Re: Origins of Jets
Posted: Fri Mar 20, 2009 3:20 pm
Harry, if you're not a smart cookie I'm a dumb crumb.harry wrote:G'day from the land of ozzz
You got to know that, I'm not a smart cookie.
APOD and General Astronomy Discussion Forum
https://asterisk.apod.com/
Harry, if you're not a smart cookie I'm a dumb crumb.harry wrote:G'day from the land of ozzz
You got to know that, I'm not a smart cookie.
You can derive the equation for cosmological redshift using GR geodesics. The redshift ends up simply as Z = [a(t1) / a(t0)] -1, where a(t1) is the cosmological scale factor when the redshift is measured, and a(t0) is the cosmological scale factor when the photon was emitted. The value a(t) is assumed by theory (supported by observation) to be monotonically increasing with time. This cosmological redshift can't become infinite except in the limit of an infinite length of time. (Careful with those examples... we're considering infinite redshift, not zero or negative redshift.)makc wrote:your reasoning is like that in the tale of Achilles and the Tortoise. it is true that f(x) = exp(-x) will never reach 0, but g(x) = 1 - x will reach g=0, cross it, and extend forever into negativity. so I am asking here what makes you think it is f(x) situation, and not g(x)?
so, if dark energy exists, galaxies will leave visible universe; it appears, we do not even need "phantom energy" and Big Rip, right?...As we now show, if w < −1 persists, then the fate of the Universe is quite fantastic and completely different
than the possibilities previously discussed.
To begin, let us review these other fates. In a flat or open Universe without dark energy, the expansion continues forever, and the horizon grows more rapidly than the scale factor; the Universe becomes colder and darker, but with time the co-moving volume of the observable Universe evolves so that the number of visible galaxies grows.
If the expansion is accelerating, as a consequence of dark energy with −1 ≤ w < −1/3, then the expansion again continues forever. However, in this case, the scale factor grows more rapidly than the horizon. As time progresses, galaxies disappear beyond the horizon, and the Universe becomes increasingly dark. Still, structures that are currently gravitationally bound, such as the Milky Way and perhaps the Local Group, remain unaffected. Thus, although extragalactic astronomy becomes less interesting, Galactic astronomy can continue to thrive.
this might sound not really scientific, but I was just thinking about simple effect like hydrogen atom consuming photon and getting excited about it - if Einstein (or anyone else) would succeed to build the theory describing electromagnetism with space curvature effects, does this situation not have to be exactly that - red-shifting photon to 0 energy? I mean, it is easy to say, photon was consumed, and the energy was used to move electron into higher orbit, and then forget about it; but if you keep thinking about it, where does photon go? how come it is magically dissolved? what about "nothing comes into/out of nothing" postulate, that have never failed us before? if we are ready to give it up just like that in this case, why not just as well accept that photon can be wiped out of reality on the edge of visible universe, or some other region with exotic curvature of space?Chris Peterson wrote:...there's no way in that case to distinguish between a photon of zero energy, and the simple absence of the photon.
ha ha, this is on wiki. well, that means the above scenario assumes different metric, let's see if I can find it.... wait a minute, it has that part "For very small variations in time (over the period of one cycle of a light wave) the scale factor is essentially a constant", maybe that's not really true in that case, so simple formula for z doesnt work any more?Chris Peterson wrote:The redshift ends up simply as Z = [a(t1) / a(t0)] -1, where a(t1) is the cosmological scale factor when the redshift is measured, and a(t0) is the cosmological scale factor when the photon was emitted. The value a(t) is assumed by theory (supported by observation) to be monotonically increasing with time. This cosmological redshift can't become infinite except in the limit of an infinite length of time.
Thanks, Makcmakc wrote:unlocked per request. feel free to spam the forum
I don't envy you your duties, Makc .. I find it hard to read the intention behind some posts, and of course I find it impossible to understand the content of many posts.makc wrote:it's getting hard to read through hundreads of genuine posts herewell, as long as I, let's say, misunderstood you, feel free to.. whatever.
What frame of reference are you going to use to define 'Actual Time', though? I'm going by the assumption that you're suggesting some variation of Newtonian dynamics, where some 'absolute' frame of reference exists?harry wrote:Hello Qev
Actual Time cannot change, relative time can because the speed of EMR can be altered during experiments here on earth and when EMR comes close to compact object...
Abstract: The question of determining the spatial geometry of the Universe is of greater relevance than ever, as precision cosmology promises to verify inflationary predictions about the curvature of the Universe. We revisit the question of what can be learnt about the spatial geometry of the Universe from the perspective of a three-way Bayesian model comparison. We show that, given current data, the probability that the Universe is spatially infinite lies between 67% and 98%, depending on the choice of priors. For the strongest prior choice, we find odds of order 50:1 (200:1) in favour of a flat Universe when compared with a closed (open) model. We also report a robust, prior-independent lower limit to the number of Hubble spheres in the Universe, N_U > 5 (at 99% confidence). We forecast the accuracy with which future CMB and BAO observations will be able to constrain curvature, finding that a cosmic variance limited CMB experiment together with an SKA-like BAO observation will constrain curvature with a precision of about sigma ~ 4.5x10^{-4}. We demonstrate that the risk of 'model confusion' (i.e., wrongly favouring a flat Universe in the presence of curvature) is much larger than might be assumed from parameter errors forecasts for future probes. We argue that a 5-sigma detection threshold guarantees a confusion- and ambiguity-free model selection. Together with inflationary arguments, this implies that the geometry of the Universe is not knowable if the value of the curvature parameter is below |Omega_curvature| ~ 10^{-4}, a bound one order of magnitude larger than the size of curvature perturbations, ~ 10^{-5}. [abridged]
A photon is a package of energy. If electron gets on "higher orbit" the photon is this energy that electron gained. It changes only its name from "photon" to "increase of energy". Then, when electron drops to "lower orbit" a photon is emitted. It is not the same photon and (on rara occasions)it may have even different energy since the electron might drop to "much lower orbit" or "a little bit lower orbit". Depenting on that the new photon will have bigger or smaller energy than the original photon. Most of the time the same sice most of the time the electron just drops to the previous "orbit" (energy level). What has to be the same is only the energy that gets in and out. Since energy can't be neither created nor destroyed. And the "gravitational force" and "the curvature of space" is the proof of that, but it is another story.makc wrote:it is easy to say, photon was consumed, and the energy was used to move electron into higher orbit, and then forget about it; but if you keep thinking about it, where does photon go?
