Questions tagged [general-relativity]

Questions about relativistic theory of gravity. General relativity describes gravity as a geometrical property of space and time.

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Parker Solar Probe and clock correction

Due to the dynamic changes in speed and the value of the gravitational field in which the Parker Solar Probe stays, the clocks should have the errors due to relativistic effects. https://physics....
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Planck epoch and time dilation

I guess this question can be broken down into three consecutive parts: Does general relativity apply during the Planck Epoch? If yes, does the gravitational time dilation prediction apply during the ...
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Order of magnitude of this phase space invariant?

So I wanted know the order of magnitude of this phase space invariant (equation $3.31a$ )$R$ in our universe (FLRW metric): $$R = \int_{p} \frac{\mathcal{N}(x,p,t)}{\mathcal{E}} dp_x dp_y dp_z$$ ...
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In between Classical Gravitational Deflection (2GM/rv^2) and General Relativity (4GM/rc^2)

While researching online I've found two expressions for the angle of deflection by gravitational lensing: $\dfrac{2GM}{rv^2},$ Classical(Newtonian) prediction $\dfrac{4GM}{rc^2},$ Relativistic ...
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How can we see black holes collapse if time inside the event horizon is infinite?

My understanding is that if you fell into a black hole, i.e. crossing the event horizon time would be speed up infinitely fast. This means I could see my whole galaxy die, new blackholes develop and ...
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Does the presence of dark matter in the Milky Way significantly distort our parallax based measurements of distance?

According to accepted astronomical wisdom, dark matter represents a large fraction of the total mass of the Milky Way. And thanks to Papa Einstein, we know that light rays can be bent when passing ...
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Why is the ring in this simulation of Sgr A* off center?

In the recent releases of images of Sgr A*, simulated versions of what they expected were included along side the actual images they were able to get. What confuses me about these simulated images (...
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Doubt regarding size and shape of black hole images published by the Event Horizon Telescope (EHT)

The recent publications of the images of black hole shadow by the Event Horizon Telescope collaboration prompts us to study black hole images in more details. According to the no-hair theorem, the ...
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How does general relativity explain gravity?

General relativity explains that gravity is the curving of spacetime by massive objects. This makes sense, like when I throw a ball, it follows the curve of spacetime, which is towards the center of ...
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Are toroidal black holes hypothetically possible?

Since toroidal planet are hypothetically possible, albeit very unlikely to actually exist, can we extend this idea to black holes? Would these unstable bodies work atleast on paper?
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Do Einstein's ten field equations use 20 or 40 variables? (2 or 4 for each tensor equation?)

One site I came across says Einstein's 10 Field Equations use 20 variables, while another said 40. There are four variables in spacetime - three for space and one for time, right? But there are two ...
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Does the Schwarzschild metric solution require two (A and B, or g11 and g44) or four components (g11, g22, g33 and g44)?

Different places on the web imply that Schwarzschild's metric uses four components or separate equations, similar to how Einstein's full set requires 6 or 10, or they say only two are needed. Is it 2 ...
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Post-Keplerian orbital parameters; is there a generally accepted set with definitions?

Strong-Field Gravity Tests with the Double Pulsar is a pretty big deal! 16 years of precision timing including "timing parallax" via VLBI has provided a dataset for which analysis requires (...
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Does the .43 arc-second per year deviation of Mercury's orbit from Newtonian predictions mean that its position is 'off' by 75 miles per year?

If I divide the elliptical circumference of Mercury's orbit by .43 arcseconds, I get an answer of almost exactly 75 miles.... BUT, it is the precession of the periapses that is off, not 'just' its ...
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Does general relativity imply that singularities cannot exist?

General relativity states that all matter in the universe is moving forward through spacetime at the speed of light. Objects that are stationary in space travel at c along the time axis, and objects ...
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What does 's' or 'ds' or $ds^2$ mean in the Schwarzschild equation(s)? [closed]

And: These are from Wikipedia on Schwarzschild metric, Derivation of the Schwarzschild metric and the last is from Science Direct, Schwarzschild metric.
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In relativity why does matter bend spacetime in a downward direction [closed]

A major flaw , I think it is in relativity.
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How do we know that objects that appear in duplicate or triplicate, etc. due to strong gravitational lensing aren't actually multiple objects?

