Widdekind

I misunderstood what you were claiming before.

——

 

Why are you using 1.3?

 

http://venus.mporzio.astro.it/~marco/gc/cluster_4.php?ggc=NGC%206287

 

V-I is given as 1.74.

Thanks for the link. Is that V-I for the complete cluster, or for the Main Sequence Cutoff ? (Are they the same, or different ?)

Arthropods' "blood" contains Hemocyanin, to transport Oxygen. And, "Oxygenation causes a color change between the colorless Cu(I) deoxygenated form and the blue Cu(II) oxygenated form".

Likewise, it is well-known, that Oxygenated Hemoglobin is blue.

And, it is well-known, that the sky appears blue, b/c atmospheric Oxygen (& Nitrogen) preferentially scatter shorter (bluer) wavelengths of light.

QUESTION: Does all this imply, that "Oxygen is just plain blue" in appearance (since it scatters shorter wavelength light) ??

Are Exoplanets unique to the Milky Way ??

(1) Interstellar Dust contains much of the mass of 'metals' manufactured since the start of spacetime (~14 Gya), which metals make planets much more probable

Cosmic dust is of fundamental importance to astrophysics. Though dust is only a tiny fraction of the baryons in the Universe, it influences the formation of planets and stars in a fundamental way and contains half of all the metals synthesized over cosmic time.

 

https://indico.nbi.ku.dk/conferenceDisplay.py?confId=78

(2) Milky Way's Dust seems special, in shape & size, and perhaps other properties

The 2175 Å absorption bump, a feature often ascribed to graphite grains and ubiquitous in the spectra of sight lines through the Galactic diffuse interstellar medium, is generally weak or nonexistent for objects outside our Galaxy. Many active galaxies seem to have Small Magellanic Cloud-type dust extinction, suggesting that the presence of the bump in our Galaxy may be exceptional. Recently, it was suggested that the spectrum of the high-ionization broad absorption line QSO UM 425 shows a 2175 Å feature. This apparent feature seen in UM 425 and the rest frame spectra of other QSOs is intrinsic to the QSO spectrum. It is the result of a relative absence of emission near 2200 Å. Thus far, no significant detection of the 2175 Å bump in a QSO has been reported.

 

http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2000PASP..112..537P

We report a superstrong 2175 Å absorption galaxy at a redshift of z_G = 0.8839 toward the background quasar SDSS J100713.68+285348.4 at z_Q = 1.047 identified from the Sloan Digital Sky Survey (SDSS) data. The bump is the strongest ever known, about 2.5 times the average in the Galactic interstellar extinction curves. About two dozens of narrow absorption lines are identified in this system in the SDSS and the follow-up Multiple Mirror Telescope (MMT) spectra, including Zn II, Cr II, Mn II, Si II, Fe II, Ti II, Ca II, Al III, Mg II, and Mg I. We have derived accurate measurements of the gas-phase column densities of most of these ions through their weak absorption lines. The combination of unprecedentedly strong 2175 Å absorption bump strength with the measured zinc column density suggests that carbon is likely to be the main carrier of the 2175 Å absorber assuming that the total abundance of the absorber relative to zinc is similar to the solar values and zinc is not heavily depleted onto dust grains. Under the same assumption, we found that dust depletion in this absorption galaxy is much less than that in the Milky Way, indicating possible different nucleosynthesis and/or chemical and interstellar medium evolution history.

 

http://www.iop.org/EJ/abstract/0004-637X/708/1/742

The 2175 Å extinction bump, first detected over 40 years ago (Stecher 1965), is an ubiquitous feature of the Milky Way ISM... the 2175 Å bump is relatively weaker in the LMC and absent in the SMC. This bump is largely absent in AGNs.

 

http://nedwww.ipac.caltech.edu/level5/Sept07/Li2/Li3.html

Note, tho, that "The broad absorption bump at 2175 Å due to dust, which is ubiquitous in the Galaxy, [is also] seen in the Magellanic clouds"*.

(3) The Galactic Disk of the Milky Way contains a Jupiter-mass of metals for every Star (System?)

