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Questions tagged [gravitational-redshift]

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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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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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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
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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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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
63 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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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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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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1answer
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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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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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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
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Does the changes to 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
246 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
68 views

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
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(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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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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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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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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0answers
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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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1answer
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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
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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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1answer
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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
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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
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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
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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
206 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
96 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 ...
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1answer
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Are most galaxies expanding from us as previously calculated?

In this question: Can a photon that is emitted from a denser part of the universe to a less dense part appear redshifted? The answers there were yes, yes and yes primarily. With our space less dense ...
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Rainbow Blackhole?

Can white light be broken into its component colors when gravitationally shifted by a black hole, in a manner similar to what a prism does? http://www.physics.utah.edu/~bromley/blackhole/index.html
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Can a photon that is emitted from a denser part of the universe to a less dense part appear redshifted?

Galaxy one is located in a dense area of the universe and galaxy two is located in a less dense part of the universe. Would galaxy one appear red-shifted to galaxy two? Is the mass density at our ...
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Why isn't the De-Broglie wavelength of massive particles redshifted in an expanding universe

It is pretty straight forward how light is redshifted in an expanding universe, yet I still can't understand why the De'Broglie wavelength of a massive particle isn't redshifted in an expanding ...
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Confusion regarding Time in a gravitational field

If time is inversely proportional to frequency. Then gravitational redshift would cause the frequency to be lower and wavelength to be higher. So if frequency is less more time has to pass by meaning ...
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1answer
79 views

How to test General Relativity?

If astronomers could measure the wavelength of light coming from the sun and compare it to the wavelength it should have without gravity, it should confirm general theory of relativity. Answer as to ...
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Energy of background radiation while falling into a black hole

As you fall into a black hole, the old story is you would be spaghettified - and this question is not about that. However passing of time would be warped, so you would see the future of the universe ...
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2answers
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Redshifting light in an expanding universe

It's evident and well known that light traveling across an expanding FLRW universe is redshifted via an equation: $$\frac{\lambda_{arriving}}{\lambda_{emitted}}=\frac{a_{now}}{a_{then}}$$ Where $a$ is ...
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How to use the gravitational redshift formula?

At hyperphysics they give this general formula: and a formula (2) "to express the frequency shift between two locations": Can you explain how to use these formulae to find the change in frequency/...
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0answers
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Why are black holes black? [duplicate]

If heard two explanations for this. One explanation is that the gravity is so strong that space is being stretched inward faster than the speed of light and thus no photons could possibly escape. The ...
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1answer
54 views

Can we produce energy by red-shifting light

The answer on my question Does light accelerate as it nears a black hole? leads me to think that light 'gains' the gravitational energy by shifting to a frequency with a higher energy (blue). Is this ...
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1answer
100 views

Is it possible to gravitationally redshift light so much that it reverses direction?

I know that redshifting does not mean that light is actually going slower but rather just reducing the energy. Is there a point that the energy is actually reduced to zero and then continues to "...
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2answers
316 views

Redshift Versus Luminosity

I understand that there is a relation between the proper distance of a cosmic object and its "measurable" redshift, i.e. once you know the value of the redshift parameter z, then you actually know how ...
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2answers
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Is the expanding of the universe also a cause which can induce gravitational waves from mass? [duplicate]

Gravitational waves arises when mass is rotating in another mass'orbital, in explosions and of course in case of colliding black holes. But are they also created when mass is moving and speeding ...
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3answers
487 views

What is the cosmological redshift of SN 1987A?

I haven't found any literature on SN 1987A, which provides me with its cosmological [not gravitational, wrong in inital question, thanks for the remark] redshift. Is it larger or smaller than $z=0.1$, ...
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Redshift due to a static gravitational field and the conservation of energy [duplicate]

I am standing on the surface of some planet. Gravity is described via General Relativity with some static metric (e.g. the Schwarzschild metric, so static means no time dependence, but the metric may ...
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2answers
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Does the density of a galaxy affect time?

Can denser galaxies appear blue shifted? Can galaxies with different densities then our own galaxy appear blue or red shifted from movement when in fact it could be from the time dilation from ...
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Time Dilation Equals Red Shift looking in or blue shift looking out

We can see the center of our galaxy. With more density near the center of our galaxy is red shifting observed from our perspective? From the center of the galaxy looking at us would a blue shift be ...