If we are looking at faraway objects, there is no parallax view, correct? So isn't there a chance that an object that appears multiple due to strong foreground gravitational lensing is actually ...
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Why does Titan's (relatively) rapid migration away from Saturn cause the planet to wobble faster, and eventually (maybe) tip onto its side?

Over the past year and a half, multiple articles in the popular press have come out talking about how unexpectedly rapidly Titan is moving away from Saturn, and how this is causing Saturn to wobble ...
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Could quasars be interior to the event horizon of a SMBH?

My question is prompted by suspicion of three current ideas in astrophysics: GR predicts a singularity at the center of a BH without regard to QM. quasar hyper-luminosity is caused by an acretion ...
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What is the best visual-aide model that most accurately depicts objects moving through warped spacetime?

so far, the best model I've seen, to help me visualize objects moving through a warped spacetime is this video... A new way to visualize General Relativity. Is there a better visual representation to ...
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What happens inside a massive collapsing shell?

I have already asked this on the physics site. I am not sure where it fits better. Consider a massive spherical shell collapsing under its own gravity. Say the mass is that of one galaxy. The ...
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1 answer
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Lunar Eclipse and relativity

I am currently working on A Depth Study for my year 12 Physics class, and am looking at relativity and time dilation of a lunar eclipse experience on the moon compared to as seen from on Earth. From ...
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Is there a better formula for gravitation, besides Newton's?

Many experiments (e.g. changes in Mercury's orbit) show that Newton's Law of Gravity is not exact. According to the theory of relativity, what is the exact formula?
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How slow would you age on a double gravity planet?

How slow would you age on a double gravity planet? Gravity of the planet A is 10 units. If you are taken from planet A to planet B where gravity is double that of A, i.e. 20 units. How slowly would ...
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How can light circle a black hole one or more times and then escape again? [duplicate]

The shadow that is cast by a black hole was beautifully captured by the event horizon telescope. A concentration of light in the photon sphere around the hole (adjacent to the event horizon) ...
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Can we say space contracts around a massive object in space?

Space expands on a cosmic scale. It makes objects accelerate away from each other, as observed. Can we say, by the same token, that space contracts around massive objects in space, with the ...
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How much does the Higgs field contribute to the energy of empty space?

The Higgs field was not spontaneously broken when the universe was young and hot (like I am not...:)). At the very high temperature that existed back then, the Higgs' energy of the Higgs field was non-...
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Is it "nonsense to even talk about" objects outside the observable universe not having gravitational influence on us? (finite speed of gravity)

In this supplemental answer to Is the zero gravity experienced in ISS the “artificial” kind? in Space Exploration SE I said: Gravity moves at the speed of light so nothing outside out observable ...
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6 votes
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Has gain in mass from accretion onto a black hole been observed?

Have we observed a black hole directly gain mass via accretion? That is, have we observed the black hole to have mass $m_1$ at time $t_1$ and then observed its mass to be $m_2 > m_1$ at a later ...
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Do relativistically measured rotation speeds (Special Relativity) change planetary mass slightly through Lorentz transformation?

Thanks @ConnorGarcia for your Answer. Avoiding 'Tidal Locking' for now - the rotational angular momentum Lrot is 10,000,000 times smaller, so negligible, but could it still be a factor in eccentricity?...
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Time of lunar eclipse relativity

Would there be a change in time in terms of the length of time it take for a lunar eclipse to cross the moon as seen from earth compared to as what would be experienced from the moons surface?
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When will Mercury have rotated an extra round around its axis?

It is well known that Mercury orbits slightly differently from a pure Newtonian orbit. Every year a slight deviation is found. Now if we observe a lot of these orbits then Mercury should at one point ...
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Scalar field displacement from the minimum of the potential gives rise to particles/dark matter, why?