According to M.H.Jones & R.J.Lambourne's An Introduction to Galaxies & Cosmology (pp. 11-32), the Galactic Disk of the Milky Way contains ~10¹¹ [math]M_{\odot}[/math] in stars, and ~10⁸ [math]M_{\odot}[/math] of dust, indicating a Jupiter's mass of dust per star in said disk. Most of this dust dwells in the Dark Clouds in the inner disk dust lanes, from 4-7 Kpc (cf. [math]R_{\odot} = 8.5 kpc[/math].)

May I please point out, that Prof. Chandra Wickramasinghe seemingly says, that this 'dust' in the disk of the Milky Way may be microbial, bacterial, spores*. If so, given that the mass of Earth's Biosphere is about ~10¹⁶ kg (~10^-11 M_J)**, there might be many billions of times more microbes per star system, in our Galaxy's disk, than is known to exist, in our own Solar System. Such seems a somewhat staggering suggestion, but one which would be of potentially profound importance, if verifiable***^,#.

Merged post follows:

Yes, but what happens then? In a globular cluster that most likely consists largely of hydrogen to begin with, the bigger, brighter stars strip away smaller stars’ dusty disks that should initially be low in metallicity. These bigger stars then go SN and pepper the surrounding stars with many solar masses of material consisting of all the elements. A low mass star that originally attracted a dusty disk by its gravity will continue to attract material for the life of the star for the same reason. Right?

Stars like our Sun will also expand to Red Giant size and lose mass, to the point where their outer planets will simply no longer orbit their parent star. Where might these rogue planets end up?

A globular cluster is not only a stellar nursery it is a planetary nursery as well. IMHO, I don’t see how over a period of billions of years somehow random events could conspire to such a degree that the perfectly attractive mass of a star would never…ever…attract a planet.

(Merry Christmas to all!)

Surely someone shall say something along the lines of capture requiring the conservation of momentum & energy to be broken, and something about 3 bodies being needed, but it seems pretty plausible to me.

(Happy Holidays !)

What am I missing ? Isn't the "Main Sequence Turnoff" that group of stars that are "still just barely" on the Main Sequence ?

According to the cited sources, the last stars still on the MS have a V-I CI of ~1.3, which theoretically corresponds to a T_eff ~ 4200 K...

which would be, as a MS star, a K-6 or K-5 class orange dwarf... yes??

So, stars smaller than K-6 are still on MS in NGC 6287, while stars bigger than K-5 have already begun (to varying degrees) to "peel off" the MS... yes ??

A big looming question: How much of that graph is just a selection effect? It is based on "155 spherules separated from 1 gram of Apollo 14 soil" (http://www.sciencemag.org/cgi/content/abstract/287/5459/1785). The authors made some sweeping / hand-waving arguments to suggest that this one gram sample of lunar soil is representative of the Moon as a whole.

 

Even worse than a selection effect, is confirmation bias going on here? The authors of this paper have a very non-consensus axe to grind (the Nemesis Hypothesis).

 

For opposing views, see (for example),

 

http://www.sciencemag.org/cgi/content/full/293/5537/1947a

http://elements.geoscienceworld.org/cgi/content/abstract/5/1/23

Thanks for the links. I wasn't aware of any kind of context for the claims. Yet it still certainly seems worth further investigation -- it doesn't seem to sound like said claims have been categorically disproven.

Shouldn't a K5-class (orange) dwarf live for roughly 4-5 times as long as the Sun ? And, if the K5-class stars in NGC 6287 are already beginning to turn off from the Main Sequence ... ??

According to Astrophysics is Easy! by Mike Inglis, as a rough rule of thumb, "everything is faster for bigger brighter stars". Thus, in their birth clusters, bigger brighter stars are seen to have formed first -- and, even, finish their life-cyles -- before smaller dimmer stars even finish forming (from protostars, ~10-100 Myr).

Thus, the bigger brighter stars start shining, and stripping away the dusty mantles shrouding the smaller stars, before they finish forming. In some such cases, that dusty mantle shrouding said smaller star can be completely stripped away (even as whole collapsing and condensing clouds can be blown apart) before it can start to settle into a circum-stellar, pre-proto-planetary, disk (as argued by Prof. Portegeis Zwart, in said cited Sci.Am. article, as per the PP).

Evidently, on average, only about half of all low-mass stars' shrouds survive such stripping processes.

