Redshift Definition and 385 Threads

Hello! I have a small question, in my textbook and everywhere I look online it states that to find the redshift of a receding galaxy from the spectrograph you divide the change in wavelength by the original point you are measuring from. The problem I have is, if there is a 20nm shift for...

Okay, from what I understand, the cosmological redshift is due to the expansion of the universe. I'm confused as to how this works. I don't understand why, if the universe is expanding, that the waves don't just have farther to travel. I also don't understand what is waving or why other...

I'm a bit confused about redshift and the apparent increase in acceleration. If I understood it correctly redshift is caused by the expansion of the universe (space itself). What I don't understand though, if galaxies further away have a higher increase in redshift vs distance than galaxies...

....This is just a concept I have been playing with for awhile... As my knowledge of GR is limited and my knowledge of Mach's principle is limited to its application to inertia I am going to use my own generalizations from them both. If my understanding or interpretation of either is wrong...

I want to discuss energy conservation and time dilation relative to the cosmological redshift. Because the elements of the redshift are coordinate specific, I’ll focus just on the FRW metric using proper distance coordinates (not comoving coordinates). As explained in Tamara Davis’s cover...

Lets say we emit a photon from the ground out towards the sky , and as the photon travels away from Earth it gets red-shifted . In stead of canceling the shift by using the Doppler effect like they did in the pound-rebka experiment , we use the zeeman effect to alter the discrete energy...

I was just curious as to if there are any graphs or data available to see a more detailed outline of the temperature vs. redshift or temperature vs. time available in any published papers, books, or even online.

I was just reading the old document by H.A. Lorentz " The Einstein Theory of Relativity" which is freely available in ebook and text format. I find it interesting to read some of the comments from those times, and Lorentz provides a nice summary of the thoughts of the days soon after a second...

Understanding the accelerating/decelerating expansion of universe based on redshift.. I am trying to understand how the expansion of the universe is accelerating, if indeed it is. It's confusing, as some people say that the expansion is accelerating, whereas I have a video lecture where the...

The following two graphics are supposed to be the same, but they are not (there is something I am not getting right). After the calculation of m ( z ) (magnitude as a function of redshift) I get the plot of the first link: -Plot at the bottom (NOT the last one) of...

I'm new to the Physics forum and thought I'd start with a couple of stupid questions. 1) How do we know that black holes are not stellar nuclei that have just collapsed to a volume less than their mass dependent Schwarzschild radius (the radius at which the speed of light is the escape...

If as a result of the equivalence principle we can derive the gravitational red shift entirely from the perspective of an accelerating body with no reference to gravity and no reference to gravitational time dilation then one is essentially just working out the Doppler shift of a signal...

I am a bit confused here. Is cosmological redshift the same as doppler redshift? This is from wikipedia: "The redshift z often is described as a redshift velocity, which is the recessional velocity that would produce the same redshift if it were caused by a linear Doppler effect (which...

We can imagine a sphere floating freely in space. Perhaps it is something like a ping pong ball. We attach a piece of string to a random position on the surface of the sphere. If we vibrate the string, the sphere will be pulled in the direction of the string. If we repeatedly move the...

In several threads where I've seen the redshift issue discussed there's been some confusion about this point, Must we treat cosmological redshift as a purely kinematic (relativistic)doppler effect or as the time dymamics of the metric space? Or both views can be made to converge?

Gravitational redshift is given by the following approximate equation; \frac{\lambda}{\lambda_o} = 1 - \frac{GM}{r c^2} From http://scienceworld.wolfram.com/physics/GravitationalRedshift.html Where \lambda is the shifted wavelength and \lambda_o is the rest wavelength. r is...

condidering a photon in expanding cosmos, it 's said that the wavenumber k remains unchanged, the wavelength \lambda increases, proportional to the scale factor a(t) of the universe, and the frequency w decreases in the opposite way, that is the cosmic redshift. so, why does k...

The CMB is believed to have started [or ended] 13.7 billion years ago. Recent estimates of Hubble constant are around 70 km/s/Mpc, or 228 km/s/Mlyr. When we look at CMB we are looking back 13700 million years into the past. Multiplying 228 by 13700 gives us 1.04 times the speed of light as...

redshift ""first year astronomy"" how do i find distance using redshift? please keep in mind that this is first year astronomy course i am currently taking having some trouble doing it. don't know where to start

From what I understand: 1. The more massive the object, the stronger the gravitational field. This leads to the light being emitted from the surface to shift down in frequency. 2. The rate of expansion of the universe causes a redshift proportional its distance away. I'm new to this, but...

Homework Statement I am trying to calculate, from their redshifts, the speed at which each of the following galaxies is moving away from us. Give your answers in both km/s and as a fraction of the speed of light. The galaxies are: Galaxy 1: Observed wavelength of hydrogen line is 659.2...

How do I calculate the redshift of a galaxy that is 650 Mpc away if I am only told its spectral lines should show a redshift z=.15?

Why is it that Quasars don't red-shift? Any ideas or speculations? http://www.physorg.com/news190027752.html Surely all the measurements across all these quasars can't all be wrong. Is it possible that the Big Bang theory is wrong? Is it possible that the universe is not expanding? If...

Homework Statement Hey :-) I want to calculate the redshift at which the Universe became vacuum dominated, with given values for the energy densities of Omega_{m} and Omega_{Lambda}. Homework Equations I know that the scale factors rho_{m} is proportional to a^{-3} rho_{r} is...

This might be a tired topic but please help me to understand. Assume a photon moving in vacuum, ignore potential interstellar medium absorption and re-emission since it is not relevant to discussion of space expansion in this context. Redshifted photons will undergo energy loss between *right...

