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Questions tagged [redshift]

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What is the current most accurate measurement of the cosmological transition redshift

Does anyone know what the current most accurate measurement of the redshift for when the Universe's expansion changed from decelerating to accelerating (with a reference)?
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Why does the black hole's matter ring in the image released on April 10th seem to lack blue/red shift? [duplicate]

If the matter around a black hole is spinning around it at nearly the speed of light, then the blue/red shift on each side should be quite visible (even though we're watching at an angle). But in this ...
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1answer
34 views

Can expanding space stretch the wavelength of GWs? [duplicate]

I have read this question: Redshifting of Light and the expansion of the universe Now analogously, we could talk about GWs traveling in the empty voids of space, where the expansion of space is ...
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When space expands where do the energy of the gravitational wave dissipate to? [duplicate]

I think it is safe to say that gravitational wave do not dissipate unless it met matter along the way imparting some of it's energy to cause some distortion or when it's frequency is stretched even ...
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4answers
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Why hasn't anybody done a two-telescope test on the speed of starlight?

It seems that even though it wouldn't be too hard, nobody has taken the trouble to use a pair of telescopes to confirm that light originating from red-shifted / distant stars is indeed traveling at c. ...
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2answers
73 views

On Distant Lanterns and Relative Speed [closed]

It is said, that by measuring distant sources, we can gather information about the past state of the universe. The further we measure, the faster things appear to recede, which brings me to my ...
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33 views

SNIa lightcurves

How do you explain the fact that in SNIa lightcurves the rate of reception of photons is less than the rate of emission by a factor of 1+z?
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1answer
39 views

Redshift z values and galactic age

Redshift for astronomical objects is often discussed in terms of z-value which I understand to be $\dfrac{\lambda_{obsv} - \lambda_{emit}}{\lambda_{emit}}$, where $\lambda$ is the wavelength. Is this ...
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1answer
40 views

If I held up a glass lens and looked at a star through it, could I see the spectrum of the light?

Given that I can see light from stars with my naked eye. And also some lenses suffer chromatic aberration. I would think that with enough training I could simply hold up a lens to a star and look at ...
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2answers
59 views

$z$ (redshift) at the inflation start up time?

The $q$ parameter is at present -ve which implies accelerated expansion , hence we can approximate our universe now to be dominated by dark energy since dark energy provides exponential growth $~e^{\...
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1answer
49 views

Hubble - Cosmological vs Doppler Red Shift

When we learnt about the Hubble Constant at school we were taught that Hubble had observed Red Shift due to the Doppler Effect, and thus the universe (and space time itself?) must be expanding. ...
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5answers
159 views

Is redshift path-dependent?

Is redshift dependent simply upon the relative velocity and gravitational potential of transmitter and receiver? Or is it path dependent; say the receiver runs away for billions of years then changes ...
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1answer
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Does the redshift have anything to do with Compton scattering? [duplicate]

The more I think about it the more I can't help but feel that the redshift must be caused by a form of Compton scattering and the interaction between particles of light and electrons. Is this ...
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1answer
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Relative size of galaxy calculation

So this is a past exam problem, however I am confused to a question which is related to this graph and the questions states: Question: On the graph, one galaxy is labelled A. Determine the size of ...
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1answer
101 views

Gravitational redshift and Energy of a photon

Let us assume that we have a large gravitational field, then the gravitational redshift can be expressed as, $$\frac {v_{\infty}} {v_e} = (1-r_s/R_e)^{1/2}$$ In this equation $v_{\infty}$ represents ...
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1answer
70 views

Why is the mainstream theory of cosmological redshift inconsistent with the mainstream theory of gravitational redshift

Gravitational redshift Cause : A reduction in the decompression of space* over distance (due to the presence of mass). Mainstream theory: Photons are emitted in a region of higher gravity with ...
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2answers
42 views

Looking for redshift database or data

I am looking for data wich contains the redshift values(z) of observed supernova or galaxies with their observed distanced(so the distance between the object and earth how we observe it now and not ...
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5answers
777 views

Why doesn't the escape of electromagnetic waves from a microwave depend on the reference frame, because of the Doppler effect?