Darwin's "warm little pond" was a deep water, warm spring, in the Archaean Era

1. Basal Eukaryote evolved in deep ocean warm springs (~2.7 Gya)

Alexander S. Bradley, in the article "Expanding the Limits of Life" (Scientific American [Dec. 2009 AD], pp. 62-67), argues that the earliest Earth lifeforms, were primitive chemosynthetic microbes, inhabiting highly alkaline warm [~90 degrees C] spring systems, like the "Lost City" formation, found 15 km west of the Mid-Atlantic Ridge, and consisting of Calcium Carbonate chimneys. In complete contrast, to the more well-known "Black Smoker" systems actually inside the Mid-Ocean Ridges -- where the water is hot [~400 degrees C] highly acidic, Sulfide minerals make sooty smoke and dark colored chimneys, and "Lifeforms are indirectly dependent upon energy from the Sun" -- warm spring systems like Lost City host organisms completely independent of Solar energy. Thus, the article argues, the earliest Earth lifeforms likely evolved in locations like Lost City.

Indeed, in a chart in the article ("Chart 1"), genetic analysis of all extant Earth organisms strongly suggests, that the Last Common Ancestor (LCA) of all Earth life was a hydrogen consuming microbe (and may have been a methane making microbe as well):

Now, note, that the basal Eukaryotic line diverged from one of these hydrogen consuming microbial groups (orange). And, this basal Eukaryote, defined by the first evolutionary appearance of a true cell Nucleus, appeared in the Archaean Era (before 2.5 Gya*), and probably by about 2.7 Gya**.

In addition, the evolution of the cellular Nucleus may have involved the migration of a Eubacterium into a host Archaeobacterium (see "Chart 2"):

And, since we strongly suspect, that the host Archaeobacterium-cum-basal-Eukaryote dwelt in the deep ocean, at an alkaline warm spring system, this merger event most likely happened in such a system. Then, referring back to "Chart 1", this location likely indicates, that the invading Eubacterium was something similar to an Aquifex Hydrogenibacter. And, indeed, completely consistent w/ our strengthening suspicions, Aquifex Hydrogenibacter is ancient, thermophilic [heat loving], and chemoautotrophic [sun independent]:

Further still, the order Aquificales stems from the phylum Aquificae, which inhabits warm, alkaline, ocean springs:

Finally, that Aquificae are primary producers, strongly suggests, that the "Nucleation event" stemmed from the incomplete consumption, of the Aquificae Eubacterium, by the Archaeobacterium.

CONCLUSION:

The basal, Nucleated, Eukaryotes evolved in a deep ocean, warm springs system (like Lost City), in the Archaean Era, roughly 2.7 Gya, when a hydrophilic, methanogenic, Archaeobacterium, consumed an Aquificae Eubacterium.

Merged post follows:

Mitochondrial merger

2. Mitochondrial Eukaryote evolved in shallow water, from merger with an Alpha-proteobacteria (~2 Gya)

Eukaryotic mitochondria are closely related to purple, Oxygen-metabolizing, Alpha-proteobacteria*. And, referring back to "Chart 1", not only are (Alpha-)proteobacteria not hydrogen metabolizers -- having long since evolved away from the early alkaline, deep water, warm springs environment of the earliest Earth life -- but neither are any extant Eukaryotes. Moreover, Alpha-proteobacteria are principally phototrophic [light-loving]**. This strongly suggests, that the second major, Mitochondrial, merger event happened somewhere in the shallows of the seas.

The first firm fossil evidence of a "[Eukaryotic] organism with a cell containing a nucleus and other organelles" is the Grypania, appearing by by about 1.9 Gya*, and possibly as early as 2.1 Gya**. This comes hard on the heels of the Great Oxygenation Event around 2.3 Gya, after which Earth's atmospheric oxygen concentrations reached a "steady 5-18%" of present levels***. This Great Oxygenation Event set the stage for the evolution of Oxygen metabolizing organisms -- in particular, the pre-Eukaryotic, Alpha-proteobacteria.

Alpha-proteobacteria are famous for their symbiotic susceptibilities:

And, in particular, the Rickettsia alpha-proteobacteria are "obligate intracellular parasites [whose] survival depends on entry, growth, and replication within the cytoplasm of eukaryotic host cells (typically endothelial cells)"**.

