Questions tagged [gravitational-redshift]

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How does one calculate the Sachs-Wolfe effect?

I start from $$\Delta T/T_{0} = - \frac{1}{3c^2}\Phi$$ where $\Phi$ is the gravitational potential which can be written in its Fourier expression as $$\Phi_k = \frac{-3}{2}\left(\frac{H_0}{k}\right)^2 ...
ArK's user avatar
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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
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When two neutron stars collide to form a black hole, for how long will last the emitted signal from the very vicinity of the new formed event horizon?

When two neutron stars collide they may form a black hole which is not a supermassive black hole but it should provoke that outside its newly formed event horizon photons are emitted as a consequence ...
Krešimir Bradvica's user avatar
0 votes
2 answers
134 views

How does gravitational redshift and blueshift work?

In a gravitational field, if a source emits a signal from below (at higher potential) every second, the signal will be received above (at lower potential) with a lower apparent frequency because time ...
externo's user avatar
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1 answer
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What is the gravitational redshift inside a thin hollow sphere? [closed]

Suppose we have a thin hollow sphere of mass M and radius R. Suppose a photon is emitted towards the centre of the sphere. What would be the gravitational redshift an observer would see in the ...
MattEdwards's user avatar
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Gravitational redshift inside a thin shell black hole

I got working on a cosmology problem that ultimately got into black holes, specifically thin shell black holes. This is a black hole where all its mass is in a thin shell with the Schwarzschild ...
MattEdwards's user avatar
5 votes
1 answer
168 views

How do you intuitively understand of the Einsteinian portion of the gravitational lensing equation?

The total gravitational lensing equation is an addition of the Newtonian Solution $\left(\frac{2GM}{c^2r}\right)$ and the Einsteinian Solution $\left(\frac{2GM}{c^2r}\right)$ thus the combined ...
Anthony Smith's user avatar
1 vote
1 answer
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Does the intrinsic energy of an object vary, if measured at different heights in a gravity field?

The gravitational redshift has different interpretations. Several quantities vary with height (or seem to), by the same equation - time, energy, mass. I wondered if measurements can shed some light on ...
user141183's user avatar
6 votes
2 answers
186 views

Neutron star accurate visualization

Has any simulation been done to produce an accurate visualization of a neutron star, as seen from an observer at distances on the order of 1 AU? (Edit: I suppose instead of 1 AU I mean "distance ...
RC_23's user avatar
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Is gravitational redshift measurable from a spacecraft observing an earthbound laser?

Aside from the calculation, the specific scenario for which I have no sense of the solution is the following: The equivalence principle proposes a parallel between the force experienced by an ...
aquagremlin's user avatar
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Photon Perpetual Motion Machine Clarification

I recently worked through problem 6.2 in Guidry which had the following setup: Take two heights, $z_1$ & $z_2$. You have a gravitational field and a photon propagating vertically in the field ...
Relativisticcucumber's user avatar
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How can gravity change the wavelength of a photon without the two peaks or troughs to accelerate one from the other?

How can gravity change the wavelength of a photon without the two peaks or troughs to accelerate one from the other? So is it possible that gravity accelerates light? Can the a certain wavelength ...
jbradvi9's user avatar
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Cosmological redshift

We have three of them (and combinations): gravitational, when light travels near masive object (red shift) Doppler's, when light is emited by moving object (red or blue) cosmological - all far ...
user61253764's user avatar
1 vote
1 answer
61 views

Enquiry about the gravitational redshift in "The young center of the Earth" by U.I. Uggerhøj et al

I was reading "The young center of the Earth" by U.I. Uggerhøj et al., lately, and the standard gravitational redshift equation given in the paper is: The link to the paper: https://arxiv....
Spectacular's user avatar
2 votes
1 answer
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Gravitational red shift and gravitational time dilation

I am a beginner in general relativity. I read the relevant section 9.1.5 in Relativity make relatively easy by Andrew Steane. After that, I thought a problem in gravitational red shift and ...
Hsu Bill's user avatar
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If we send a signal to an object closely orbiting a BH would the reflected signal be the redshifted original?

If we send a signal to an object closely orbiting a BH would the reflected signal be the redshifted original? Only that I am sure is that there would be time dilation of the signal...
Krešimir Bradvica's user avatar
1 vote
1 answer
131 views

Relativistic Redshift and understanding it's approximation

I was reading an article, and I saw the expression $$ 1+z=\frac{(g_{\mu\nu}k^{\mu}u^{\nu})_e}{(g_{\mu\nu}k^{\mu}u^{\nu})_o}, $$ where $e$ represents the emitter frame, $o$ the observer frame, $g_{\mu\...
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How would a person under gravity observe a person on a nearby planet but under 1000 times of that gravity?