If an observer traveling towards a microwave oven at almost the speed of light blue shifts the microwaves enough to be visible light, how can the mesh on the oven door still stop to waves from ...
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2answers
75 views

How can the red shift due to Hubble flow be consistent with the law of conservation of energy? [duplicate]

Given that there is no change in relative kinetic energy attributable to the expansion of the universe, what accounts for the difference in energy emitted vs energy absorbed (i.e. the red shift ...
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4answers
94 views

Determining the acceleration of the Universe from a single star?

It Occurs to me we might be able to find an entirely independent method of determining the Universe's acceleration using a single source. If one was to watch a single high source consistently one ...
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0answers
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At what rate does a photon blue shift as it falls toward a black hole and red shift as time slows close to a black hole?

Perhaps I am thinking about this incorrectly when a photon arrives at an event horizon, from an observers perspective time has essentially stopped for it and the photon has red shifted completely. ...
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2answers
74 views

What part of special relativity is factored in in relativistic redshift velocity equations?

While doing research into redshift equations (doppler redshift and cosmological redshift), both types of redshift had two equations for finding recession velocity: a 'non-relativistic' equation and a '...
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1answer
62 views

BAO : Relation between redshift, Hubble constant and radial

From this link https://en.wikipedia.org/wiki/Baryon_acoustic_oscillations#Measured_observables_of_dark_energy , I can't get this relation : $$c\Delta z = H(z)\Delta \chi\quad\quad(1)$$ with $z$ ...
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1answer
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Disregarding expansion of space, are there any processes which can redshift light over billions of light-years?

Assume there are 10 molecules per cubic meter, on average, in interstellar space--in effect, a very thin gas. Assume that the source of light is ten billion light years away, the tunnel through which ...
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3answers
129 views

Is cosmological redshift at a given time has a constant value?

On one hand, people say that various cosmic events occurred at various redshift values. For example, recombination happened at $z=1100$. This would imply that at any given point in time, in the ...
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1answer
116 views

Cosmological redshift : “time of emission” vs “during travel”

Let’s consider a very distant galaxy, suppose it has no peculiar velocity, and let’s assume space expansion; If I understand correctly there would be a redshift due to the value of space expansion at ...
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1answer
79 views

How is red shifting explained with quantum mechanics? [duplicate]

Light travels as waves through space, and since space is expanding, the light gets stretched out. This is the explanation for red shifting I learned before. Now I know some more and that explanation ...
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1answer
54 views

CMB - Excess Energy? [duplicate]

Today in physics we were looking at how the energy of a photon is the product of Planck's constant and the frequency of the photon, therefore the lower the frequency, the lower the energy of the ...
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1answer
61 views

Cause of observed galactic red shift or acceleration in expansion of the universe: velocity vs gravity.

Scientist look out at the universe and observe red shifts for galaxies that are roughly proportionate from their distance from us and attribute it to a velocity away from us. Also there is an ...
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1answer
104 views

Is the expansion of the universe really accelerating? Or does it just look like it?

I pulled this quote from an article on the Hubble Constant: "...for example, if the Hubble Constant was determined to be 50 km/s/Mpc, a galaxy at 10 Mpc, would have a redshift corresponding to a ...
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2answers
94 views

Is the space between galaxies that are close to each other contracting? [closed]

The Milky Way and Andromeda are moving towards each other as indicated by blueshift. Are they just moving towards each other through space or the space between them contracting?
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2answers
69 views

Is space expansion causing increasing distances between galaxies?

I read/heard that the expansion of the universe would lead to any observer not being able to see other galaxies as time goes on, due to their light not reaching them anymore. But there's something I ...
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1answer
84 views

How scientists know that the Redshift is because of moving objects and not due to local phenomena

I'm from engineering background and not firmly familiar with cosmological equations and concepts. but i know what Redshift is and how it is related to the Doppler effect. My question is how ...
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Does converting light's linear momentum into angular momentum (SAM or OAM) cause it to redshift?