CONCLUSION:

The Mitochondrial merger event happened, roughly 2 Gya, somewhere in the shallows of the seas, where Oxygen concentrations were comparatively high, and when a purple parasitic Rickettsia alpha-proteobacterium infected an evolved basal Eukaryote. This suggested scenario explains "merger 2" in "Chart 2".

Merged post follows:

Chloroplast merger

2. "Chloroplastal" Eukaryote evolved in shallow water, from another merger, with a Cyanobacterium (~1.2 Gya)

Plant Chloroplasts are closely related to photosynthetic Cyanobacteria*. Such Cyanobacteria clearly lived in the sea shallows, likely along the sea shore, alongside stromatolites , which are colonies composed (partially) of such Cyanobacteria(as seen in Shark Bay, Australia). As photosynthesizers, Cyanobacteria are "primary producers", and were the "principal primary producers throughout the Proterozoic Eon (2500-543 Mya**)". Finally, the first fossil evidence, for primitive plants, are algal mats, known by about 1.2 Gya***.

CONCLUSION:

The "Chloroplastal"merger event happened, roughly 1.2 Gya, somewhere in the shallows of the seas, surely along a sea shore, when a predatory Mitochondrial Eukaryote incompletely consumed a "principal primary producer" Cyanobacterium. This suggested scenario explains "merger 3" in "Chart 2". These 3 merger events each happened roughly every 700 Myr (a time-scale longer than existence of complex, post-Cambrian Explosion, organisms upon this planet [!!]).

According to the Nov. 2009 AD Scientific American article The Long Lost Siblings of the Sun, stars that do not have planets lost their circumstellar disks to disruption, by nearby neighbors in their birth cluster "cradle" (as it were). Only stars that escaped such close encounters kept their proto-planetary systems.

Thus, this process of disruption, in the early parent "cradle" cluster, produces precisely the appropriate division of stars (no planets vs. planets) that correlates with the presence or lack of lithium (respectively).

So, it certainly doesn't seem likely, as it seems "backwards", but could this process of disruption in the cradle cluster account for the "lithium litmus test" ??

Not necessarily.

 

You have not made any claims for the lunar tidal locking time. This needs to be less than the 61 million years it took for the Moon's crust to form to justify your claim. An easy alternative: The Moon is asymmetric because it formed from an asymmetric mass distribution and cooled so quickly that that initial asymmetry became frozen. The Moon is somewhat random because it was born that way.

 

http://www.springerlink.com/content/l2652w08h5l28513/

(Thanks for the ref !)

According to Carroll & Ostlie (op. cit.), the Moon's crustal structure is not random -- rather, there is a strong general trend, of increasing crustal thickness, from the Near Side to Far Side.

According to the article you cited:

My original suggestion seems in complete accord with Ransford & Sjogren (1972), whose model makes the Moon's core ~2.6x closer to the Near Side surface [572 km] than to the Far Side surface [1504 km].

Furthermore, your cited article certainly seems to say that the thinner crust, on the Near Side, could account for the Maria impact basins:

Thus, the combination of a thinner Near Side crust, along with with a hotter mantle "region of molten mare source material", b/c of a moderate core migration (~466 km), could explain the presence of the Moon's maria. Indeed, if some process (presumably Earth's gravity) could completely skew the shape of one Lunar layer (crust), it could conceivably affect lower-lying layers as well (mantle, core).

However, if the Moon's crust is actually random, in its various distributions, that lack of any "Earth oriented" global structure to the Lunar crust could mitigate against any similar such structures to lower-lying Lunar layers (core). It does not seem possible to reconcile M.Kobrick's article, w/ Carroll & Ostlie's text & figure. Which one is a more accurate picture ?

NGC 6287 is the oldest Globular Cluster in the Milky Way Galaxy. And, according to this article, the cluster's Main-Sequence Turnoff happens at a V-I Color Index of ~1.3.

Then, according to this site, that V-I Color Index corresponds, according to the formula:

to an effective surface temperature of roughly T_eff = 4200 K.

Finally, according to the appendix of Carroll & Ostlie's Introduction to Modern Astrophysics (1st ed.), that effective surface temperature corresponds most closely with Spectral Class K5, which has [math]M \approx 0.67 M{\odot}, L \approx 0.15 L_{\odot}[/math]. Such a star should have a stellar lifetime longer than our Sun's by a factor of roughly (M / L) = 4.5.