So, imagine I am standing in a region in space where the gravity is, say 1g. Now, on a nearby planet, there is my friend who is under the influence of much stronger gravity, like 1000g. According to ...
Rameez Ul Haq's user avatar
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1 answer
56 views

When e.g. a star falls into a black hole would that part of the event horizon extend for a while?

When e.g. a star falls into a black hole would a part of the event horizon at that point extend for a while due to extra gravity due to the incomming star? And when the star starts to disappear even ...
Krešimir Bradvica's user avatar
0 votes
1 answer
37 views

Components in the calculation of the Sun to Earth redshift

When I see calculations of the Sun’s redshift as seen from Earth I believe, as I understand it, that 1) the gravity potential at the emission point near the Sun is taken into account, then 2) the Sun’...
Mikael Jensen's user avatar
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2 answers
156 views

Why the CMBR redshift is so higher than the redshift of the most distant therefore oldest galaxies in the universe?

Why the CMBR redshift is so higher than the redshift of the most distant therefore oldest galaxies in the universe? We know that cosmological redshift rises with distance from the object but at ...
Krešimir Bradvica's user avatar
1 vote
3 answers
453 views

Does a blueshift mean that time goes faster?

This is a follow-up question to this answer. The assumption in this answer is that time dilation always causes a small redshift when an observer looks at an object moving at a significant fraction of ...
Molten Ice's user avatar
2 votes
1 answer
75 views

Do gravitational redshift depends on reference frames?

I just want to know is the effect of redshift depending on the frames of reference or the photon really does lose energy when it escaped from a gravitational well? Imagine a spaceship is shooting a ...
user6760's user avatar
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Clocks in gravitational field

"In a gravitational field clocks slow down" - this is an effect of gravitational redshift. Are the following statements correct? If I take a "clock" from the surface of the Earth ...
Rene Kail's user avatar
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1 answer
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Is gravitational redshift reversible?

Imagine a scenario where a LASER beam is shot from the surface of one planet to a detector on another. Assume there are no atmosphere and nothing affects the beam in any way between the planets. ...
Derek Seabrooke's user avatar
2 votes
1 answer
121 views

Can a photon lose all of its energy due to gravitational redshift?

Imagine a photon that is emitted by a star that is at infinity with respect to me. We can observe the gravitational redshift happening to that photon with respect to my reference frame. I was ...
sachin shajil's user avatar
2 votes
1 answer
292 views

Do particles at rest gain energy in an expanding universe?

It is commonly understood that as the Universe expands with scale factor $a$ the energy of a photon drops like $1/a$ whereas the energy of a particle at rest is constant. In the analysis below I ...
John Eastmond's user avatar
1 vote
2 answers
72 views

Did Chou, Hume, Rosenband, Wineland (2010) account for redshift when analysing their experiment with clocks at varying heights?

In widely reported experiments by C. W. Chou, D. B. Hume, T. Rosenband, D. J. Wineland ("Optical Clocks and Relativity" (2010)) they [...] first compared the frequencies of [their] two ${\...
user12262's user avatar
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2 votes
1 answer
126 views

What does the $O$ mean in "$O(v^4)$"?

I am currently studying General Relativity and I am using the book by Schutz. I encountered a problem when I was reading about the gravitational redshift experiment. Here is the website (it is not the ...
BigDicj's user avatar
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2 answers
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Is a star that orbits a black hole, emitting different spectra while close or far from the black hole?

Is a star that is orbiting a black hole emitting different spectra respectively while close and far from the black hole? Also is that star light, when reaching our eyes, some kind of delayed while the ...
Krešimir Bradvica's user avatar
0 votes
2 answers
149 views

How the wavelength of a photon is affected by an uniform gravitational field

In the presence of a uniform gravitational field two observers at fixed positions obtain different measurements of frequency of the same photon. One observer at the origin of some coordinate system ...
Генивалдо's user avatar
1 vote
1 answer
206 views

Exercise 4, Chapter 6 in Wald's book [closed]

I would like to understand the solution of point b) in the mentioned exercise, which reads Let $(M,g_{ab})$ be a stationary spacetime with timelike Killing field $\xi^a.$ Let $V^2=-\xi^a\xi_a$. a) ...
samario28's user avatar
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3 answers
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Hughes argument (based on Schild's argument) for gravitational redshift

In his lecture notes on General Relativity (2nd page of the pdf, labelled page 7) and in the lecture itself, Scott Hughes puts forward a thought experiment to justify the existence of gravitational ...
Metropolis's user avatar
2 votes
1 answer
254 views

Is energy conserved in a geodesic?