I dont think that the condition are similar. Big bang is an explosion of the spacetime. And supernova is only a star explosion.bongman wrote:Would the local conditions of a supernova be similar or equal to those found at a "big bang"? For the first 10^-43 would the area be domintated with Radiation and Plasma? or are these explosions not thought to be that powerful?
And yet .. the mysterious 'replusive force' which some say is driving the universe apart, if it is a force, must be energy, and seems to be in the process of constant creation.JimJast wrote: "...Since energy can't be neither created nor destroyed. And the "gravitational force" and "the curvature of space" is the proof of that, but it is another story.
Mark, did you check these two urls out? Absolutely fantastic about the possibilities.mark swain wrote: All i can say to this, there,s a lot we don,t understand, there are things we can,t see to explain why we don,t...
all the evidence is not there to see,, But there is evidence of some things, which makes us want to know why?
Anybody else lost a bone round here?
Mark
Abstract: In loop quantum cosmology, the universe avoids a big bang singularity and undergoes an early and short super-inflation phase. During super-inflation, non-perturbative quantum corrections to the dynamics drive an inflaton field up its potential hill, thus setting the initial conditions for standard inflation. We show that this effect can raise the inflaton high enough to achieve sufficient e-foldings in the standard inflation era. We analyze the cosmological perturbations generated when slow-roll is violated after super-inflation, and show that loop quantum effects can in principle leave an indirect signature on the largest scales in the CMB, with some loss of power and running of the spectral index.
I don't understand in what way dark energy is in "constant creation". The energy budget of the Universe is fairly well defined, and there's nothing I'm aware of that suggests the total energy is changing.aristarchusinexile wrote:And yet .. the mysterious 'replusive force' which some say is driving the universe apart, if it is a force, must be energy, and seems to be in the process of constant creation.
I guess we're reading different information, Chris .. and of course my unorthodox views will not allow me to see as "infallible" the theory that energy cannot be created or destroyed .. and while the following paragraph is mere musing I will suggest that Coulomb's Law as well as energy budget can be 'overcome' (in the loose sense of that word) if the spin of spirals creates the 'repulsion' (although I don't like that word) creates the energy which moves galaxies and groups apart as if they were balloons separated by like-charges. Also, I suggest the possibility that instead of the theoretical Dark Matter reducing the charge between galaxies ("If the charged objects are present in water, the value of k can be reduced by as much as a factor of 80) DM may add to the energy, accounting for the increasing rate of expansion the further out we go. Of course, we would then have to explain why groups of galaxies form if spirals are creating division, and while admitting I haven't of course examined many galaxies or groups, I suggest that that the non-spiral galaxies, for instance those surrounding our Milky Way, may inhibit the energy which separates spirals, allowing Andromeda and Milky Way to draw together, but with the seeming preponderance of spirals in groups would create the hypothectical energy which separates the groups, causing the expansion .. and that we are really just beginning to understand energy, I think, is illustrated by this:Chris Peterson wrote:I don't understand in what way dark energy is in "constant creation". The energy budget of the Universe is fairly well defined, and there's nothing I'm aware of that suggests the total energy is changing.aristarchusinexile wrote:And yet .. the mysterious 'replusive force' which some say is driving the universe apart, if it is a force, must be energy, and seems to be in the process of constant creation.
Exactly why we shouldn't accept theory as fact, like Big Bang for instance .. and the fact that it's accepted as fact by many is obvious from the many books which begin with the Bang, eg. 'No one knows what existed before the Big Bang.' However, I admit I view my anti-gravity bubbles causing the expansion nearly as fact, so I guess I'm as human as any other man in love with Anita Ekberg, or that blonde I met the other day, or anyone who appreciates a slice of good pizza when they're hungry.mark swain wrote:Biography
Prof. Dr. Dr. h.c. Kenneth J. Hsu,
Got to tell you mate, Biography of Dr Kenneth is not easy reading. And the three who rejected his paper maybe thought the same. The great distance of time/Matter is like a Maze, a giant Computer program waiting to be solved. If any one of the great, get it wrong, how many will get to the same dead end?
Mark
http://www.sdss.org/includes/sideimages/sdss_pie2.html wrote:
Slices through the SDSS 3-dimensional map of the distribution of galaxies. Earth is at the center, and each point represents a galaxy, typically containing about 100 billion stars. Galaxies are colored according to the ages of their stars, with the redder, more strongly clustered points showing galaxies that are made of older stars. The outer circle is at a distance of two billion light years. The region between the wedges was not mapped by the SDSS because dust in our own Galaxy obscures the view of the distant universe in these directions. Both slices contain all galaxies within -1.25 and 1.25 degrees declination.
Credit: M. Blanton and the Sloan Digital Sky Survey.