CONCLUSION (?!?): Since our Universe is purportedly under 14 billion years old, and then even if NGC 6287 is nearly as old, our Sun should have a lifetime of at most 14 Gyr / 4.5 = 3.1 Gyr. And, conversely, if our Sun really has a lifetime of roughly 10 Gyr, then NGC 6287 (and the Universe) must be at least 45 Gyr old.

What went wrong ??

The giant impact hypothesis naturally leads to an asymmetric distribution of crustal material. The lunar magma ocean crystallized fairly quickly (~100 million years) after formation. That quick crystallization meant the crustal material did not have time to spread over the surface uniformly. The center of mass of the Moon's crustal material is about 2 kilometers from the Moon's center of mass. On the other hand, the Moon's core is quite close to the Moon's center of mass.

Can you cite your source for that figure please?

Also, any asymmetry could only have arisen after the Moon became Tide-locked to the Earth, yes ? For, the Moon's ceaseless spinning, before that point, would have continually redistributed any burgeoning asymmetry. Only after the Moon's Earthward face was fixed, would the Moon have started to "sag" into its asymmetric shape, yes ?

Thanks for the info !

What if you replace "GRB" with "nearby SN explosion" ?

In the Lunar geologic [Lono-logic??] timescale, the "Early Imbrian Epoch" (3850 - 3800 million years ago*) is associated with the Late Heavy Bombardment, and the resulting huge impact basins, which would later fill w/ lava to form the Lunar Mare, during the ensuing Late Imbrian Epoch (3800 - 3200 million years ago). This happened when "the mantle below the lunar basins partially melted and filled them with basalt"**.

Now, it is well-known that the Moon first formed roughly 15 times closer to Earth than its present orbit today*. And, that early Moon was not, yet, Tide-Locked to the Earth. But, by the present period, not only is the Moon Tide-locked to the Earth, but it's whole inner iron Core has shifted Earthwards inside the Moon, thinning the Crust & Mantle on the Near Side, while thickening the same on the Far Side**.

CONCLUSION: We must explain why, during the Late Imbrian Epoch (3800 - 3200 million years ago), impact basins on the Moon's Near Side flooded with lava, when the Mantle beneath them suddenly heated & melted. But, we have seen, that once the Moon became Tide-locked to the Earth, its whole inner iron Core migrated towards the Earth — and the Near Side surface. And, moving all that hot material towards the Near Side surface could easily explain the melting of the overlying Mantle, and subsequent flooding of the Mare.

This strongly suggests, that by about 3800 million years ago, the Moon had become Tide-locked to the Earth — even as deep basins had been punched into the Lunar surface from the Late Heavy Bombardment. And, over the next 600 million years, the Moon's inner iron Core migrated ever Earth-wards, continually melting the ever-thinning over-lying Mantle on the Near Side, which then flooded the Near Side surface basins with basalts, making the Mare.

Indeed, in essence, once the Moon became Tide-locked to the Earth, the Moon's molten inner Core almost melted its way through the Moon, towards the Earth (!!). Had the Moon been bigger, and hence hotter for longer, perhaps the Moon's molten Core could have melted out of the Moon, and fallen back down towards the Earth (!!).

Prof. Richard A. Muller has shown that the Lunar cratering rate actually increased, beginning about 400 Mya*:

By extension, the cratering rates on the Earth, and even across the Inner Solar System, likely increased too, from ~400 Mya.

A.J. Meadows (The Future of the Universe, pp. 118-125) says that, as our Sun orbits around the Galaxy, it travels into, thru, and out of, our Galaxy's Spiral Arms; and, that these can cause close encounters with Star Forming Regions, on ~200-500 Myr time scales:

And, in addition, the Ordovician Mass Extinction Event (~450 Mya) could, conceivably, have been caused by a powerful Supernova explosion occurring near our Solar System*.

Finally, the KT Mass Extinction Event (~65 Mya) was probably caused by an asteroid born from the Baptistina Family, the rubbled remains of a massive body which was broken apart about 160 Mya (and likely caused the crater Tycho on the Moon, about 110 Mya, as well)*. This shows that gravitational disturbances can take ~50 Myr to propagate down into the Inner Solar System, and that they can last for as long as ~100 Myr.

