Questions tagged [redshift]

Redshift refers to the difference in frequency of an electromagnetic wave as measured by a source versus a receiver in relative motion.

Filter by
Sorted by
Tagged with
0 votes
0 answers
23 views

Resolution of Einstein prediction of brightness loss with acceleration

Stars moving at velocities relative to us nearer to light speed are predicted to have lower brightness as well as red shift. Brightness loss has not been observed, however. Could this be due to ...
Hugh's user avatar
  • 1
0 votes
0 answers
38 views

Up-tunneling of vacuum with high-energy events?

I was reading these papers by Sean Carroll (https://arxiv.org/abs/1405.0298 ; https://arxiv.org/abs/1505.02780) in which, among other things, he argues against vacuum up-tunneling occurring in the ...
vengaq's user avatar
  • 2,224
1 vote
1 answer
182 views

Why are physicists not more concerned that there are too many explanations for redshift in the universe?

There are speculative explanations for red shift such as the tired light theory, but I am not referring to those. There are three mainstream explanations Red shift due the expansion of the universe ...
John Hobson's user avatar
0 votes
1 answer
53 views

Why do successive redshifts multiply rather than add?

I understand the argument presented in the answer to this question on how successive redshifts combine, such that $$1+z = (1+z_1)(1+z_2) = 1 + z_1 + z_2 + z_1z_2 \\ \therefore z = z_1 + z_2 + z_1z_2.$$...
Josh's user avatar
  • 37
0 votes
1 answer
51 views

Cosmological redshift without approximations

The classical proof of cosmological redshift that leads to the relation: $\frac{\lambda_0}{\lambda_e}=1+z=\frac{a\left(t_0\right)}{a\left(t_e\right)}$ is quite well known as for example (among many ...
Vincent ISOZ's user avatar
1 vote
2 answers
129 views

Is cosmological redshift associated with recession velocity when the light left or when it arrived?

Is the cosmological redshift $z$ associated with the recession velocity when the light left, when it arrived, or something in-between?
user avatar
1 vote
0 answers
34 views

Blueshift and redshift of a radially infalling photon [closed]

An observer, initially at rest in infinity, is radially infalling through a Schwarschild black hole of mass M. Also a photon is radially infalling, almost cathing up the observer at a radial distance ...
qwerty's user avatar
  • 11
-3 votes
2 answers
106 views

Would continuously increasing curvature of space explain seeming expansion of the universe? [closed]

Could expanding universe phenomenon be explained by slowly but continuously increasing curvature of space around masses like galaxies and galaxy clusters? In other words, I am curious whether the ...
Roland Pihlakas's user avatar
2 votes
1 answer
28 views

Advantage of a single large telescope over many small ones for optical/infrared spectroscopy?

In a thought experiment where we would like to do optical/infrared spectroscopy on distant galaxies, and in which we would like to increase as much as possible the resolution of the spectroscopy (...
Vincent's user avatar
  • 1,069
1 vote
0 answers
25 views

Gravitational redshift inside tunnel that goes to the center (where the light comes from) of massive body of radius $R$ a distance $r$ from the center

I'd like to know the general formula of the gravitational red shift for light emitted from the center of a massive body of density $\rho$ and radius $R$ where the light is emitted from the center of ...
Relativist's user avatar
0 votes
0 answers
37 views

Is there a formula for gravitational time dilation at the cosmological scale?

There is a standard formula for gravitational time dilation used in eg the operation of the global positioning system. It is based on the integration of g(h) where g is a function relating ...
John Hobson's user avatar
1 vote
1 answer
37 views

Why only Lyman alpha transition suffer Redshift in the epoch of Recombination in Cosmology?

