Re: redshift vs distance answer
Posted: Fri Apr 03, 2009 5:20 am
Seriously flawed.ipaqgeek wrote:What do you guys think of this answer:
http://wiki.answers.com/Q/What_is_the_r ... d_distance
APOD and General Astronomy Discussion Forum
https://asterisk.apod.com/
Seriously flawed.ipaqgeek wrote:What do you guys think of this answer:
http://wiki.answers.com/Q/What_is_the_r ... d_distance
Agreed, this site has some serious problems. I have occasionally gotten good information from sites like this, but you really need to be able to judge the quality before you go there. So for most people, it's worse then nothing at all.apodman wrote:But this is an excellent example of why nobody should trust any answer they get from any of the "ask anyone" sites on the web. In my experience, every answer I have seen on all of these sites (whether it's wiki answers or one of the others) is completely worthless. And you click on the "recommend contributor" link, and instead of letting you rate the answer poorly as it should be rated, it just adds one more to its "contributor trust" score and thanks you. Amateur from top to bottom.
Thanks for the link. It sure beats fishing in a pond where there are no fish.Chris Peterson wrote:madsci.org
Hubble did not agree with the expansion idea and thought that the redshift was an "hitherto unknown principle of nature". The redshift is due to the conservation of energy:E= - mGM/r + mcv giving in the Continuity Equation :
GM/r^2 = cDel.v = (cv/r)cos(p) giving cos(p) = v/c = z.
Hubble's Constant is H=Del.v = (v/r)cos(p) = fcos(p).
There is further confusion about the redshift, the centrifugal force cDel.v causes center-fleeing behavior not center-seeking behavior. The deflection is away from the gravity center not towards the gravity center. This redshift is the "source" of the "dark energy" , moving masses.
Abstract: The use of photometric redshifts in cosmology is increasing. Often, however these photo-zs are treated like spectroscopic observations, in that the peak of the photometric redshift, rather than the full probability density function (PDF), is used. This overlooks useful information inherent in the full PDF. We introduce a new real-space estimator for one of the most used cosmological statistics, the 2-point correlation function, that weights by the PDF of individual photometric objects in a manner that is optimal when Poisson statistics dominate. As our estimator does not bin based on the PDF peak it substantially enhances the clustering signal by usefully incorporating information from all photometric objects that overlap the redshift bin of interest. As a real-world application, we measure QSO clustering in the Sloan Digital Sky Survey (SDSS) and find that our estimator improves the clustering signal by a factor equivalent to increasing the survey size by a factor of 2 to 3. Our technique uses spectroscopic data to anchor the distance scale and it will be particularly useful where spectroscopic data (e.g, from BOSS) overlaps deeper photometry (e.g., from Pan-STARRS, DES or the LSST). We additionally provide simple, informative expressions to determine when our estimator will be competitive with the autocorrelation of spectroscopic objects. Although we use QSOs as an example population, our estimator can and should be applied to any clustering estimate that uses photometric objects.
Abstract: The power spectrum of density fluctuations is a foundational source of cosmological information. Precision cosmological probes targeted primarily at investigations of dark energy require accurate theoretical determinations of the power spectrum in the nonlinear regime. To exploit the observational power of future cosmological surveys, accuracy demands on the theory are at the one percent level or better. Numerical simulations are currently the only way to produce sufficiently error-controlled predictions for the power spectrum. The very high computational cost of (precision) N-body simulations is a major obstacle to obtaining predictions in the nonlinear regime, while scanning over cosmological parameters. Near-future observations, however, are likely to provide a meaningful constraint only on constant dark energy equation of state 'wCDM' cosmologies. In this paper we demonstrate that a limited set of only 37 cosmological models -- the "Coyote Universe" suite -- can be used to predict the nonlinear matter power spectrum at the required accuracy over a prior parameter range set by cosmic microwave background observations. This paper is the second in a series of three, with the final aim to provide a high-accuracy prediction scheme for the nonlinear matter power spectrum for wCDM cosmologies.
Obviously your culture is not as sophisticated as ours in Canada, Apeman, or at two years of age you would have known Duct Tape fixes anything, not Scotch Tape. Your culture can be forgiven, though, as Red Green is, after all, a Canadian.apodman wrote:My parents told me that when I was two years old I thought Scotch tape could repair anything. Kinda similar sophistication in thought, only I grew up a little since then.