I have a question.. So far, from what I've browsed on the forums, I haven't found an answer to it, and I figured this would be the best place for it. I'm aware of the balloon analogy, but I have a question regarding blueshifts and redshifts. If you take the balloon analogy, everything in the...

A redshift survey has identified a galaxy cluster for which it infers a di stance of 520 Mpc. At what redshift is this cluster observed to be? You may use H0 = 72 km s−1 Mpc−1 Now call me old fashioned but don't i need some kind of relativistic speed to calculate the redshift, i mean i have a...

I know about cosmic expansion, but I was just curious, could the observations of redshift be caused because space is cooling, not expanding. From what I understand, as things cool they redshift. If the universe started cooling after the big bang, wouldn't everything we saw from the early...

Hello. This is one of my coursework questions I was wondering if I could get some insight here.. here is the question: The size of the Universe if conveniently parameterized by a scale factor, a(t), which simply describes how big the Universe is at other times relative to its present size...

Hello. This is question for my course work, I was wondering if I could get some insight, here is the question: Assume that the vast majority of the photons in the present Universe are cosmic microwave radiation photons that are a relic of the big bang. For simplicity, also assume that all the...

I've been trying to find out more about cosmic background radiation, but I am unable to find any information on the variations in the measured cosmic background radiation. I'm talking about these WMAP images. Most of the images you'll find on Internet are the versions after being corrected...

the figure 1.73 is approximate...given uncertainties, somewhere around 1.7. We see galaxies out beyond z = 7, of course, and the ancient background light has redshift 1090, so we see ancient matter emitting light, before it even formed stars and galaxies. But as of now, the standard model...

http://img76.imageshack.us/img76/2711/virgocluster.jpg Look at this image of the Virgo cluster of galaxies, for images of galaxies extending as far as the eye can see, some appear to exist in a swarm around the sub cluster at the core, others are in streamers and wisps of galaxies extending...

I am reading Wald's book. There is a problem confused me: page 158, problem 4,(b). An symptotic statoinary flat space, two stationary observer connected with a rope. One observer A is at finite r and the other B is at infinity. Observer B is really stationary by other forces and holding the...

I’ve made several efforts to provide a simple description of how the cosmological redshift works. Each has been closer to the mark than its predecessor, and now I think I’ve got it nailed. The premise underlying the redshift is simply that a photon must travel at a local velocity of c through...

If an atom in a distant galaxy emits a uv photon, the photon would have had enough energy to cause photoelectric emission from a negatively charged zinc plate. By the time the photon reaches me on Earth it has been sufficiently 'redshifted' so that it could not cause photoelectric emission if...

While objects closer to us tend to shift both in direction red or blue, depending on their movement in relation to us, distant objects such as galaxies tend to only shift to the red. As I understand this is the base of the idea that the universe is expanding. But how are we sure that is the...

I was looking at section 7.6 of Longair's Galaxy Formation, and in it, he is talking about the flatness problem, or fine-tuning problem. In it, he shows that if you define a general (i.e. varies with cosmic time and hence with redshift) density parameter \Omega_m for matter by analogy with...

I have read on a NASA website amongst other places that "Many astronomers believe that Seyfert galaxies and high-energy quasars are basically the same type of objects, but we are simply viewing them differently". But on the same website it also says that "by measuring their redshifts, we find...

Here is an interesting observation, which I would like to know the validity of. The momentum of a relativistic 'cosmological' particle in a homogeneous universe can be written as ^{[1]} L = \gamma m a v_{pec} = K where \gamma=(1-v_{pec}^2/c^2)^{-0.5}, m the rest mass, v_{pec} the peculiar...

If light is moving on a curve, for instance, if light were bent around a massive body thus curving due to gravity, does it undergo any redshift of blueshift? I ask this because the universe may not be expanding (what we see as redshift), but may just be affected by gravity, and curving, thus...

Surely it is possible to take a spectrum, deduce the redshift, then use this as a definitive distance indicator for all distances. Why is it we use the distance ladder?

I am stuck on a few cosmological points I could use some help on. The first being "redshift" as an indication of inflation. To me red shift just seems like it's a result of the degradation of light quanta over long distances. Since light slows down in environments close to absolute zero...

It seems quite common to more or less equate gravitational redshift to gravitational time dilation. For example, the two might be explained as follows. We have two observers. A is standing on the surface of the earth, B on the top of a tower. A sends light up to B with some frequency, B...

Gravitational redshift seems to be measured as if gravitational time dilation has no effect upon it. What effect if any does gravitational time dilation have on the measurement of gravitational redshift?

Are there any alternative theories/explanations of why light from distant galaxies is redshifted by an amount proportional to the distance away from us, other than the popular universal expansion explanation? Maybe some theory about light losing energy when traveling over such large distances...

does the expansion itself redshifts photons (if so, does the expansion affect the photon in his frame of referance?) or is it because the distant object that emits them is seemingly moving away from us (in cases where the expansion is much more dominant of course)? The latter doesn't makes much...

I understand the concept, but not the math. For example, let's say a galaxy is moving away from us, and we observe one absorption line at 400 nm, and another absorption line at 500 nm. Let's also say that we determine that the radiation was emitted originally at 200 nm and 300 nm...

Which statement is true? A The apparent speed of recession of a galaxy is given by the product of the Hubble constant and the distance to the galaxy. B The further away a galaxy is, the lower its apparent speed of motion away from us. C A galaxy with a redshift of 5.37 is situated at a...

I have a hopefully straightforward question. It is well known that in the Schwarzschild metric the gravitational redshift is given by 1+z=(1-r_{s}/r)^{-1/2}. Clearly this is just the ratio of observed to emitted frequencies (or energies). I understand this so far. However, for the case of the...