House Atmospheres. Perhaps they still undergo "Rock-Ice Volcanism", and the like. Perhaps they could be used to study, and model, Geological Activity on Terrestrial-type planets too.

Wow. How does GR explain the infalling particle's increased energy, [math]\gamma m c^{2}[/math] ? Where does the KE come from ? Merged post follows: Consecutive posts merged That's true. I was only making an Order-of-Magnitude estimate, since I suspected that something was amiss, w.r.t. GR vs. Newtonian.

That's not fair -- we can actually observe 6 billion humans, in enough detail, to disprove that claim. The fact is this -- everywhere we've looked, to the maximum of the detail our primitive detectors, we have observed Life (Earth), possible Life (Mars), and the necessary pre-cursors to Life (ISM, GMCs). A better revision of your "beard analogy" would be this: You're near-sighted, 20/400... You know you've got a beard... And everywhere you look around your room, your blurry vision sees dark splotchy shadows on peoples' faces precisely where beards would be if they wore them. Does that guarantee that everybody in that room has a beard? No. But it's perfectly consistent w/ that possibility -- that possibility, that everybody there has beards, is not flagrantly false. And, here's a counter-example -- "The Moon is made of Cheese". The obvious rebuttle is, "The Moon's density is completely incompatible w/ that". That is a fair & balanced example, of something, that is completely & blatantly & flagrantly false. But, that is absolutely dis-similar from a "Blurry Vision & Beards" situation, which is what Mankind currently faces, w/ his primitive detection equipment, & limited lack of data. We've excavated 1% of the archaeological site... and, so far, all the data is consistent w/ a really big building. "The jury's still out, but it looks promising" -- fair & balanced summary of situation

OBSERVATION: The Biomass of various living species decreases w/ increasing species Complexity & Intelligence. For example, on Earth, there is one Civilized species (H. sapiens), several reasonably intelligent species (Chimpanzees, Dolphins, Octopuses, Squid), many cunning species (Wolves, Crows, Ravens, Elephants, Lions, etc.), and so on, until ultimately there is more Biomass in microbes than all other Earth Life-forms combined. And, surely (?), there is more mass in non-living Organic Chemicals, than Organic Chemicals in living creatures. CONCLUSION: If we lived in a very fertile Universe, supporting Life across the Cosmos, the most basic observable "footprint" of that fact, apparent even to our present primitive detection capacities, would be copious quantities of Organic Chemicals distributed liberally & ubiquitously across the Cosmos. This is exactly what we observe. Thus, although, at present, our data is very limited -- Complex Life is known on 1 of 1 intensely studied planets*, and basic Organic Chemicals are blatantly apparent across the Cosmos -- everything we know is consistent with our Universe being very fertile, supporting an abundance of Life. * Venus may still support microbes up in its Sulphuric Acid clouds, as survivors from its long-evaporated oceans (T. Haines & C. Riley. (BBC) Space Odyssey: Voyage to the Planets ; National Geographic Channel Naked Science -- Deadliest Planets (TV)). And, on Earth, there is more Biomass of microbes in the deep subsurface, than Biomass of all Life on the surface (Discovery Channel Inside the Earth (TV)), implying that Mars, too, may indeed still support primitive microbial-type Life-forms in its deeper, and warmer, subsurface, as survivors from its warmer & wetter past.

The Mass Distribution of stellar (star) populations is described by the Initial Mass Function (IMF), denoted N(M) dM, which describes the number of stars between masses M & M+dM, in some specified volume of space. The IMF is typically modeled as a Power Law, with exponent [math]\alpha[/math] around -7/3: [math]N(m) dm \propto M^{-\alpha}[/math] Now, Stellar Luminosities scale as L* ~ M*4(Bowers & Deeming. Astrophysics I: Stars, pg. 28). So, from the IMF, we can calculate the expected overall Mass-to-Light Ratio of that population of stars: [math]\Upsilon \equiv \frac{M_{tot}}{L_{tot}} = \frac{\int M \times N(M) dM}{\int L(M) \times N(M) dM} \approx \frac{\int M \times M^{-\alpha} dM}{\int L_{\odot} \times \left(\frac{M}{M_{\odot}}\right)^{4} \times M^{-\alpha} dM} = \left(\frac{M_{\odot}^{4}}{L_{\odot}}\right) \frac{\int M^{1 - \alpha} dM}{\int M^{4 - \alpha} dM}[/math] [math] = \Upsilon_{\odot} \; M_{\odot}^{3} \left( \frac{5 - \alpha}{2 - \alpha} \right) \frac{ M^{2 - \alpha} |_{M_{min}}^{M_{max}} }{M^{5 - \alpha} |_{M_{min}}^{M_{max}} }[/math] [math] = \Upsilon_{\odot} \left( \frac{5 - \alpha}{2 - \alpha} \right) \frac{ \mu^{2 - \alpha} |_{\mu_{min}}^{\mu_{max}} }{\mu^{5 - \alpha} |_{\mu_{min}}^{\mu_{max}} }[/math] where [math]\mu \equiv M / M_{\odot}[/math]. Plugging in approximate values for the IMF exponent ([math]\alpha \approx 7/3[/math]), as well as the minimum & maximum star masses ([math]\mu_{min} \approx 0.1, \mu_{max} \approx 100[/math]), we obtain: [math] \frac{\Upsilon}{\Upsilon_{\odot}} \approx 7.2 \times 10^{-5}[/math] However, the normalized Mass-to-Light Ratios ([math]\frac{\Upsilon}{\Upsilon_{\odot}}[/math]) of most Galaxies range from 2 - 10, some 5 Orders-of-Magnitude greater. CONCLUSION: Standard stellar populations cannot account for the observed Galactic Mass-to-Light Ratios. This could be consistent with the inference of copious quantities of Dark Matter in the same.

