Questions tagged [gravitational-redshift]

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Light from a star orbiting a black hole, as measured by a distant observer

The spectrum of a hypothetical star has an absorption line at a frequency $f_\text{emit}$. The star orbits a non-rotating black hole with a mass $M$. The circular orbit is at Schwarzschild coordinate $...
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Doubt on proper time explicit integration

I have a doubt on explicit calculation of proper time. Considering that the metric is given by: $$ds^{2} = -Adt^{2} + B^{-1}dr^{2}+Cd\Omega^{2} -2Ddtd\phi \tag{1}$$ where $d\Omega^{2}$ is the solid ...
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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 ...
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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 ...
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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 ...
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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=...
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Is Eddington Luminosity at event horizon infinite?

I was reading up on a paper here. Where the author asserts that relativistic form of Eddington limit as defined in his earlier paper should be this, which is: $L_{ed} = \frac{4\pi G M_{x} c }{\kappa}(...
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1answer
33 views

Do we have to observe gravitational red/blueshift from a single frame?

I have read this question. Gravitational redshift and Energy of a photon In the answers and the comments it states that the redshift/blueshift has to be observed from the same single frame. It says ...
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61 views

Calculation regarding redshift and black hole

Reading this entry: http://www.scholarpedia.org/article/Bekenstein_bound I was wondering about one calculation mentioned. They say an object that descends adiabatically to almost a black hole's ...
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55 views

Part of a bigger question about spacetime geometry

This is a two-part question. First: I'm imagining that a laser with infinite coherence length is used to shine light toward a black hole from far away. A mirror is placed a few Schwarzchild radii ...
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64 views

Does gravitational red shift test the equivalence principle or general relativity?

These comments seem to say gravitational redshift experiments would only verify theories that obey the equivalence principle (ep), not specifically general relativity: https://arxiv.org/ftp/arxiv/...
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Is the GW170817 event evidence or counter evidence for Dark Energy?

I've always figured there must be a simpler explanation for the observed extra red shifting that has lead astronomers to hypothesize Dark Energy. Or at least there must be a simpler explanation of ...
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How is the global time coordinate $t$ (“observer at infinity” time) defined operationally e.g. in the Schwarzschild metric?

This is a question about coordinate time versus clock time / observed time, which I want to understand because I am teaching a GR course. Consider the Schwarzschild metric for specificity. I ...
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124 views

Gravitational Redshift

I want to calculate the gravitational redshift for schwarzchild spacetime. If we take the emitter(source of light) and observer stationary, how can be redshift found? Frequency seen by observer : $w=-...
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72 views

Black hole, gravitational redshift, Doppler effect

I'm studying up on the physics around black holes and got myself confused with the concepts of gravitational redship and Doppler effect. Imagine a spacecraft orbiting a non-spinning black hole. It ...
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Bad or valid expression for gravitational redshift

In my lecture of General Relativity, teacher takes the following metric : $g_{\mu\nu}(x)=\eta_{\mu\nu}+h_{\mu\nu}(x),~ {\rm with}\ h_{\mu\nu}\ll1$ Qquestion 1) I understand its first demonstration ...
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1answer
65 views

Are objects repelled by the cosmological horizon in Lambda-CDM cosmology?

When an observer watches a distant object, is there a gravitational influence of the horizon on that object? ("Distant" here is meant to mean: at a distance that is a sizeable fraction of the Hubble ...
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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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Gravitational lensing redshift around a Kerr black hole

Light from a source passes by a Kerr black hole on two sides at the equator and converges at the observer. The axis of rotation of the black hole is perpendicular to the direction of light. Two rays ...
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303 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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146 views

Can a photon circle a black hole indefinitely?

Does a photon lose energy or redshift as it circles? Will it's wavelength be the rest wavelength with centripetal and gravitational forces exactly cancelling?
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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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116 views

Gravitational redshift discrepancy?

I want to compute the redshift of a signal emitted by a static observer in $r=R_1$, $\phi=\phi_1$and recieved by another static observ at $r=R_2$, $\phi=\phi_2$ with $R_2>R_1$, in Schwarzschild ...
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1answer
79 views

How does gravitational redshift not violate the Second Law of Thermodynamics?

Suppose we had two black bodies at distinct heights in an uniform gravitational field. They are connected by an insulating tube that only allows the exchange of electromagnetic radiation. Since ...
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1answer
117 views

Energy density, pressure and temperature for massive neutrinos in cosmology

I want to be able to numerically compute the mean energy density and pressure for a massive neutrino species in cosmology, at any given scale factor $a$. These are given in terms of the distribution ...
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1answer
129 views

What does the gravitational potential of the Milky Way do to the CMB?

We sit in a gravitational potential, so there should be a blue shift on the CMB light from the potential of the Milky Way. Is this blue shift dependent on direction? Is it being subtracted from the ...
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3answers
433 views

As light travels upward in the earth’s gravitational field, it loses energy, and so its frequency goes down?

I have read this question: Light frequency and time relation where it says: As light travels upward in the earth’s gravitational field, it loses energy, and so its frequency goes down. (This ...
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2answers
380 views

Consequences of infinite redshift in the event horizon of a Schwarzschild black hole

I am familiar with the usual derivation of the fact that it is impossible for someone to observe an object enter a black hole, because of the fact that light gets infinitely redshifted as its source ...
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What were the measurements taken when S2 reached periapsis that were the 'best test of GR to date'?