I was reading Baumann's book on cosmology (topic: Effective three level system). There it is said that in the epoch of recombination to form Hydrogen molecule two type of transition happens. $$ 2S \to ...
Kazi Abu Rousan's user avatar
1 vote
1 answer
127 views

Redshift near Kerr Black Hole

The question is related to Sean Carroll's Spacetime and Geometry ex 6.6. Consider a Kerr black hole with an accretion disk of negligible mass. Particles in the disk follow geodesics. Some iron in the ...
Tachon's user avatar
  • 83
1 vote
0 answers
51 views

How to derive deceleration parameter in terms of redshift?

How do I get q in terms of $z$ specifically of this form: I want to derive the second equation from the first but I'm getting an additional $ \frac{a^2}{H^2}\ $ in the second term $$ q= -\frac{\ddot{a}...
Scribbles and scratches's user avatar
0 votes
2 answers
86 views

If the expansion of space causes the elongation of light waves, why isn't this elongation observed within the Milky Way?

The elongation of light waves occurs not because galaxies are moving away from each other, but because light waves are stretching along with the fabric of expanding space (cosmological redshift). ...
Dinislam Maushov's user avatar
0 votes
0 answers
43 views

Clocks at different redshift: does calculating luminosity distance shift the frame of reference?

Luminosity is energy per time. When we calculate a luminosity distance, using angular diameter distance times $(1+z)^2$, I think we are correcting the energy (from redshifted photons) by $(1+z)$ and ...
MikeHelland's user avatar
0 votes
1 answer
95 views

Maths behind red/blue-shifting [closed]

I watched this video of silly science facts, on of which stated "you can avoid red lights by travelling at around 114,000,000mph (51,000,000m/s) because the red light would be blue shited enough ...
Ethan's user avatar
  • 131
1 vote
0 answers
42 views

How can we accurately tell distances of celestial bodies when considering superluminal expansion [closed]

If parts of the universe are moving away from each other faster than the speed of light relative to my position in space, how can we accurately tell the age or distance of other celestial bodies ...
Spatium et Tempore's user avatar
0 votes
0 answers
143 views

Constraints on the CMB temperature redshift dependence at matter-radiation equality?

As pointed out in the 2011 paper Constraints on the CMB temperature redshift dependence... here the relation between redshift and the CMB temperature, $T_{CMB}(z)=T_0(1+z)^{1-\beta}$ (with $\beta=0$ ...
Mr Anderson's user avatar
  • 1,399
1 vote
1 answer
76 views

The linear growth factor of perturbations today should be 1 but I am unable to derive it

The definition of the linear growth factor $D(z)$ of perturbations in a cosmological setting is usually normalized to unity at redshift $z=0$. So, $$\delta(z) = D(z)\times \delta(z=0) \tag{1}$$ where $...
Matrix23's user avatar
  • 1,200
0 votes
0 answers
23 views

Casimir Effect & Redshifting

The classic plate experiment highlights how omitted wavelengths of light create an energy differential and pressure. This pressure is dependent on the distance between the plates, including how this ...
Eric Roche's user avatar
0 votes
1 answer
65 views

How fast would you have to go in space to be warmed to a comfortable temperature?

How fast would you have to go in space, not near a star, such that the Cosmic Microwave Background is blueshifted enough to warm you to a comfortable temperature (70 F or 21.111 C)? Expressing it in ...
Jonathan's user avatar
  • 213
0 votes
2 answers
166 views

How is a photon being consumed by electron in QM?

I'm not a physicist in any way, but I'm curious enough to watch and attend some pop-science lectures. Let's imagine the following situation - there is a free-standing unbound electron. It has its wave-...
abyss.7's user avatar
  • 555
1 vote
3 answers
104 views

Why do we See Black Holes?

The image of things falling into a Black Hole stays frozen on the event horizon forever. So how is it that we don't see the image of a dying star where a Black Hole formed? We see the black, with an ...
talanum1's user avatar
6 votes
3 answers
836 views

"Artificially" time dilated photons

If you bang on the table you create a single thump, but if you keep doing so with shorter and shorter intervals, eventually it'll start to sound like a note with a particular pitch. Now, if I used a ...
Cosmo's user avatar
  • 303
-6 votes
1 answer
203 views

Was doppler effect for light proven experimentally?

