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About redshift and distant objects observation

I did a few Time&Length dilation factor calculations. This is for a distant clock away from any field and a clock on Earth on the equator with the moon passing over clock coordinates, the factors ...
olivierlambert's user avatar
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Numerical evaluation of gravitational light bending

I am looking into how light is being bent by objects of large masses with the intention of creating a numerical simulation of this (basically a ray tracer taking this phenomenon into account). I was ...
Pandicon's user avatar
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How does the light from distant stars change for an observer at the center of the collapsing or falling sphere?

At the center of a spherically symmetric thin solid static shell lies a point observer. For this observer, distant stars appear violet shifted slightly more $\frac{{G \cdot M}}{{{c^2} \cdot r}}$ ($\...
Imyaf's user avatar
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How is wavelength defined when it's changing continuously?

Take an observer, who is receiving an electromagnetic wave signal, which is constantly changing. It can be for example from a source of light falling into a black hole, so the observed wavelength is ...
Mikael's user avatar
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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
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1 answer
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Acceleration in flat space-time and gravitational redshift

Consider two observers in flat space-time, of which one, called Terrence, is stationary, while the other, called Stella, moves in an accelerated way. I am particularly interested in the case where ...
aleph's user avatar
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Derive this gravitational time-dilation formula

How is the following gravitational time dilation formula from this Wikipedia article derived? $$T_d(h) = \exp\left[\frac{1}{c^2}\int_0^h g(h') dh'\right]$$ where $T_d(h)$ is the ''total'' time ...
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2 answers
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What is missing in this gravitational time dilation derivation?

I am confused about one derivation of the gravitational time dilation. Consider a one dimensional time-independent gravitational field. Two clocks are at rest with respect to the gravitational field ...
Hans's user avatar
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139 views

Gravitational redshift and doppler effect in Schwarzschild metric

I am trying to calculate the change in frequency of a photon emitted by beacon that has a circular orbit with $r=r_1$. In $r_2 >r_1$ there is a static observer that observes the photon when he, the ...
Demetrio's user avatar
2 votes
3 answers
100 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
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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
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2 answers
263 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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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
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467 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 ...
Python House'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
253 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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3 answers
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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
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1 answer
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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
144 views

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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1 answer
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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
185 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\...
seVenVo1d's user avatar
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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
62 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
61 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
194 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
725 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
82 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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1 answer
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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
60 views

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
138 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
365 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
81 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
137 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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1 vote
2 answers
31 views

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
170 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
242 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
182 views

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
335 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
445 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 ...
Alex Trounev's user avatar
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1 vote
1 answer
44 views

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
74 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
166 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
236 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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