In old school physics we know that Work done (resulf of energy) $=$ Force $×$ displacement. But, according to Einstein, free-fall is not a result of a force but just the result of objects following ...
llDarkFlowll's user avatar
4 votes
1 answer
373 views

Light scattering on the rotating black hole in the Kerr geometry

To simulate light scattering on the rotating black hole we have used this paper and this code. First, we made animation for light beam scattering in the equatorial plane For not equatorial plane the ...
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1 answer
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If an astrophysical jet contains gamma rays does it mean that at the source poles there is small gravitational redshift?

If an astrophysical jet contains gamma rays does it mean that even though the source has incredibly strong gravitational pull, at the source poles there is small gravitational redshift? Maybe there is ...
Janko Bradvica's user avatar
1 vote
2 answers
62 views

Has anyone considered a gradual change in Gravitational Potential across the universe as a cause for cosmic red shift?

Since the formation of fundamental particles at the beginning of the universe (roughly the time of the CMB emission, and after the inflationary epoch of Big Bang theory), the gravity wave front of all ...
WhetScience's user avatar
1 vote
3 answers
126 views

Would light emitted from a white hole be red-shifted or blue-shifted?

if it's not that straight-forward, what factors would effect the resulting appearance of light emerging from a white hole?
Shedbot's user avatar
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12 votes
3 answers
1k views

If I live on a planet that is heavy enough, would the CMB get blue shifted to be in the visible spectrum?

If I live on a planet that is heavy enough, would the CMB get blue shifted enough in the atmosphere of this heavy planet, due to gravitational blue-shifting, that the CMB would be in the visible ...
bubakazouba's user avatar
2 votes
1 answer
179 views

Gravitational red shift and equivalence principle

Two persons A, B are uniformly accelerating in the positive z direction by amount $g$. $A$ flashes two pulses of light with an interval $T_a$. The time interval between two flashes of light in $A$ ...
Kashmiri's user avatar
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1 vote
0 answers
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Redshift + Collapse [closed]

Let a radio transmitter on the surface of a collapsing spherical star emit monochromatic waves, let the distant observer, at the same theta and phi, as the transmitter, receive the waves. Show that at ...
LSS's user avatar
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1 vote
1 answer
159 views

Mössbauer effect to verify the gravitational redshift

"The tower used by Pound and Rebka in 1960 to exploit the Mossbauer effect is only about h = 20 meters high, and so the effect (gravitational redshift) is only $(GM/(Rc^2))(h/R) ∼ 10−15$! How ...
Gabriela Da Silva's user avatar
3 votes
1 answer
82 views

Does matter redshift light via gravity?

Imagine a photon passes by a stationary atom in a large void of empty space. We know that the gravity of the atom will bend the path of the photon. It will also blue shift as it approaches the atom ...
Derek Seabrooke's user avatar
0 votes
1 answer
203 views

Gravitational redshift in terms of wavelength

I know that Einstein’s theory of general relativity predicts that the wavelength of electromagnetic radiation will lengthen as it climbs out of a gravitational well. Photons must expend energy to ...
Erika's user avatar
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3 answers
261 views

Does the Hubble law make sense?

The Hubble law says that if an object is at a distance $r$, it should have a velocity $Hr$ and therefore any light signal from that object will be correspondingly redshifted. However, the light ...
Eric David Kramer's user avatar
2 votes
2 answers
641 views

How accurately has general relativity's prediction of gravitational redshift been measured?

According to Einstein's general relativity, massive bodies should cause gravitational redshift. How accurately has this been measured?
Zamicol's user avatar
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1 answer
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Is color perception of an celestial object effected by red shifting?

Assuming I stand on the edge of the gravitational well formed by our Sun. If I was to move infinitely closer to the Sun- and was staring at it without a filter (and wasn't harmed in doing so)- would ...
Thecodeanator 's user avatar
1 vote
0 answers
61 views

What is the frequency of a freely falling light-source measured by observer standing on planet?

Assume that a light source is falling freely on a planet with a nearly uniform gravitational field. If the light source, reaching a velocity $v$, emits a photon towards an observer standing on the ...
Mohammad Javanshiry's user avatar
0 votes
2 answers
157 views

Is this anomalous phenomenon about the gravitational blueshift effect experimentally tenable?

According to relativity [1], if there is a light source $B$ with a frequency $\nu_B$ at a distance $d$ from an observer $A$ inside a uniform gravitational field of $g$, the frequency of the light ...
Mohammad Javanshiry's user avatar
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0 answers
38 views

What is the effective radius of stellar graviton emission?

White dwarfs have been used to accurately determine photon gravitational redshift:https://scholar.google.co.uk/scholar?as_ylo=2016&q=white+dwarf+gravitational+redshift&hl=en&as_sdt=0,5#d=...
cumfy's user avatar
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