If so, provide me with the data sources. From what I read, doppler for light is taken for granted. Or sometimes based on theoretical formulas. But if one wants to theorise, light is a mix of photons ...
MrFramm's user avatar
  • 11
0 votes
2 answers
74 views

Detectability of cosmological redshift in an empty part of universe

I'm pretty new to the concept and I want to get a better idea about it. I've seen a video in which a light wave is stretched since the space itself is stretching. Another analogy is that cosmological ...
Shirish Kulhari's user avatar
0 votes
0 answers
34 views

Since the general formula of redshift only depends on the metric of the source and the observer, how do we end up with Integrated Sachs-Wolfe effect?

To my knowledge, the most general expression of the redshift in cosmology is the following: $1+z=\frac{\left(g_{\mu\nu}k^{\mu}u^{\nu}\right)_{S}}{\left(g_{\mu\nu}k^{\mu}u^{\nu}\right)_{O}}$ where : $...
Vincent's user avatar
  • 1,069
1 vote
1 answer
60 views

Mass redshift degeneracy for binary black holes at all order in post-Newtonian perturbation theory

When you compute the inspiral signals of a binary black hole to lowest order in the post-Newtonian formalism, and study how this solution propagates through an expanding spacetime, you find that the ...
konstle's user avatar
  • 758
0 votes
0 answers
34 views

Has the speed of light always been constant? [duplicate]

Is there any evidence to suggest that the speed of light (or its other properties) has been unchanged since the beginning? The particular curiosity stems from the redshift observed in distant galaxies....
A McKelvy's user avatar
  • 277
8 votes
2 answers
707 views

At what distance can I assume peculiar velocity is negligible compared to expansion velocity, to use Hubble's law?

I am working on a high school physics assignment and am trying to figure out a method to determine if the star is a giant or main sequence from its spectral and photometric data (from SDSS). I picked ...
Hossam Dahshan's user avatar
3 votes
1 answer
284 views

Do LIGO O4 Gravitational waves observations distance estimates account for redshift?

A new LIGO detection today has a mean distance estimate of 7412 Mpc. Does that mean that this LIGO distance calculation does not account for redshift, since that mean distance estimate translates to ...
Max Kislik's user avatar
0 votes
1 answer
394 views

Methods for calculating the orbital speed of a star in a binary system

As I understand it, to calculate the speed of rotation of a star in a binary system that is receeding, that is in the same plane as us (inclined at 0 degrees) the method is use the Doppler formula: Δλ/...
tomd7824's user avatar
  • 103
-4 votes
1 answer
74 views

Is it possible to measure the one way speed of light with redshift [duplicate]

By this I mean say you had and entire galaxy to work with, and you could measure the exact wavelengths of the waves you send out and record it. You would shoot this light beam across the galaxy and ...
Baker Rentmeister's user avatar
2 votes
1 answer
72 views

Why does a distant observer experience gravitational redshift and not blueshift?

The model I am learning to explore Schwarzschild spacetime is where solution modes to the scalar equation originate at null infinity, propogate through a massive body (only inside the mass is the ...
Tawny's user avatar
  • 91
1 vote
1 answer
218 views

Taylor Expansion of the scale factor in terms of redshift

I was reading about the Taylor expansion of the scale factor from visser,2004 He writes: $$ \frac{a(t)}{a_0} = 1 +H_0 (t -t_0) - \frac{q_0}{2} {H_0}^{2}(t-t_0)^2 + \frac{j_0}{3 !} {H_0}^{3}(t-t_0)^3 ...
Alucard's user avatar
  • 299
0 votes
1 answer
114 views

Why does redshift happen?

If an object B does NOT move away from us, doesn't matter whether it's 10 km or 5,000,000 km away from us, I think redshift wouldn't happen. Now, if the object is moving away from us, it's said that ...
Matt's user avatar
  • 367
0 votes
4 answers
146 views

How cosmologists know if the observed redshift of galaxies is due to expansion and not intrinsic to the galaxy?