All this seemingly suggests a scenario, wherein, during a transit across a Spiral Arm, our Sun closely encountered a Star Forming Region & Supernova ~450 Mya. Radiation from the Supernova immediately caused the Ordovician Mass Extinction, but was also associated with a gravitational disturbance of the Oort Cloud — which, after a further ~50 Myr, caused increased cratering rates across the Inner Solar System (called a "Comet Swarm"). Perhaps there is even some kind of connection to the vigorous resurfacing events on Venus over the last 300-500 Myr.

If I could please ask you to do so, or provide the reference, that would be much appreciated, thanks !

BACKGROUND: Scale-independent (Harrison-Zeldovich) Initial Curvature Fluctuations

According to Prof. Martin Rees (New Perspectives in Astrophysical Cosmology, pp. 40-80), the most "natural" assumption, regarding the growth of density fluctuations in the early Universe, is that when any region becomes causally connected, it's density contrast ([math]\delta \rho / \rho[/math]) has become the same constant Q, for all regions across all scales at all times. (Of course, this argument is made solely in a statistical sense, and actually applies to the mean density contrast.)

During the matter-dominated epoch, these causally-connected "Hubble Volumes" contain, at time t (>t_eq), a mass equal to (ignoring the slight over density):

Now, in their linear regime, slight over-densities grow linearly with the Universal Scale Factor R(t) (Carroll & Ostlie. Intro. Mod. Astrophys., pp. 1295-1300). Thus, whereas at time t, mass M(t) has compacted into an over-density of Q, back at the Recombination era, that over-density was less by a factor of:

Note that, whereas, back at time t when it had attained density contrast Q, mass-scale M(t) spanned the "Hubble Distance" c t, at the present epoch t₀ that mass-scale has stretched by the factor of R(t₀)/R(t) = (t₀/t)^2/3, and now spans the size-scale:

Thus, in particular, the spectrum of "initial" density fluctuations, at Recombination, which falls off as M^-2/3 in mass, falls off as L^-2 in size (see below)*.

But, consider the causally-connected Hubble Volume at the transition from Matter- to Radiation-dominated epochs. Up until that equilibrium, "acoustic" effects in the "photonic-plamsa" apparently damped the gravitational growth of density contrasts. Thus, the Mass-scale [math]M_{crit} \equiv M_{0} ( t_{eq} / t_{0} )[/math] defines a threshold — above this amount of mass, density contrasts were largely unaffected by the (comparatively) brief period of Radiation-dominance and had developed to density contrasts proportional to Q x M^-2/3 at Recombination; but, below this amount of mass, density contrasts were largely damped down to the same amplitude:

Now, if this analysis were strictly & utterly true, we would see the following spectrum of Initial Curvature (Density-Contrast) Fluctians (curve overlain in green):

But, in fact, at Recombination, there were apparently slightly larger density fluctuations, at "small" scales (M < M_crit), than this simple model suggests. And, yet, those "initial" density fluctuations were not as large as indicated by standard CDM computer simulations*.

QUESTIONS:

(1) Our threshold mass-scale (M_crit) seems special. For, not only does it distinguish between "Large-scale Structures" (Superclusters, Cosmic Web) and "Small-scale Structures" (Galaxies, Groups), but it is also just beginning to go non-linear at the present epoch. Thus, the Universe is "middle aged" (if you will), in that all Small-scale Structures (M < M_crit) have already virialized, while all Large-scale Structures (M > M_crit) have yet to do so. Is this some sort of special coincidence, and what could account for it ??

(2) Prof. Rees seems to say, that S-CDM computer simulations treat DM as "cold" and "weakly-interacting", so that (in the computer-simulated Universe) the DM can begin to gravitationally coalesce even before the Recombination era, giving DM a "head-start" on forming the gravitational potentials into which the (simulated) baryons only later begin to fall. Is this true (of the simulations), and does the above analysis imply that DM is also actually (partially) damped at small scales (M < M_crit) along with the baryons ??