The paper Lyman-alpha Constraints on Ultralight Scalar Dark Matter by Kobayashi et al. says, at the beginning of Section 3.1: A light scalar field stays frozen at its initial field value in the early ...
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Gravitational time dilation

Did clocks run more slowly in the early universe due to gravitational time dilation? Or, alternatively, do they appear to be running more slowly when observed from today, if that is not the same thing?...
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FLWR and curvature

The FLWR metric or model I believe results from Einstein's equations of general relativity if it is assumed the universe is 1. homogeneous and 2. able to expand (or contract). Solutions can have ...
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Do gravitational waves produce a surrounding gravity field?

Massless light beams produce a surrounding gravity field. A massive particle will move towards it and at the same time be dragged along in the direction of the beam's velocity. But what will happen ...
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What would be the electric potential and the energy produced in a cable connecting two electronic devices on the magnetic poles of the earth? [closed]

The earth is a large magnet moving in the magnetic field of another large magnet the sun. And if we connect the two poles of the earth by a cable there would be energy and an electric potential in ...
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Does the sun have a notable frame-dragging effect on the planets?

Frame-dragging is a general relativistic effect that can be imagined as the effect that the momentum of mass-energy has (the stress elements in the stress-energy tensor) on mass-energy in the ...
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About the strange case of Bonnor beams

Bonnor beams are light beams of infinite extent and small thickness. They have an associated spacetime (related to their energy and momentum which shapes the stress-energy tensor) of which Bonnor ...
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Was there a formula-first hypothesis for gravity?

Being a mathematician I wonder, has there been an attempt to blindly approximate a formula for gravitational attraction that would match the data, based on "normal" matter we can see plus ...
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Why is the FLRW universe (general relativity solution(s)) sometimes called the 'FRW universe'?

Why is the letter L for Georges LeMaîtres often, or even usually, left out? Does he, or does he not, deserve some credit for this cosmological solution to Einstein's general relativity?
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Is there anything different about the gravitation around a non-spinning black hole and a neutron star of the same mass?

If we perform a simple experiment by orbiting identical spacecraft around a non-rotating black hole and a non-rotating neutron star of equal mass at a "safe" distance, and ignore differences ...
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Can Newton's gravity equation explain why black holes are so strong?

I was just wondering why black hole's gravitational forces are so powerful. I know it's usually explained by Einstein's relativity which states that when an object becomes infinitely dense (a compact ...
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What exactly is space-time fabric?

I have heard about space-time fabric but I can't understand its definition. Is space-time fabric a physical thing or did Einstein imagine it to assist him with general relativity?
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How fast would an observer have to travel in order to be able to study an entire star's life in one human lifetime?

Humans live for about 80 years. A star, however, lives from 1 million to trillions of years, depending on its mass. If humans want to have a detailed study of the life of a $1 M_\odot$ star, how fast ...
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Would studying massive stars that are experiencing time dilation due to proximity to a black hole be useful?

I saw this question (Could a star closely orbit a black hole long enough for the star to have lost 0.5B+ years to time dilation?) and came up with an interesting thought. Massive stars live for less ...
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Does General Relativity predict anything about the creating of a singularity, once enough matter collapses inward to form an event horizon?

Ignoring quantum gravity, which we don't know much about, current theory (GR) states that an event horizon forms when there is enough matter/energy density to create it, and logically, a singularity I ...
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Is there a closest free-return trajectory to a black hole?

The scenario I am imagining is a test particle falling from infinity with an initial off-center velocity. In Newtonian mechanics the path would be a hyperbola. But I assume that, near a black hole, ...
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Has GAIA learned anything about General Relativity looking near Jupiter? (Gerry Gilmore: "oblate rotating mass moving in a deeper (Solar) potential")

From Gerry Gilmore (2018) Gaia: 3-dimensional census of the Milky Way Galaxy 4.4 Fundamental physics Relativistic effects are highly significant for Gaia measurement accuracy, with tests of General ...
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