Please ponder the Gravitational Potential Well of a massive central body: [math]U = - \frac{G \; M}{R}[/math] Crucially, Gravitational Potential Energy is negative. Thus, other bodies placed into this Gravity Well will lose Energy -- and, hence, by Einstein's Mass-Energy Equivalence (E = m c2), they should lose Mass, equal to: [math]\Delta M = \frac{U}{c^{2}} = - \frac{G \; M}{c^{2} \; R}[/math] Plugging in appropriate numbers, this yields Fractional Mass Loss effects of order: At Earth's surface -- 10-9 At Earth's orbit -- 10-8 At Sun's surface -- 10-5 At Neutron Star's surface -- 10-2 At Black Hole Event Horizon -- 1 Thus, by these admittedly primitive classical arguments, objects passing through a Black Hole's Event Horizon have lost more Energy than their Rest Mass Energy Equivalent (!!), ignoring of course any gains of Kinetic Energy*. * It seems strange, to this author, that, from the perspective of a distant observer, Time slows for objects accelerated to large positive Kinetic Energies, and for objects dropped down into large negative Potential Energies.

Smaller, dimmer stars typically produce far fewer Terrestrial-type planets, but make more Jupiters & Kuiper Belt Objects: http://www.physicsforums.com/showthread.php?t=278029&page=2 Merged post follows: Consecutive posts merged That is an excellent extension of the reasoning ! Merged post follows: Consecutive posts merged The cited Wikipedia article accounts for that: Merged post follows: Consecutive posts merged You raise a valid concern. However, how does the Escape Velocity of Earth compare with that of the Sun, from Earth's Orbit ?? Isn't the latter basically Earth's Orbital Velocity ? And, isn't Earth's Orbital Velocity ~30 km/sec, or around 3x that of its Escape Velocity ? Moreover, don't Gravitational Potential Wells "add" or "super-impose" ? Thus, if you put the same planet, down deeper into a low-mass stars' Habitable Zone, havn't you actually twice-increased the Energy costs ?

I think this is the link: http://www.nasa.gov/mission_pages/hubble/news/brown_dwarfs.html Note that the Brown Dwarf Desert applies only to "companions to normal stars": Indeed, according to the article Unlikely Suns, Improbable Planets in the June 2009 AD issue of Scientific American, Brown Dwarf sub-stars are as common as true stars, in the Sun's vicinity. Thus, although the nearest Star System is the Alpha Centauri Trinary at 4.3 light-years, Brown Dwarf sub-Star Systems could be closer still. And, Brown Dwarfs could also likely have planets. So, it seems that Brown Dwarfs are quite common "on their own", but not as Stellar Companions.