(3) To account for high redshift compact objects (e.g. Quasars, z ~ 5), the density fluctuations, at Recombination, and on the smallest scales, must have been about 0.005 (see above). Adding this information, to the afore-cited figure, with a linear best-fit (overlain in cyan), yields the following figure:

Thus, it seems that S-CDM is accurate at large scales (M > M_crit), and at "tiny" scales, but is an over-estimate for intermediate mass scales. Does this say something subtle & significant ??

Thanks !!

According to Stephen Eales' Planets & Planetary Systems, pp. 73-75, earthquake longitudinal Compression Waves (P-Waves) travel w/ velocity:

while transverse Shear Waves (S-Waves) travel w/ velocity:

where "K is the bulk modulus of the rock, [math]\mu[/math] is its shear modulus, and [math]\rho[/math] is its density". His discussions seemingly suggest, that the bulk & shear moduli of rock remain roughly constant, across the range of conditions encountered in planetary interiors.

Since earthquake wave velocities are inversely proportion to density, earthquake waves might travel faster, on smaller, lighter, lower-gravity, less-dense worlds, like the Moon & Mars. Conversely, such waves might travel slower on larger, more-massive, higher-gravity, higher-density worlds, such as "Super Earths".

According to the National Geographic Channel documentary Naked Science — Incinerator Earth (TV), as well as the History Channel documentary Jurassic Fight Club — Armageddon (DVD), chemical analysis of the Iridium layer, deposited by the Chicxulub impactor, strongly suggest that said impactor, was an asteroid, from the Main Belt, from the Asteroid Family known as Baptistina. Another large fragment, from this family, roughly 3 km across, created the Tycho Crater on the Moon, around 110 million years ago.

That's very nice, Widdekind. This of course has nothing to do with Andromeda and the Milky Way. They did not start at rest with respect to one another at essentially infinite distance.

Working backwards, from a current relative velocity of ~130 km s^-1, Andromeda would have been about 4 million light-years further away, around 10 billion years ago — or around 6 million light-years away in total.

So, what is a better approximation to the initial conditions ? Cosmologists apply Newton's Laws for estimating masses of Galaxies (~100 thousand light-years), and Galaxy Clusters (~1 million light-years) (yes ?). And so, what is the maximum spatial "cut-off" of applicability, for Newton's Laws, before relativistic effects (e.g. Cosmological Expansion) "kick in" ?

Merged post follows:

Widdekind, answers to posts should reflect the current theories and models of science, rather than speculation. Further, they should be on-topic with regard to the original post.

(I got booted off the computer.)

I was "answering" what seemed to me to be a "speculative question", w/ my own "speculative question(s)" — I thought it would be preferable to keep such "speculative questions" confined to a single thread. But in the future, I will post my questions separately, and make the questions themselves ("?") more obvious & clear, if that is preferable.

I would like to ask why we feel the need to be snide ("that's very nice, Widdekind"). I wasn't snide, I was clear, cogent, and polite. I'm absolutely convinced, of course, that we would all be polite to me to my face. But, why the need to be, of all things, snide (or seemingly so) ? Why not just say answer my "speculative question" w/ as much courtesy and directness as that of the OP ("no, you are not correct...") ? Everybody else asks questions, and they are treated politely; then I ask a question, and I'm treated differently (or seemingly so).

According to QM, a particle of mass m is associated w/ a spatially extended (normalized) Wave Function [math]\psi(\vec{r})[/math]. At any given point in space, that WF corresponds to a Mass Density of [math]m \; \psi^{*}(\vec{r}) \; \psi(\vec{r})[/math]; an Energy Density of [math]\psi^{*}(\vec{r}) \; \hat{E} \psi(\vec{r})[/math] (where [math]\hat{E} = i \hbar \frac{\partial}{\partial t}[/math] is the Energy Operator); and a Momentum Density of [math]\psi^{*}(\vec{r}) \; \vec{p} \psi(\vec{r})[/math] (where [math]\vec{p} = - i \hbar \vec{\nabla}[/math] is the Momentum Operator).

These well-defined spatial quantities, all of real values, could be plugged straight into the Stress-Energy Tensor of GR. Likewise, the Metric (e.g. Schwarzschild Metric) could be used to adjust the time & space derivatives in those above Operators.

Also, given GR's Mass-Energy Equivalence, how come the Rest Energy doesn't appear as an Operator ([math]m \; c^{2} \bullet[/math]) in the Hamiltonian Operator in QM ??