If Dark Matter exists, could these large flares affect its temperature?harry wrote:G'dafrom the land of ozzzzz
This paper goes back to 2003
Still quite interesting.
Latest Sun Flare Put at X28, Strongest on Record
To understand cosmology you need to read and most what you read maybe crap, thats the 80/20 principle.Abstract: Free streaming in a \emph{mixture} of collisionless non-relativistic dark matter (DM) particles is studied by implementing methods from the theory of multicomponent plasmas. The mixture includes Fermionic, condensed and non condensed Bosonic particles decoupling in equilibrium while relativistic, heavy non-relativistic thermal relics (WIMPs), and sterile neutrinos that decouple \emph{out of equilibrium} when they are relativistic. The free-streaming length $\lambda_{fs}$ is obtained from the marginal zero of the gravitational polarization function, which separates short wavelength Landau-damped from long wavelength Jeans-unstable \emph{collective} modes. At redshift $z$ we find $ \frac{1}{\lambda^2_{fs}(z)}= \frac{1}{(1+z)} \big[\frac{0.071}{\textrm{kpc}} \big]^2 \sum_{a}\nu_a g^{2/3}_{d,a}({m_a}/{\mathrm{keV}})^2 I_a $,where $0\leq \nu_a \leq 1$ are the \emph{fractions} of the respective DM components of mass $m_a$ that decouple when the effective number of ultrarelativistic degrees of freedom is $g_{d,a}$, and $I_a$ only depend on the distribution functions at decoupling, given explicitly in all cases. If sterile neutrinos produced either resonantly or non-resonantly that decouple near the QCD scale are the \emph{only} DM component,we find $\lambda_{fs}(0) \simeq 7 \mathrm{kpc} (\mathrm{keV}/m)$ (non-resonant), $\lambda_{fs}(0) \simeq 1.73 \mathrm{kpc} (\mathrm{keV}/m)$ (resonant).If WIMPs with $m_{wimp} \gtrsim 100 \mathrm{GeV}$ decoupling at $T_d \gtrsim 10 \mathrm{MeV}$ are present in the mixture with $\nu_{wimp} \gg 10^{-12}$,$\lambda_{fs}(0) \lesssim 6.5 \times 10^{-3} \mathrm{pc}$ is \emph{dominated} by CDM. If a Bose Einstein condensate is a DM component its free streaming length is consistent with CDM because of the infrared enhancement of the distribution function.
You cannot alter your measurement of the passage of time in your own frame of reference, period; the idea doesn't even make sense without a comparison to another frame. Relative motion will cause you to measure the time passing in other frames of reference differently, though.harry wrote:G'day from the land of ozzzzzz
Apply the black box approach.
What ever happens within the Gyr box cannnot effect time outside.
You cannot alter time in one area and not effect time in another.
The "unknown principle" turned out in 1985 to be the old principle of conservation of energy. It turned out that Einstein's original general relativity requires, because of this principle, that there is a drop of proper time rate per unit of distance from the observer, equal to the curvature of space (which makes the "accelerating expansion of space" an illusion). But the cosmologists already updated general relativity with the assumption of real accelerating expansion of space which would have to be rejected if Einstein's original general relativity were to be reinstated. Einstein was already dead for 30 years and there were lots of living cosmologists trying to make careers in cosmology, so the editors of scientific journals decided to delay publishing the news about the predictive power of Einstein's general relativity. Even when it turned out in 1998 that the value of acceleration of this apparent expansion is exactly as Einstein's original general relativity predicted.link quoted by harry wrote:Hubble did not agree with the expansion idea and thought that the redshift was an "hitherto unknown principle of nature".
Yep yep yep,,,,,,,,,I agreeYou cannot alter your measurement of the passage of time in your own frame of reference, period; the idea doesn't even make sense without a comparison to another frame. Relative motion will cause you to measure the time passing in other frames of reference differently, though.
In the past month I read of light being sped 300 times beyond c in (cessium gas?)Chris Peterson wrote:
There is certainly no doubt that light travels slower than c in any medium.
I agree except, unfortunately, that Civil Engineers must be held accountable for their lack of discipline also, especially because itJimJast wrote: "...careers of living people are more important to predictions of old theories. Especially in astronomy, which "unlike in civil engineering, one may be 100% wrong and nobody is hurt" (as my astronomy teacher from Harvard, Alan Lautman, kept saying).
cause deaths.does
It is not the speed of light but only the phase speed of light. Some people keep dropping adjectives. Then non physicists who read this stuff get confused.aristarchusinexile wrote:In the past month I read of light being sped 300 times beyond c in (cessium gas?)