Is there a way to experimentally test if the cosmological red shift observed is due to the expansion or intrinsic to the galaxy? If anyone knows how to do this or how to extract from the data please ...
Markoul11's user avatar
  • 3,849
-1 votes
1 answer
51 views

Confusion regarding redshift

I've just learned about redshift a couple of days ago, and i found myself questioning why relative motion to the observer is the only thing that could affect the intensity of the red shift of the ...
Andrés de Fonollosa's user avatar
2 votes
0 answers
26 views

When light gets red shifted by the expending universe it's energy decreases. What happens to that energy? [duplicate]

If a Photon of light is red shifted its wavelength increases and therefore its energy decreases. What happens to that energy as energy should be conserved right?
Jakob Boyes-Jensen's user avatar
0 votes
1 answer
66 views

Electromagnetic energy-momentum tensor with allowance for gravitational redshift

Is there an electromagnetic energy-momentum tensor that takes into account the gravitational redshift? If so, what does it look like and where can I read more about it?
LeoShab's user avatar
2 votes
0 answers
76 views

Keck versus Webb: discrepancies in the redshift measurements of the galaxy GN-z11 (the most distant galaxy discovered with the Hubble Space Telescope)

Two years ago Nature Astronomy published a paper based on measurements from the Keck Telescope stating that the redshift of the galaxy GN-z11 (discovered by Hubble) is: $$ z=10.957 \pm 0.001 $$ Source:...
Albert's user avatar
  • 507
0 votes
1 answer
149 views

Energy conservation in the redshifted light by expansion of the universe [duplicate]

I asked chat-gpt the same question, and this is her answer: The energy of light that is redshifted due to the expansion of the universe doesn't disappear, it is simply transformed into other forms of ...
lukek1101's user avatar
1 vote
0 answers
41 views

Does the Doppler effect work either way?

I know that the Doppler effect is when waves get compressed or stretched. For light this causes red shifts and blue shifts. My question is if we were moving towards or away from the source of light, ...
Anish Kommireddy's user avatar
1 vote
0 answers
42 views

How would the Redshift of a Photon be influenced if it travels through a volumetric gas disk?

so me and a buddy have been working on a Black Hole render engine for quiet a while now. And at this point we have most of the technical stuff worked out. Which results in images like these; Note, ...
ErikHall's user avatar
  • 298
1 vote
1 answer
115 views

Different definitions of recession velocity

I have encountered two definitions of recession velocity that seem to refer to different concepts, but I am wondering whether the two are actually the same. Definition 1 If we denote the scale factor, ...
Wild Feather's user avatar
0 votes
1 answer
61 views

Blueshift caused by dark energy?

Galaxies that are sufficiently far away from our point of view are receding from us due to the accelerated expansion of the universe (supposedly caused by dark energy) and therefore their light is ...
vengaq's user avatar
  • 2,224
1 vote
1 answer
125 views

Doesn't the increase in redshift of galaxies over larger distances mean that the expansion of the universe is slowing down? [duplicate]

This question seems too simple to not have been asked, but I cannot seem to find an explanation. So apologies if this is a duplicate. The current explanation for the expansion of the universe as I ...
Zach's user avatar
  • 21
1 vote
1 answer
85 views

Distance $r$ between galaxies inside the galaxy cluster

I am currently working on the dynamics of the galaxy cluster, so i am trying to get the distance $r$ between the galaxies inside the galaxy cluster from its centre. As a input i have RA , DEC and Z ...
Atul's user avatar
  • 11
3 votes
1 answer
67 views

Frequency shift of photon using magnetic field

According to GR, it is possible to redshift the frequency of a photon using a magnetic field as demonstrated by the Gerstenshtein Effect: https://web.archive.org/web/20210225134450/http://jetp.ac.ru/...
Phil Bouchard's user avatar

1
2 3 4 5
8