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Questions tagged [redshift]

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0answers
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What is wrong about the following reasoning concerning hypersphere cosmology? [on hold]

Light traveling through a hypersphere would constantly curve while appearing to go straight in three dimensions. This would mean light gets stretched over greater distances than those we measure based ...
0
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1answer
35 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 ...
1
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2answers
53 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^{\...
0
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1answer
30 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. ...
5
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5answers
149 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 ...
-3
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1answer
35 views

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 ...
0
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1answer
19 views

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 ...
2
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1answer
66 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 ...
-6
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1answer
46 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 ...
1
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2answers
35 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 ...
14
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5answers
763 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 ...
0
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2answers
67 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 ...
2
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4answers
91 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
38 views

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. ...
2
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2answers
64 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 '...
0
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1answer
55 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 $z$ ...
0
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1answer
42 views

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 ...
0
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3answers
116 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 ...
0
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1answer
86 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 ...
0
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1answer
77 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 ...
1
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1answer
47 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 ...
0
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1answer
46 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 ...
0
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1answer
75 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 ...
0
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2answers
93 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?
1
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2answers
65 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 ...
3
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1answer
82 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 ...
0
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2answers
66 views

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.
3
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3answers
108 views

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 ...
16
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3answers
3k views

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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0answers
56 views

How is the redshift related to the energy and time?

Cosmologists talk about redshifts instead of time to describe the past of the Universe. For example, the recombination happens at $z=11.00$. Knowing the redshift how can I convert it to the energy and ...
1
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2answers
70 views

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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5answers
2k views

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 ...
0
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1answer
50 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 ...
0
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1answer
76 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 \ \...
3
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3answers
158 views

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 ...
0
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1answer
85 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 ...
1
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1answer
105 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 ...
0
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3answers
192 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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0answers
32 views

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 ...
0
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2answers
150 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 ...
1
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1answer
80 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 ...
0
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1answer
31 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 ...
53
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4answers
10k views

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 ...
0
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1answer
218 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 ...
0
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1answer
22 views

Information contained in red shifted “light”.

A source of light is traveling away from us at .95c. Its emr reaches us with a big redshifted wave pattern yet still arrives at the speed of light. So if our light source moves away from us at say 1....
2
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2answers
60 views

Red-shifting due to emitting gravitational waves

Light waves exert their own gravitational pull and must be emitting gravitational waves, losing energy in the process. Does this mean that light becomes red-shifted as it travels even without the ...
1
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1answer
58 views

are redshift and Doppler effect identity with speed of light?

we know that redshift and Doppler effect say wavelength and energy are relative to the speed of cause body, so how can I understand the special relativity which said that the speed of light is same ...
2
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1answer
109 views

What is the cosmological redshift drift effect? [closed]

What is the redshift drift effect in cosmology? What are the necessary cosmological conditions for there to be a measurable redshift drift effect?
3
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1answer
132 views

If an arbitrary “signal” at an arbitrary frequency was received at Earth, would there be any way to tell if it was redshifted?

I've been thinking a lot about SETI and aliens, and, just for fun (layman), learning a lot about redshift: why it's possible despite $c$ being constant, how we know stars are red- or blueshifted. But ...
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3answers
93 views

How do astronomers know what wavelength the body will emit when it is at rest? [duplicate]

In the book of The First Three Minutes by Weinberg, at page 21, he talks about how do astronomers measure the speed of a luminous body along the line of sight by Doppler affect, i.e. the fractional ...