With light it is the wave that is the light .. with water the wave is in the water.JimJast wrote:It is not the speed of light but only the phase speed of light. Some people keep dropping adjectives. Then non physicists who read this stuff get confused.aristarchusinexile wrote:In the past month I read of light being sped 300 times beyond c in (cessium gas?)
The phase speed can be anything since it is only the speed of the picture of the wave. It is like setting a line of people and tell each of them to raise his hand and certain predefined time. The observer may see a "wave of hands" moving along the line with certain speed. This speed may be greater than speed of light, since it can be anything. It has no physical connection to any physical speed. It is only an image of a "wave of hands" in the eye of observer. Similar effect with "speed of waves" on water. The waves "move" while water stays, just oscilates a little bit making an impression of fast or slow waves.
Actually, when evaluating speed of light claims, it is best to avoid the wave model completely, and simply consider the energy carriers, photons. The question becomes whether you can transmit a photon faster than c, or restated, whether you can transmit information faster than c.aristarchusinexile wrote:With light it is the wave that is the light .. with water the wave is in the water.
But talking about knowing our world better and about astronomy, it might be remided that those sophisticated cosmologists have ruled out "Einstein's universe" since they enhanced general relativity, against Einstein's better judgement, with the axiom of expanding space. This axiom is supported only with another axiom saying that cosmological redshift is surely Doppler shift and not somethng that follows from Einstein's gravitation (which it is and it could be easily demonstrated if it were legal in this forum)."Most of us live in urban worlds where we think everything's totally well known," Beehler said. "It's a little bit of a reminder, just a wake up call, that we really need to know our world better so we can manage it better."
And yet phase velocity (the one greater than c) refers to the phase of wave. Only the phase can move with speed greater than c since it is not a physical speed and it is only the "speed of an image in human brain" and this one can "move" at any speed. It is also the "apparent speed" of wave front. While this is true that light is not a wave, most people keep talking about "water waves", "radio waves", etc. since they can imagine them this way. Like they can imagine that the universe is expanding, despite it is not possible physically (because Einstein's general relativity necessarily complies with the principle of conservation of energy and Hubble redshift solely due to expansion would violate this principle).Chris Peterson wrote:Light is not a wave [...]
My point exactly.Chris Peterson wrote:Actually, when evaluating speed of light claims, it is best to avoid the wave model completely, and simply consider the energy carriers, photons. The question becomes whether you can transmit a photon faster than c, or restated, whether you can transmit information faster than c.aristarchusinexile wrote:With light it is the wave that is the light .. with water the wave is in the water.
Light is not a wave, at least not in a way analogous to water waves. A "light wave" isn't in anything, nor is the light itself a wave. Light consists of particles, and QM describes the way that all particles, not just light, can exhibit wave-like behavior.
1. What causes the beams?
Material at the center of M87 is drawn inward by the black hole's strong gravitational grip. This material forms a rapidly spinning flat disk, called an accretion disk. Astronomers believe that some material escapes along the poles of this disk, forming a wide jet. Magnetic fields in the disk may pinch the jet into narrow beams. Black holes are compact, dense powerhouses at the core of galaxies.
2. What does this finding mean?
Astronomers always had speculated that the jet had to be made by some mechanism relatively near the black hole, but as they looked closer to the center, they kept seeing an already-formed beam. Now astronomers have shown that M87's jet is formed within a few tenths of a light-year of the galaxy's core, presumed to be a black hole three billion times more massive than the Sun. This new information will help scientists decipher how these powerful "engines" work.
So, to be clear, you're agreeing that every observer experiences their own unique flow of time, and that there is no such thing as 'Actual Time'?harry wrote:G'day Qev
Qev said
Yep yep yep,,,,,,,,,I agreeYou cannot alter your measurement of the passage of time in your own frame of reference, period; the idea doesn't even make sense without a comparison to another frame. Relative motion will cause you to measure the time passing in other frames of reference differently, though.
and so on."We've seen many jets produced by black holes, but this is the first time we've seen one punch into another galaxy like we're seeing here," said Dan Evans, a scientist at the Harvard-Smithsonian Center for Astrophysics and leader of the study. "This jet could be causing all sorts of problems for the smaller galaxy it is pummeling."