Thanks again for the info

Consider two masses, M₁ & M₂, initially at rest, and very far from each other. As they begin to approach each other, from the Newtonian 2-Body Problem, we find that, as they gravitationally collapse towards each other down to a distance D, their approach speed V is:

where M_tot = M₁ + M₂. Thus, by knowing the separation distance D, and relative approach velocity V, we may estimate the combined mass M_tot:

We apply this below to two well-known situations.

Application — Andromeda & Milky Way

According to Science Illustrated [Mar./Apr. 2008 AD], pg. 30, "the Milky Way is hurling towards the Andromeda galaxy, at a speed of about 290,000 mph". At a separation distance of 2.2 million light-years, this implies a combined mass of:

The currently estimated Luminous Mass of the Milky Way is [math]\approx 30 \times 10^{9} \; M_{\odot}[/math], with that of Andromeda being a bit bigger.

CONCLUSION: Currently visible Luminous Matter can account for the observed approach speeds, w/o resorting to "dark forces", "dark matter", or "dark energy".

Application — Great Attractor & Milky Way

According to the same cited source, the Milky Way is "also being drawn, at a rate of about 1,300,000 mph, toward an enormous Super-Cluster, the Great Attractor, which lies 250 million light-years away". These numbers imply a combined mass of:

And, the estimated Luminous Matter of the Great Attractor is [math]\approx 1000 \times 10^{12} \; M_{\odot}[/math].

CONCLUSION: Once again,currently visible Luminous Matter can account for the observed approach speeds, w/o resorting to "dark forces", "dark matter", or "dark energy".

ADDENDUM:

According to Science Illustrated [Nov. / Dec. 2008 AD], pg. 18, "regions of space long believed to be devoid of stars are actually teeming w/ them, according to new observations", by NASA's GALEX satellite, and NSF's VLA radio telescope. They showed:

Thus, as observations improve, Luminous Mass estimates may increase even further, which would also eat into the 'necessity' of "dark forces".

Where is the need for Dark Matter ? What is wrong w/ the above estimates for the combined masses of said systems ??

(1) Disk stars orbit their Galaxy's center, on orbits that primarily pass through, and along, that Galaxy's spiral arms (OP).

(2) And, most spiral Galaxy's — especially, apparently, big ones, like the Milky Way — have much straighter arms, that project outwards, "radially", much more rapidly (Wikipedia). To wit, the arms of the Milky Way are much more "limp", and are wound up much more tightly.

CONCLUSION: Since the Milky Way's "limp" arms are much more circular (more like the rim of a wheel), disk star orbits, which must pass through & along those arms, can also be much more circular. Conversely, in most other spiral Galaxies, their straighter arms (more like the spokes of a wheel), so that their stars' orbits must be much more elliptical.

This could have (potentially profound) implications, upon the possibility of Life, in the Galactic Habitable Zones amidst such straight-armed Galaxies, b/c highly elliptical orbits would take said stars deep into their Galaxies' cores (exposing said Star Systems to copious quantities of collisions & radiations), and then far out towards their Galaxies' rims. To wit, such orbits could take said stars beyond both the inner & outer edges of their Galaxies' Habitable Zones.

Merged post follows:

so, even on the Galactic scale, "Metals track mass" — which is essentially saying the same thing as "denser Disk regions are much more 'Metallicitious'" (where there's more mass, there's more Metals)[/color]

The following journal article corroborates this "Galactic Mass-Metallicty (M-Z) Relation":

It's also worth asking why other animals don't have it? Why do they rely on pheremones and vision? We don't have anything they don't, and they've got plenty of senses we don't. To think that something as useful as telepathy has only cropped up in one species out of trillions is silly.

Telepathic abilities correlate to brain structures involved in "higher intelligence", like "the Frontal & Parietal Lobes (Sixth Sense), Temporal Lobes (Clairvoyance), & Occipital Lobes (Remote Viewing)". Please see bullet points 1-3 in the post below, which cites specific sources (points 4+ are speculations based upon said cited sources, and are not directly relevant to your specific point):

CONCLUSION: Telepathic abilities would only arise with "higher intelligence", which has only appeared relatively recently amongst mammalian primates.