Can all of an electromagnetic wave's momentum be changed to orbital angular momentum? I'd imagine this would be easier to test with radio waves.
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How do you explain cosmological red shifting in terms of gravitons?

We know that the photons from the big bang are continually being red shifted and losing more and more energy. In terms of the graviton view, how would you explain that? Where is the energy going? Are ...
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Does the Earth's rotation affect redshift measurements?

How do you account for the spin of the earth in the mechanical sense, when measuring redshift? Does the relatively slow speed of the earth have a major change in the measurement because of distance?
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2answers
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How certain do science believe the universe is expanding?

The continue and increased rate of expansion is backed up by red shift, but that can also be true for a slowing down universe. Can the acceleration of expansion be reducing, still causing red shift ...
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Can we use redshift measurements to determine absolute velocity?

Here's a thought experiment: suppose I'm in a large box in space without windows or sensors, and I fire a laser in 6 different directions and measure the redshift along each direction. Could that data ...
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1answer
52 views

Light speed and red shift

D. Giovanni et al. showed that the speed of photons through space can be variable if certain structure is imposed on the photons themselves (see their arxiv submission or their published work in ...
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1answer
80 views

Converting from spherical to Cartesian in cosmology

So I want to find the distance between two different objects at different red shifts. My plan so far is to calculate the line of sight (LOS) co moving distance using the formula $$D_C=D_H\int_0^z \ \...
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Proof for photon energy loss due to cosmological redshift

According to Doppler redshift, the frequency of the EM radiation decreases if the emitting object is receding from the observer - this produces the problem in the quantisation of energy - the observed ...
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1answer
172 views

How do you calculate the recession velocity?

$$ \begin{alignat}{7} && \frac{\Delta \lambda}{\lambda} & = \frac{v}{c} \\[2.5px] &\therefore & v & \approx \frac{\Delta \lambda}{\lambda}c \end{alignat} $$ If you want to find ...
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1answer
116 views

Given redshift how do I obtain distance in parsec? [duplicate]

I have a catalog I am experimenting with that has some spectroscopic red shift data available (in the range from 0.5-1) as well as total Ks (K -short band) flux data available, how would I go about ...
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3answers
266 views

Redshift - How can Z be greater than 1?

I'm having trouble understanding the equation for redshift: z = Δλ/λ ≈ Δf/f ≈ v/c If z = v/c and c = speed of light, how can z>1 (as nothing can exceed the speed of light)?
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Can the age of the universe at the time of emitted light be calculated with Hubble's Law?

Let there be an object being observed, distance D away. D equals the speed of light times the time it takes the light to arrive (but space expands while the light is propagating, which is most likely ...
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2answers
163 views

Recession velocity, redshift and different cosmological models?

Equation 1 (page 5) in “Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the universe” by Davis and Lineweaver gives the general relativistic ...
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1answer
89 views

Given a fixed spectral resolution, what is the minimum detectable redshift?

Given an spectral resolution $R$ (for example $R=1000$), what is the minimum redshift which I can measure? How is this related to the minimum velocity among galaxies? If this velocity is related with ...
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1answer
32 views

Is the mean CBM frequency more red-shifted since discovered in the 1960's?

If the universe is uniformly expanding at rate x, is possible to measure that the CBM has increased its red-shift value over time? If the red-shift is a static value, is it possible that the ...
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4answers
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Red shifted to what?

I searched and found a lot of questions and answers about red shift here but none with the answer to mine. (sorry if it is there somewhere and I did not find it.) Everyone is saying the light from ...
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1answer
275 views

Redshift of matter-radiation equality from $T^4$

I am trying to solve the following problem. Argue on dimensional grounds that the energy density of blackbody radiation at temperature T should scale as $T^4$. Use this to find the redshift of ...