Work-Night Rough Draft Stars are born from Giant Molecular Clouds (GMCs), in big "batches" that become -- upon the condensation & dispersal of the parent GMC -- Open Clusters. Now, "stars inside an Open Cluster are at first tighly packed, moving at the same speed around the center of the Galaxy"*. Such Open Clusters typically persist for several hundred million years, before becoming disrupted**. * Open Cluster - Reference Library - redOrbit ** Sun's siblings may have seeded Earth life - space - 26 September 2008 - New Scientist ; cf. http://www.astronomyforum.net/planetary-forums/84613-how-find-suns-sibling-stars-exo-planets.html Now, the Ursa Major Cluster is an aged (~500 million years old*), and partially disrupted Open Cluster. After half a billion years or so, a classic Open Cluster such as the Pleiades or the Hyades (both in Taurus) tends to be disturbed by external factors (such as Molecular Clouds passing by), setting its stars moving at slightly different speeds, and so causing them to drift apart, exactly like the one in Ursa Major has done. When this happens, the [Open] Cluster becomes a stream of stars, not close enough to be a cluster but all related and moving in very similar directions at similar speeds... Sirius is a former member of this [Open] Cluster and our sun is in the outskirts of what is called The Ursa Major Stream, a group of stars that are all ex-members of the Ursa Major Cluster spanning over a thousand light years in space**. These partially disrupted post-Open Clusters are called Moving Groups, and can be up to 2 billion years old***. But, typically, After a billion or so years, the Cluster is totally lost. Some stars will be on the far side of the galaxy, some on the near. The sun's original cluster is like this, there is no way to tell which are former members and which just happened to have formed at the same time but somewhere else. Indeed, "extremely dense Open Clusters can stay together for longer, but no Open Cluster could stay together for the age of the Sun, five billion years**". However, the HR 1614 Moving Group could be about 5 to 6 billion years old#. * Ursa Major Moving Group - Wikipedia, the free encyclopedia ** Open Cluster - Reference Library - redOrbit *** Moving group - Wikipedia, the free encyclopedia # http://adsabs.harvard.edu/abs/1992AJ....104.1906E

Inspired by the National Geographic documentary Journey to the Edge of the Universe (DVD), it occurred to me, that our visual observations of the Cosmos could, quite conceivably, be sufficient for "retro-dicting" the Known Universe (Causally Connected regions of Spacetime beneath our Lightcone), and "pre-dicting" the Unknown Universe (Causally Disconnected regions of Spacetime above our Lightcone) -- including, in particular, the Modern Universe (what's happening, right now, across the Universe, even though the Light from those regions & events won't reach us for millions & billions of years more). "A picture's worth a thousand words", so please see the attached figure. Conceptually, such a simulation would amount to "total situational awareness", at the ultimate Cosmic scale.

I would like to point out, that iron is not a product of blast furnaces. Smelting only extracts previously existing Iron from rocks. An apt, and accurate, analogy would be: Iron is produced by Big Stars, and distributed by Supernovae. The presence of Iron implies the past presence of Big Stars, and Supernovae. I'm sure, however, that there are Industrial Byproducts specific to Smelting & Blast Furnaces. And, the presence of those specific "Smelting signature compounds" (as it were) would, in fact, imply the presence of Heavy Industry on our hypothetical planet, yes? I am glad everybody found this discussion stimulating. Logically, the link between Methane & Biology, coupled with the ubiquity of the former, suggests the possible ubiquity of the latter. Merged post follows: Consecutive posts merged Are Molecular Clouds, where most Methane is apparently observed, Reducing Environments ?

On Earth, Methane is primarily produced by Biological processes*. So strong is that link, that Methane in Mars' atmosphere strongly suggests the presence of sub-surface Methanogen micro-organisms: Methane is a product of Biology. For Methane to be in Mars' atmosphere, there has to be a replenishable source... The most obvious source of Methane is organisms. So if you find Methane in an atmosphere, you can suspect there is Life**.And, Methane is commonly observed across the Cosmos. * Martin Ince. [Rough Guides] Earth, pp. 256-257. ** http://www.telegraph.co.uk/scienceandtechnology/science/sciencenews/4243321/Mars-methane-discovery-hints-at-presence-of-life.html; cf. http://news.nationalgeographic.com/news/2004/10/1007_041007_mars_methane.html, http://dsc.discovery.com/news/2009/01/15/mars-methane-life.html; Volcanoes ruled out for Martian Methane, see: http://www.newscientist.com/article/dn8256-volcanoes-ruled-out-for-martian-methane.html CONCLUSION (?): If all Methane comes from Biological processes, and if Methane is common across the Cosmos, then perhaps Biology is common across the Cosmos.

Perhaps the Big Bang was the Explosive Evaporation of a "Hyper-Massive Black Hole": http://www.scienceforums.net/forum/showthread.php?t=39313 Perhaps your SMBHs are "chunks" of BH material blown outwards by that explosion, akin to knots of gas blown out by Supernovae. Those "BH fragments" then formed the seeds of Galaxies w/in our Universe -- to wit, inside the expanding "Explosion Remnant" (akin to Supernova Remnants).

http://www.sciencemag.org/cgi/content/abstract/1172740v1?sa_campaign=Email/pap/21-May-2009/10.1126/science.1172740