There were a few news articles in the popular press and in journals like Science that claimed that the periapsis (or peribothron, as I learned today) of the star S2 orbiting around Sagittarius A* was "...
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1answer
53 views

Solar gravitational redshift problem

At hyperphysics the formula is: $$ \frac{\nu_\infty}{\nu_0} = \sqrt{1 - \frac{2GM}{c^2r}} $$ I found this article in which the authors have studied the wavelengths of a large number of solar iron ...
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100 views

Could mass also experience a form of gravitational redshift?

Main question Gravitational redshift for photons are a wellknown phenomena where the electromagnetic radiation is reduced in frequency and thus the wavelenght is increased. The wave–particle ...
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Time dilation due to gravity [duplicate]

I'm getting conflicting statements when it comes to time dilation due to gravity. Some sites say time slows down near the source of gravity and some say it's faster. Can anyone she'd some light on ...
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3answers
122 views

Do the changes in gravitational time dilation caused by the observable universe expanding explain the observed redshift from distant objects?

My thought process, where have I gone wrong? Question 1: There is no gravitational force at the center of the earth is there still gravitational time dilation. Answer: Yes, there is a potential ...
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1answer
338 views

What is the speed of light escaping a neutron star? [duplicate]

If the escape velocity of a neutron star is just less than that of light, will light come out very slowly from the star?
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1answer
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Black holes and red light

A friend of mine is reading the book "Black Holes: The Reith lectures" from Stephen Hawking. He is reading the French version, so I cannot give you the exact line, but on page 38, it is said that if ...
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2answers
523 views

(How) does gravitational lensing affect red shift?

In all the measurements taken over the years, has anyone ever observed any effect of gravitational lensing on red shift? So: if we would look at 2 galaxies at, say, 250 million lightyears away, where ...
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1answer
64 views

Frequency difference between electromagnetic wave generated in gravitational field and far beyond

Lets take the hydrogen line frequency of $h_0=1420405751.7667\,\text{Hz}$. This is the frequency we get if the generating hydrogen atom is located far away in space where there is (nearly) no gravity. ...
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2answers
927 views

What were the findings of the Pound-Rebka Experiment?

I am currently learning very basic astrophysics, more specifically, the principles of Einstein's General Relativity. In my notes, one of the paradoxes is the Pound-Rebka Experiment. The paradox is ...
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277 views

Do massive particles redshift the same way as photons in a gravitational field?

Let's assume two observers $A$ and $B$ hovering in a gravitation field. $A$ sends a radio transmission of frequency $f_1$ to $B$. $B$ receives this transmission and finds it has frequency $f_2$. As ...
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108 views

Gravitational red shift compared to expansion red shift

From the gravitational red shift: $$\lambda(r)=\lambda(e)\left(1+\frac{gd}{c^2}\right)$$ where $r=received,\,e=emitted$ sources. Therefore light coming from a distant star to earth would be more red ...
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Red shift and the expanding universe pertaining to gravity wells

is it possible that gravity's effect on the energy level of light could be causing the red shift in light arriving from other galaxies and not an expanding universe? it is impossible, after all, to ...
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1answer
299 views

Is the event horizon of a black hole wavelength-specific?

The event horizon is the boundary surrounding a black hole from which not even light can escape. There's a certain negative potential energy level associated with the event horizon. Now, some shorter-...
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120 views

Cosmological, gravitaitonal and doppler redshift power?

I am trying to get my head around the concept of redshifts and their relation to powers. Consider the observe $O$ at rest (who is measuring the power) and emitter $E$ in one of the three following ...
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The energy of a photon and gravitational red shift [duplicate]

The general formula for gravitational red shift is given by: $$ \newcommand{\p}[2]{\frac{\partial #1}{\partial #2}} \newcommand{\f}[2]{\frac{ #1}{ #2}} \newcommand{\l}[0]{\left(} \newcommand{\r}[0]{\...
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1answer
271 views

Two possible processes in gravitational redshift

I note there are many question about gravitational redshift and I realize that my question might be buried in one of those but I can’t see it. I am thinking about two different processes in relation ...
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1answer
80 views

Would gravitational waves detected at GW150914 have been redshifted?

Would the gravitational waves detected in September 2015 (announced Feb 2016) have been gravitationally redshifted as they escaped from a black hole of 62 solar masses? If so, how would that have ...
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Did Hubble consider gravitational redshift? [duplicate]

When Hubble first looked at redshifts of light from distant galaxies, and calculated the speed at which they were 'retreating from us' (or, the speed at which the space between them and us is ...
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1answer
120 views

Why the space suit looks white in Millers planet in the movie Interstellar? [closed]

The accretion disk of Gargantua (the black hole in the movie) is red (or orange) in color (probably because of red shift due to intense gravity?). And the Millers planet is revolving around this black ...
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1answer
251 views

Gravitational time dilation from the perspective of an accelerating rocket

A common thought experiment illustrating gravitational time dilation involves Alice and Bob in an accelerated rocket. Alice is above Bob. Bob fires periodic signals upwards. Alice observes the signals ...
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1answer
103 views

Can be possible that a neutron star has a negative gravitational surface redshift?

I am looking for some strange stars that is gravitationally blue shifted. A star surface redshift determines mass-radius relation for chargeless star. Can be possible that a charged neutron star ...